New data on the distribution of Pallas's spadefoot toad ( (Pallas, 1771)) and fire-bellied toad ( L., 1761) (Anura, Amphibia) on the territory of the Saratov region and adjacent territories

New data on the geographical distribution of Pelobates vespertinus and Bombina bombina in the Saratov region and adjacent districts of the Volgograd, Voronezh, Penza and Ulyanovsk regions are presented. The habitation of B. bombina and P. vespertinus populations in 25 and 22 localities, respectively, was established. Most modern populations of these species of anuran amphibians have been recorded near water bodies in river valleys.

Identification key for anuran amphibians in a protected area in the northeastern Atlantic Forest

The identification of anuran amphibians is still a challenge in megadiverse assemblages. In the Neotropics, the Atlantic Forest harbors more than 600 anuran species, and many studies in this ecoregion report anuran assemblages surpassing 30 species. Taxonomic keys facilitate the identification of biological diversity, however only a few are available for anuran assemblages in the Atlantic Forest. Herein we present an identification key for 40 anuran species distributed across 20 genera and nine families, occurring in the Environmental Protection Area of Catolé and Fernão Velho, northeastern Atlantic Forest. Thirty-five morphological characteristics were used in the key, all of which can be easily observed in living and museum specimens. This pioneer study provides the first identification key for an amphibian assemblage in the northeastern Atlantic Forest and this baseline information acts as the starting point for the development of evolutionary and ecological research in this conservation unit.

Independent pseudogenizations and losses of sox15 during amniote diversification following asymmetric ohnolog evolution

Background Four ohnologous genes (sox1, sox2, sox3, and sox15) were generated by two rounds of whole-genome duplication in a vertebrate ancestor. In eutherian mammals, Sox1, Sox2, and Sox3 participate in central nervous system (CNS) development. Sox15 has a function in skeletal muscle regeneration and has little functional overlap with the other three ohnologs. In contrast, the frog Xenopus laevis and zebrafish orthologs of sox15 as well as sox1-3 function in CNS development. We previously reported that Sox15 is involved in mouse placental development as neofunctionalization, but is pseudogenized in the marsupial opossum. These findings suggest that sox15 might have evolved with divergent gene fates during vertebrate evolution. However, knowledge concerning sox15 in other vertebrate lineages than therian mammals, anuran amphibians, and teleost fish is scarce. Our purpose in this study was to clarify the fate and molecular evolution of sox15 during vertebrate evolution. Results We searched for sox15 orthologs in all vertebrate classes from agnathans to mammals by significant sequence similarity and synteny analyses using vertebrate genome databases. Interestingly, sox15 was independently pseudogenized at least twice during diversification of the marsupial mammals. Moreover, we observed independent gene loss of sox15 at least twice during reptile evolution in squamates and crocodile-bird diversification. Codon-based phylogenetic tree and selective analyses revealed an increased dN/dS ratio for sox15 compared to the other three ohnologs during jawed vertebrate evolution. Conclusions The findings revealed an asymmetric evolution of sox15 among the four ohnologs during vertebrate evolution, which was supported by the increased dN/dS values in cartilaginous fishes, anuran amphibians, and amniotes. The increased dN/dS value of sox15 may have been caused mainly by relaxed selection. Notably, independent pseudogenizations and losses of sox15 were observed during marsupial and reptile evolution, respectively. Both might have been caused by strong relaxed selection. The drastic gene fates of sox15, including neofunctionalization and pseudogenizations/losses during amniote diversification, might be caused by a release from evolutionary constraints.

Gynogenetic diploids, tetraploids, or octoploids, and a path to polyploidy in Anuran Amphibians

Unreduced gametes have been implicated in the evolution of polyploid species of plants and animals and are normally produced by female anuran amphibians. Such eggs may initiate the evolution of polyploid species that have independently arisen in several anuran families. Polyploid females could also produce unreduced eggs that might lead to species with higher ploidy levels or their eggs may develop gynogenetically to reduce the ploidy level. Diploid Hyla chrysoscelis (2n=24) and tetraploid H. versicolor (4n=48) are sibling cryptic species of North American Grey Treefrogs. Artificial crosses using H. versicolor females and genetically distant diploid males were performed to produce haploid H. versicolor and to assess the production of unreduced eggs in this tetraploid species. Gynogenetic diploid (haploid H. versicolor), allotriploid, gynogenetic tetraploid, allopentaploid, autohexaploid, and gynogenetic octoploid tadpoles were confirmed using chromosome counts from tadpole tail tip squashes. Transformation and survival of the different ploidies varied. Gynogenetic diploids transformed but expressed aspects of the haploid syndrome and died before or shortly after transformation.

Correction to: Eye‐body allometry across biphasic ontogeny in anuran amphibians

A correction to this paper has been published: https://doi.org/10.1007/s10682-021-10109-w

Safety Bubbles: A Review of the Proposed Functions of Froth Nesting among Anuran Amphibians

The adults of several anuran amphibian species deposit their eggs externally in mucus secretions that are purposely aerated to produce a froth nest. This type of clutch structure has evolved independently several times in this group and has been proposed to serve a variety and often simultaneous adaptive functions associated with protecting offspring from sub-optimal conditions during embryogenesis and later stages after hatching has occurred. These functions range from buffering offspring from sub-optimal temperatures and desiccation, to defending against predation and improving oxygenation. This versatility has likely helped facilitate the reduced reliance of egg development on water and thus the penetration of anurans into environments where permanent aquatic systems are not always available. In this paper, I review the hypothesised functions of the anuran froth nest as a mucus-based solution to the environmental challenges offspring face during development, with consideration of the functions of froth nest breakdown and communal froth nesting, as well.

Olfaction across the water–air interface in anuran amphibians

Extant anuran amphibians originate from an evolutionary intersection eventually leading to fully terrestrial tetrapods. In many ways, they have to deal with exposure to both terrestrial and aquatic environments: (i) phylogenetically, as derivatives of the first tetrapod group that conquered the terrestrial environment in evolution; (ii) ontogenetically, with a development that includes aquatic and terrestrial stages connected via metamorphic remodeling; and (iii) individually, with common changes in habitat during the life cycle. Our knowledge about the structural organization and function of the amphibian olfactory system and its relevance still lags behind findings on mammals. It is a formidable challenge to reveal underlying general principles of circuity-related, cellular, and molecular properties that are beneficial for an optimized sense of smell in water and air. Recent findings in structural organization coupled with behavioral observations could help to understand the importance of the sense of smell in this evolutionarily important animal group. We describe the structure of the peripheral olfactory organ, the olfactory bulb, and higher olfactory centers on a tissue, cellular, and molecular levels. Differences and similarities between the olfactory systems of anurans and other vertebrates are reviewed. Special emphasis lies on adaptations that are connected to the distinct demands of olfaction in water and air environment. These particular adaptations are discussed in light of evolutionary trends, ontogenetic development, and ecological demands.