Title: Glycolysis and swimming performance in juvenile American alligators
Full Citation
Permanent Link: http://ufdc.ufl.edu/UF00066449/00001
 Material Information
Title: Glycolysis and swimming performance in juvenile American alligators
Physical Description: Book
Creator: Gatten, Robert E. Jr.
Congdon, Justin D.
Mazzotti, Frank J.
Fischer, Robert U.
Affiliation: University of North Carolina -- Department of Biology
University of Florida -- Department of Wildlife and Range Science
Publisher: Society for the Study of Amphibians and Reptiles
Publication Date: 1991
General Note: Drawn from Journal of Herpetology, Vol. 25, No. 4, pp. 406-411, 1991
 Record Information
Bibliographic ID: UF00066449
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.


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loirnal of 'ol. 25, No. 4, pp 406-411, 1991
Copyrghs for the Shidy of Amphibians and Reptles

Glycolysis and Swimming Performance in
Juvenile American Alligators


'Department of ... .l University of North Carolina, Greensboro, North Carolina 27412, USA,
'Savannah River Ecology Laboratory, Drawer E, Alken, South Carolina 29801, USA, and
'Department of Wildlife and ** Science, Uniersity of Florida, Broward County Extension ( ,;
3245 < '.. .' Avenue, Davie, Florida 33314, USA

ABSTRACT.-Swimming speed of juvenile American alligators increased between 15 and 20 C but not
between 20 and 30 C. Speed declined with time during the 4 min trials. Post-exercise lactate concentration
increased with temperature and with duration of swimming. The rate of lactate formation during exercise
increased with temperature and was higher in the first min of excerise than in the subsequent 3 min. Once
the effects of temperature, body mass, and body length were removed, there was no relationship between
the intensity of glycolysis and the distance covered in 1 min of swimming. In contrast, the alligators that
swam the greatest distance in 4 min had the lowest lactate concentration. Thus, the relationship between
the intensity of glycolysis and distance traveled varies with the duration of exertion in these animals
during induced swimming.

Because crocodilians swim like fish, gallop
like mammals, and exhibit an unusual "high
walk" during routine terrestrial locomotion,
their locomotor behavior and mechanics have
intrigued biologists for many years f ,-
1940; Colbert et al., 1946; Zug, 1974; Fish, 1984;
Turner et al., 1985). It is implicit in such studies
of locomotion that the results seen at the level
of behavior are directly or indirectly traceable
to, and dependent upon, .. .. .. physio-
logical processes. There is ample evidence link-
ing locomotor behavior and locomotor physi-
ology in reptiles and .. -- :.: For example,
species with high locomotor stamina usually
possess a high aerobic capacity whereas species
with low endurance i t exhibit a low rate
of oxygen consumption and a high reliance on

glycolysis during intense exercise (Bennett,
1982; Taigen and Pough, 1985; Gatten et al.,
1992). In spite of our extensive knowledge of
the association between locomotor physiology
and behavior among species of :'-.: or am-
phibians, there is very little evidence to support
the contention that this linkage between phys-
iological capacity and behavioral ability exists
among individuals of a single species. For ex-
ample, individual toads with a high rate of ox-
ygen consumption during exercise did not ex-
hibit better locomotor performance than
individuals with a low aerobic capacity either
in laboratory trials '..- 1988) or in field
tests (Wells and Taigen, 1984; Walton, 1988).
Likewise, there was no direct association be-
tween sprint speed and limb muscle glycolytic


enzyme activity among individual lizards
(Gleeson and Harrison, 1988) or frogs (Marker,
1990). These results are surprising in light of
the generally held belief that behavior is lim-
ited by the capacities of :-- . 1 : .; processes.
During short-term intense exercise, most rep-
tiles rely on glycolysis to provide a major por-
tion of the ATP used by active muscles (Bennett,
1982). For example, during exhaustive exercise
lasting 4.6-7.0 min, juvenile crocodiles, Croco-
.:.::. :.. .. derived 60-80% of the needed ATP
from glycolysis (Wright, 1986). Other studies
with crocodilians indicate that both glycolysis
and aerobic metabolism increase with muscular
S;: ::. (Coulson and Hernandez, 1979; Bennett
et al., 1985; Lewis and Gatten, 1985; Seymour
et al., 1987). In most cases, glycolysis is most
important during the early phase of a bout of
exercise when the respiratory and cardiovas-
cular systems have not yet reached their peak
ability to deliver oxygen to the active muscles
(Gatten, 1985; Wine, 1988). However, even in
:.... :. activities such as .. :... migration
and nest construction, glycolysis may play a
minor role (Congdon and Gatten, 1989). The
ability of juvenile American alligators,,: *
mississippiensis, to escape from aquatic predators
such as fish, turtles, snakes, birds, and conspe-
cifics may well depend on their capacity to uti-
lize glycolysis to power vigorous swimming
shortly after they perceive a predator. There-
fore, in this study we chose to examine the
strength of association between locomotor per-
formance, a behavior that is likely to be of con-
siderable ecological significance, and glycolysis
in a groupofyoung ..... Wehypothesized
that individuals with high locomotor perfor-
mance during intense exercise will be those in-
dividuals with high reliance on glycolysis.

