Title: Annual reproductive cycle of the male pocket gopher (Geomys pinetis)
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00097716/00001
 Material Information
Title: Annual reproductive cycle of the male pocket gopher (Geomys pinetis)
Physical Description: 1 online resource (viii, 69 leaves.) : ill. ;
Language: English
Creator: Ewel, Katherine Carter, 1944-
Publication Date: 1970
Copyright Date: 1970
Subject: Pocket gophers -- Reproduction   ( lcsh )
Genre: bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )
Thesis: Thesis--University of Florida.
Bibliography: Bibliography: leaves 61-63.
General Note: Manuscript copy.
General Note: Vita.
General Note: Description based on print version record.
 Record Information
Bibliographic ID: UF00097716
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 004816956
oclc - 503002583


This item has the following downloads:

PDF ( 2 MBs ) ( PDF )

Full Text


MALE POCKET GOPHER (Geomys pinetis)






I am indebted to Drs. David W. Johnston, John H1. Kaufmann, E. G.

Franz Sauer, and Daniel 8. Waard for their encouragement and helpful

criticism during the course of this project. In addition, Dr. John

Thornby offered considerable advice on the statistical analysis of the

data; Thomas Krakauer assisted me several times in trapping; Robert

McFarlane gave assistance in the preparation of photographs; Dr. Gordon

N. Prine provided environmental data from the Agronomy Farm Weather

Station; and Dr. John F. Gerber assisted in the interpretation of soil

moisture data.

Permission to trap on Stengel Field was kindly granted by Mr..

A. Arano.

The University of Florida Computing Center provided the facilities

for the statistical analysis.



ACK~NOWrLEDGIENITS ............................................ ii

LIST OF TABLES ............................................. iv

LTST OF FIGURES ............................................ v

ASSTRACT ................................................ vii

INTRODUCTION~ ................... ................... ............. 1

Pockcet Gopher Environment and Physiological Adiaptations ..... 2
crf;sts of Envirosnment: on Activity Cycle .................... 3
Reproductive Cycles in Pockiet Cophers ....................... 3
The Reproductive Cycle of Geomys pinetis .................... 5

CharacteL; r: i;Ticsj rf feproductive runs.....................

1Instological Lethod ..........ai~a1.............................. 1
Exammattra~:'?;r j ofr. .he Tstis................................... 1

Examianon f theEptilerate............................... 13~
Crniminatinl Jf the Accessor, Glands .......................... 13

~ii- lccn ..*Che C am es in Reproductinle .re.n..................... 12

C clT Ch..............:3,si -pan.te rse................ il

Compncrtson of ilch e iin Reproducci c o.erin ..........ns..
5;lTeIsi:,~ in C:rad '11 .Or~ ures ....... ..................****** 51

Quartcrl:, ,* Sangle ................... ..........................

LI~~cTERAtUE CITED ........................................... 61l

biE;liG.AHIA SKETCH ....................................... 0



1. Means of mecasuremecnts from male pocket Cophers ........... 18

2. Independent factors in measurements fromn male
pocket goph~ers ................................... 19

3. Numbers of pocket Gophers withl acini at a given stage
of secretary activity in the prostate glands .............. 22

4. Relationships between thle production of sperm
and accessory gland activity .............................. 23

5. Niumlber of males caught in each trapping period ............ 24

6. F ratios from univariate analyses of variance
shlowiny, significance of diferences between means
of reproductive parameters in 15 trapping periods ......... 26

7. Distribution.of significant peaits among the parameters .... 38

8. Results of canonical analysis ............................. 43

9. Mean values of environmental parameters over the
specified periods of time before approximate
conception dates ......................................... 48

10. Sex, age, and reproductive status of animals captured
in each quarterly sample .................................. 50



1. Criterion for separating mature from im~mature
male pocket gophers ..........,..................,,,........ 9

2. Testicular volume~s throughout the trapping periods ........ 27

3. Diameters of the testis tubules throughout the
trapping periods ..,......,,....................,.......... 28

4. Diam~eters of the Leydig cells throughout the
trapping periods ................,,............,,,........ 29

5. Volumles of Leydig cell tissue throughout the
tr pring periods **....................................... 30

'..';llo-es io the stages of spermatogenesis
rlwl:.u, uc the trapping periods ........................... 32

.~. .11.tir :f the ep~ididymal tubule throughout'
tra~~ r~c ppin,-, period= ...................................... 33

i. I:ll he.ChS~cr in rhle ..ca5 .lar.:i al pc:roci t. (1and

11 r' -.at l_ .tnl t 11- t ;.jrj i rl !i.e r <[,0~ n ..r.. ;,0.1 mi~~~~~air.,u

.'~ tLrl .. .....isur = ...................................... 395

12.~~i~ F".*er.i n.nchl .oil ruel.cure...... ................... .... -

toi their~~ cirl.cur. ................... ................... .... ;

Lr, th,?. c r..~i'.U ............................~.......***** ;1

15. Pcriodls of reproductive activity based on
all projected conception dates ................................ 47

16. PNonthly soil temperatures andl rainfall
during, quarterly samplinge period .............................. 4'9

17. Periods of reproductive activity accordling to
projected conception dates in quarterly samples ............... 52

18. Level 8 testis (100%) ......................................... 65

19. Level 3 testis (430S) ......................................... 65

207. Level 7 testis (430S) ......................................... 65

21. Epididiynal tubules fromn a male
in active reproductive condition (100X) ....................... ;66

22. Epididymal tubules from inactive male (100X) .................. 66

23. Actively secreting acinus from dorsolateral
prostate gland (430X) ......................................... 67

24. Inactive acinus from dorsolateral
prostate gland (430X() ......................................... 67

25. Lumen and part of cell boundary from an active
seminal vesicle (100X) ........................................ 68

26. Inactive seminal vesicle (100X) ............................... 68

Anut; act of I?/.\artAtion~ Pr." e~nt.--i to the iGraduat~e Coiincil
in~ lartial Fulfillmecnt of tri. r.. .ute=,-n.*nt for Eno iDegr.?i of
licCorl of Uilo opphy

iiALE PrjIl.E T ST1COME (0 ra. va',*= g )


IE:cherlne Car~L~terLull

Juine, 1970

ihairmsni Daytd W~. Johnston
;a jor De~partme~nci Zoclogy

Ain jnalyst5 ~.is made~ nf the reprjdructive crcle of th- southr-

easteirn poclrac rgopher, ocoways pIngy~ j i, to detemnine btch the pacttern

o;f reprodu~ction in chts =pec; 8jies an the marlnittude~ of envLO~irorwntal

influ..nces on reproduction in a fossoriail habhitac ncir Gainesville,

Florida. The primary focus of the investieatiion ias the irale repro-

ductive icycl, but Igros; Ineasulrements of the reproductive.- cond~ition

of the. females ucre jlso usedl.

Thr rien c estis, its rpididymis, and the pro*::imal accessory

glans (;seininl vesicles and1 prostate Pland~js) of 76 ale pocket~

gopher s ollected moicnthly Detween Majrch, 1967, and.j July, 196j8, were

sectionecd ond examir~ned histolo;~teally to hsscss the degree of repro-

IJuctiLe acttvity of coch orrgan. A onc-dajy inalysts of varijnce was

per~formdc onh ejch of the Iramasurer~lent made on the various arrans to,

determine if j monthly cycle of activity was present. A principal

components analysic. was also performed to find out what ir~iterelation-

ships might exist btweeun the parameters. Finally, a canonical

analysis related those parametersj whlch showed cyclical difference;

during the trapping period with corresponding soil temperature anid soil

moisture values to compare the Effects of the environmental pa-a-Pters

on the reproductive cycle.

During a subseqluent tw~elve-month trapping, period, qluarterly popula-

tion samples were made in the same study area. Only gross measureme~nts

of the reproductive condition were made on the 60 individuals in this

part of the investigation.

The reproductive cycle in the male pocket pgopher was found to be

closely correlated with soil temperature and to a lesser degree with

soil moisture. Naximum reproductive activity occurs wlhen environmental

conditions create a friable soil, suggesting an increased likelihood

of intraspecific contacts. Very warm external temperatures and lowJ

soil moisture inhibit reproductive activity indirectly, presumably by

restricting activity within the burrow.

Leydig cells show a net decrease in size and number with age,

after an initial increase at puberty. Increased reproductive activity

is correlated with an increase in Leydie cell diameter. Spermato-

genesis was non-cyclic, but did not cease in the entire population

during the study period. The activity of the accessory glands and

the epididymis served as a more reliable index of an individual's

reproductive condition.



