Interspecific variation in the emetic response of anurans

1. The emetic response of seven species (four genera) of frogs to apomorphine hydrochloride, copper sulfate, antimonyl potassium tartrate and mechanical stimulation at the esophageal orifice was surveyed. Xenopus laevis and Rhacophorus schlegelii were more sensitive to systemically administered apomorphine than were the other species tested.2. The sensitivity of Rana rugosa to apomorphine varied with the season.3. All of the species showed vigorous vomiting behavior after the oral administration of either copper sulfate or antimonyl potassium tartrate.4. Mechanical stimulation also induced vomiting in all species. Although the species differed in sensitivity to the different emetic stimulants, the adaptive significance of this interspecific variation is not known.5. From the stand point of the mechanics for ejecting gastric contents, there is little difference between frogs and mammals.6. Frogs, particularly Xenopus laevis, may be a useful non-mammalian model for studying emesis.     

Auditory processing in anurans.

Anurans (frogs and toads) represent an example of peripheral specialization of the auditory systems. Their inner ear contains two distinct auditory organs: the amphibian papilla and the basilar papilla. Each organ is tuned to different species-specific frequency ranges. Because of this peripheral specialization, anurans offer an excellent opportunity to explore neural decoding of complex sounds in the central auditory system.     

Basidioboliasis in anurans in Florida

Members of the genus Basidiobolus, a saprophytic fungus, have been associated with the digestive tracts of a wide variety of amphibians and reptiles. To elucidate the relationship of Basidiobolus sp. with amphibians in central Florida (USA), we document the occurrence of the fungus in the digestive tracts of Bufo terrestris, Buffo quercicus, Hyla femoralis, Hyla cinerea, Hyla gratiosa, Hyla squirella, Osteopilus septentrionalis, and Rana utricularia. Species that occupy terrestrial habitats (B. terrestris, B. quercicus, and R. utricularis) were found to harbor Basidiobolus spp. more frequently (83, 78, and 91%, respectively) than those that occupied a more arboreal habitat (H. cinerea, H. squirella, H. femoralis, H. gratiosa, and O. septentrionalis (50, 56, 55, 56, and 70%, respectively).     

四川无尾两栖类的繁殖模式

依据Duellman和Trueb(1986)的定义,对四川无尾两栖动物的繁殖模式多样性进行了研究。研究结果如下:(1)73种四川无尾类可以划分为2类共5种繁殖模式。水内产卵是比较原始的一类繁殖模式,又分2种:静水产卵(模式1)和流水产卵(模式2),68种(93%)是在水内产卵;水外产卵是较进化的一类繁殖模式,又分3种:卵产在近水塘的泥窝中(模式12),卵泡产在近水域的土穴中(模式21)和卵泡产在近水域的树上或灌丛上(模式23),仅5种(7%)在水外产卵。(2)模式1、12、21、23的两栖动物,雌雄性的体型较模式2的物种为小,产卵的数量大,但卵径较小;蝌蚪的生态表型均可归入静水型,共同特点是蝌蚪体型小,在静水中觅食,生长发育快。模式2的两栖动物,雌雄性的体型较大,产卵的数量少,而卵径较大;蝌蚪的生态表型可归入流水型,特点是蝌蚪体型大,在流水中觅食,生长发育慢。(3)水内产卵的两栖动物的窝卵能量投入方式可以分为两种:静水产卵(模式1)的物种通过增加卵的数量来增加投入,接近于r-选择物种;流水产卵(模式2)的物种通过增大卵径来增加投入,接近于k-选择物种;是两种适应不同环境条件的的繁殖策略。     

Sexual size dimorphism in anurans

Several hypotheses have been proposed to explain the direction and extent of sexual size dimorphism in anurans (in which males are usually smaller than females) as a result of sexual selection. Here, we present an analysis to test the hypothesis that sexual dimorphism in anurans is largely a function of differences between the sexes in life-history strategies. Morphological and demographic data for anurans were collected from the literature, and the mean size and age in each sex were calculated for 51 populations, across 30 species and eight genera. Comparisons across 14 Rana species, eight Bufo species and across the genera showed a highly significant relationship between size dimorphism, measured using the female-male size ratio, and mean female-male age difference. A comparison of a subset of 17 of these species for which phylogenetic information was available, using the method of independent contrasts, yielded a similar result. These results indicate that most of the variation in size dimorphism in the anura can be explained in terms of differences in the age structure between the sexes in breeding populations. If sexual selection has an effect on size dimorphism in anurans, it is likely to be only a secondary one.     

Patterns of fluctuating asymmetry in the limbs of anurans

It has been hypothesized that fluctuating asymmetry (FA) may provide an indication of the functional importance of structures within an organism, with structures that more strongly impact fitness being more symmetric. Based on this idea, we predicted that for tetrapods in which the forelimbs and hindlimbs play an unequal role in locomotion, the less functionally important limb set should display higher levels of FA. We conducted a multispecies test of this hypothesis in anurans (frogs and toads), whose saltatory locomotor mode is powered by the hindlimbs. We also tested whether FA in the forelimbs, which play a more important role during landing, differed between families that differ in the degree of forelimb use in locomotion (Bufonidae vs. Ranidae). We calculated FA from the lengths of humeri and femora measured from disarticulated skeletal specimens of four anuran taxa (Bufonidae: Anaxyrus americanus, Rhinella marina; Ranidae: Lithobates catesbeianus, Lithobates clamitans). Our findings were consistent with the hypothesis that natural selection for increased locomotor performance may influence patterns of FA seen in vertebrate limbs, with all species displaying lower mean FA in the hindlimbs. More subtle functional roles between the forelimbs of bufonids and ranids, however, did not elicit different levels of FA.     