iA i. ; .' eggs were obtained from nests on the
Rockefeller Wildlife Refuge, Grand Chenier,
Louisiana, and transported to the Savannah
River Ecology Laboratory where they were
placed in incubators in moistened vermiculite
at 30 or 34 C until hatching. Juveniles were
maintained in a covered building exposed to
natural variation in photoperiod and tempera-
ture for 10 weeks. Animals from each clutch
were randomly distributed among treatments.
A total of 69 alligators (mean mass = 65.40 g,
range = 38.50-97.67 g; mean snout-vent length
= 13.8 cm, range = 11.1-16.0 cm; mean total
length = 28.8 cm, range = 22.0-34.0 cm) were
used in studies of locomotion at 15, 20, and 30
C. The arena used for these tests was an oval
trough, 920 cm in mean circumference and 32.5
cm wide, with water 8 cm deep. The water was
maintained at 14.8-15.2, 20.0-20.3, or 29.9-30.2

C by circulating it between the trough and ex-
ternal tubs cooled or heated to a constant tem-
perature. Prior to testing animals were kept
overnight in a constant temperature cabinet at
15, 20, or 30 C. Animals were removed individ-
ually from the constant temperature cabinet and
placed in the arena at the starting line. We in-
duced the alligators to swim by prodding them
with a blunt stick and recorded the distance
they had traveled after 1, 2, 3, and 4 min. The
animals swam at the surface of the water with
their limbs pressed against their bodies and with
propulsive force being provided by lateral un-
dulations of the tail. Animals were prodded
whenever their forward movement ceased. Im-
mediately after a stimulus by the blunt stick,
they usually exhibited a brief burst of intense
swimming followed by vigorous, continuous
swimming at the surface. Some animals were
removed from the arena at 1 min whereas others
were observed for the entire 4 min period be-
fore being removed. Upon removal, each ani-
mal was quick-frozen by immersion in liquid
nitrogen. In addition, animals that had been
resting overnight at 20 or 30 C were quickly
removed from the constant temperature cabinet
and frozen to serve as references for the swim-
ming animals.
Frozen animals were analyzed for total body
lactate concentration by homogenizing them in
perchloric acid, centrifuging and filtering the
homogenate, and analyzing the homogenate in
duplicate for lactate by an enzymatic technique
( .... 1974). See Gatten (1987) for details.
Data were analyzed with the General Linear
Models program of SAS (SAS Institute, 1985).
Swimming performance (distance covered in
each minute = speed in cm min ) was initially
assessed by analysis of covariance, with total
body length as the covariate, and temperature
and duration of swimming (1, 2, 3 or 4 min) as
independent variables. This analysis utilized a
repeated-measures design within each temper-
ature because each animal's performance was
measured at four different times. Subsequently,
the relationship between : .f .. ... during
minutes 1, 2, and 3 and performance during
subsequent minutes was analyzed using Spear-
man's rank correlation analysis. Total body lac-
tate data were subjected to analysis of covari-
ance, with body mass as the covariate, and
temperature and duration of swimming as in-
dependent variables. In order to assess the re-
lationship between lactate concentration and
distance covered in I or 4 min of swimming,
the effects of body mass, total body length, and
temperature on post-exercise lactate level and
on distance at 1 or 4 min were computed by
multiple analysis of variance. The differences
between the observed values and those pre-


TABLE 1. Swimming performance of :,' - al-
ligators (in cm min '). Values shown are the mean
distance traveled per minute (=speed) in each of the
four minutes of swimming, adjusted for differences
in body .. . :- .... the 95% confidence intervals. Q,,
values, which indicate the effect of temperature change
on swimming speed, are also shown. Nine animals
were used at each temperature.

