A study of ovarian follicular kinetics, oviduct, fat body, and liver mass cycles in laboratory-maintained Rana cyanophlyctis in comparison with wild-caught frogs.

Ovarian follicular dynamics and fluctuations in fat body, oviducal, and liver masses were studied in captive Rana cyanophlyctis in comparison with wild-caught frogs, sampled at monthly intervals over a period of 12 months. In both the captive and wild-caught frogs first growth phase (FGP) and second growth phase (SGP) or vitellogenic oocytes were produced throughout the period examined; however, changes in ovarian and oviducal weights were less marked in the former group. In the captive frogs SGP oocyte production was reduced by 50%, and, maximum ovarian weight and SGP oocyte number were attained 2-3 months earlier than in wild-caught controls. The FGP oocyte pool in laboratory-maintained frogs, however, was comparable with that of the corresponding wild-caught frogs. Captivity caused a threefold increase in atresia and reduced the number of oocytes reaching SGP. The depletion of fat stores in fat bodies during the later phases of captivity suggests that the deposition of lipids into oocytes (for SGP) was given priority over storage in the fat bodies. The low oviducal weights of captive frogs was correlated with a reduced number of SGP oocytes, which are the source of estrogen. On the other hand, liver weight remained high, indicating adequate hepatic vitellogenin synthesis. Possible reduction in its output was not detected, possibly due to the reduced number of follicles reaching SGP. The findings indicate that stress of captivity decreases gonadotrophins and estrogen levels. Oviducal growth is reduced in captive frogs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mechanisms regulating the ovarian cycle in the frog Rana cyanophlyctis: effect of unilateral ovariectomy, season, feeding, human chorionic gonadotrophin, and estradiol-17 beta

Effects of 30-day unilateral ovariectomy (ULO) on compensatory ovarian hypertrophy (COH) was studied in adult frog Rana cyanophlyctis in relation to reproductive phase/season, feeding, and treatment with human chorionic gonadotrophin (HCG) or estradiol-17 beta. Compensatory growth of the remaining ovary was assessed in terms of weight as well as changes in the dynamics of the pool sizes of different oocytes viz., first growth phase (FGP), medium-sized second growth phase (MSGP), large-sized second growth phase (LSGP), and atretic oocytes. The frogs were fed with live guppies 6 days a week. The effect of underfeeding on COH was studied in the frogs fed once a week. The ovaries removed at operation and those of the sham-operated frogs were used for comparison (controls). COH occurred in both pre- and postbreeding phases (February and November, respectively). In both instances follicular atresia was greatly reduced. In February, COH was due to recruitment of both MSGP and LSGP oocytes. The number of these oocytes increased significantly over controls, and the ovarian weight nearly doubled. However, in November COH occurred because of an increase in FGP oocytes and therefore total oocytes, but there were no changes in the ovarian weights. Administration of 20 IU HCG (6 days a week) had no influence on the basic pattern of COH-response exhibited by the remaining ovary in relation to reproductive phase/season, but it increased the recruitment of oocytes, i.e., FGP oocytes in November and SGP oocytes in February. Follicular atresia was drastically reduced with HCG. Underfeeding or treatment with estradiol-17 beta abolished the COH in both February and November.(ABSTRACT TRUNCATED AT 250 WORDS)     

Role of environmental temperature and photoperiod in regulation of seasonal testicular activity in the frog, Rana perezi.

To analyze the role of environmental temperature and photoperiod in the regulation of the annual testicular cycle in Rana perezi, we performed experiments combining high (25 +/- 1 degrees C) or low (6 +/- 1 degrees C) temperature and different photoperiod regimens (18L:6D, 12L:12D, and 6L:18D (hours light:hours dark)) during three phases of the reproductive cycle: winter stage (December) and prebreeding (February) and postbreeding (May, June) periods. Low temperature and short photoperiod in winter induced the arrest of the maturation phase of spermatogenesis and the activation of primary spermatogonia proliferation and spermiohistogenesis. Rana perezi testis responded to long days stimulus in winter, even at low temperature, with induction of the maturation phase of the cycle. Exposure of male frogs to either high temperature or long photoperiod induced a decrease in testosterone levels in winter. During the prebreeding period, an increase in environmental temperature caused a reduction in testosterone, and a lengthening in photoperiod produced the opposite effect. Photoperiod had no effect on testosterone levels during the postbreeding period, but low temperature increased testosterone plasma levels. These results suggest that both temperature and photoperiod effects can vary seasonally, depending on the phase of the annual reproductive cycle in R. perezi.     

