NAG-infection in grass frogs (Rana temporaria) subjected to hypothermia]

Rana temporaria kept under hypothermic conditions approaching anabiosis were inoculated with NAG-vibrios and examined clinically, bacteriologically, histologically, and electron microscopically. Oral inoculation of hypothermic frogs with NAG-vibrios resulted in 18 to 24 hours in the development of acute NAG-infection resembling the cholera-like syndrome, and characterized by general intoxication and local enteropathogenic effects. NAG-vibrios persisted in the frog gastrointestinal tract for a long time after the cessation of the acute period of the disease.     

Helminth communities of two green frogs (Rana perezi and Rana saharica) from both shores of the Alboran Sea

The helminth communities of two populations of green frogs from both shores of the Alborón Sea (Western Mediterranean) were studied. Of the 79 frogs examined for helminths, 39 individuals of the species Rano saharica were collected from Bob-Taza (Morocco), and 40 of the species Rona perezi were collected from the Natural Park of the Sierra de Grazalema (Spain). Although the species richness of helminths was identical in the two sampled areas, the differences observed in the structure of the helminth infracommunities were quite important. Statistically, significant differences were found between the species richness and the diversity of the infracommunities of R. perezi female population and the other three studied statistical populations. The helminth component communities of these two green frogs can be considered as depauperate, although their infracommunities present interactive features.     

Seasonal changes in angiotensin converting enzyme activity in male and female frogs (Rana esculenta)

Gonad, lung, kidney and serum angiotensin converting enzyme (ACE) activities were determined by specific substrate hydrolysis in male and female Rana esculenta over 1 year. Ovary ACE activity showed the highest values among the different tissues, with a significant peak (223+/-52 nmol min(-1) mg protein(-1)) in late winter-early spring. Testis ACE activity followed a significant seasonal cycle, increasing from September to peak in April (2.5+/-0.8 nmol min(-1) mg protein(-1)) and then decreased in the post-reproductive period. Lung and kidney ACE activities were not correlated with the annual reproductive cycle phases. In serum a peak of activity was present in the post-reproductive period both in male and female frogs. The present data show a correlation between ACE and the annual reproductive cycle of R. esculenta.     

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.     

A study on hearing in frogs (Rana pipiens and Rana clamitans)

Zusammenfassung Die relative Reizschwellkurve für die Schallempfindung bei den Fröschen Rana clamitans und R. pipiens wurde in dem Frequenzbereich von 30–15000 Hz bestimmt. Die Kurve ist dieselbe für beide Geschlechter. Versuche zeigten, daß Schälle entweder inhibierend oder stimulierend auf die Atmungsbewegungen wirken können. Diese Wirkung wird nicht von der Frequenz oder der Intensität der Schälle bestimmt, sondern von dem physiologischen Zustand des Tieres.Die Latenzzeit zwischen Reiz und Effekt ist unabhängig von der Tonfrequenz, wird aber von den Intervallen zwischen aufeinanderfolgenden Reizen beeinflußt; sie wird kürzer, wenn die Intervalle verlängert werden.Dressurversuche mit 18 Tieren, unter Anwendung von Strafung durch elektrische Schläge und einem Dressurton von 300 Hz, ergaben positive Erfolge bei zwei Individuen von R. clamitans.

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Contribution No. 67 of the Department of Biology, Hamilton College, McMaster University, Hamilton, Ontario.     

Response of efferent vestibular fibers to horizontal rotation in frogs (Rana esculenta L.)]

The activity of efferent vestibular fibres has been recorded on the nerve of the left vertical anterior semicircular canal detached from its ampulla during rotations in the horizontal plane. Different types of responses have been found; they are noted in table I and pictured on fig. 2.     

The physiology of hibernation in Canadian leopard frogs (Rana pipiens) and bullfrogs (Rana catesbeiana)

Canadian northern leopard frogs (Rana pipiens) and bullfrogs (Rana catesbeiana) were acclimated to 3 degrees C and submerged in anoxic (0-5 mmHg) and normoxic (Po(2) approximately 158 mmHg) water. Periodic measurements of blood Po(2), Pco(2), and pH were made on samples taken anaerobically from subsets of each species. Blood plasma was analyzed for [Na(+)], [K(+)], [Cl(-)], [lactate], [glucose], total calcium, total magnesium, and osmolality. Blood hematocrit was determined, and plasma bicarbonate concentration was calculated. Both species died within 4 d of anoxic submergence. Anoxia intolerance would rule out hibernation in mud, which is anoxic. Both species survived long periods of normoxic submergence (R. pipiens, 125 d; R. catesbeiana, 150 d) with minimal changes in acid-base and ionic status. We conclude that ranid frogs require a hibernaculum where the water has a high enough Po(2) to drive cutaneous diffusion, allowing the frogs to extract enough O(2) to maintain aerobic metabolism, but that an ability to tolerate anoxia for several days may still be ecologically meaningful.     

Enterobacteriaceae and Aeromonas hydrophila in Minnesota frogs and tadpoles (Rana pipiens)

In 222 Rana pipiens frogs and 34 tadpoles captured in and near Minnesota, Aeromonas hydrophila and 29 species of Enterobacteriaceae, including yersinia enterocolitica and Salmonella arizonae, were isolated from intestines. The prevalence of members of the family Enterobacteriaceae was lowest in frogs captured in early spring and highest in frogs captured in late summer.     