Min- Temperature (C) and Q,,
M in- ------------------
ute 15 Q,, 20 Q, 30
1 717 3.46 1334 1.19 1583
611-823 1087-1581 1292-1874
2 415 3.94 824 1.22 1002
296-534 616-1032 795-1209
3 318 4.26 656 1.05 688
234-402 481-831 525-851
4 227 5.53 534 1.04 555
119-335 379-689 370-740

dicted by the model were then calculated. The
relationships between the residuals for lactate
level and the residuals for distance were then
analyzed and partial correlation coefficients
were calculated. Linear regression was used to
examine the relationship between the 4
in performance during the 4 min trials and the
lactate concentration at the end of 4 min for
each temperature and for all temperatures com-
bined. Statistical significance was declared at P
< 0.05.

Swimming Performance.-The locomotor per-
formance of the ,::,..,. ., as measured by the
distance traveled in each minute, increased with
total body length (F,,a = 8.08, P = C: .-' -- In
general, the distance traveled (adjusted for dif-
ferences in body length) increased with tem-
perature (F,,3 = 25.58, P < 0.0001; Table 1).
However, the effect of temperature was appar-
ent only between 15 and 20 C (P < 0.001); swim-
ming speed did not change between 20 and 30
C (P = 0.2468). This pattern was the same when
data for each minute were analyzed individu-
ally. The distance traveled in each minute de-
creased over the four minutes of swimming (F,,
= 114.12, P < 0.0001; Fig. 1). Furthermore, there
was an interaction between temperature and
the swimming interval (F6,72 = 5.07, P = 0.0002);
this means that the effect of temperature on
performance changed as the animals continued
For all temperatures combined, swimming
distance in any one minute was positively as-
sociated with performance in any subsequent
minute (Spearman's r > 0.65, df = 25, P < 0.0005
in all six comparisons). This means that an al-

------ 30C
---*-- 20C
------ 15C

4 S

Time (min)
FIG. 1. Swimming performance of juvenile alli-
gators during four minute,' ., ,.
Each point indicates the distance covered in a single
minute of swimming. Values shown are means and
95% confidence intervals.

'. that swam well in the first minute was
likely to swim well in subsequent minutes.
However, this relationship varied with tem-
perature. At 15 C, the distance covered in any
one minute interval had no relation to the dis-
tance swum in any subsequent interval (r <
0.49, df = 7, P > 0.18 in all six comparisons).
This lack of an association at 15 C was in part
due to the fact that swimming performance var-
ied less among individuals at this temperature
than at higher temperatures (Fig. 1). For alli-
gators at 20 C, the distance traveled in the first
minute was positively associated with perfor-
mance in the third minute; other positive cor-
relations were between distance in minutes 2
and 3 and in minutes 3 and 4 (Table 2). At 30
C, performance in the first minute had no re-

TABLE 2. Spearman rank correlations between per-
formance in each one minute interval and all sub-
sequent one minute intervals at 20 and 30 C. In each
case N = 9, df = 7.

Tem- Subsequent
perature Minute minute
(C) interval interval r P
20 1 2 0.58 0.0972
1 3 0.72 0.0289
1 4 0.47 0.2039
2 3 0.73 0.0239
2 4 0.45 0.2230
3 4 0.85 0.0041
30 1 2 0.25 0.5215
1 3 0.30 0.4372
1 4 0.22 0.5802
2 3 0.93 0.0005
2 4 0.80 0.0097
3 4 0.75 0.0195


TABLE 3. Lactate concentration of juvenile *ii, *
tors (in Ag g '). Values shown are the mean values
for animals sampled at rest and after one and four
minutes of swimming, adjusted for differences in body
mass, (sample size), and 95% confidence intervals.

Temperature (C)
Minute 15 20 30
0 51 (7) 94 (7)

167 (9) 559 (10)
76-258 474-644

799 (9)

TABLE 4. Rate of lactate formation (pig lactate g
min ) in swimming alligators. Calculations are based
on values in Table 3. Q, values are also shown.