Influence of temperature on survival, growth and fecundity of the freshwater snail Indoplanorbis exustus (Deshayes).

To note the effect of temperature on survival, growth and fecundity, newly hatched (zero day old) snails Indoplanorbis exustus were cultured at 10 degrees, 15 degrees, 20 degrees, 25 degrees, 30 degrees and 35 degrees C constant temperatures and room temperature (17.5 degrees-32.5 degrees C). Individuals exposed to 10 degrees C died within 3 days while those reared at 15 degrees, 20 degrees, 25 degrees, 30 degrees, 35 degrees C and room temperature survived for a period of 6, 27, 18, 16, 12 and 17 weeks respectively. An individual added on an average 0.21 mm and 0.45 mg, 0.35 mm and 7.94 mg, 0.63 mm and 15.5 mg, 0.81 mm and 27.18 mg, 1.07 mm and 41.48 mg and 0.78 mm and 31.2 mg to the shell diameter and body weight respectively at those temperatures per week. The snails cultured at 15 degrees C died prior to attainment of sexual maturity. On an average, an individual produced 31.9 and 582.77, 54.86 and 902.18, 56.01 and 968.45, 49.32 and 798.68 and 62.34 and 1143.97 capsules and eggs respectively at 20 degrees, 25 degrees, 30 degrees, 35 degrees C and room temperature (17.5 degrees-32.5 degrees C).     

Growth and formation of toxin by Clostridium botulinum in peeled, inoculated, vacuum-packed potatoes after a double pasteurization and storage at 25 degrees C

A process that claims to use a double pasteurization to produce vacuum-packed potatoes for storage at ambient temperature has been evaluated. After the first pasteurization, potatoes are vacuum-packed and stored at 25 degrees-35 degrees C for up to 24 h, which is intended to allow germination of bacterial spores, and are then pasteurized again. When potatoes were inoculated with spores of Clostridium botulinum and subjected to this double-pasteurization process a high proportion of spores remained viable and resulted in growth and formation of toxin within 5-9 d at 25 degrees C. To provide an appropriate reduction in the risk o survival and growth of Cl. botulinum, peeled, vacuum-packed potatoes for storage at ambient temperature should be given a heat treatment equivalent to an F(0)3 process. If they are not given such a heat treatment they should be stored at a temperature below 4 degrees C.     

Dynamics of oogenesis in the tropical anuranRana tigrina (Amphibia: Ranidae) with special reference to vitellogenic cycles in wild-caught and captive flogs

The ovarian cycle ofRana tigrina was analysed by quantifying the developing oocytes (classified into stages on the basis of diameter) and atretic ones at monthly intervals. Stages I to IV represent oocytes in the first growth phase and the remaining ones the vitellogenic or second growth phase. Stages I–III occurred year round but exhibited significant variation in their number. The number of stage II oocytes always dominated the other stages. Recruitment of oocytes to stages IV and V in April marked the initiation of vitellogenic growth in all specimens. Of the 30 to 35% second growth phase oocytes, 25 to 28% reached ovulatory sizes by June. After spawning the ovarian mass declined drastically from 15 to 0.2% of body mass in July. Atresia was maximal (5%) in August. In other months, it was less than 1.5% of the total oocytes. Oogenic episodes occurred in March and July yielding new oocytes. The number of first growth phase oocytes fluctuated from 65 to 95%. The fluctuation was inversely correlated with the second growth phase oocytes indicating a 30 to 35% annual turnover rate of oocytes in the frog. The final egg number/ovarian mass is positively correlated with the snout-vent length as well as body mass of the frogs.R. tigrina produces about 4000 eggs/100g body mass. Further, the mean number of yolky eggs/100 g body mass and the total volume (V) of eggs/frog were highly correlated. Frogs living in captivity produced fewer eggs compared to the wild ones (3594 ± 227 in captivevs 4704 ± 317 in wild frogs). Also, these frogs failed to breed though they showed amplexus with breeding males. Injection of desoxycorticosterone acetate however induced spawning in 4 out of 5 frogs. They released about 3000 eggs each. Captivity seems to mainly impair breeding and to a little extent the vitellogenic growth of oocytes inR. tigrina.     

