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.     

Response to pinealectomy and blinding in vitellogenic female frogs (Rana perezi) subjected to high temperature in autumn

The present experiments were carried out to investigate the effects of pinealectomy and bilateral enucleation on the ovarian activity in Rana perezi frogs maintained in 12-h light--12-h dark photoperiod and 20 +/- 1 degrees C during the vitellogenetic growth in late autumn. These environmental conditions, mainly temperature, induce a gonadal and metabolic response similar to that observed in the natural habitat in summer: a marked ovarian follicular regression, a depletion of the energetic resources from fat bodies and liver, and a minimum in oestradiol circulating levels. This response is partially blocked by pinealectomy and blinding. Protein phosphorus, as an index of vitellogenic proteins, and total ovary lipid content were significantly higher in pinealectomized and blinded frogs with respect to sham-operated animals. Likewise, oestradiol concentrations showed a significant increase during the dark phase of the daily photocycle in pinealectomized and blinded animals. From our results, we can suggest that the arrest of vitellogenesis, the depletion of energetic resources, and the regulation of oestradiol levels induced by the high temperature in Rana perezi frogs can be influenced, at least in part, by the pineal complex and lateral eyes.     

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.     

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.     

Phylogeny of the New World true frogs (Rana)

Phylogenetic relationships among the species of true frogs (Rana) from North, South, and Central America were investigated based on the sequences of approximately 2 kb from the mitochondrial genome, sampled from most of the described species, as well as eight undescribed species. This analysis, combined with previous studies of the phylogeny of New World Rana, served as the basis for a revised classification of the group. The American species of Rana are not monophyletic; the western North American Amerana is more closely related to the R. temporaria group of Eurasia (together, these frogs form the group Laurasiarana). The remaining species from the Americas form the monophyletic group Novirana, which includes: R. sylvatica; Aquarana (the R. catesbeiana group); Ranula (the R. palmipes group, including the mostly upland Levirana species and the mostly lowland Lithobates species); Torrentirana (the R. tarahumarae group, or Zweifelia, plus R. sierramadrensis), Stertirana (the R. montezumae group, or Lacusirana, plus R. pipiens), Nenirana (the R. areolata group), and Scurrilirana (most of the southern and tropical leopard frogs). The mitochondrial sequences supported many of the previous hypotheses of relationships of New World Rana, although there were some differences involving the placement of the species R. pipiens, R. sierramadrensis, and R. sylvatica. Parametric bootstrap analyses indicated significant support for the relationships inferred from the mtDNA sequences, and rejected the previous hypotheses of relationships for these three species.     

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.     

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 and development of larval green frogs (Rana clamitans) exposed to multiple doses of an insecticide

Our objective was to determine how green frogs (Rana clamitans) are affected by multiple exposures to a sublethal level of the carbamate insecticide, carbaryl, in outdoor ponds. Tadpoles were added to 1,000-l ponds at a low or high density which were exposed to carbaryl 0, 1, 2, or 3 times. Length of the larval period, mass, developmental stage, tadpole survival, and proportion metamorphosed were used to determine treatment effects. The frequency of dosing affected the proportion of green frogs that reached metamorphosis and the developmental stage of tadpoles. Generally, exposure to carbaryl increased rates of metamorphosis and development. The effect of the frequency of carbaryl exposure on development varied with the density treatment; the majority of metamorphs and the most developed tadpoles came from high-density ponds exposed to carbaryl 3 times. This interaction suggests that exposure to carbaryl later in the larval period stimulated metamorphosis, directly or indirectly, under high-density conditions. Our study indicates that exposure to a contaminant can lead to early initiation of metamorphosis and that natural biotic factors can mediate the effects of a contaminant in the environment.     

Helminth communities of two sympatric skinks (Mabuya agilis and Mabuya macrorhyncha) from two "restinga" habitats in southeastern Brazil

The helminth fauna of two sympatric congeneric skinks (Mabuya agilis and M. macrorhyncha) from two distinct "restinga" habitats (Praia das Neves and Grussaí) in southeastern Brazil were studied, totalling four data sets (sample sizes ranging from 11 to 28). A total of ten helminth species were associated with the skinks: Raillietiella sp., Paradistomum parvissimum, Pulchrosomoides elegans, Oochoristica ameivae, Hexametra boddaertii, Parapharyngodon sceleratus, Physalopteroides venancioi, Physaloptera sp., an unidentified acuariid nematode and an unidentified centrorhynchid acanthocephalan. Except for Hexametra boddaertii (found only in Grussaí) and Pulchrosomoides elegans (found only in Praia das Neves), all helminth species were present at both localities. Half of the helminth species were present only as larvae and, in most cases, appear to represent paratenic parasitism. Overall prevalences of infection were high for both host species in both localities. Mabuya agilis tended to have richer and more diverse infracommunities than M. macrorhyncha. Some parameters of infection by individual helminth species seem to be related to the ecology of each Mabuya species. The parasite faunas were qualitatively very similar among species and/or localities, but quantitative similarities were more varied, due to differential representativeness of individual helminth species among host populations. The helminth communities of both skink species can be classified as non-interactive, being composed of site-specialists and immature stages of non-lizard parasites.     