Interspecific variation in the emetic response of anurans.

1. The emetic response of seven species (four genera) of frogs to apomorphine hydrochloride, copper sulfate, antimonyl potassium tartrate and mechanical stimulation at the esophageal orifice was surveyed. Xenopus laevis and Rhacophorus schlegelii were more sensitive to systemically administered apomorphine than were the other species tested. 2. The sensitivity of Rana rugosa to apomorphine varied with the season. 3. All of the species showed vigorous vomiting behavior after the oral administration of either copper sulfate or antimonyl potassium tartrate. 4. Mechanical stimulation also induced vomiting in all species. Although the species differed in sensitivity to the different emetic stimulants, the adaptive significance of this interspecific variation is not known. 5. From the stand point of the mechanics for ejecting gastric contents, there is little difference between frogs and mammals. 6. Frogs, particularly Xenopus laevis, may be a useful non-mammalian model for studying emesis.     

Conservation biogeography of anurans in Brazilian Cerrado

The increasing rates of declines in anuran populations worldwide are creating demands for urgent strategies to maximize conservation efforts. This may be critical in regions for which few detailed data on diversity, abundance and distribution are available, such as in the Cerrado of Central Brazil. In this paper, we used a macroecological approach based on the extent of occurrence of 131 species of Anura (Amphibia) in the Cerrado region to design a regional network of potential areas that preserves all anuran species. The final network, obtained using a simulation annealing algorithm based on complementarity, has a total of 17 cells, widely distributed throughout the biome. Minimum costs solutions were obtained in respect to total human population size, soybean production and bovine density, because these are the factors associated with human occupation that historically are more likely to cause broad scale habitat losses. The macro-scale approach used here can provide overall guidelines for conservation and define the focus for more local and effective conservation efforts.     

Morphological abnormalities in anurans from southern Brazil

In recent years, the progressive decline in populations of anuran amphibians has left many species increasingly vulnerable to extinction. The potential role of morphological abnormalities as a mechanism of this decline has attracted attention in many recent studies. We investigated the occurrence and frequency of morphological abnormalities in anurans from northern of the state of Rio Grande do Sul, Brazil. We sampled 1674 individuals from three different environments – forest, farmland and peri‐urban areas – between 2001 and 2017. We recorded 89 individuals with morphological abnormalities, with 12 different types of abnormality in 19 anuran species. We recorded nine types of abnormality in forest and seven in the farmland, with brachydactyly being the most common abnormality in both areas. Only three abnormalities were recorded in the peri‐urban area, and all three were equally frequent. Studies of morphological alterations provide important insights into the potential effects of environmental impacts on anuran populations and may be essential for the planning of effective conservation strategies.     

蛙的早期胚胎发育

根据多年来对一些经济蛙类的繁殖习性及胚胎发育的观察,并结合国内外有关的研究报道,介绍了两栖动物的繁殖类型及蛙类早期胚胎发育的过程,为教学提供有益的参考资料。     

Physiological control of water exchange in anurans

Research on water exchange in frogs has historically assumed that blood osmotic potential drives water exchange between a frog and its environment, but here we show that the “seat patch” (the primary site of water exchange in many anurans), or other sites of cutaneous water uptake, act as an anatomic “compartment” with a water potential controlled separately from water potential of the blood, and the water potential of that compartment can be the driver of water exchange between the animal and its environment. We studied six frog species (Xenopus laevis, Rana pipiens, R. catesbeiana, Bufo boreas, Pseudacris cadaverina, and P. regilla) differing in ecological relationships to environmental water. We inferred the water potentials of seat patches from water exchanges by frogs in sucrose solutions ranging in water potential from 0 to 1000‐kPa. Terrestrial and arboreal species had seat patch water potentials that were more negative than the water potentials of more aquatic species, and their seat patch water potentials were similar to the water potential of their blood, but the water potentials of venters of the more aquatic species were different from (and less negative than) the water potentials of their blood. These findings indicate that there are physiological mechanisms among frog species that can be used to control water potential at the sites of cutaneous water uptake, and that some frogs may be able to adjust the hydric conductance of their skin when they are absorbing water from very dilute solutions. Largely unexplored mechanisms involving aquaporins are likely responsible for adjustments in hydric conductance, which in turn, allow control of water potential at sites of cutaneous water uptake among species differing in ecological habit and the observed disequilibrium between sites of cutaneous water uptake and blood water potential in more aquatic species.     

Association of anurans with pathogenic fungi

In a study of 450 Amazonian anurans, we isolated yeasts and yeast-like fungi from 54 animals (Bufo granulosus, B. marinus, Dendrophrynyscus sp., Hyla geographica, H. lanciformes, Ololygon rubra, Adenomera hylaedactyla, Eleutherodactylus fenestratus, Leptodactylus fuscus, L. ocellatus, L. pentadactylus). The internal organs of these animals did not show any macroscopic anomaly nor histopathology. We recovered 105 fungal isolates from the anuran liver, lung, kidney, spleen, heart and gonad. The isolates were made up of 30 fungal species, 9 of which (48 isolates, 46%) were fungi with known pathogenic potentials, namely: Candida guilliermondii, C. parapsilosis, C. tropicalis, C. glabrata, Geotrichum candidum, Aureobasidium pullulans, Wangiella dermatitidis, Trichosporon cutaneum and Exophiala werneckii. Eleven animals harbored identical fungi in more than one of their internal organs; seven animals had more than one fungal species colonizing a single organ. Our findings indicated probable natural subclinical infections of candidiasis, geotrichosis or phaeohyphomycosis, and also symbiotic presence of non-pathogenic fungi among neotropical anurans.