Leptodactylus Ocellatus Research Articles

Relationship between steroidogenesis and spermiation in Rana catesbeiana and Leptodactylus ocellatus

The present study employs an in vitro system to analyse the role of steroid hormones in hCG-induced spermiation in two species of anuran amphibian: Rana catesbeiana and Leptodactylus ocellatus. In vitro spermiation was induced with 10 IU hCG and the effect of different steroid-biosynthesis inhibitors was analysed. Cyanoketone (10(-5)M), an inhibitor of 3-oxo-4-ene steroid biosynthesis, did not block hCG-inducing activity even when biosynthesis of androgen was significantly reduced. These results clearly showed that, in both species, spermiation-inducing action of hCG does not depend on the biosynthesis of 3-oxo-4-ene steroids. Moreover, when combined inhibitors, aminoglutethimide (10(-5)M) plus cyanoketone (10(-5)M), were employed, spermiation evoked by hCG was not modified while hCG-induced androgen secretion significantly decreased. Additionally, none of the steroids used, progesterone, 17, 20 alpha-dihydroxy-4-pregnen-3-one, testosterone and 5 alpha-dihydrotestosterone, were able to induce spermiation in the absence of hCG, confirming that steroids are not involved in that process. In conclusion, as previously described in Bufo arenarum, in L. ocellatus and R. catesbeiana hCG-induced spermiation does not depend on steroid biosynthesis.

Chytrid fungus parasitizing the wild amphibian Leptodactylus ocellatus (Anura: Leptodactylidae) in Argentina

The present contribution is the first report of parasitosis by a chytrid fungus in wild anuran amphibians in Argentina, as well as the first case of amphibian mortality documented to date in Argentina. We report the presence of the chytrid fungus in dead adult Leptodactylus ocellatus. It has been suggested that chytridiomycosis is the main cause of death in several amphibian populations worldwide. Our study demonstrates that chytridiomycosis afflicts L. ocellatus, a common widespread amphibian species, and is the first report of chytridiomycosis in the Argentinian lowlands. The occurrence at this latitude would indicate an extended distribution of this fungus in wildlife populations. It is also the first report of amphibian mortality due to chytrid fungus in our country. It is noteworthy that the site of collection is situated very close to sea level in a temperate climate zone and that this represents the southern most record for South American wild amphibians.

Trophic and Spatial Niches of two Large-sized Species of Leptodactylus (Anura) in Southeastern Brazil

Leptodactylus ocellatus (LO) and L. labyrinthicus (LL) are known to prey on other frogs. Here we compare their food habits based on the analysis of stomach contents and their spatial distribution when in sympatry. LO was found most frequently near stream banks, and LL on the margins of lakes and ponds. LO was found within 10 m of permanent water bodies; LL frequently used ponds far from lakes and rivers. Coleoptera, Formicidae, and Isoptera comprised 52% of the prey types identified in the LO sample, whereas Coleoptera and insect larvae represented 58% of the prey items of LL. Frogs were not frequent in the diet of either species but, in volume, represented the second most important category for LO and the first for LL. LO showed a larger trophic niche breadth than LL. The trophic niche overlap between the two species was 68.3% for percentage of prey items. The present work confirms the relative importance of frogs in the diet of both species. The greater capacity of LL in moving far away from permanent water bodies may generate better opportunities for prey selection and a narrower trophic niche breadth. The large range of prey used by these two species indicates they are generalist/opportunistic feeders.

Ocellatins: New Antimicrobial Peptides from the Skin Secretion of the South American Frog Leptodactylus ocellatus (Anura: Leptodactylidae)

The emergence, in recent years, of microbial resistance to commonly used antibiotics has aroused a search for new naturally occurring bactericidal and fungicidal agents that may have clinical utility. In the present study, three new antimicrobial peptides were purified from the electrical-stimulated skin secretion of the South American frog Leptodactylus ocellatus by reversed-phase chromatographic procedures. Ocellatin 1 (1GVVDILKGAGKDLLAHLVGKISEKV25-CONH2), ocellatin 2 (1GVLDIFKDAAKQILAHAAEKQI25-CONH2) and ocellatin 3 (1GVLDILKNAAKNILAHAAEQI21-CONH2) are structurally related peptides. These peptides present hemolytic activity against human erythrocytes and are also active against Escherichia coli. Ocellatins exhibit significant sequence similarity to other amphibian antimicrobial peptides, mainly to brevinin 2ED from Rana esculenta.