Variation of BM224 microsatellite in green frogs of the genus Rana

The variable microsatellite repeat BM224 has been discovered in the genomes of eight species of green frogs (Rana ridibunda, R. cf bedriagae, R. cretensis, R. esculenta, R. lessonae, R. shquiperica, R. saharica, R. nigromaculata). Earlier, this repeat had been observed in members of the genus Bufo. In this paper, a possibility of usage of this genetic marker for species identification is discussed.     

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.     

Helminth communities of loggerhead turtles (Caretta caretta) from Central and Western Mediterranean Sea: The importance of host's ontogeny

We investigated the factors providing structure to the helminth communities of 182 loggerhead sea turtles, Caretta caretta, collected in 6 localities from Central and Western Mediterranean. Fifteen helminth taxa (10 digeneans, 4 nematodes and 1 acanthocephalan) were identified, of which 12 were specialist to marine turtles; very low numbers of immature individuals of 3 species typical from fish or cetaceans were also found. These observations confirm the hypothesis that phylogenetic factors restrict community composition to helminth species specific to marine turtles. There were significant community dissimilarities between turtles from different localities, the overall pattern being compatible with the hypothesis that parasite communities reflect the ontogenetic shift that juvenile loggerheads undergo from oceanic to neritic habitats. The smallest turtles at the putative oceanic, pelagic-feeding stage harboured only the 2 digenean species that were regionally the most frequent, i.e. Enodiotrema megachondrus and Calycodes anthos; the largest turtles at the putative neritic, bottom-feeding stage harboured 11 helminth taxa, including 3 nematode species that were rare or absent in turtles that fed partially on pelagic prey. Mean species richness per host was low (range: 1.60–1.89) and did not differ between localities. Variance ratio tests indicated independent colonization of each helminth species. Both features are expected in ectothermic and vagrant hosts living in the marine environment.     

Growth and body size in populations of mink frogs Rana septentrionalis from two latitudes

Age, longevity, and growth in mink frogs Rana septentrionalis from two latitudes in Quebec, Canada, were assessed by skeletochronological and back-calculation methods in order to document proximate causes for intraspecific variations in adult body size. In both study sites, females grew faster and were on average 11% larger than males. Mean age and maximal longevity were significantly higher in females than in males only in the southern populations. There was thus an interpopulation difference in the relative contribution of age and growth to sexual size dimorphisms. Sex-ratio also favored females (males sulfering higher mortality) only in the southern populations. Specimens from the northern population had higher mean ages (but not higher longevities) and were 17% larger than specimens from the southern populations. Annual growth rate appeared similar at the two study sites despite a shorter growing season at the northern locality. Maturity was reached by both sexes after 1 yr of post-metamorphic life (PML) in the southern populations but after 2 yr of PML in the northern population. There are indications that tadpoles metamorphose at larger body size at the northern locality after a prolonged larval period. It is concluded that growth rate, delayed maturity, greater mean ages, and eventually size at transformation, all contribute to the larger size of adult mink frogs at northern localities.     

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.     

Metazoan parasites on the gills of the skipjack tuna Katsuwonus pelamis (Osteichthyes: Scombridae) from the Alboran Sea (western Mediterranean Sea)

The gills of 31 skipjack tuna Katsuwonus pelamis (L.) caught in the Alboran Sea (western Mediterranean Sea) were examined for metazoan parasites, and the gills of 4 specimens from the Balearic Sea (also western Mediterranean Sea) were analysed for comparative purposes. Nine -species of parasites were found, including 8 didymozoid trematodes (Atalostrophion cf. bio-varium, Didymocylindrus filiformis, Didymocylindrus simplex, Didymocystis reniformis, Didymoproblema fusiforme, Didymozoon longicolle, Koellikeria sp. and Lobatozoum multisacculatum) and 1 caligid copepod (Caligus bonito). Koellikeria sp. and L. multisacculatum were not recorded in the Balearic Sea. Most of the parasites (79.2% of all specimens) were didymozoids. Didymozoon longicolle was the dominant species; A. cf. biovarium, D. simplex, D. fusiforme and L. multisacculatum are reported from the Mediterranean Sea for the first time. No correlation was found between the intensity of infection of any parasite species and host size or sex. Most of the parasites, particularly didymozoids, showed a high site-specificity. Significant differences were found between the parasite assemblages of K. pelamis from the Alboran Sea and from the Atlantic Ocean. D. fusiforme, D. longicolle and L. multisacculatum are suggested as potential tags to follow skipjack tuna migrations between the Atlantic Ocean and Mediterranean Sea.