Urodela

The origin of extant amphibians (Lissamphibia: frogs, salamanders and caecilians) is one of the most controversial questions in vertebrate evolution, owing to large morphological and temporal gaps in the fossil record. Current discussions focus on three competing hypotheses: a monophyletic origin within either Temnospondyli or Lepospondyli, or a polyphyletic origin with frogs and salamanders arising among temnospondyls and caecilians among the lepospondyls. Recent molecular analyses are also controversial, with estimations for the batrachian (frog-salamander) divergence significantly older than the palaeontological evidence supports. Here we report the discovery of an amphibamid temnospondyl from the Early Permian of Texas that bridges the gap between other Palaeozoic amphibians and the earliest known salientians and caudatans from the Mesozoic. The presence of a mosaic of salientian and caudatan characters in this small fossil makes it a key taxon close to the batrachian (frog and ...

Spermatogenic cycles of hynobiid salamanders are interesting for the study of male reproductive adaptations in amphibians living under different environmental conditions. In order to detect the main differences between sperma-togenic cycles of hynobiids, we studied the spermatogenic cycle of Salamandrella keyserlingii from the suburbs of Tomsk (southeastern Western Siberia) and compared it with those in the literature of hynobiids from different regions of Asia. We histologically and histochemically examined the testes of males captured from April to September. In April, the testes of males entering breeding sites contained bundles of spermatozoa (Sz) and primary (Sg I) and secondary spermatogonia (Sg II). After spermiation and breeding, Sg II began to proliferate. Meiosis of spermatocytes occurred in late June through July. The spermiogenesis began in late July; spermatids and Sz appeared in August. In September, Sz, Sg I, and Sg II were found in testes, which was also when Sg II proliferated. There are two types of spermatogenic cycles in the studied sala-manders. The first one includes one period of spermatogonial proliferation (SP) in the first half of the active season. The second type consists of two periods of SP, with one occurring at the beginning and the other at the end of the active season. To identify possible differences in hynobiid spermatogenic cycles, we tested the relation of the duration of active season (DAS), the duration of SP period in the first half of cycle (DSPP), and the number of SP periods per year (NSPPs), considering environmental (air) temperatures in these species' habitats. We could not find a direct relationship between NSPPs and air temperatures, but DAS and DSPP were correlated with temperature. We assume that two periods of SP can play the most apparent adaptive role in S. keyserlingii in a subarctic climate and in Batrachuperus tibetanus under mountain conditions.

In this study we describe the growth of several different larval cohorts (i.e. half-siblings of the same mother born on the same day) of a rare, xeric-adapted salamander Salamandra s. infraimmaculata Martens, 1885, under constant density and food conditions from birth to metamorphosis. The larvae spend the critical first phase of their lives in water, mostly in temporary ponds. Age and weight at metamorphosis were highly affected by varying food conditions. We have identified six different growth modes that these larvae use, both fast growing and slow growing. Each larval cohort was found to use 2–4 different such growth modes regardless of their initial weight. Fast growing modes (I–III) will enable larvae to survive dry years, and metamorphose bigger. Slow growing modes (IV–VI), used by 8% of the larval population, will enable survival only in rainy years. These last growth modes effect differential temporal dispersal in wet years by delaying the emergence of postmetamorphs onto land. Distribution of growth modes in the larval population is affected by food but not by density conditions. Late-born, fast-growing larvae will have an advantage in dry years being able to metamorphose and disperse, whereas the slow-growing larvae will survive only in wet years.

Nous présentons la biologie, l'écologie et la biogéographie des trois espèces de salamandres relictes qui constituent le genre Echinotriton NUSSBAUM & BRODIE, 1982 : E. andersoni, E. chinhaiensis et E. maxiquadratus, en confrontant les connaissances actuelles sur ce genre et nos données de terrain originales. Ces Urodèles aux caractéristiques particulières sont très menacés et de nouvelles populations ou des formes cryptiques existent probablement ; elles risquent de disparaître avant d'être décrites. Nous présentons également quelques données d'élevage utiles dans le cadre de programmes de conservation in situ et ex situ.