Diet of the South American frog Leptodactylus ocellatus (Anura, Leptodactylidae) in Uruguay

The diet of Leptodactylus ocellatus (L., 1758) was studied in specimens collected at Maldonado Department (Uruguay), where monthly surveys were made between August 1998 and March 2000. A total of 143 frogs were collected, measured, sexed, and dissected, to assess stomach contents. The anurans were grouped into three age classes and four categories (considering sex and capture date). The trophic amplitude for each age class and sex-season category was quantified using Shannon-Weaver Index, and the trophic niche overlap between ages and categories by using the Pianka Index. Comparisons among treatments were made by G-tests. The most important prey items were coleopterans (IRI = 2547), and significant correlations were found between predator and prey sizes. The major differences on diet composition were found between extreme age classes (froglets and adults). Significant differences were also detected between sexes in the cold season but not in the warm season. Any of these changes in diet may be related with the availability of prey.

Chromosomal studies after differential staining and fluorescence in situ hybridization using telomeric probe in three Leptodactylus species (Leptodactylidae, Anura)

Abstract Leptodactylus ocellatus, L. knudseni and L. pentadactylus were cyto-genetically analysed following conventional and Ag-NOR staining, C- and R-banding and FISH using the sequence (TTAGGG)n as probe. These species show similar karyotypes with 2n = 22 and Ag-NORs located in the short arm of pair 8. Species-specific C-banding patterns were detected involving centromeric, telomeric and interstitial bands. The comparative study of chromosomes after R-banding allowed the establishment of homeologies among the six largest pairs and the NOR-bearing pair in all species. The sequence (TTAGGG)n was detected in the telomeric regions of the chromosomes and nowhere else.

Estufas climatizadas para experimentos ambientais com rãs, em gaiolas

Foram construídas seis estufas climatizadas, instaladas inicialmente no Ranário Experimental da Universidade Federal de Viçosa e, posteriormente, no Ranário Experimental da Fundação Universidade Federal do Rio Grande, com o objetivo de realizar experimentos para avaliar os efeitos do ambiente sobre o desempenho de rãs em gaiolas de fibra de vidro. Ambientes com temperaturas de 25ºC e fotoperíodo de 12/12 horas de luz/horas de escuridão (h L/E) serviram para adaptação das rãs por 15 dias antes de cada experimento. Os tratamentos consistiram em simular ambientes com temperaturas variando de 20 a 35ºC e fotoperíodos de 8/16, 12/12 e 16/8 h L/E. Foram realizados experimentos com rã-touro (Rana catesbeiana Shaw, 1802) e rã-manteiga (Leptodactylus ocellatus Linnaeus, 1758). Nessas estufas foi possível estimar que: a) os maiores ganhos de peso de rã-touro foram obtidos entre 27,6 e 29,7ºC, com melhor crescimento entre 28,2 e 30,1ºC; para rã-manteiga os melhores ganhos e conversão alimentar foram observados a 28,6 e 28ºC, respectivamente; b) a temperatura interage com fotoperíodo sobre o desempenho das rãs e seu desenvolvimento gonadal; c) a 27,7ºC (temperatura de conforto térmico) haverá menos rãs dentro d'água; d) a maior temperatura cloacal de rã-touro, 32,1ºC no seco e 33,8ºC dentro d'água, a 35ºC, evidenciou que as rãs se termorregulam; e) os níveis de tetraiodotironina (T4) no plasma decrescem na temperatura de conforto térmico; f) rã-manteiga condiciona-se ao manejo de rotina, reunindo-se ao redor do cocho na hora da alimentação.

Caffeine-induced depolarization in amphibian skeletal muscle fibres: role of Na+/Ca2+ exchange and K+ release.