Effect of androgens on oviductal growth in skipper frog Rana cyanophlyctis

Effects of exogenous androgens (testosterone, testosterone propionate and dihydrotestosterone) and estradiol-17beta on the oviductal growth/hypertrophy were studied in young and bilaterally ovariectomized (BLO) adult frogs (Rana cyanophlyctis) during postbreeding phase of the reproductive cycle. Estradiol-17beta injections induced oviductal hypertrophy to the maximal extent among hormone treated groups. In androgen treated frogs also there was an increase in the oviductal dry weight and protein content both in young and BLO adult frogs, suggesting the role of endogenous androgens in controlling the growth of oviduct in R. cyanophlyctis.     

Effect of ambient temperatures during oocyte recovery on in vitro production of bovine embryos

Recovery of oocytes from ovaries collected at slaughter was carried out at three ambient temperatures (25 degrees, 30 degrees and 35 degrees C) to assess the effect on subsequent embryonic production in vitro. Oocytes recovered at each temperature were thereafter maintained at temperatures > or =35 degrees C as they were subjected to in vitro maturation, fertilization and culture (IVM/IVF/IVC). The oocytes and resulting embryos within each temperature group were subsequently evaluated for their rates of fertilization, cleavage and development to blastocysts, as well as for the number of cells/blastocyst. The results demonstrate that exposure of cumulus-ocyte-complexes (COCs) to temperatures below 35 degrees C during oocyte recovery is detrimental to optimal embryo production. Although the fertilization and cleavage rates of oocytes recovered at temperatures below 35 degrees C were not significantly lower than that of the controls, the percentage of oocytes recovered at 35 degrees C that developed to the blastocyst stage following fertilization and culture (33.7%) was significantly greater than those from oocytes recovered at either 25 degrees C (22.4%) or 30 degrees C (19.5%). The mean numbers of blastomeres/embryo were significantly lower in embryos derived from oocytes collected at either 25 degrees or 30 degrees compared with those collected at 35 degrees C. The results of this study suggest that exposure of COCs to temperatures below 35 degrees C during oocyte recovery may significantly decrease both the quantity and quality of embryos produced by in vitro methods.     

Vitellogenic cycles in laboratory-maintained females of the leopard frog, Rana pipiens

As a part of studies on the reproduction of laboratory maintained frogs, wild-caught Rana pipiens were ovulated and maintained at 22-27 degrees C for up to 18 months. Vitellogenic oocytes were periodically staged and counted, and a "maturity index" was calculated to assess the progress of the vitellogenic cycle. The initial cycle was similar to that of wild frogs except that the first oocytes to reach stage 5 (mature eggs) usually began to degenerate before later starting oocytes became mature. In addition, a second cycle began before the first was completed. After more than 1 year at room temperature, abnormal cycles were common. Ovaries of such animals contained very few mature eggs. Many of their oocytes were in early stages of vitellogenesis or, if pigmented, had begun to degenerate. These deficiencies were partially corrected in females placed in 4 degrees C for 4-6 weeks. The average number of mature eggs increased 15-fold and ovary weights more than doubled. Oviduct weights almost doubled. Although the rates of cooling, photoperiod, and nutritional status could be important influences, the results imply that cold treatment alone increases estrogen secretion. We suggest that low estrogen secretion may account for the reproductive deficiencies seen in R. pipiens cultured at room temperature.     

Seasonal variation in conduction velocity of action potentials in squid giant axons

To determine whether the electrical properties of the squid giant axon are seasonally acclimated, action potentials, recorded at different temperatures, were compared between giant axons isolated from Loligo pealei caught in May, from relatively cold waters (approximately 10 degrees-12 degrees C), and in August, from relatively warm waters (approximately 20 degrees C). Parameters relating to the duration of the action potential (e.g., maximum rate of rise, maximum rate of fall, and duration at half-peak) did not change seasonally. The relationship between conduction velocity and temperature remained constant between seasons as well, in spite of the fact that May axons were significantly larger than August axons. When normalized to the fiber diameter, mean May conduction velocities were 83% of the August values at all temperatures tested, and analysis of the rise time of the action potential foot suggested that a change in the axoplasmic resistivity was responsible for this difference. Direct measurements of axoplasmic resistance further supported this hypothesis. Thus seasonal changes in the giant axon's size and resistivity are not consistent with compensatory thermal acclimation, but instead serve to maintain a constant relationship between conduction velocity and temperature.     