Fossorial rodents are unique among terrestrial mammals in being

isolated from most of the environmental factors that control daily and

annual biological cycles in many other organisms. Typical of these

cycles is reproduction, which may be controlled or influenced in many

mammals by the available food supply, temperature, photoperiod, or

rainfall. In studying reproduction of a fossorial mammal, these ex-

ternal factors must be translated to their effects on the environment

of the burrow. In this investigation, emphasis is given to an analysis

of environmental effects on the reproductive cycle of a fossorial

rodent, the southeastern pocket gopher (Geomys pinetis Rafinesque).

This animal spends almost its entire life underground and is

well adapted to a fossorial existence, as indicated by its relatively

broad, flattened skull, small eyes and pinnae, stout forelimbs, and

elonejted foreclawrs. It: feeds chiefly on roots obtrined from Lts

burrow, js we-ll as on occjsionjl leajvis pulled into the shallower parts

of the burrow. It is adoomi seen above Eround3, and as. exposed to daiy-

Iirght onl, duirinfi short: perious when mjktng fresh moundls. Pr-s~uilably,

pocket gophers are influincedo more by the environmental of the turrow

than by light. Particularly Iimportant influences would include temi-

parature changEs, gas comiposition, and soil characteristics.

Pockect Gop~her Environment and Physiological Adaptations

Kennedly (1964) found that the temperature within the burrow of

Coomvs bursarius in central Texas is more constant than environmental

temperatures, and that the range of burrow temperatures becomes narrower

at increased depths. McNab (1966) noted that temperature changes within

burrows of G, pinetis in Florida are also less extreme than outside

temperatures. Because of the temperature stability in the burrow,

Wilks (1963) reasoned that there might be less selection pressure

towards strict homothermy. Poor thermoregulation has indeed been found

to be characteristic of fossorial rodents (Gunther, 1956; Wilks, 1963;

McNab, 1966). M~cNab (1966) claimed that conductance is facilitated by

a scanty fur coat, an increase in peripheral circulation, and a general

decrease in body size and mean weight in areas of higher soil tempera-

ture. The greater stress of summer temperatures, accentuated by the

burrow's saturated atmosphere (MlcNab, 1966), might still pose a problem;

the pocket gopher could, however, avoid heat loading by retreating into

the deeper, cooler part of its burrow system. From 10 to 20% of the

burrow systems of Thomomys bottae and G. bursarius lie well below the

superficial runways, which are within 12 inches of the surface (Miller,


The oxygen and carbon dioxide concentrations in the burrow system

fluctuate more widely than does temperature. Increased soil moisture

cause; the carbon dioxvide content, which is initially several times

Sreater than the atmospheric concentration,, to rise even more, probably

due to decreased diffusion through the soil pores (h'ennedly, 1904).

As a result, according to m~easurements mlade~ in Florida by Mci:ab (1966),

- 3 -

the carbon dioxidec concentration in the burrow rejches~ as mulcr aj

20 to 35 times the atmospheric concentration. The oxygen concentra-

tion remains within 80 to 95% of the atmospheric concentration.

Effects of Environment on Activity Cycle

Little is known about the influence of soil moisture and soil

temperature on pocket gopher activity. No published data on activity

cycles within the burrow are available, and Vaughan and Hansen (1961)

remarked that the usual indicator of activity -- the appearance of

fresh mounds -- is really only indicative of surface or near-surface

activity. Trapping experience, however, indicated to these authors

and to Wilks (1963) that soil temperature is an important factor con-

trolling the pocket gopher's daily activity cycle.

Miller (1948) found that the amount of burrowing (determined by

the appearance of fresh mounds) is primarily controlled by soil moisture,

the greatest activity occurring when the soil was most friable.

Kennedly (1964) came to the same conclusion, but the correlation seemed

weaker to him.

hcoroducti-e Cycles in Pocket Caphers

Reprodulctive activity In most5 species of poclket Ccphrs is

limited by their usually solitary behavior, although instanes of

multiple captures uithin one burrow jysterm have been reported for nany

speciies of Genomy5 andl Thomowsj (e.e., E~ni-lish, 1932; Vaughan, 19)62;

W~ls, 963 N~ler L96).Both Vau~nnn (1962) jnd Wilks (1963)

observed that these multiple captures werc miost frequent during the

breeding season and usually involved antmals of opposite sexrs.


Uine (1960) listed only one multiple capture in G.. pinltgg, involving

an adult male and a post-partum female. She also cited 14l instances

during one year of collecting in which a pocket gopher was caught in

one trap when the second trap had been sprung. This, however, could

have been accomplished by one animal's blocking one trap before being

caught in the other. In general, it appears that pocket gophers remain

solitary within their burrows most of the year.

Ecological aspects of reproductive cycles have been studied in

several species of pocket gophers. In east Texas, English (1932)

showed that only one litter per year was characteristic of G. breviceps,

whereas Wilks (1963) reported at least two litters per year for G.

bursarius in south Texas. Peak~s of reproductive activity in G.

bursarius were found in December January, and April May, with

some activity in July September. Wilks suggested that temperature,

humidity, and rainfall were interacting to inhibit summer breeding.

C. bursarius in Colorado produced litters only in the spring (Vaughan,

1962). In this case, the breeding season seemed to be timed so that

the young appeared in late M~ay or June at the peak of vegetative

growth and when the soil was most friable. The adults began to come

into reproductive condition in late winter while the ground was still

frozen to a depth of six inches.

According to Miller (1946), T. bottae in California has only one

breeding season in the northern, more mountainous part of its range,

4hercas the breedint, season in the Eouthern part seemrd to extend

throul-h part of~ the uint-r rainy: season to allow two or three larttrs

Per ye'ar. D~ixon (1929) felt that thi; cycle was attuln1 primarily to

the? appearance of the po et gopher's most iLaportant food plants at


the beginning of the season. Hie found that~ in the- central Sar.~ Joaqlinn

Valley, where alfalfa and other green forage crops were available

throughout the summer, the breeding season was longer. Gunther (1956)

also described the breeding season of this species as restricted to the

cool, wet weather of winter and spring in nonirrigated portions of the

range, but being more protracted in irrigated areas. Bond (1946)

suggested that whereas availability of food might affect the sexual

development of a pocket gopher, contact between the sexes at the op-

timum time for reproduction depended more on the friability of the soil.

W~ing (1960) described the breeding cycle of G. pinatis in Florida,

but made no correlations with environmental factors. Pregnant females

were encountered in her collections throughout the year, but they

ippea~red more frequently in early spring and late summer. Probably

some females had produced at least two litters per year, since double

sets of placental scars occurred in seven females collected between

April and July. Her work included a thorough examination of the females

as well as gross measurements of the male reproductive tracts and epidid-

yrjl spe~rm jsmears. Thil males In her samplFes: showed greatest reprodu..-

tive activity' from Jinuar) Auut,:UL ;h?reaS F:mallCS were most arctive'

in bajrch and July Augusat.

Thec Reprod.uctive Cycle o~f CIoomvS CnetLS

Unli;e ither- species of pockce rophers that Inhabit temip:rte~

rergions, G. plngtlj doecs not ;pp'ar to njve a iell-defined br~eeding

cyile thit can be eastly actltruted to enetironmental 'Iff~-ets n'ing

has suse~r: sted that breeding continues~ throughoutr the- yea-r btil not at

the S;Lme intensity. ThrlET are at least four diiffernt ways in which


the male reproductive cycle could be operating to Generate this

patterns 1.) The males may remain in an active reproductive state

all year, but the females come into breeding condition only at

presumably propitious times. 2.) The males do not remain in an

active state of spermatogenesis all year, but instead store sperm

for a certain period of time after spermatogenesis has ceased, mean-

while retaining a propensity toward mating. 3.) The males may show

fluctuations due to environmental conditions, although never completely

losing the ability to reproduce. 4.) Some males may maintain at least

a threshold ability to reproduce whereas others regress significantly;

a well-defined cycle is therefore not maintained in the population.

The purpose of this investigation was to determine which re~pro-

ductive pattern exists for G. pinetis near Gainesville, Florida, and

to examine in greater depth the influence of environmental factors.


Study Area and Trapping Nethods

At least five male pocket gophers were trapped every month from

Clarch, 1967, through July, 1968, within a five-mile radius of Gaines-

ville, Florida. After July, 1967, all trapping was done at Stengel

Field, three miles WSWJ of Gainesville. This field, containing a

fairly large population of pocket gophers, was characterized by Pensa-

cola bahia grass sod over Arredonda fine sand and was mowed fairly

regularly throughout the trapping period. Part of the field was used

as an unpaved air strip. The animals were captured in Victor gopher

traps which were checked every two to three hours to avoid excessive

decay of the tissues in the dead animals.