We report ecological observations of Bolitoglossa altamazonica and B. peruviana in the Peruvian Amazon with suggestions on their conservation. Two localities are provided for both species in one protected area, Allpahuyo-Mishana National Reserve and in Puerto Almendra near the city of Iquitos, northern Peru. A different type of B. altamazonica was also discovered in Allpahuyo-Mishana. It is similar to B. madeira with a reddish coloration on the dorsal parts. Another " grey " type was also reported living between Puno and Madre de Dios departments at higher elevations. However, all the specimens found through their range in Peru have shown colour variation which complicates species identification. New taxonomic studies are needed to confirm their status. The Peruvian salamanders appear to be semi-arboreal species living in primary unflooded terra firme rainforests near water bodies where humidity is high at lower elevations as previously reported (96–118 m a.s.l.). Despite most of the Bolitoglossa species occur in protected areas, a deadly threat was recently reported in frogs (Batrachochy-tridium dendrobatidis) that may cause loss of salamanders in Peru. For example during our field surveys we were unable to observe B. digitigrada. New assessments are urgently needed for the protection and conservation of Peruvian salamanders. Data on biology, ecology and environmental parameters are also lacking to really protect their microhabitats, and to establish suitable ex situ keeping and breeding programs with the difficult perspective of subsequent reintroduction.

The branching times of molecular phylogenies allow us to infer speciation and extinction dynamics even when fossils are absent. Troublingly, phylogenetic approaches usually return estimates of zero extinction, conflicting with fossil evidence. Phylogenies and fossils do agree, however, that there are often limits to diversity. Here, we present a general approach to evaluate the likelihood of a phylogeny under a model that accommodates diversity-dependence and extinction. We find, by likelihood maximization, that extinction is estimated most precisely if the rate of increase in the number of lineages in the phylogeny saturates towards the present or first decreases and then increases. We demonstrate the utility and limits of our approach by applying it to the phylogenies for two cases where a fossil record exists (Cetacea and Cenozoic macroperforate planktonic foraminifera) and to three radiations lacking fossil evidence (Dendroica, Plethodon and Heliconius). We propose that the dive...

Cave organisms occupy a special place in evolutionary biology because convergent morphologies of many species demonstrate repeatability in evolution even as they obscure phylogenetic relationships. The origin of specialized cave-dwelling species also raises the issue of the relative importance of isolation vs. natural selection in speciation. Two alternative hypotheses describe the origin of subterranean species. The ‘climate-relict’ model proposes allopatric speciation after populations of cold-adapted species become stranded in caves due to climate change. The ‘adaptive-shift’ model proposes parapatric speciation driven by divergent selection between subterranean and surface habitats. Our study of the Tennessee cave salamander complex shows that the three nominal forms (Gyrinophilus palleucus palleucus, G. p. necturoides, and G. gulolineatus) arose recently and are genealogically nested within the epigean (surface-dwelling) species, G. porphyriticus. Short branch lengths and discordant gene trees were consistent with a complex history involving gene flow between diverging forms. Results of coalescent-based analysis of the distribution of haplotypes among groups reject the allopatric speciation model and support continuous or recurrent genetic exchange during divergence. These results strongly favour the hypothesis that Tennessee cave salamanders originated from spring salamanders via divergence with gene flow.

A structural and ultrastructural study was carried out on the cutaneous glands in some species of Rana (R. dalmatina, R. iberica, R. italica, R. “esculenta,” and R. perezi), giving particular attention to the mucous secretory units. Two different types of mucous glands occur in R. dalmatina, R. iberica, and R. italica. Besides the ordinary mucous units, which are randomly distributed over the body surface in both males and females, a further population of mucous glands was observed on the male dorsal skin. The latter is recognizable by the peculiar morphology of the epithelial cells and some characteristics of the secretory product. Specialized mucous glands are absent in both sexes of R. “esculenta” and R. perezi. The possible adaptive role of the specialized mucous glands is discussed in light of the absence of vocal sacs in males of R. dalmatina, R. iberica, and R. italica. Chemosignals released by sexually dimorphic mucous units may replace vocal communication during the breeding season and so play an important role in female attraction and/or territorial announcement. The morphology and possible function of the specialized mucous glands in the three species of Rana are compared with the breeding glands of other frogs and with the hedonic glands of some urodeles (Salamandridae and Plethodontidae), which are known to produce pheromonal substances during courtship. J. Morphol. 254:328–341, 2002. © 2002 Wiley-Liss, Inc.