Development to live young from bovine small oocytes after growth, maturation and fertilization in vitro

Bovine oocytes (90 to 99 microns in diameter) were isolated from early antral follicles (0.5 to 0.7 mm in diameter). Cumulus-oocyte complexes (COC) with pieces of parietal granulosa were embedded in collagen gels and cultured for 14 d. After in vitro growth culture, oocytes recovered from the collagen gels were further matured, fertilized and cultured in vitro, and then were transferred to recipient cows. After 14 d of growth culture, 37% of the oocytes (203/556) showed normal morphology in the collagen gels. The mean diameter of the oocytes was 110.1 +/- 6.0 microns, significantly larger (P < 0.01) than before growth culture (94.8 +/- 2.7 microns), and 77% were at the germinal vesicle stage while 23% had undergone germinal vesicle breakdown. After 24 h of maturation culture followed by insemination, 27% of in vitro-grown oocytes reached the second metaphase, and 42% of the oocytes were normally fertilized. After insemination, 18.2% of in vitro-grown oocytes cleaved and 3.7% developed to the blastocyst stage. Three blastocysts obtained from in vitro-produced 90- to 99-micron oocytes were transferred to 3 recipients. One recipient subsequently became pregnant and delivered a live calf on Day 277. These results demonstrated for the first time that 90 to 99-micron oocytes from early antral follicles can complete growth and acquire full developmental competence in vitro so that live young can be produced after maturation, fertilization, subsequent culture in vitro, and transfer to recipient cows.     

Plasma membrane water permeabilities of human oocytes: the temperature dependence of water movement in individual cells.

Membrane water permeability values were measured in individual fresh human pre-ovulatory oocytes using real time microscopy in a microscope diffusion chamber. The cells were exposed to anisosmotic conditions, their volume responses measured, and from these data the Lp values were computed employing the Kedem-Katchalsky analyses of irreversible thermodynamics. Lp values were measured at four temperatures for each oocyte between 37 degrees C and 10 degrees C, and the temperature-related Arrhenius activation energy (Ea) calculated. It was apparent that individual oocytes exhibited a wide range of Lp values; at 37 degrees C Lp values ranged between 0.33 and 1.80 microns/atm/min. However, each oocyte exhibited the expected inverse linear correlation between Lp and temperature, with high linear correlations (R2 values between 0.73 and 0.96). A mean value for Ea of 8.61 +/- 5.11 Kcal/mol was computed. It is apparent that pre-ovulatory human oocytes express a range of biological diversity in terms of membrane water transport, and this fact needs to be considered when attempting to formulate cryopreservation protocols for storage of these oocytes.     

Sequential deposition of yolk components during oogenesis in an insect,Aedes aegypti (Diptera: Culicidae)

Vitellogenesis in Aedes aegypti of uniform body size was followed at 27 degrees C in narrow time intervals throughout their first reproductive cycle by measuring the length, diameter, and volume of follicles and oocytes, the latter as an expression of the yolk mass (vitellus). Independent of all experimental conditions, a two-step process of elongation was recognized for both follicle length and yolk length, so that growth curves were consistently composed of two linear regressions with different slopes against time. Follicle lengths started to increase immediately after the blood meal, while oocytes took up to 6 h to show a measurable increase in yolk length. The first linear phase continued until 30 h, when yolk length reached 268+/-22 micro m. At this point, a transition occurred where the linearity shifted sharply for the next 6 h to 2-4-times higher slopes for both regressions. This second growth phase represented a 40% elongation of oocytes and follicles. Then, both curves leveled off at their final size, characteristic of mature ovaries: 462+/-10 micro m for oocytes, 489+/-11 micro m for follicles. These values remained constant until oviposition.The first linear growth phase was associated with an equicaloric and synchronous protein and lipid incorporation into the oocytes; levels of these substances reached their maximum by the end of this first phase and remained constant until oviposition. The second linear growth phase was characterized by rapid glycogen incorporation into oocytes from 20 to 100% of the maximum. Subsequently, the surface pattern of the exochorion became visible, marking the end of yolk incorporation. Since eggs are always laid on moist substrates, within 2-3 h of oviposition they double in volume and fresh weight, driven by more than tripling of their water content.When blood-fed females were exposed to five different temperatures between 17 and 37 degrees C, the distinction between the two linear growth phases persisted, but the slopes of the respective regressions, and therefore their durations, were affected. Eggs still matured at 37 degrees C but never hatched and at 12 degrees C only 18% hatched, whereas at all the intermittent temperatures hatching was 80-90%. Oogenesis appears to be limited to the range between 12 and about 32 degrees C.The effects of age, maternal body size and the source of the blood on vitellogenesis were also examined. These parameters affected the onset and/or extent of oogenesis in various ways.     