In addition, samples of 15 pocket gophers, including both sexes,

were trapped in N~ovember, 1968, and in February, May, and August, 1969,

to obtain quarterly population samples in Stengel Field.

n total of 106 majles and 91 lamTales was obtained for~ analysis in

the preSent trraVCiestigatio

Enlcnrilronmnta iata

Climlatological data were- obtained from thie Agronomy Farm Ue~athcr

Station, an ar?a one rntle east of' Stevecl Exeldl and quite similarr to

it in soil characceristiCS and rOVOC. The? LO~pcrJaures usedl in the

statistical analyses kere soil temperatures at a depth of four ir~nces


-8 -

and were averages between the daily maxima and minima. Estimates of

soil moisture were obtained by combining weekly estimates of evapo-

transpiration with total weekly rainfall. Field capacity, defined

as the ability of a soil to hold water against the pull of gravity, is

13.52) by volume for the top two feet of Lakeland fine sand (Hammond

et al., 1967). Harmmond (pers. comm~.) estimated that this value is

probably very similar to the figures for the Arredonda fine sand in

the trapping area and at thle Agron~omy Farm. With rainfall as input

and evapotranspiration as output, soil moisture was calculated for

each week beginning at a time when field capacity had 'Deen obtained.

Evapotranspiration values were obtained frorm measurements that had

been taken daily on two lysimreters at the Agronom~y Farm. Daily out-

put (leachate) was subtracted from input (2000 mm of irrigation

water daily plus any rainfall) to give a rough indication of soil

moisture (Tosi, 1968). This method should be reliable when used on

a weekly basis, and should certainly provide a relative indication of

periodic soil moisture cycles.

Characteristics of Reproductive Organs

Certain standard measurements were taken of all specimens:


* **
? **

Nature *ivdu

Immature Individuals

6000 -


3000 -

2000 -




L .I l l I I I
51' 70l 100 20030050

Body; Usigiht )~

Fig. 1. Crnteriors for SeparTiCng macure from irrianaturr mole
pocketc Copr~ers

- 10 -

altered at puberty, and he noted that this wras reflected in a

change in the log log slope of org~an weight vs. body v~eight,

When the testis volume and3 hodyr weight for all -rocket gophers were

comparred on a logarithm~ic scale, two distinct clusters appeared,

separated by a difference of nearly 900 rmm3 in testis volume measure-

ments. Three individuals intermediate between the clusters were

classified as imm.ature males, because measurements of the epididymal

tibules and the accessory glands were infantile.

Reproductive conditions of females were defined by conditions

of the nipples (furred or exposed), the uterus (degree of vascularity

and swelling) and the pubic bone (the symphysis is resorbed at puberty

(Hisavy 1923)).

Histological Methods

Sections were made of various reproductive organs. The right

testis, cauda epididymis, and the entire proximal set of accessory

glands (prostates and seminal vesicles) from each male were preserved

in Bouin's fixative. After being embedded in paraffin, these organs

were sectioned at 10 a? and stained with Heidenhain's iron-hematoxylin.

Sections were m~iade from regulria spaced intervals throughout the

length of the testl; and the iepj.d:,idas Srrsal sections of the acces-

sory glands were ipr:;-'ajr: tofi~litat_ trra:irn the tubules. 3:0.e

with enlarged set. o :i,;l nd., i~ ~..Ee sa.ion v::-~ again chosen a: inteir-

vals to .':- art i_, i::a~icuation --.f lirre unbe~.rs of slides.

- 11-

Examiniti-on of the fe';tic

Several criteria were used to determine the reproductive condition

of the testis. The initial Gross measurements included the lengths of

the two axes of the testis, as though it were a perfect ellipsoid. The

volume was then determined by the equation: V = 4/3 TT ab2~ na"~ being,

the long axis and "b" the short axis.

An average value for testis tubule diameter was calculated for

each individual from ten randomly selected round tubules.

The spermatog~enic values of twenty tubules, randomly selected among

the round tubules in several sections, were also determined according

to the following scale adapted from Roosen-Runge and Ciesel (1950),

with some modifications proposed by Johnson and Buss (1967)1

Level 1. Liccle cell dOfferentxation, no( Ilumen, spar;e germ
cell population

'. Immiature ctubule' with fu primary) ;FpermatoC'Cy~es

3. IMo;tl:, primary' pE~rmac~cy:cs, some se~ondary;
;perna~ctecyte fewr spermaicids

4. Ilucrh spermiiatid formiiation

5. Spe~rma~tius unde~rloing clongation buc not~ yet in

6. Sporl~rmaids In b~undlej moringl touardii woule

7. Spcrmal~to.-oca noting from pe'rip~hery to lume~n;
"ubeecl-;poke" stage

3., SpermatZO'O lininC lunenn

An "icttvc" rst~i; would have i certain proiport-ion of tubule~s In

Levcls 3 8, ;ince the Leve.l 1; tuoulcs revere to Levcl 3 after losing

-12 -

their spermatozoa. Inactive testes, i.e., those lacking tubules

that are actively producing, sperm, may have Level 1 and Level 2

tubules as well as Level 3 and occasionally Level 4 tubules.

The specific stage of spermatogenesis shown by each animal was

determined accordinG to the following, characteristics

Stage 0. N'o spermatocytes, totally inactive

1. Primary spermatocytes present

2. Secondary spermatocytes present, some spermatids

3. Many spermatids in Level 4

4. Most advanced spermatids in Level 5

5. M~ost advanced spermatids in Level 6

6. Spermatozoa present in Level 7 only

7. 5%L of tubules contain spermatozoa in Level 8

8. 10% of tubules contain spermatozoa in Level 8

9, 15% of tubules at Level 8

10. 20% of tubules at Level 8

11. 25%

12. 30%

13. 35%

14. 40%

15. 4S%

Since the Leydir. calls in the intersrtital tissue are believed

to secrete te~stosterone, the njle hormone that controls the activity

of the secondary sex characteristles (Ploom and Faucatt, 1962), those

Ley'die cells with visible? nuclear and cell rre.-branes +ere measured.

both the cell diameter and the nuclear diamete?~r of round cells erer

recorded at 1000X.

- 13 -

The total volulme of Leydip, cells in the testis was obtained by

the following method, after Groome (1940). Using an ocular grid

measuring 1.92 x 10" mm2 at 1000X and focusing through the 10 a

depth of the section, the total number of Leydig cells in several

randomly selected fields was counted. Since the volume of each field

was known (1.92 x 10-6 mm3), the average number of cells per field

was multiplied by the number of field-volumes contained in that

particular testis to get the total number of Leydig cells in the

testis. The average Leydig cell diameter in each animal was used to

calculate the total volume of the Leydig cell tissue in the testis;

this value was divided by the testis volume for a measure of the

percentage of the total volume.

Examination of the Epididymis

The epididymis consists of three regions the caput epididymis,

which contains both the opididymal duct and efferent ducts from the

rete testis; the corpus epididymis; and the cauda epididymis. The

tubule diameter, cell height, and nuclear diameter were each jveraged

over ten tubules in the cauda cpididymiis.

Eiaminatio~n of thr' AcScEsoY TGlandlS

Each ductus deflercns receives secretions from the seminal

vesicles and the prostate flands before joining the ur~ehrj.

Th~e seminal~ vesicle In the younF. animal andl in the inactive

adult is stronely lobulated, but the cavties~ and recesses ejssntiallyg

disappear during active secretion, when lume~Fn e~xpands. The cells in

the recesses appear to be the miost active secretory units (lioare iet al. ,

- 14

1930); ten such cells were measured among the sections from each

individual to give an average height, and the relative amount of

secretion present in the lumen of the vesicle (0, 1, or 2) was noted.

If no secretion was found, the rating was 0. A trace amount was

given a rating of 1, and the presence of enough secretion to cause

distension of the vesicle was rated as 2.

The prostate Gland is divided into three sections dorsal and

lateral units, which are considered as one unit here, and the ventral

unit, which is interior and anterior to the others and seems to be

much less extensively developed (Macklin and Macklin, 1963). Ten

cells from acini of each of the two sections were measured and the

relative secretary activity was also recorded as in the seminal


Statistical Analysis of the Data

Correlation coefficients were calculated for all possible pairs

of measurements (including 16 reproductive parameters and four

environmental parameters) by eliminating from the calculation of a

given coefficient those individuals which lacked either or both of

the measurements. A program from the University of Florida Statis-

ticall Progral: Ltocacy, "Interccrre~lation with D:iSsing~ Dt);E"

(UFj5iLO2), computced those coefficients. This correlatton COclit"

cient miacrix served as input for the Bionedical Coilputecr Protram,

"Factor Analysis" (aI0003i). because the correlation coathicetent

were use~d as the input rather than tnc raw data, thts program pro-

ividea only a principal components analysis. Th~e techniques reduce;

the correlation coefficient m~atrix to a smaller num~ber ofT uco~rrelhteu


variables, or factors, which :oupF the mo~lst shv~ilar parlTm-etrs. Eaich

of the original variables is usighted~ accordingg to the stroniteh of

its relationship with all the other variables in each factor. The

most important factor is the first, since it contains the greatest

proportion of the total variance.

