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.     

Helminth communities of green frogs Rana clamitans Latreille, from southwestern Michigan.

A total of 239 green frogs Rana clamitans, collected between June 3 and August 27, 1998 from 6 locations in southwestern Michigan, was examined for helminths. Of the 26 helminth taxa found, the larval cestode Mesocestoides sp. had the highest mean intensity, followed by the larval trematode Fibricola sp. Of the helminths that mature in frogs, Haematoloechus varioplexus had the highest prevalence and Gorgodera amplicava had the highest mean intensity. Frogs from 118th Pond had the highest species richness (20), mean helminth species richness (5.2), and mean helminth abundance (153.7). Frogs from Constantine East had the highest mean helminth species diversity (0.8778) and evenness (0.6033), followed by frogs from 118th Pond. In all comparisons of mean helminth community species richness, abundance, diversity, and evenness, adult frogs had significantly higher or higher values than did juveniles at each location. Jaccard's coefficients of similarity for the helminth communities for location pairs ranged from 0.545 to 0.823. Nine and 2 core helminth taxa occurred at the local and regional levels, respectively. The differences in several helminth community measures in green frogs among locations stress the importance of local ecological conditions on helminth community structure.     

Helminth infracommunities of the frogs Rana catesbeiana and Rana clamitans from Turkey Marsh, Michigan

One hundred twenty-seven bullfrogs, Rana catesbeiana, and 120 green frogs, Rana clamitans, collected in July and August 1987 from Turkey Marsh, Michigan, were examined for helminths. Of the 16 helminth species found, Falcaustra catesbeianae had the highest prevalence and mean intensity in bullfrogs. In green frogs, Megalodiscus temperatus had the highest prevalence and Haematoloechus parviplexus had the highest mean intensity. Taxonomically, 1,030 (30.5%) trematodes and 2,348 (69.5%) nematodes occurred in bullfrogs; 2,874 (96.4%) trematodes, 2 (0.1%) cestodes, and 105 (3.5%) nematodes were found in green frogs. The larger and more aquatic of the 2 hosts, R. catesbeiana, had the highest mean number of helminth species, helminth intensity, diversity, and evenness. Adult frogs of both species had a significantly higher mean number of helminth species than did juveniles. Significant correlations existed between the number of helminth species and frog length. Although the helminth communities of Turkey Marsh frogs are isolationist in character, they are more diverse than other helminth communities studied in amphibians.     

Growth and development of larval northern cricket frogs (Acris crepitans) in relation to phytoplankton abundance

SUMMARY. 1. Tadpoles of Acris crepitans were collected from two ponds in central Illinois, Depth, water temperature, distance from shore and water samples were taken at each sample site. The potential for food limitation and non-random habitat selection were examined.
2. Algal densities from water samples averaged over 1.0× 10⁶ cells ml⁻¹ in Scott's pond hut only 4.6×10³ cells ml⁻¹ in Vic's pond.
3. Guts of tadpoles from Scott's pond contained more algal cells than did guts of tadpoles from Vic's pond. Tadpoles from Scott's pond were consistently larger and more advanced in development than tadpoles collected from Vic's pond at the same lime. Therefore, tadpoles of Scott's pond were able to utilize the higher algal densities whereas tadpoles of Vic's pond may be food-limited, causing reduced growth and development.
4. Canonical discriminant analysis was used to test whether sites with different numbers of tadpoles could be distinguished based on environmental variables. Canonical function I was primarily a measure of water depth at a sample site. This function was significant in Scott's pond only. Sites containing one or more tadpoles were not easily distinguished from each other, but were found in consistently shallower water than sites where no tadpoles were found.     

Echinostome metacercariae cyst elimination in Rana clamitans (green frog) tadpoles is age-dependent

Host response to parasite exposure is an important determinant of the outcome of host-parasite interactions. Factors such as host body condition and age can strongly influence host response to parasites and infection. This study followed Echinostoma revolutum infection levels in larval green frogs (Rana clamitans) exposed at 2 different ages. Tadpoles at early developmental stages are more susceptible to the adverse effects of echinostomes. Green frog tadpoles approximately 2 wk apart in age and of the same developmental stage can exhibit dramatically different responses to echinostome infection, with the younger tadpoles having high rates of mortality and the older tadpoles experiencing no mortality. The goal of the present study was to begin to explore the mechanism underlying the striking age-dependent response of tadpoles to echinostomes. I conducted 2 controlled infection laboratory experiments in which tadpoles were preserved at 6 time points ranging from 4 hr to 1 wk postinfection (PI). Tadpoles infected at the younger age did not eliminate echinostome metacercariae. However, tadpoles that were 13 days older at the time of echinostome exposure steadily eliminated metacercariae during the hours and days PI. The absence of echinostome cyst elimination in the younger tadpoles likely contributes to their elevated, infection-induced mortality rates.     