Interval Temperature (C) and Q,,
(min) 15 Qo 20 Q,, 30

116* 19.18 508
35 6.04 86
55* 12.19 192

1.39 705
1.38 119
1.38 265

Based on a resting lactate value of 51 ig g-', determined
at 20 C

4 272 (9) 817 (9) 1155(9) that swam the greatest distance had the lowest
181-363 726-908 1064-1246 lactate concentration (r = -0.62, df = 21, P =
0.0017; Fig. 2). The rate of change in swimming
speed during the 4 min trials was not correlated
on to swimming distance in subsequent with the total body lactate concentration at the
nutes; however, distance traveled in minute end of the trial at any temperature (15 C: r =
ias positively correlated with performance 0.04, df 7, P 9090; 20 C: r 0.31, df
minutes 3 and 4 (Table 2). Likewise at 30 C, 7, P = 0.4177; 30 C: r = -0.40, df = 7, P = 0.2822).
tances in minutes 3 and 4 were positively However, when data for all temperatures were
related (Table 2). The absence of negative pooled, the animals with the steepest decline
: i.. between distances in various in- in swimming speed over the 4 min test were
vals means that there were no animals that the individuals with the highest lactate con-
re good "starters" but poor "finishers," or centration at the end of the trial (r = 0.69, df
e versa. = 25, P < 0.001).
e versa.
-. Lactate concentration of resting DIScussION
gators did not vary with temperature (F,, Perfr ce-The swimming be,
.00, P = 0.3397; Table 3). Active animals had Performance-The swimming be-
igher lactate level than did resting animals havior of the alligators in this study was essen-
44 = 227.54, P < 0.0001). Lactate concentra- tially that described by Manter (1940), Fish
nof swimming ,:... ,: .. increased with body (** i: and Turneretal. (1985). There were brief
ss (F,,, = 6.12, P = 0.0170); thus, body mass intervals of burst swimming interspersed among
s used as a covariate in all subsequent anal- longer periods of intense but steady effort at
. T, i .1 ,. .. ;i .. i ;-. the water surface. Animals sometimes appeared

yse I Ie v x g m
creased with temperature (F.,, = 182.37, P <
0.0001) and was higher for animals ..:......
for 4 min than for those active for only 1 min
(Ff,,4 = 56.17, P < 0.0001). Furthermore, there
was an interaction between temperature and
duration of exercise (F,,, = 5.21, P = 0.0090);
this resulted from the fact that as temperature
increased from 15 to 30 C, the increase in lactate
concentration between 1 and 4 min of swim-
ming became larger.
The rate of lactate formation during swim-
ming increased with temperature, more steeply
between 15 and 20 C than between 20 and 30
C (Table 4). The rate at which lactate accumu-
lated during the first minute of exercise was
3.3-5.9 times that during the subsequent three
minutes (Table 4).
Relation between Performance and Glycolysis.-
Once the effects of body length, body mass, and
temperature were removed, there was no rela-
tionship between lactate concentration and dis-
tance covered in 1 min of swimming (r = -0.01,
df = 22, P = 0.9670). A similar analysis for data
at 4 min of swimming indicated that the animals

400 -

> *
a Sa

O0 -600 0 S00 1200

Residual for Distance (cm)
FiG. 2. The relationship between whole-body lac-
tate concentration and distance covered in juvenile
i. mming for 4 min. The points shown are
the residual values remaining after removal of the
effects of temperature, body mass, and body length.
The linear regression equation is: y = -0.11 0.14x,
r = -0.62, df = 25, P < 0.001.