Since the trapping was divided into 15 periods, a one-way

analysis of variance was performed on each of the parameters (BMID01V,

"Analysis of Variance for one-Way Design"). The means of those paran-

eters showing significant F ratios at the .05 level of significance

were then tested for significance, again at the .05 level, by Duncan's

N'ew Multiple Range Test adjusted for unequal sample sizes (Steel and

Torrie, 1960).

Fariaiit-rs rhowiac jignifica~nt diffirrnc-s (i.., e*,clical chjnCes

ever clve 16-rFonth triapin g perlIod) uiere Frollped togEther ni ccmparod

v-ich a _er t~ of environmental parimeters in i second multivarriate tech-

nique;, canonical anailysi; (EI:)6I, "Canns;ical Anailisir"). dnly the 31

individuslr +ith co.,plete ;ets of lita for the signifcant parameters

were u;sed. Ecr g;ach ind]iv;idul, the alerage soil moi:ture and roil

tenp'?r; tuiC values for thC two-uce;: irnd fourT-i e:-k pr~~iod~ Prei~'ous to

the: datec of captu~r; werr cailcu.lated.j The~~ c-nonical analysisz treated

the- reprodu~cti'.' psrametecrs as one :et of dnca, the encrirorirental

pac~rtmeter; as; another. To linEer functions; of the Cen:ral forms

Y = "1 1 + *** nt nr:l were conlplted for ealch 3et, ILuch thlat 71 and~ Y2

re re ari:.;-jlly con-l a cd. The "a" inlificiints Cive th~e rclativ' e

im~parrance o'f carh payiraer i --.in cal~llaciing cho, co-fficientE Y.

F?ur clinical anialyse3 were rcan, each1 prograrn including the

jsiame reprodu!ICTive :ataII but e~ .it differren cominatiojci n of sort te~n-

16 -

perature and soil moisture values. Thus data on soil temperature for

the two wooks prior to capture were paired with the soil moisture for

two weeks prior in one program and four weeks prior in the second

program. The data on soil temperature for four weeks prior were sim-

11arly pairedi with each of the soil moisture sets in the last two pro-

g~rams. Two independent canonical correlations were calculated in each

program, each correlation maximizing a different environmental parameter.

Each successive correlation was less significant than the preceding one.

Glandular activity between the different kinds of glands and in

individuals of varying degrees of reproductive activity were compared

using the chi-square criterion at the .05 level of significance.


Noncyclic Changes in Reproductive Organs

While the intent of this investigation was to study the cyclic

changes in reproductive activity, it was obvious that non-cyclic, or

age-dependent, changes might also be occurring. Table 1 lists the

differences between the means of measurements in mature and immature

animals, but gives no indication of what further variations might occur

after puberty has been reached. Changes in one organ ma3y also be

correlated with changes in another organ or group of organs; this

may be an important factor that is missed by studying the isolated

parameters. The principal component analysis provided a means of

looking at the set of parameters as a whole, rather than individually.

It selected from the entire set of measurements from mature animals

a small number that accounted for most of the intercorrelations of the

- L7-

Parameter Immature N Mature N

Body Length (mm) 141.0 14 178.9 .61

Body W'eight (g) 106.2 13 214.5 62

Testis Volume (mm3) 219.4 1Li 3282.8 59

Testis Tubule Diameter (u) 66.8 11 160.4 61

Stage of Spermatogenesis 1.1 11 9.3 61

Leydig Cell Diameter (u1) 5.6 11 8.2 59

Nucleus-Cell Ratio of Leydig Cell (%) 84.4 11 67.4 59

Leydig Cell Tissue Volume (mm3) 21.0 11 370.2 55

Leydig Cell Tissue, % Testis Volume 9.9 11 11.3 55

Epididymi~l Tubule Diameter (u) 48.5 9 226.3 52

Epididymoit: Cell Height (u) 11.3 9 22.5 52

Epididymal1 Cell-Tubule Ratio (%) 23.6 9 12.5 52

Seminal Vesicle Diameter (mm) 0.4 7 1.9 52

Seminal Vesicle Cell H-eight (u) 11.5 7 17.5 54

Dorsolateral Prostate Cell Height (u) 9.3 12 17.4 51

Ventral Prostate Cell Height (u) 10.1 7 14.9 36

- 18 -

Table 1. Means of measurements from male pocket gophers

Table 2. Independent factors in measurements from nale pocket gophers


Parameter 1 2 3

Body L~ength .8553" .0717 -.0244

Body lleight .1373 -.0403 .1853

Testis Volume .5449* .1625 .2069

Testis Tubule Diameter .8860 -.0316 .2910

Stage of Spermatogenesis .9322* -.0521 .1934

Ley~dig Cell Diameter -.6497* .1868 .7099*

Nucleus-Coll Ratio of Leydig Cell -.7208* -.4241* -.0321

Leydig Cell Tissue Volume .3342 .8337* .1660

Leydig Cell Tissue, % of Testis Volume -.1238 .9373*' .0600

Ep'ilid)-nal Tubule Diameter .3919 -.0199 .4130*x

Epididymil Cell Height -.1932 -.1202 .1307

Epididymil Cell-Tu'oule Ratio .5357* .1172 .5303*

Seminal Vesicle Diameter .0348 -.2060 .4868t

Seminal Vesicle Cell Height .1755 .0785 .8616s

Dorsolateral F.rastiet Cell Height .1841 .0575 .8621*

'.'.antrol Frrostate Ce;ll H1ight .195 .20 .75,2"

- 19 -

-indiicate ;oot Inrurtant loadtnes


Hiost of the measurements increased in magnitude with age. The

Leydig cell diameter decreased, however, as did the proportion of

the nucleus to the cytoplasm. The loading for Leydig cell tissue

volume may not have been significant, but its magnitude suggested

that this parameter also increased with age. The percentage of volume

taken up by Leydig cells did not increase, however.

Factor 2, which has no relationship to age or to Factor 1,

showed thst Leydig cell tissue volume and the percentage of Leydig

cell tissue in the testis increased with an increase in the proportion

of cytoplasm to nucleus in the Leydig cell. Since Factor 1 did not

associate increase in percentage of Leydig cell tissue in the testis

with age, but did show that the nucleus-cell ratio increased with

age, Factor 2 suggested that there was actually a cyclic increase

and decrease of both tissue and cell volume.

In Factor 3, the Leydig cell diameter increased with glandular

activity in each of the accessory glands that was studied. Leydig

cell diameter was also related by this factor to the epididymal cell

height, which increased disproportionately to the epididymal tubule

diameter with age. This w~as also reflected in the high loading in

Factor 1, indicating that the epididynis cell increased in height in

relation to the tubule size.

The increase in testis volume wras attribulctable primarily to the

increase in :ize oE theI teatis tubules,, is ind~irrtd by th` dacr?je

in pe~rcenltae of Lcydip sell tissue. Th~e high lo!inf on spe-rmico-

5renesir in Fictor 1 Ehowed that active iperm production ion a not

cyclic in the F1_11-,yojur .. aul, but teameis morei or less constant.


Interrelationships among a~ctivity l.vels in the acces.ory r.14ndis

were considered important even though they did not appear In the

factor analysis. The wa~surements of~t activity were all sign~ificarntly

correlated with one another. Ho~uc.? comparison by means of a chi-

square test of the relative amounts of secretion (absent = 0, slight

r 1, substantial P 2) in the acini or vesicles examined showed that

within a single animal there was no significant difference at the .05

level between the proportions of acini (and of secretary units in the

seminal vesicles) at each stage of secretary activity in the various

glands (Table 3). The accessory glands therefore appeared to secrete

as a unit, rather than varying individually.

A comparison of glandular activity was also made between those

adults with active sperm in their testes (Stages 7 15) and those

without active spermatozoa. The proportion of dorsolateral prostate

acini in each of three stages of secretion was not significantly

different between the two groups. Some secretion in the seminal

vesicle also took place in both groups, but there was signillcantly

grreater secretion in those animals with scti~e spermi. These results

are shown In rable .

Cyclic Changes5 in Reproductive organj

Tne 16-mointh total trapping period ujs broken up into 15

separate perious Lasting from one day to as miuch as 31 days, the

average length being 10 days. At least two weeks usually separated

each trapping period from the adjacent ones. The periods are defined

In Table 5.

-22 -






II o




r O.