Caffeine (4 mM) produces a depolarization of about 10 mV in frog muscle fibres (Leptodactylus ocellatus). The aim of this work was to study the mechanisms of this effect. An approximately threefold rise in membrane resistance [Cl--free (SO(4)2-) medium] substantially increased, and both Na+-free medium and Ni2+ (5 mM) reduced, the caffeine-induced depolarization. In voltage-clamped (-60 mV) short fibres from lumbricalis muscle of the toad (Buffo arenarum), caffeine generated an inward current of 4.13 +/- 0.48 microA cm(-2). This caffeine-induced current was reduced by 60% in Na+-free medium, 44% in the presence of 5 mM amiloride and 48% by 5 mM Ni2+, suggesting that the activation of the Na+-Ca2+ exchanger in its forward mode may play a role in the observed electrical effects of the drug. Caffeine also produced a marked release of K+. Net K+ efflux increased from 3.5 +/- 0.2 (control) to 22.1 +/- 2.3 pmol s(-1) cm(-2) (caffeine). It is shown that in the presence of the drug, [K+] in the lumen of the T tubules may well increase to levels which could produce, in part, both the observed depolarization and the caffeine-induced current under voltage clamp conditions. The caffeine-induced K+ efflux was not reduced by 5 mM Ni2+. At a holding potential of 30 mV the caffeine-induced current was reversed (outward) and roughly halved by 5 mM Ni2+. The Ni2+-sensitive fraction of the caffeine-induced current, assumed to represent the Na+-Ca2+ exchanger current, had an estimated reversal potential close to 12 mV ([Na+]o = 115 mM; [Ca2+]o = 1 mM). In conclusion, the depolarizing effect of caffeine described here would be produced by two mechanisms: (a) an inward current generated by the activation of the Na+-Ca2+ exchanger in its forward mode, and (b) the rise of the external [K+] in restricted spaces like the T tubules.

First record of <i>Leptodactylus ocellatus</i> (Linnaeus, 1758) (Amphibia, Anura, Leptodactylidae) in Bolivia and comments on related species

The distributions of Leptodactylus ocellatus, L. chaquensis , and L. macrosternum in Bolivia are reviewed and discussed. Leptodactylus chaquensis and L. ocellatus are easily distinguished morphologically but L. chaquensis and L. macrosternum are indistinguishable. In Bolivia, L. ocellatus is known only from a single locality in the Paraguay River basin, which is reported here for the first time. Leptodactylus chaquensis occurs in the Chaco region of southeastern Bolivia, but it is unknown to what extent this species enters the Cerrado. The distribution boundaries and putative overlapping areas of L. chaquensis and L. macrosternum are unknown.

Changes in Plasma Sex Steroids in Females of Two Sympatric Leptodactylus from Subtropical South America

Changes in Plasma Sex Steroids in Females of Two Sympatric Leptodactylus from Subtropical South America

Characteristics of Na(+)-Ca2+ exchange in frog skeletal muscle.

1. Fluxes studies were carried out to investigate the Na(+)-dependent outward movement of Ca2+ in intact frog sartorius muscle from Leptodactylus ocellatus, a preparation for which published data on the subject are sparse. 2. Under normal resting conditions the Na(+)-Ca2+ exchange was not readily detectable. 3. When muscles were exposed to 4 mM caffeine, the rate of fractional loss of Ca2+ (kCa,o) increased by about 50%. Most of this increase exhibits characteristics typical of the Na(+)-Ca2+ antiport working in the forward mode found in other cells. 4. The increase in kCa,o promoted by caffeine was decreased by: (a) 72% in the absence of external Na+ (Nao+); (b) 73% in Na(+)-loaded muscles ([Na+]i = 98 mM); (c) 70% when fibres were depolarized to -27 mV ([K+]o = 50 mM); and (d) 80% in the presence of 5 mM amiloride. 5. Ni2+ (5 mM), an inhibitor of the Na(+)-Ca2+ exchanger current, unexpectedly increased the caffeine-promoted rise in kCa,o. This effect of Ni2+ was associated with a concomitant caffeine-stimulated Ni2+ influx. In the absence of caffeine Ni2+ did not affect kCa,o. 6. It was concluded that: (a) under resting conditions the sarcolemmal Ca2+ pump suffices to handle the cytosolic calcium concentration ([Ca2+]i); (b) Na(+)-Ca2+ activity becomes apparent when [Ca2+]i is substantially increased by caffeine-induced Ca2+ release from the sarcoplasmic reticulum; and (c) the blocking effect of Ni2+ on the current generated by a Na(+)-Ca2+ exchange with a coupling ratio > 2 might actually represent a shift of the antiport mode toward an electroneutral 1 Ni(2+)-1Ca2+ exchange.