Phosphate metabolism during muscular contraction in starved frogs (Rana catesbeiana)

• 1.1. The muscle tension and the state of high-energy phosphate metabolism during contraction of the sartorius muscle in frogs (Rana catesbeiana) starved for 1–5 months was studied by in vivo³¹P-NMR spectrometry.
• 2.2. Muscle tension began to decrease after 2-month starvation compared with the control group and decreased to about one-third of the control value after a 5-month starvation.
• 3.3. Muscle contraction induced by electrical stimulation or the use of anaerobic perfusion fluid did not decrease the concentration of creatine phosphate (PCr) or β-ATP, and only negligibly changed the PCr/Pi ratio from starvation.
• 4.4. These results suggest a decrease in creatine kinase activity in the muscle of starved frogs.

     

Intracelomic use of tricaine methanesulfonate for anesthesia of bullfrogs (Rana catesbeiana) and leopard frogs (Rana pipiens)

The use of intracelomic injection of dissolved tricaine methanesulfonate (MS-222) as an anesthetic agent in two anuran species was studied. Intracelomic MS-222, at dosages of 100, 250, and 400 mg/kg, rapidly induced tranquilization or anesthesia. Effects were less pronounced or nonexistent at the 50 mg/kg dosage. Depth and duration of anesthesia were dosage related. At the 100, 250, and 400 mg/kg dosages, Rana pipiens attained a greater depth of anesthesia and remained anesthetized for a significantly greater duration than did R. catesbeiana. Dosages of between 250–400 mg/kg reliably induced deep anesthesia without mortality in bullfrogs. Dosages of less than 250 mg/kg are recommended for leopard frogs, since variable mortality was noted with higher dosages. Solubilized tricaine methanesulfonate did not cause gross or histopathological lesions to celomic tissues. Tricaine methanesulfonate injected intracelomically can provide rapid, efficient anesthesia in some anuran species. However, due to the observed intra- and interspecies variation in effect, it should be used cautiously, especially in unfamiliar species. © 1992 Wiley-Liss Inc.     

The effects of blinding,pinealectomy and exposure to constant dark conditions on gonadal activity in the female goldfish,Carassius auratus

Synopsis The effects of pinealectomy, blinding, and exposure to constant darkness were examined in female goldfish during different seasons. Neither blinding nor pinealectomy under short or decreasing photoperiod conditions, nor exposure to constant darkness had an effect on ovarian activity in goldfish during fall and winter. In spring, constant darkness has an inhibitory effect on ovarian activity. Pinealectomy under increasing photoperiod conditions partially inhibits reproductive activity, but not to the extent of constant darkness. Blinding, under the same regime also inhibited to some extent the ovarian response to increasing photoperiod. Our data suggest that retinal pathways and the pineal organ are involved in the photosexual response to increasing day lengths.Address correspondence to: Dr. V. L. de Vlaming, Marquette University     

Plasma aldosterone concentrations in wild and captive western spotted frogs (Rana pretiosa)

Plasma aldosterone concentration (1.33 ± O.10 ng/ml) was substantially lower in a wild population of Rana pretiosa than in frogs from the same population held in captivity for three weeks (4.48 ± 0.55 ng/ml). The aldosterone value for the wild population was much lower than circulating levels previously reported for laboratory amphibians but higher than those reported for other vertebrates.     

Echinostome infection in green frogs (Rana clamitans) is stage and age dependent

The increasing threat of emerging infectious diseases in both wildlife and humans has spurred interest in the causes of disease emergence, including the role of anthropogenic change. A prior field study of infection patterns in amphibians suggests that echinostome infection may be an emerging disease of green frogs Rana clamitans living in urbanized environments. We examined the impact of echinostome infection on green frog tadpoles at a wide range of developmental stages (Gosner stage 25–39). Echinostome infection was associated with green frog mortality rates of up to 40% in an early developmental stage, and none in later developmental stages. Tadpoles exposed to higher echinostome doses exhibited higher edema rates, a potential sign of compromised renal function. Histopathological analysis further supported the hypothesis that echinostome-induced tadpole mortality resulted from compromised renal function. Given that the timing of highest cercarial shedding can coincide with the most vulnerable stages of green frog tadpole development, echinostomes could significantly impact green frog survival in nature.     

Pathophysiology in mountain yellow-legged frogs (Rana muscosa) during a chytridiomycosis outbreak

The disease chytridiomycosis is responsible for declines and extirpations of amphibians worldwide. Chytridiomycosis is caused by a fungal pathogen (Batrachochytrium dendrobatidis) that infects amphibian skin. Although we have a basic understanding of the pathophysiology from laboratory experiments, many mechanistic details remain unresolved and it is unknown if disease development is similar in wild amphibian populations. To gain a better understanding of chytridiomycosis pathophysiology in wild amphibian populations, we collected blood biochemistry measurements during an outbreak in mountain yellow-legged frogs (Rana muscosa) in the Sierra Nevada Mountains of California. We found that pathogen load is associated with disruptions in fluid and electrolyte balance, yet is not associated with fluctuations acid-base balance. These findings enhance our knowledge of the pathophysiology of this disease and indicate that disease development is consistent across multiple species and in both laboratory and natural conditions. We recommend integrating an understanding of chytridiomycosis pathophysiology with mitigation practices to improve amphibian conservation.     

Interspecific spawning between Common frogs (Rana temporaria) and Common toads (Bufo bufo)

The interaction between Common frogs (Rana temporaria) and Common toads (Bufo bufo) during the breeding season was studied at a small pond on Portland, Dorset. Although the frogs started and finished spawning earlier than the toads there was a period during which interspecific spawning between female toads and male frogs took place. This appears to have resulted from reduced male toad activity caused by the cold breeding season given that spatial, temporal and behavioural species separation did not occur.     

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.