U -

.7 .




r --
5 u )

-23 -

O I ~O

hervI 0 0

ao .au I

.o CIa a 0

UOFI : a) \o
puc I ,Ml I i 10 1

.1. r I I X

ar -r O
ae o N hi
~ r d I ~I II X 1
a~x rn

Table 5. Number of males caught in each trapping. period

- 24

Total Nlumber
Males Caucht

Total Nulmber
of Mature?
Males Caueht



3/19/67 4/16/67

5/11/67 5/31/67

6/8/67 7/8/67

8/1/67 9/1/67

9/14/67 9/28/67

10/12/67 11/7/67

11/25/67 11/25/67

12/7/67 12/29/67

1/11/68 1/25/68

2/13/68 2/17/68

3/7/68 3/13/68

4/14/68 4/25/68

5/16/68 5/21/68

6/8/68 6/10/63

7/8/68 7/9/68

Table 6 lists the results of the analysis of variance test run

on each of the reproduction parameters. The F ratios are listed in

descending order of significance, and are starred according to whether

or not differences between the means of each period were significant.

Changes in the Testis

Changes in testis volume throughout the year are shown in Fig. 2.

Multiple range tests showed that the peaks in Periods 3 and 11 were

significant, but the peak in Period 7 vas not significantly different

from the lows in Periods 5, 6, and 9, perhaps because it was a mean

of only two values. It will be considered significantt here, however,

primarily because of the significance of the corresponding peak,

which included a third individual, in the cycle of testis tubule

diameters (Fig. 3). Period 8 also contributed to the first signi-

ficant peak in Fig. 3. The second significant peak, extended from

Period 11 through Period 13.

Changes in Leydig cell diameter are outlined in Fig. 4. There

are significant peaks at Periods 3 and 11. The changes in the ratio

of nuclear diameter to cell diameter in Leydig cells were also tested

and found to be significant. The resulting pattern was essentially

Table 6. F ratios from univariate analyses of va~Riance
showing significance of differences between
mneans of reproductive paramelters in 15
trapping periods

Parame ter F

Epididymadl Tubule Diameter 4.45**r

Testisc Tubule Diameter 4.36"*

Leydig Cell Diameter 4.04**"

Seminal Vesicle Cell Height 3.63**

Epididpzal Tubule-Cell Ratio 3.57**~

Seminal Vesicle Diameter 2.53*

Dorsolateral Prostate Cell Height 2.52*

Leydig Cell Tissue Volume 2.30*

Nucleus-Cell Ratio of Leydig Cell 2.16*

Testis Volume 2.03*

Ventral Prostate Cell Height 2.03

Body iWeighlt 1.63

St2, a :- E :: ;--:-Ii rvatop n3 5i 1 3.

Epidio,--el~i iilHigt13

- 26

5000 *


* I 1~

3000 A S N *

1 7 8 9 0 1 *3 4 1

...pin * *

fi 200 ecclr 'c~l5cruiot h rpig pros ~~d in
conne~s ~can vlue*

- 27 -



0 1 2 1 4 1

irppn *i

~~6 1. ~~ueres ofeheccsis ub~ics nro CI-out the rapin GF~rsd*
.14 ~ -in *oncjiea iu

- 28 -

- 29 -

11 *



5~~~~~ .* L L ~--I
A I: J J k S Ii ir i F : I J
10~7 i~*.
9- 3 n 1 2 1 ; i

i ~ ,*in Pel

Fi. L. Dil~trs J ~p riJt: cl r~ru* *~~r rapn
period *oi lecncc~m~ jus

_ __I _~

- 30 -






200 *

A J J A 3 O N U J E iNi A Mi J
196~7 1908j~
1 2 3 6 5 3 7 9 10 11 12 13 11 15

Trap~ping Period

Fig,. 5. Volumes of Lcydig cell assueL throughout the trapping
per iods. Sol id iinr cornncecs mran valur-:.


~lchiilll~h the F ratio for -r:-ri~l~.~ijierl;sis vj; not iCnllic.Lic, the

cycl: ouclinad bp the nein; in Pir. ~ ;:~-~-I eiJ correspc~nd to thos~ oi

the previous FarJs.l~trrs. The lack of significance here 'r;ls c~~Isec! by

the great amount of variation around each of the 13eans.

Changes in the Epididymis

Changes in th ratio of epididymal cell height to tubule diaraeter

were, as in the Leydig cells, ruirr~r images of the changes in tubule

diameter. Fig. 7 therefore sh~s significant peaks in epididym~l

tubule diameter at Period 3 and Periods 11 and 12. Corresponding

significant losrs occurred in the ratio of cell height to tubule diam-


C~~ins:~ in ~hs ~ccr-_sorv Cl;nds

;he pslk oi the I~C~S~O~y;land n~~u~-;r.eats uire la~; *;11

d~iinA~ rllin cli3sg in the cFiaio~iiis and ~i;cis ~~ra~TI~cer;.

P~rl) i~ai \raj ~enc~allp suiierJ~-J b~ a Ira, relatlv:lg CCntE cuc~'c.

in tile da~Eol~tril prortjce (Fie. 3), tne firr~ p~j:: YaS T~drh?'j at

Pcriol ~, ~hc~~;J t;i~ 9:Lord Fcltij~Cd r~O;r~ pari.~j i to F-riO3 11

i~:- ;~mlnjl :f~i~?~ ccll I-l~llir: (~~c. CI) r~dsh~-l a p~:il! in Fec~od 3

jn2 ;CJiil florrr I'~ci,-l ~ ~h~':L~t'li Ij Th ;Iliinlll ~.csisle Ji~u~letPr

iFiG. T'';, Iio~'~~cr, rlid nG~~ reach ; sirrriiicsne Fca?: un~ll lice in

the ~r~FFir:- pcricdr iih:n it r.~siin~j I~r~e froii Fec~isij 11 th~ou~h

13. Fl;irJ~~s 1; ir~~~ 15 rrl~:_he hi~~ b~~-n irrclu:r~~ ~n this FI-al', tuc r.cre

;iCnillc~nt!y Invr cnan P:riod 13.

7Fig. 6. Values for the staCes of' spermator~npsenehsii~s rughu the
trapping periods. Solid linf connercts mean values.

_ _____ I ___I_~____


? 10

1 2

- 32 -

16 E

10 C I





J J An :Lb

3 4 5 67


11 12 13 1:. 15

Tra~ppng Peri~od

_IX_ __ _I_~~ ~~~_____~__

- 3 -

.40 t


. 30 C

.25 E


.10j C

I 1_.L_. ...' 2I'--L L. .1__ .1 I
.1 1; .1 .r A i O : L J F il
19*?; 10* 8
1 27 3 's : 6 ; r e 103 11

.0 I_ I-
rr lI -

12 13 1.5 15

itempptry Period

ite. 7. i.F.i'tacrt- L 5f Cthe el.I;.I;H..yrsa rIL-Ubul. thlrou ~r <.c l
pw ol. . ln enr?: nc \ lu s

rhc triFPing


- 34 -



20 -


14 r; *j

; : ,L

rrjy~in e Prii0

12~. *,C~l lc~e nr o~ltrl pott iad~r u~o~:

thetrppngpeiod. J~d in cnnr~smen ile*

-35 -


1 *,
v e

16 *


I t i i I I 1 ~ I I I I*
A E, 3 J 5 i :j D F A ~ J*
13:* .rj

G I 0 1 2 3 1. 1

ir0l~ Pr~

12~ -. *p .rlh;n ceimnl~eil tio~hu h
tr~pinG cr ids. oli lin con~ct mcn vauc*

- 36 -


1 2- * 0 1 2 1 4 1
.i *yl: .5ri

D~~-,~rc-; cf ti~e ~i~lll~ '.!iC1~jtJIC~IIOU: ~e
ei~2n ~:is

-37 -

Comparison of Channgs in TF.-lrrbl:tive~ Crgans
with Environmental Featulres

Table 7 demonstrates considerable overlapping of the peaks among

the parameters. The interpretation of this synchrony requires a close

looke at the environmental features.

Fig. 11 is a summary of the monthly averages of soil temperature

max;ima and minima and of rainfall. Fig. 12 shows the average monthly

values of soil moisture, a function of both rainfall and temperature.

Periods of high soil moisture occurred at times of high rainfall and

high temperatures, and at times of moderate rainfall and low tempera-

tures. Figures 13 and 14 were abstracted from the previous two figures

and present the mean of the environmental histories of the pocket

gophers within each period. Only the two-week-prior soil temperature

history and the four-week-prior soil moisture history are shown. The

two main reproductive peaks matched those of soil moisture fairly well,

and corresponded to intermediate periods of increasing soil temperature.

In spite of this visual correspondence, soil moisture showed no

correlation with any one of the reproductive parameters, and soil

temperature was correlated at the .05 level of significance with only

five of the 14 parame~ters. Since the initial analyses tested only re-

lationships bsetween single factors -- a highly artificial sttuntion --

a m~ultivariatc ana~lysi was chosen that would jccounlt for knocractrion

amo'nG the two sets5 of parameIters.