Effects of cooling ovaries before oocyte aspiration on meiotic competence of porcine oocytes and of exposing in vitro matured oocytes to ambient temperature on in vitro fertilization and development of the oocytes

Experiments were conducted to evaluate the effects of cooling porcine ovaries to low temperature (4 degrees C, 15 degrees C, 20 degrees C, 25 degrees C or 30 degrees C) for 1 h on the meiotic competence of their oocytes. Moreover, it was determined whether or not the exposure of in vitro matured oocytes to ambient temperature (20 degrees C, 25 degrees C or 30 degrees C) for 1 h affects the fertilization and developmental competence of the oocytes. There was no difference between the proportions of oocytes that underwent maturation to metaphase II when isolated from control ovaries held at 35 degrees C and ovaries exposed to 30 degrees C. However, the percentages of oocytes from ovaries exposed to 25 degrees C or less were significantly lower than those of oocytes from ovaries exposed to 30 degrees C and control ovaries. The proportions of total and normal fertilization of oocytes that had been exposed to 20 degrees C before in vitro fertilization (IVF) were significantly lower than those of control oocytes maintained at 38.5 degrees C. However, cooling in vitro matured oocytes had no effects on their cleavage and development to blastocysts after IVF. These data suggest that exposing porcine ovaries to a low temperature of 25 degrees C or less before aspiration of oocytes may adversely affect their subsequent in vitro maturation. It may be necessary to maintain the oocytes at a temperature of more than 25 degrees C during manipulation of oocytes for retaining the fertilizability of the oocytes.     

Enhanced protein synthetic capacity in Atlantic cod (Gadus morhua) is associated with temperature-induced compensatory growth

Atlantic cod (Gadus morhua) were held either at seasonal ambient temperatures (-0.3 to 11 degrees C) or at a relatively constant control temperature (8-11 degrees C) to investigate aspects of protein synthesis during a period of compensatory growth. Protein synthesis rate, total RNA, and RNA-specific protein synthesis rate were determined in white muscle and liver when ambient temperatures were -0.3, 4.5, and 11 degrees C in February, June, and July, respectively. To allow for comparisons between treatment temperatures, fish were also acutely transferred to a comparable assay temperature in February and June. Over the transition from 4.5 to 11 degrees C (June to July), the ambient-held cod had a significant increase in size and a substantially higher growth rate relative to control-held fish over the same period, consistent with cold-induced compensatory growth. During the onset of this enhanced growth, in June when ambient temperature was approximately 4.5 degrees C, ambient-held fish elevated their capacity for protein synthesis in the white muscle and liver via elevation of the RNA content. When ambient temperature reached the same point as for the control fish (11 degrees C), the rate of white muscle protein synthesis remained higher in the ambient-held vs. that in the control-held fish, a process facilitated by elevated RNA content and greater RNA-specific rate of protein synthesis. In the liver, all measured characteristics of protein synthesis were the same for ambient and control fish in July. The latter suggests that compensatory growth may be in part explained by improved efficiency of protein synthesis.     

The effect of liposomes on thermotropic membrane phase transitions of bovine spermatozoa and oocytes: implications for reducing chilling sensitivity

We have examined the effects of combinations between egg-phosphatidylcholine (EPC) or dipalmitoylphosphatidylcholine (DPPC) liposomes with either bovine spermatozoa or oocytes on cellular chilling sensitivity, lipid phase transition temperature (T(m)), and the ability of the oocytes to develop to the blastocyst stage. Spermatozoa and oocytes were exposed to EPC and DPPC liposomes at various temperatures (spermatozoa: 4, 12, 16, and 25 degrees C; oocytes: 4, 16, and 32 degrees C). The membrane integrity of the spermatozoa-control group decreased significantly following exposure to 16 or 12 degrees C, compared to ambient temperature (25 degrees C). In contrast, the EPC-sperm group had a greater resistance to chilling at each temperature and showed a decline in membrane integrity only at the lowest temperatures investigated. However, the DPPC-sperm group was injured significantly at all temperatures tested. Similar to the sperm, oocytes from the control group that were exposed to 16 degrees C were injured more severely than oocytes that were electrofused with EPC or DPPC liposomes. The membrane integrity of the oocytes at 16 degrees C that were electrofused with either EPC or DPPC liposomes was approximately the same as the control group held at 32 degrees C (normalized to 100%), compared to 46% in the control group at 16 degrees C (P<0.01). The transition temperatures of the sperm and oocyte membranes revealed different T(m) for the different liposome treatments. All groups had a significantly higher cleavage rate, as well as increased blastocyst formation when oocytes were exposed to temperatures above or below their T(m). We suggest that the T(m) of spermatozoa or oocytes can be changed by spontaneous association or electrofusion of liposomes with cellular membranes and, consequently, the chilling sensitivity can be altered. The resulting possibility is that embryo development after cryopreservation could be improved with such a method.     