2 w


= 1


to ventilate their lungs but we recorded no data
on frequency of breathing during the exercise
bouts. Larger: . ...... animals swam faster than
smaller (shorter) ones, which was expected.
Temperature exerted a strong effect on swim-
ming performance between 15 and 20 C but no
effect between 20 and 30 C, a pattern similar to
that found by Turner et al. (1985) for burst speed
in swimming fi:. :
Swimming speed was highest in the first min-
ute of the trials and then decreased over the
subsequent 3 min. In general, animals retained
their rank for swimming speed over the 4 min
trial; the best swimmers in the first minute were
also the best performers in subsequent minutes.
The decline in speed over time was presumably
the result of the accumulation of metabolites of
glycolysis which lead to fatigue in crocodilians
and other vertebrates (Bennett et al., 1985; Sey-
mour et al., 1985, 1987; Nosek et al., 1987). The
speed of our alligators in the first minute of
swimming was only 26-31% of the speed of
those of Turner et al. (1985) that were engaged
in burst swimming lasting only 3-6 sec at the
same temperatures we used. This comparison
between our results and Turner's is complicated
by the fact that his animals had body masses
about 10 times those of ours, and by the fact
that his data were not adjusted for differences
among individuals in body length. Stamina in
swimming crocodiles (Crocodylus porosus) is size-
dependent; animals of less than I kg exhaust in
about 5 min, whereas large adults may not ex-
haust until after 30-50 min of effort (Seymour
et al., :i'-. Thus, studies of locomotor perfor-
mance in crocodilians must always control for
variation in body size among individuals.
-Larger animals had higher post-
exercise whole body lactate levels than smaller
animals. Bennett et al. (1985) report a similar
i,:. .. ..; between body size and blood lac-
tate concentration in crocodiles (Crocodylus po-
rosus) exhausted during capture in the field. In
the present .. -1., large animals swam farther
than smaller ones whereas in the study of Ben-
nett et al. (1985), large animals struggled longer
than smaller ones. Therefore, the high amount
of lactate accumulated in large -.. .. : .' in
comparison with smaller ones, may reflect a
greater cumulative effort and/or a higher tol-
erance for blood acid base disturbance.
The thermal sensitivity of !. !. : between
15 and 20 C during the first minute of exercise
(Qi = 19.18) was much greater than during the
subsequent 3 min (Q0 =- 1.39). The former very
high value is atypical of that for other reptiles
in which Q,o for glycolysis is generally between
1.1 and 1.3 (Bennett, 1982). Likewise, the pat-
tern of an abrupt change in Q,, for glycolysis
between 15-20 C and 20-30 C is most unusual

for reptiles (Gatten, 1985, eq. 1). Furthermore,
the absolute value for the rate of lactate for-
mation found here for animals active for 1 min
at 15 C is only 15% of the comparable value for
squamate reptiles (Gatten, 1985, eq. 1). Togeth-
er, these facts indicate that the ability of juve-
nile i..: ...... to power short-term locomotion
by '.. below 20 C is very low. Glycolysis
at all temperatures during the early portion of
exercise was more intense than during the latter
portion, a pattern typical of other reptiles (Gat-
ten, 1985).
t'.. and Performance.-In spite of the
substantial accumulation of lactate during the
first minute of exercise .. : .- at 20 and 30
C), there was no relationship between post-ex-
ercise lactate level and distance traveled. This
result implies that although active muscles are
generating ATP by glycolysis, the magnitude
of this process is not directly coupled with the
extent of forward movement in the first minute
of exercise. This finding is contrary to our gen-
eral understanding of the importance of gly-
colysis to locomotor performance during short-
term burst exercise in ...., : .. .. and reptiles
(Gatten, 1985). Perhaps the "stress" induced by
the experimental conditions elicited catechol-
amine-induced glycolysis (Coulson and Her-
nandez, : .- in this case, the lactate level at
the end of swimming reflected that due to gly-
colysis in active muscles and that due to hor-
mone-stimulated -1. :. : in the liver.
When the i:. .. ; between lactate con-
centration and performance at 4 min is exam-
ined, the result is that there is an inverse re-
lation between these two variables: the animals
relying least on :.1 I : swim the greatest
distance. Furthermore, the rate of decline in
swimming speed over the 4 min trial was most
pronounced in animals with a high lactate level.
These findings imply that (1) extensive reliance
on glycolysis is detrimental to prolonged lo-
comotion, and (2) the best performers (in terms
of distance covered in 4 min) are those that .
least on .- ' It is possible that a high rate
of glycolysis early in a prolonged bout of ex-
ercise results in levels of glycolytic endproducts
that inhibit aerobic processes, leading to a re-
duction in . locomotor ability. It
would appear that the negative effects of gly-
colytic endproducts on muscle function and/
or blood gas transport outweigh the benefits of
glycolytic ATP generation during 4 min of in-
tense effort in juvenile .:: .. : .. This -:.. ..,.
reinforces the understanding that 1 ..1 : is
most important during the early stages of ex-
ercise in ectothermic vertebrates and that vig-
orous locomotion lasting more than one minute
must be powered largely by aerobic, rather than
anaerobic, pathways.


/. .' -Funding for this research
was provided through contract DE-ACO9-
76SR00-819 between the United States Depart-
ment of 7 - .. and the University of Georgia's
Savannah River Ecology Laboratory; the De-
partment of Biology and Research Council of
the University of North Carolina at Greensboro;
and Oak Ridge Associated Universities Travel
Contracts S-1942 to REG, Jr., and S-3244 to FJM.
We are grateful to R. Wine for technical assis-
tance and D. Ludwig for statistical assistance.

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Accepted: 7 June 1991.


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