Contribución al conocimiento de la alimentación de larvas de la rana criollaLeptodactylus ocellatus(Amphibia, Leptodactylidae) en el Paraná medio, Argentina

The object of this work was to analyse in a quali‐quantitative way the composition of tadpoles’ diet of Leptodactylus ocellatus by studying the content of their intestines. Twenty digestive tubes were individually analyzed. Their content of feeding items was identified and quantified applying Lackey's Drop Microtransect Counting Method (1938). It allowed the calculation of the percentual‐size relation as well as occurrence frequency. The results show that L. ocellatus’ diet is mainly composed of diatoms and green algae, detritus and plant residues.

Revision of the Brazilian species of the genus Halipegus Looss, 1899 (Trematoda: Derogenidae)

Halipegus dubius Klein, 1905 is redescribed and illustrated from a Brazilian frog Leptodactylus ocellatus. The type-material of Halipegus genarchella (Travassos, Artigas & Pereira, 1928) and Halipegus parva (Travassos, Artigas & Pereira, 1928) are redescribed with original figures. New synonyms are proposed: Halipegus salmini Yamaguti, 1958 is considered a synonym of H. genarchella, H. tropicus (Manter, 1936) sensu Kloss (1966) of H. parva and Genarchella lenti Fabio, 1984 of H. overstreeti (Brooks, Mayes & Thorson, 1979) n. comb.

Studies on the urinary nitrogen waste products in south american anurans from different habitats

1. 1. Urinary nitrogen waste excretion and urea concentration in plasma of juvenile Bufo arenarum and adult Bufo arunco, Bufo fernandezae and Leptodactylus ocellatus were studied; they are terrestrial, cave dweller and semi-aquatic species, respectively. 2. 2. The urinary NH3-N, urea-N and uric acid-N, and plasma urea concentration were measured in samples from animals fasted for 15 days and acclimated at constant temperature over 4 days before sampling. 3. 3. The percentages of urinary urea-N, ammonia-N and uric acid-N were 95.3, 4.3 and 0.12 for Bufo arenarum; 95.0, 5.0 and not determined for B. arunco; 95.3, 4.6 and 0.09 for B. fernandezae; and 91.1, 8.9 and 0.08 for L. ocellatus, respectively. 4. 4. The percentage of urinary nitrogenous compounds was shown to be independent of the habitat and of the body weight of the animals. 5. 5. Plasma urea concentration (in mM) and the U/P ratios were: 19.8 and 1.8 ( B. arenarum); 37.9 and 1.6 ( B. arunco); 19.3 and 1.8 ( B. fernandezae) and 7.6 and 5.2 ( L. ocellatus), respectively.

The in vivo effect of low body temperatures on the degree of polymerization of tubulin in brain and testes: A comparison among some species of vertebrates

1. 1. The tubulin of both brain and testes of the amphibian Bufo spinulosus, Leptodactylus ocellatus and Odontophrynus occidentalis and of the fish Salvelinus fontinalis were partially depolymerized when the animals were maintained on ice for 90 min. 2. 2. Recovery of the animals at room temperature restored the normal degree of polymerization in both organs. 3. 3. The cerebral tubulin of the saurian Phymatura palluma and of the mammalian Myotis chiloensis instead, were not depolymerized in these conditions. 4. 4. The results suggest that the depolymerization in vivo of tubulin by lowering body temperature at 0–2°C, is common to many, but not all species of vertebrates. 5. 5. The existence of a cold stabilizing factor in the brain of some species is suggested. A comparison is made between these results and those of other authors who observed microtubule disaggregation by cold with the electron microscope.