The results of the canonical analysis are shown in Tablz 9. Of

the four proCgress that were run, only che results from the one sho inr:

the highest correlation -- the combination of soil moisture two weeks

prtor to capture and soil temperature four weeks prior to CapcureP --

-38 -



r o
Frl r
WI 0









lc .

u v,


ar a
E u
d 0

*r F
14 5

t J


Soil Temper iture (oF)

Z8 R- 8 o.-
I 0:

.*.". .

.'.*.* ".'
.*.*,".". (,'

z .0

.*.*.*. 0~

5~ C

. *..**. o

E *M J

*E u,
(s 4u ) t i

- 40-




.. Z M

...1 I .._

(*Io;,-O v 2,p;10

- .1 -



1 1 I I 1-1 I 1 I 3-
L .r..??: Ij J k*! i

11 3 .\ : i 7 li. 9 10 11 1? 13 10 ;5

irbppin3 Friodc~

rlig. 13. Averyc~ soit ccannerarture 11Eones~ Of pooril:eC Cop;II.CIrl wantn
ecjo crnpptra, pcrii-! io; tio I:-TE-lo prior to that~ captur e


- l2 -




a~I IJ--U-1-M
1-, J J A 5 0 0 i J F : ijJ
19.:.? I9;6E
1 .' 3 5 6 ; ; 9 13 11 12 13 1; 15

i~r.:pp.n,3 Face...

FiC. 11. A-tecr;.:. soil ci;;L tur hlSis ri? J POC poc; It celi.**ra IIChin eCjl h
t~r7ppin; ?erlm] fo~r focur ;ear:~ s prior to the'ir .'Pture.

Table 8. Results of canonical analysis

inae .1M i:,t otatlaIn

- 03 -

Canonical Correlations
1 2
.8512 .4306


0.0954 1.0802

1.0330 0.3299


Soil Mioisture -- 2 weeks

Soil Temperature -- 4r weeks

Testis Volume

Testis Tubule Diameter

Leydig Cell Diameter

Nucleus-Cell Ratio of Leydig Cell

Leydig 7sll Tissue Volume

Ep?did:Tal TubulD Man t*20 :

D~orrseljaterl P'rosta-:- C01 I!11 ht






0.3 06

-0.571 ?~;

I:. 2~ ?3.








are listed. The next highest correlation was from the combination

of soil moisture four weeks prior and soil temperature four weeks pri-

or. The canonical correlation coefficients in the second set were

quite close to those in the first, suggesting that there is little

difference in the effects of soil moisture between the trlo- and four-

waeek values. The other twro programs had coefficients significantly

lower than these.

The canonical correlation showed that soil temperature over a

four week period was much more important than soil moisture in

relating the two sets of variables. The second correlation implied

that some of the variables were definitely affected by soil moisture,

but the great difference between the two coefficients indicated that

these second values were not so reliable. No formal significance

test was performed; however, all coefficients greater than 0.3000

were considered highly important.

Not all the reproductive organs seemed to respond with the same

magnitude of change, or even in the samne direction. Three of the

parameters did not show significance in either correlations dorso-

lateral prostate call height, epididym~al tubule diameter, and Leydig

cell tissue volume. For the most part, however, the relationship was

anl inverse? one: the measurements of reproductive organs decreased with

an increase in soil temperature. M~ost of the second set of coeffi-

-5 -

Immnature Animals and Pregnant Females

Little is known about the gestation and weaning periods of

Gr. pinetis. Howard and Childs (1959) estimated the gestation period

of T. bottae to be 30 days, but Schramm (1961) observed two pocket

gophers (T. bottae) giving birth only 19 days after copulation; their

young weighed 2 3 g. Barrington (1940) found that the weight of

three newborn G. pinetis averaged 5.1 g, and he estimated that the

gestation period in this species is 30 days. Miller (1946) reported

that weaning takes place in T. bottae after 35 to 37 days, and sexual

maturity is reached after three months. Wing (1960), however, indicated

that from the evidence provided by seasonal percentages, G. pinetis

of both sexes take nearly six months to reach sexual maturity.

Wing (1960) described the largest embryo in her collection as mea-

suring 39 mmn from crown to rump. After estimating the gestation

period to be one month and assuming that the maximum crown-rump

length of an embryo is 40 mmr, an approximation of each embryo's age

in days may be calculated. This information can then be used to

estimate the date of conception.

- 46 -

Males Fem~ales

Uei ght Age Weight Age
g months CI months

65 2 t0 2

90 3 80 3

115 4 100 4

140 5 120 5

165 6 140 6

Again estimating the Gestation period to be about one month,

the date at which conception took place can be calculated by adding

one month to the age and subtracting the total from the month of


Fig. 15 shows the distribution of approximate conception dates

for both pregnant females and immature animals over the total trapping

period. Table 9 compares the average soil moisture and soil tempera-

ture histories, averaged over two-week and four-iweek periods, respec-

tively, before each projected conception date in both the immature and

the pregnant female groups.

A; crot.11 rof ;in! oe'reei eocpher 3 ..ms c~irgipe :rin l th. quarc erlyy

i...plFing p-ad;....ij, 15 ircm e4ach penaol. 'ie. 1; -haows th-? [.-.ittern ot"

TDb-l 103 givec :he petrcentage ofi animal3 In eichi sevr grou', age,

plap, n peera rprouctveitse.The llireproductivE rondition ofI

r'.4 fe~n:l 1c Ir bjased on the~ size anJ **.i:-.llarr ity of rth. Ilter s-: mal c

1..:r-c C:r. nderal: to L. inl acci.':' rli!.riJduct:'-: c:.nditic.n If~ th- te,-tes

- .










. I I I (.

snoraowr. 30 .a.D:E*3* M

Table 9. M;ean values of environmental parameters over the
specified periods of time before approximate
conception dates. Overall means are calculated
from capture dates of males throughout the year.

Soil Soil
Moisture Temperature
(Itwo-!Neek Average) (Four-!eck Average)
Croup Z-Vol. OF

Immature Animals 9.62 69.78

Pregnant Females 7.24 71.73

All Estimated
Conception Dates 8.67 70.52

Overall M~eans 6.82 + .68 74.24 + .14

- 8 -

Soil T-unneccturer ('':
o~ ~ a
o ~ ~ ;c O\

-5 i-

.". C

::::: :::: :-

******'*'** *'



(1 w

:Cn ut v u E

Table 10. Sex, age, and reproductive status of animals captured in
each quarterly sample

Quarterly Sampylel

Grouo 1 2 3 4

Percent Immature A~nimals 7 13 20 60

Percent of Adult Famales
which are Pregnant 0 28 50 0

Percent of Adult M~ales and Females
in Active Reproductive Condition 36 85 73 33

11: 11/9/68 11/12/68

21 2/20/69 2/23/69

31 5/26/69 6/5/69

4r 8/11/69 8/13/69

-50 -


were enlarged andi dark~, and if the epididymal tubules were easily

visible to the naked oye.

The projected conception dates for both immature animals and

pregnant females were combined and are shown in Figl. 17.



O e-





r-4 A

1. j _5 1 ...L .-

suspeu.:D .0le~yu.; pemps

- 52 -


The reproductive organs of the male pocket gopher show seasonal

changes that are related to changes in soil temperature and soil mois-

ture. The possibilities that males maintain active spermatogenesis

all year or that cessation or fluctuations in spermatogenesis occur

synchronously throughout the population were, therefore, eliminated.

Instead, it appears most likely that while some periods seem optimnum

for all male pocket gophers, unfavorable periods do not cause abridge-

ment of reproductive activity to the same degree in all the males in

the population. In reaching this conclusion, much insight was gained

into age~-dependentllc changes. Particularly valuable was information

provided on changes within the testis.

Even after sexual maturity is reached, the testis volume, for

example, was found to increase wlith age. This would be due to two

factors increases in testis tubule size and in interstitial tissue.

Testis tubule diameter also increased with age, but the increase in

voiljume of the cocal Lejidi :011 c;useu provedFI ntI to bC ;1Loniituant.

TheC Per~:CJnCar of Leydxglt cCll Cissue voaI~TCe toi coalj ':ILB volum i sred o

agec. Tih.: diineter ofth clLeyic;~'i c 11 nucleus also de~~crat ed sitatft-

iantly with~ ar;e r:lanee to the~ Jia~iter of thei entir c;ell.

Thil; situation sugg2ert that eh.. raEE ofE Leyail,: cell d~ivltionI

ia;cel-re~rat at pulb-rty, accom~pant~sa bi a disprspjrtio atce incriase in

the Crouth rite of ths c;tjplam relstive to chi nucl~:us. Atot

- 54 -

the post-pubertal Leydie cell is larger than the pre-pubertal cell,

its diameter decreases with age. Conaway (1959) recorded a similar

phenomenon in the eastern mole (Scalopus aquatius) The infantile

testis was characterized by abundant but small Leydig, cells with very

little cytoplasm. Early increases in testis volume were due primarily

to increases in Leydig cell volume until testis tubule enlargement

and the concurrent beginning of spermatogenesis became significant

at puberty. After this stage, the diameter of the Leydig cell decreased

by one-third, increasing again slightly at the end of the active

breeding period. The cell diameter was found to be largest during the

period of sexual inactivity.