Effect of photoperiod and temperature on ovarian cycle of the frogRana tigrina (Daud.)

The effect of varying photoperiod regimes (LD: 20,4; 4,20; 6,18; 18,6 and 12,12) on ovarian follicular development was analysed in the frogRana tigrina maintained at ambient and constant 30° ± l°C for 3 months. The experiments were conducted in early recrudescent and quiescent phases. The frogs were fed guppiesad libitum on alternate day. None of the photoperiod regimes had any effect on the ovaries or the fat bodies, whereas exposure to constant high temperature (regardless of photoperiod) during recrudescent phase induced production of greater number of eggs (∼ 18000 vs 13000 in controls) of ovulatory sizes (> 1400 μm) compared to the corresponding controls maintained at ambient temperature. Hence, ovarian mass also increased in these frogs. In the quiescent phase, high temperature merely enhanced growth of previtellogenic oocytes. In both the phases high temperature caused a reduction in the fat bodies over the respective controls, possibly due to increased metabolic activity. The above findings indicate that temperature plays a key role in the regulation of ovarian cycle ofRana tigrina and that the photoperiodic mechanisms may not govern the annual recrudescence of ovaries in the frog. The study also shows that the frog exhibits the phenomenon of “phenotypic plasticity” in its reproductive behaviour by producing significantly greater number of eggs in response to elevated temperature.     

Response of intestinal flora of laboratory-reared leopard frogs (Rana pipiens) to cold and fasting.

The bacterial flora of the large intestine was examined in 35 laboratory-reared leopard frogs (Rana pipiens) subjected to one of the following four treatments: (i) normal feeding at 21 degrees C (10 frogs); (ii) fasting for 2 weeks at 21 degrees C (8 frogs); (iii) chilling for 1 week at 4 degrees C (9 frogs); and (iv) simulated hibernation for 3 weeks at 4 degrees C (8 frogs). Bacteria from the intestinal contents and mucosa were counted microscopically and by colony counting after strictly anaerobic culturing. The predominant bacteria were isolated and partially characterized. Fasting for 2 weeks produced no significant changes in total counts or in the types of bacteria cultured. Chilling, whether rapid or in the course of simulated hibernation, was associated with a decrease in the numbers and variety of bacteria. Thus it appears that the lowering of temperature rather than the absence of food is the important factor in the reduction of bacterial flora seen in hibernating frogs. However, the bacteria showed some adaptation to the low temperature, as the longer the host had been at 4 degrees C, the higher the proportion of bacteria which could grow when cultured at that temperature.     

Cricket frogs maintain body hydration and temperature near levels allowing maximum jump performance

One goal of this study was to determine the combination of hydration and temperature in the northern cricket frog Acris crepitans that allowed maximum jump distance in the laboratory. Second, environmental variables in the field were measured to determine the best predictor(s) of mean body temperature and hydration and to determine whether frogs maintain levels of temperature and hydration yielding maximum jump distance. Laboratory data revealed that hydration and the hydration-temperature interaction significantly affected jump performance. Frogs at 95% and 85% hydration jumped significantly better than frogs at 75% hydration, but frogs at 95% hydration at 15 degrees C jumped significantly poorer than those at 95% hydration at 30 degrees C. Animals at 85% hydration at 30 degrees C and 85% hydration at 15 degrees C jumped just as well as those at 95% hydration at 30 degrees C. Mean body temperature of 55 frogs in the field was 28.0 degrees C, and hydration was 97.4%. Sky condition (sunny, cloudy, or partly cloudy) was the best predictor of frog hydration, and air temperature was the best predictor of frog body temperature. Cricket frogs in the field maintain a hydration and temperature near those found to yield maximum jump distances in laboratory trials. This may be a behavioral adaptation to allow maximum jump distance during predator avoidance.