Diet and Foraging Mode of Bufo marinus and Leptodactylus ocellatus

The relationships between foraging mode and diet were investigated for two large nocturnal anurans, Bufo marinus and Leptodactylus ocellatus. The results agree with generalizations derived from studies of diurnal leaf-litter frogs in that the bufonid forages more widely and eats more social insects than the leptodactylid. However, the morphologies of the species and sizes of prey eaten did not fit the generalizations. These relationships may be habitat specific.

Cell mediated immune response of Bufo arenarum and Leptodactylus ocellatus (amphibia, anura) to mycobacterial antigens

1. l. The lymphocyte transformation test was applied to the study of cell mediated immune (CMI) response in vitro to mycobacterial antigens in Bufo arenarum and Leptodactylus ocellatus previously inoculated with a suspension of Mycobacterium tuberculosis. 2. 2. The stimulated samples of blood both in B. arenarum and L. ocellatus showed a significant increase in the percent of blastic dedifferentiation (almost 100% with respect to controls) suggesting the presence of a positive CMI response to PPD. 3. 3. The differences were observed on the fifth day of incubation and lasted until the seventh day.

A comparative study of lecithin:cholesterol acyltransfer in plasma of five species of amphibians from Northeast Brazil

1. 1. Lecithin:cholesterol acyltransfer (LCAT) was studied radiochemically in plasma from five species of Salienta, Bufo paracnemis, B. granulosus, Rana palmipes, Hyla raniceps and Leptodactylus ocellatus. 2. 2. Large inter- and intra-species variations in plasma LCAT activity were observed but activity correlated significantly with plasma triglyceride concentrations. 3. 3. The effects of pH and inhibitors on LCAT activity in amphibian plasma were similar to those described for mammalian plasma. 4. 4. Storage at −15°C for several weeks reduced LCAT activity in amphibian plasma but not in human plasma. 5. 5. Cholesteryl esters synthesised by LCAT were predominantly monoenoic in plasma of Bufo species and polyenoic in plasma of other species.

Studies on chloride permeability of the skin of Leptodactylus ocellatus: I. Na+ and Cl- effect on passive movements of Cl-.

The outflux of chloride through the isolated skin (JCl31) of the South American frog Leptodactylus ocellatus (L.) is carried by a mechanism that saturates at high concentration of chloride on the inside, and is stimulated by the presence of Cl- in the outer solution (trans side). The presence of Na+ on the outside, by itself, does not increase JCl31. However, when JCl31 is already increased by chloride on the trans side, the addition of Na+ produces a significant further increase. At low concentration of Cl- on the outside JCl31 is carried by an exchange diffusion mechanism. At high concentrations of Cl- outside, JCl31 proceeds through a route which involves changes in electrical parameters. The results suggest that both mechanisms are located on the cell membranes and, therefore, that the fluxes would cross through the cytoplasm of the cells. Na+ stimulates the second mechanism only.

Studies on chloride permeability of the skin of Leptodactylus ocellatus: II. Na+ and Cl- effect of inward movements of Cl-.

At low concentration (1 mM) of Cl- in the outer solution, the influx of chloride through the isolated skin (JCl13) of the South American frog Leptodactylus ocellatus (L.) seems to be carried by two mechanisms: (i) a passive one that exhibits the characteristics of an exchange diffusion process, and (ii) an active penetration. Studies of the influx and efflux of chloride (JCl13 and JCl31) indicate that the presence of a high (107 mM) concentration of Cl- in the outer solution activates the translocation of this ion through the cells. Studies of the unidirectional flux of Cl- across the outer barrier (JCl12) indicate that Na+ out stimulates the penetration of Cl- at this level. Cl- out, in turn, stimulates the JNa12, but this effect is only detected at low concentrations of Na+ out.