Meiotic chromosomes of green frogs (Rana esculenta complex) of the Ukraine territory

In this work meiotic chromosomes of R. ridibunda, R. lessonae and their hybrid form R. esculenta of the Ukraine territory are described for the first time. These chromosomes are connected in diakinesis more often by two chiasma, rarely by one or three chiasma in 13 bivalents. Bivalents with one chiasma in R. ridibunda are typical only for large bivalents, in R. lessonae only for small ones. Three chiasma in parental species are typical only for small bivalents. In the hybrid form R. esculenta chromosomes with two, one and three chiasma are typical both for large bivalents, and for small ones. In the hybrid form (R. esculenta) chiasma frequency noticeably decreases, comparatively with parental species that, possibly, specifies the aberration of normal meiosis realization. The chiasma frequencies of the hybrid form of the eastern and the southern parts of Ukraine are almost the same, but the types of chromosomes are different in such regions. In the eastern region chromosomes of the hybrid form are represented by two or one chiasma, in the southern region by two, one or three chiasma.     

Kin recognition by larval wood frogs (Rana sylvatica): effects of diet and prior exposure to conspecifics

Summary We investigated kin recognition by larval wood frogs (Rana sylvatica) in blind laboratory experiments using spatial affinity as a recognition assay. Tadpoles reared with full-sibs displayed a significant preference for familiar full-sibs over unfamiliar non-kin, but failed to discriminate between unfamiliar full-sibs and unfamiliar paternal half-sibs. Tadpoles reared in social isolation (with or without maternal egg jelly) from the two-celled embryonic stage displayed a significant preference for unfamiliar full-sibs over unfamiliar non-kin. Tadpoles reared on a meat diet with their full-sibs: 1) exhibited a significant preference for unfamiliar full-sibs fed meat over unfamiliar non-kin fed meat, 2) failed to discriminate between unfamiliar full-sibs fed lettuce and unfamiliar non-kin fed meat, 3) exhibited a significant preference for unfamiliar non-kin fed meat over unfamiliar non-lin fed lettuce, 4) failed to discriminate between unfamiliar full-sibs fed meat and unfamiliar full-sibs fed lettuce, and 5) displayed a significant spatial preference for odors associated with meat (a familiar food) over odors associated with lettuce (an unfamiliar food). Our results, together with those of Cornell et al. (1989), indicate that the recognition cue of larval R. sylvatica has both genetic and environmental (dietary) components. Our findings establish that previous exposure to maternal egg jelly, kin, or conspecifics is not necessary for the development of kin recognition ability in larval R. sylvatica. Our results are more consistent with the self-learning of recognition cues (a form of phenotype matching) than with a recognition mechanism that involves a genetically fixed recognition template. Finally, our results indicate that increasing similarity between the recognition template and perceived cue does not necessarily result in increasing spatial affinity for kin.     

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.     

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.     

Metamorphic changes in the vagal innervation to the alimentary tract in the green frog, Rana clamitans (Ranidae).

The alimentary tract of typical anurans shortens extensively at metamorphosis, when the microphagous tadpole transforms into a macrophagous frog. We used methylene blue vital stain and Sihler stain, in conjunction with microdissection, to map the distribution of the gastric branch of the vagus nerve in green frogs (Rana clamitans) before and after metamorphosis. After metamorphosis, terminal divisions of the gastric branch can be observed on the tunica musculosa extending as far as the pylorus. In the tadpole, the gastric branch ends abruptly on the esophagus. The premetamorphic pattern of innervation is consistent with the absence of digestive activity in the foregut before metamorphosis. Preliminary experiments, involving stimulation of the gastric branch of the vagus in the tadpoles, confirm the anatomical observation of the absence of vagal innervation before metamorphosis.     