In studies on the rat, Clegg (1966) found that the number of

Leydig cells actually declined following puberty. He suggested that

the accessory reproductive organs, which showed their maximum growth

acceleration at that stages were more sensitive to the androgens being

produced by the Leydig cells.

Albert (1961) indicated that Leydig cells in bulls also decreased

in size from 5 to 15 years, after an initial increase in both number

and size fromt two years to five years. According to the same source,

the number of Leydig cells in man declines wiith age.

The percentage of Leydig cell tissue volume in the hippopotamus

testi; decreased fromii 641 in rthe ver ;ou~n5 jnimit to 32' at putercy,

Th~e djJcrdi se in size ofl Lcydir cell: in paclkac oph'ri 1E r:ll

n;t an unumuail situationn. Facter r ?rel.tedl th:~ increase in L;:dry

cell diame~ter wiith7 th: ri3 in acti.;ety Of th4 accessor gla'5ndl, a .

- 55

well as ~ichi the increase in the dia.-eterr of' the epidid:.-ilal tubules;

relative to the epidid),nal :?ll hei::hts. UnlikeG th2 siri~tuaon des--

cribed earlier in molrr (Counavay, 1959), bol~rilonel SecCrtll on 15 PremnT-

ably associated with both a tempo.r3ry increase in diameter of the

Leydig cells as well as an increase in the ratio of cytoplasm to

nucleus. Enis evidence, tog~eher vith the associations in Factor 2

which herer nentioned earlier, leaves little doubt that a cyclic

increase aind delCeasle of both Leydig cell diameter and of the tissue

volume is imposed on the long-term pattern of diminution.

The height of the epididymal cell was found to increase in

relation to the tubule diarieter with age. The cell height was also

a~ssociiccd un~h Lcydi2 ~cll diise-ltar in factor 2. Ine utterr rasponre

CO;.~rteslewi Co th2 ojbse~Vations sIrwar~izeaC by :13nn (1965), which

showed that~ Jcr~ital of rperm tr. an cpididysiiras sever: friomi che testi;

was J.2pe'r.:?nt on th? continued pr:senze of che testis in thie tody. He

:onclu:ed that~ the condition of the~ epithe~lium in the opididynall tubule

4.15 itrcn,_ly influenc~d by the male Eev bcrcoone. Th: cfunction oC thle

Iplid-id..sh I'snn ;urnised, ii* th?r:for not ojnly to Nerve as j

rap,strry for. speCrm but also: toj produc? a sccretrion san:h-:iru cffc-

the~ in yreservinee or parhalps naturintg thr rperm.

Well-defIneaL1 cy.cles durinL thi saud~ periost were found onily to

the tesicis :O~lume, L-.yd-iS :?1 c ll it6anret andl cissu: volumeo, and

opl~igl.-altutal-1di:ietr in cel heght 15 stage of sp:r..atogen-

.sir **ai t.18:-.1y depe:ndent~ on ie, th2 .arijticen in stages~ :u'Ong the

iiket Coiler: 1.1 aCllh Ltr'Pping pe~iod b-:-in: suffiici:nt to reject

rto possibility of there taken a ;ynchronized populationn cycle in the

prods:C,-.io n of :90tn;-~tlro Jea 41terllehl dcfin tE~ cycles v~rre dcctected in

- 56 -

the activities of the seminal vesicles and the dorsolateral prostate,

they were less distinct than the cycles mentioned earlier. Moreover,

activity in the prostate glands did not necessarily cease when sperm

were not being produced. The seminal vesicles, however, showed a pro-

nounced increase in activity in animals with active sperm production.

Price and iiilliams-Ashman (1961) found that testicular hormones pro-

vided most of the control over activity of the accessory glands. They

also concluded that the chief function of these glands is to secrete

th~e seminal plasma.

Internal control of the reproductive system in the male pocket

gopher seems to rest at the hormonal level. Maximum size of the

Leydig cells reached two significant peaks which corresponded to

similar peaks in size of the epididymis and accessory glands. The

lack of complete correspondence is likely attributable to a low

threshold in glandular response to testosterone. Van Tienhoven (1968)

has also suggested that maintenance of secondary sex characteristics

outside thle breeding season may be the result of androgen secretion

by extra-testicular sources such as the adrenal cortex.

Strongly influencing hormonal control, however, is environmental

control. In the canonical analysis, most of the measurements taken

of thre reproductive organs decreased in rmaginitudel or otherwise

denoted less activity, under conditions of high soil temperacture and

- 57 -

Soil moisture is latecally t~h? lesr iimprrcanc: jf the Cjto calli

it seldom dips below 507. of the field capacity, and therefore shows

comparatively little variation. The distribution of G. pinetis may

well be limited by soil moisture, since this species is found only

in the well-drained sandy soils in the Southeast (McNab, 1966). The

possibility mentioned earlier that excessive Soil moisture might

prompt a pocket gopher to dig to the surface, and perhaps more ex-

tensively underground as well (fMiller, 1948), may be valid, but

apparently this response does not serve as the sole cue for timing

the reproductive cycle.

Temperature does affect the cycle strongly, most likely in an

indirect fashion. Because the largest p~roportion of the burrow lies

near the surface of the ground, it may be inferred that this is where

the greatest amount of digging takes place. The pocket gopher,

however, is a poor thermoregulator and therefore cannot long with-

stand the heat stress of diggeing in a shallow, warm burrow. Gunther

(1956) proposed a tehivi.-ral mechanism in which the gopher makes use

of deeper, cooler Ilace of its burrow system in the summer, plugging

some of the shallow feeding tunnels. The diminished amount of digging

r~ltini froml this ciJsatio'n of acci.:ity r..uld PreS1Lalyjl le-dj to

d~innIshedI Intraspelciifc contacc. Thiis rculatlon of acci\-c would

Effecove.ly restrict mosti rcFpretterie ictivity to cerratn times~ of

th3 yea.t

Dil r .r_luictiv c:le Cive:~ nor avide~nce of tsing .triiCtly Cjimed.

Is:rnac~Ojeneslt, for inrIcance, iras four.1 to be n)n-cy'clir ac least

dur~ing th-is rrat) dy priod. .4 nacre carefu'll Ltudy of thc repFroducltiv

tri.e itself mighe rrecal :.0000i C; ChF spenO a: some pliCe alongi

- 58 -

the ductus deferens. The great variation in sperm production at any

one time convincingly suggests that the reproductive cycle is not a

strict endogenous rhythm, but is influenced by environmental fluc-

tuations and could be triggered by the right circumstances -- i.e.,

favorable environmental conditions and the presence of a receptive

female -- at any time of the year. Since there was a low level of

reproductive activity that continued throughout much of the study

period, at least some random encounters in the "off season" might

be fruitful.

Probably little selection pressure operates to channel repro-

duction into a strictly timed cycle. Food is certainly most abun-

dant in the spring months but is still available, particularly in a

grassy area such as Stengel Field, in sufficient quantity throughout

the year so that a newborn gopher would not starve. Contact between

pocket gophers of the same sex frequently results in harmful injuries

to one or both animals (Mliller, 1964; Vaughan, 1962). Such contact,

if it should occur between a male and female,raight also be harmful

if neither were in active reproductive condition. It would obviously

be advantageous to a pocket gopher to be capable of mating should an

indjtivdual. OE~ RO o;pposite 3p:; be enconjrllt:tered. PIO1;eveTr, Fnding:

cvery; ct-r ed maintaining~ the ~crcpruc-tiver r: t~ In an -acti'a state~

dulcti\ .:Criv'ity..ilnn me:imuni cotacat is I p:i cte:d, bu~t rellhionoes

ch cr.tir: populjtioon cOcrcc- to 2n in:ctile j~3re jt jch,;-r tim,?r.


The reproductive cycle in the male pocket gopher (Geomys pinetis)

is closely correlated writh soil temperature and to a lesser decree

with soil moisture, but does not seem to be strictly controlled by

either of those parameters. Very rarm external temperatures and lowl

soil moisture appear to restrict activity within the burrow at certain

times of the year, and according;ly reduce intraspecific contacts.

Maximum reproductive activity corresponds to those environmental con-

ditions that create a friable soil.

Internal seasonal changes in the reproductive organs and glands

are presumably in turn effected by hormones, particularly testoster-

one, which is secreted by the Leydig cells. Leydig cells in adult

pocket gophers 'are larger in diameter and more numerous than those in

immature animals. A not decrease in both size and number of Leydig

cells occurs after puberty, but the cells still increase in diameter

at times of increased reproductive activity, suggesting increased

normaon11 production. This cyclic change is correlated with increases

In use1 hcllp~h of thei ;rrEarcto., epithd~l~uns in thec jcces~sory Il.nd:,. and

Spe;;;c ~rmatognest has foun-1 to rbe norn-c,.clic" during; the ;tudyl: riod.