Interaction of an insecticide with larval density in pond-breeding salamanders (Ambystoma)

1. Amphibian populations residing in or near agricultural areas are often susceptible to pesticide contamination. Recent evidence suggests that the effects of pesticides on amphibians often exceed those estimated in laboratory toxicity tests because other environmental factors (e.g. predators, resource abundance) can influence pesticide toxicity. 2. To examine the effects of an insecticide (carbaryl) on two species of Ambystoma salamanders experiencing the natural stress of competition, we manipulated chemical concentration (control, 3.5 and 7.0 mg L^?1) and larval density (low and high). We determined the effect of treatments on snout‐vent length (SVL), growth rate, lipid reserves, time to metamorphosis, per cent survival and per cent metamorphosis. 3. Carbaryl negatively affected all response variables of Ambystoma maculatum significantly, and significantly reduced survival and metamorphosis of A. opacum. Increased density significantly influenced SVL, lipid reserves, growth rate and metamorphosis of A. maculatum. 4. The effects of carbaryl and increased density on per cent metamorphosis were nearly additive, but were generally less than additive on other variables. 5. The negative effects of chemical contamination on salamanders were likely because of pesticide‐induced reductions of food resources, as zooplankton abundance decreased by as much as 97% following carbaryl application. 6. Our study demonstrates the importance of the interactive effects that chemical contamination and natural environmental factors have on salamanders.     

The genetic asymmetry of the hybrid green frogs Rana esculenta (Amphibia: Ranidae) complex of Ukraine

Research of the alleles of the species-specific genes in the gametal cells of Rana kl. esculenta hybrids proved the existence of three local populations within the territory of Ukraine. Their hybrids reject either the genome of lake frog (Danube lowland), either the previous one or another one genome (basin of Severskiy Donets river), either the genome of pond frog (the residuary territory of the areal). The research of skin transplants rejection of hybrids' parental species has shown that despite the orientation of genome elimination of this population the graft of lake frog always starts identifying and rejecting earlier. That is why the genetic skewness of hybrids becomes apparent at the skin level and corresponds to its manifestations at the organism level.     

Growth, maturation and survival of frogs Rana temporaria L.

A total of 1560 breeding frogs were collected in three consecutive years at sites in the west of Ireland. Alt were weighed and measured and the ages of 702 individuals were determined by skeletochronology. The length-weight relationship differed between gravid females, spent females and males, with the gravid females showing the largest weight gain for any increase in length. The majority of males bred for the first time at two years, but most females delayed maturity until they were a year older. While the two-year olds were of similar size, the females subsequently grew at a faster rate and achieved larger maximal sizes than the males. However, both sexes exhibited a decelerating growth rate with age. There was no apparent difference between the sexes in post-maturation survival, which was estimated to be about 50% annually. The oldest frogs were seven years old.     

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.     

Purification and characterization of antimicrobial peptides from the skin of the North American green frog Rana clamitans

Ten peptides with differential growth-inhibitory activity against the gram-positive bacterium, Staphylococcus aureus, the gram-negative bacterium, Escherichia coli, and the yeast Candida albicans were isolated from an extract of the skin of a North American frog, the green frog Rana clamitans. Ranatuerin-1C (SMLSVLKNLGKVGLGLVACKINKQC), ranalexin-1Ca (FLGGLMKAFPALICAVTKKC), ranalexin-1Cb (FLGGLMKAFPAIICAVTKKC), ranatuerin-2Ca (GLFLDTLKGAAKDVAGKLLEGLKCKIAGC KP), and ranatuerin-2Cb (GLFLDTLKGLAGKLLQGLKCIKAGCKP), are members of three previously characterized families of antimicrobial peptides, first identified in the North American bullfrog Rana catesbeiana. In addition, five structurally related peptides (temporin-1Ca, -1Cb, -1Cc, -1Cd, and -1Ce), comprising 13 amino acid residues and containing a C-terminally alpha-amidated residue, belong to the temporin family first identified in the European common frog Rana temporaria. Peptides belonging to the brevinin-1, brevinin-2, esculentin-1, and esculentin-2 families, previously isolated from the skins of Asian and European Ranid frogs, were not identified in the extract. The data support the hypothesis that the distribution and amino acid sequences of the skin antimicrobial peptides are valuable tools in the identification and classification of Ranid frogs.