Although ch? ncan :p~-~~ernatop e iclu?; for ijch pcrto.1 foillowed

c:.cili pjttern~ simlsr t.:- the on.: cullined by the L~yplc cell axanat-:C,

th1 varixtenn jbout the mean: uali tao rgreat to illou~ SjtlatiCtIc al 1-

ntfican~ce jprerm Fgraduction Ehrougho~~u t the3 ropullation thor'fre con-


tinuedl at least at a threshold level throughout: the study period, and

reproductive activity at the organ level was restricted more by the

condition of the accessory glands and the epididymis than by the

availability of sperm.


Albert, AZ. 1961. The mammalian testis, p. 305-365. In HJ. C. YounC
(od.), Sex and internal secretions. Vol. 1, 3rd ed. W~illiams &
Hilktins Co., cat~iLnaiCi

BarrinCgton, B. A., 1940. The natural history of pocket rgophers. Ml.S.
Thesis, Univ. of Fla. 194 p.

Bloom, ii. and D. WJ. Fawcett. 1962. A textbook of histology. Wi. D.
Saunders Co., Philadelphia. 720 p.

Bond, R. M!. 1946. The breeding habits of Thomonmys bottae in Orange
County, California. J. hNammL~al. 27: 172-174.

Clegg, E. J. 1966. Puoortal growth in the Leydig cells and accessory
rieprod!uit ti.. G;r;;ins of the~ rat. .T. Anat. Tr0: 367-370.

5Anatoy, 1 1'.'. 193"*. I--5.~. l ...uJactr i n .jE l of th~iE IEaster,\l mll .; lrh3

Engllirh, P. F. 192;-.2. Some habitsic c the~ pocket ,7.oph-ir, IEco-c.3 L~cc:-teep

Groom1, J. F-.. 19-au. Th n;usanahl me-olificatter, oi the interjtitril
tlizzc of th-: cath in the fraJc tat (rcropos).j) Proc Co. 3~.;:..
London 1101 j;-;L.

Gunt~h-:F ,1. li. 1G56. 5tudlie on th~e nile rep-rodu.:clt'. s..ac.1m of the~

nirdergrrou~ 3nil ahlt brriersj onl wats. Fctantion andl me...r~ne nto
Lakla~ind fine sind. 5011 and Crop Lo.:. of Fla., Proc~. T's 11-1C'.

Hua r, F. L. 1923j. The~ absor~pt;io of th-; p:-to ......phys;id of thle pC3. etr
3oph*:r I6000-*3 burySciusl i;hau). nlmer. :'jt. 55: 93-G6.

Howard, W. L. jJnd fl. E. rhild~s, Jr. 195-). EcloC:.' of pa:!:et poph~rj
writh emphjSIj on ThirmemEL I-trrj icuj. Hilgardia 29: 2??-jMC.

--61 -

- 62 -

Johnson, 0. 18. andi I. 0. Duss. 1967. The testis of the African ele-
phacnt (Loxodocnta africana). I. Hlistoloygical featu~res. J. Reprod.
Fort. 13: 11-21.

Ken~nerly, T. E3. Jr. 1964. Microenvironmental conditions of the pocket
eopher burrow. Tex. J. Sci. 26, 395-441.

Laws, R. NI. and G. Cloug-h, 1966G. Observations on reproduction in the
hippopotamus H~iopopotamus amphib~ius Linn., p. 117-140. In I. W.
Rowlandls (ed.), Comnparative biology of reproduction in mammals.
Zool. Soc. of London, Academic Press.

Macklin, C. C. and M. T. Ma!cktlin. 1963. The seminal vesicles, prostate
and bulbourethral Glands, p. 1773-1822. In E. V. Cowdry (ed.),
Special cytology. Vol. III, 2nd ed. Hafner Publ. Co., N'ew York.

M~ann, T. 1964. The biochemistry of somen and of the male reproductive
tract. 2nd ed. John Hdiley & Sons, Inc., New York. 493 p.

Mic~ab, 8. K. 1966. Thie metabolism of fossorial rodents a study of
convergence. Ecology 47: 712-733.

Miller, Mi. A. 1946. Reproductive rates and cycles in the pocket gopher.
J. EMamm~al. 27: 335-358.

.1948. Seasonal trends in burrowing of pocket gophers (Thomomys).
J. M~ammal. 29: 38-44.

Miller, R. S. 1964. Ecolog~y and distribution of pocket gophers
(Geomyidae) in Colorado. Ecology 45s 256-272.

M~oore, C. R., 5. Price, and T. F. Callagher. 1930. Rat-prostate
cytology as a testis hormone indicator and the prevention of
castration changes by testis-extract injections. Amner. J. Anat.
451 71-107.

Price, D. and Hi. G. W~illiams-Ashman. 1961. The accessory reproductive
glandls of mammals, p. 36G-448. In i. C. Young (ed.), Sex and inter-
nal secretions. Vol. I, 3rd ed. Williams & W~ilkins Co., Baltimoore.

Roosen-Runge, E. C. and L. 0. Giesel, Jr. 1950. Quantitative studies
on spermatogenesis in the albino rat. Amler. J. A~nat. 871 1-30.

63 -

Tosi, J. A. 1968. C1culo del balance hidrica, p. 42-48. In 2-01, J. J.T
and A. Madriz, Zonas de vida de Venezuela. Republican !de '":r-~~:nel ,
M~inisterio de A~ricultura y Crfa, Direcei6n de Investigaci6n.

Van Tienhoven, A. 1968. Reproductive phy~siology of vertebrates. I. B.
Saunders Co., Philadelphia. 498 p.

Vaughan, T. A. 1962. Reproduction in the plains pocket gopher in
Colorado. J. M~ammal. 43: 1-13.

,and R,. MI. Hansen.. 1961. Activity rhythm of the plains pocket
gopher. J. Mlammal. 42: 561-543.

!lilks, B. J. 1963. Some aspects of the ecology and population dynamics
of the pocket gopher (Geoms burarius in south Texas. Tex. J.
Sci. 15: 241-283.

Nting, E. S. 1960. Reproduction in the pocket gopher in north-central
Florida. J. Mammlal. 41: 35-43.


- 5

Fie. 18. Level 8 tests (100X)

Fig. 19. Level 3 testis (430X)

Fig. 20. Level 7 tesjtis (430%~)


- 66 -

Fig. 21. Epididymal tubulcs from a male in active
rcproductive condition. The lumiina are
filled with sperm. (100X)

* Fig. 22. Epididymal tubules from inactive male (100X)

- 67 -

Fig. 23. Actively secretinp: acinus from dorsolateral
prostate Gland (430X)

Fi~g. 26. Inactive acinus from dorsolateral prostate
gland (430X)


Fig. 25. Lumen and part of cell boundary from an active
seminal vesicle (100X)

Fig. 26. Inactive srminal vesicle (100X)


Kathorine Carter Ewel was born September 30, 1944, at Clens

Falls, New York. During the summer of 1961, she attended Cornell

University on a National Science Foundation Summer Fellowship, and

Graduated from Clens Falls H~igh School in June, 1962. In June, 1966,

she received the degree of Bachelor of Arts with a major in zoology

from Cornell University. During the summer of 1966, she participated

in a field biology course at Tulane University on a USDHENI Environ-

mental Training Crant and in the fall of 1966 enrolled in the Craduate

School of the University of Florida. She worked as a teaching assis-

tant in the Department of Zoology until Arugust, 1967, and was awarded

an NDEA Title IV Fellow~ship from September, 1967, through August,

1969. During the summer of 1968, she was enrolled in the tropical

biology program at the Universidad de Costa Rica under an N'SF Graduate

Research Fellowrship awarded by the Organization for Tropical Studies.

She is currently employed: as a Temporary Instructor in Zoology at Duke

University while completing her work toward the degree of Doctor of

Philosophy at the University of Florida.


This dissertation was preparedl under ther direction of the

chairman of the candtidate's supervisory commoittoo andi has been

approved by~ all memlbers of that commnittee. It wras submitted to

the Dean of the College of Arts and Sciences and to the Craduate

Council, and was approved as partial fulfillment of the reqluire-

ments for the degree of Doctor of Philosophy.

June, 1970

Dean, Co~llee of Arts S~l sciences

D an, Graduate Schoo

Supervisory Committee:


University of Florida Home Page
© 2004 - 2010 University of Florida George A. Smathers Libraries.
All rights reserved.

Acceptable Use, Copyright, and Disclaimer Statement
Last updated October 10, 2010 - - mvs