Early ontogeny and sequence heterochronies in Leiuperinae frogs (Anura: Leptodactylidae)

Patterns of allometric and heterochronic changes in the early ontogeny of species of Physalaemus (Anura: Leptodactylidae)

We studied the relationship between shape, size, and developmental time in the embryonic ontogeny of 15 species of the frog genus Physalaemus. As in other anuran exotrophic embryos, shape changes are correlated with size increase and mainly concern tail elongation, decrease in body height, and increase in fin height. Size ranges and developmental times vary interspecifically. Embryos of the P. signifer Clade and the P. gracilis Group are among the largest, are slightly peramorphic, and develop fast regarding congeneric species. Embryos of P. cicada combine the smallest sizes with fast development and the most peramorphic shapes. The paedomorphic shapes of embryos of P. biligonigerus and P. henselii groups are correlated with fast vs. slow developmental times respectively. Trajectories in the P. cuvieri Group are diverse and in general differ in size and developmental time. The embryos of P. cristinae and from the Argentinean lineage of P. cuvieri stand out with the longest development. Sequences of developmental events are overall conserved in the genus, and main differences concern mouthpart ontogeny. This study constitutes the first attempt to evaluate morphological, allometric, and heterochronic parameters of the early ontogeny of anurans and how these can vary and contribute to diversification in taxonomic groups.

Larval morphology of Amazonia foam-nesting frogs of the genus Engystomops (Anura: Leptodactylidae: Leiuperinae)

The highly differentiated anuran larvae make them an interesting and complementary source of information to understand anuran evolution. Among neotropical foam-nesting frogs, the available information on tadpole morphology for the subfamily Leiuperinae remains largely incomplete and variably reported among genera; in the monophyletic genus Engystomops it is still incipient. Herein, we summarize available information on larval morphology for five of the nine known species of Engystomops, three of them for the first time, reporting external morphology, buccopharyngeal cavity, and skeleton. The tadpoles of the genus have an overall generalized morphology and many traits are conserved across species. Nevertheless, many characters are systematically informative and some are diagnostic for some species, as the paravertebral gland in E. petersi and the dorsally directed spiracle in E. puyango. Other characters provide support for some subclades within the genus. Moreover, some traits, such as the direction of the vent tube, supports the close relationship between Engystomops and Physalaemus, whereas other support the existence of these two as distinct genera, such as the overall shape of the lateral ridge papillae and the presence of a processus pseudopterygoideus. This article is protected by copyright. All rights reserved.

Finding a pathway through the rocks: the role of development on the evolution of quasi-terrestriality and the origin of endotrophism in cycloramphids (Anura)

Anurans have served as models in evolutionary studies on reproduction and development. Several generalizations have emerged but it is unclear whether they represent the diversity of the entire group. We studied the development of two species of the Neotropical family Cycloramphidae. Frogs in this family have peculiar spawning sites and developmental biologies. Whereas some cycloramphid tadpoles are exotrophic, quasi-terrestrial and thrive in films of water that flow over rocky outcrops, others are endotrophic, terrestrial and complete their development outside the eggs laid on the forest floor, under logs or in crevices. Cycloramphid tadpoles have aspects of their morphology distinct from those of pond and stream dwellers; they hatch in more advanced stages of development and have typical tadpole structures, either in a modified form or absent. Herein we present a study of the tadpoles of C. lithomimeticus and T. miliaris, in order to document and discuss alterations in the ontogeny of several larval structures. These changes seem to be associated with adaptations to life in the peculiar habitats where the tadpoles thrive. We infer that the observations we present are explained by development being associated with aspects of terrestrialization and endotrophism.

Combined phylogenetic analysis of Pleurodema (Anura: Leptodactylidae: Leiuperinae)

The genus Pleurodema comprises 15 species distributed through the Neotropical region, from sea level up to 5000 m.a.s.l. A total-evidence analysis of Pleurodema is provided based on the parsimony criterion. The combined dataset included morphometric, phenotypic, and DNA evidence (34 taxa, 4441 characters). The parsimony analysis yielded one most-parsimonious tree. Pleurodema was recovered as a well-supported clade composed of two major subclades. One subclade has an identical topology to that of previous analyses, the P. brachyops Clade (P. alium, P. borellii, P. brachyops, P. cinereum, P. diplolister, and P. tucumanum). The other subclade includes the remaining nine species of the genus, exhibiting a topology different from that of previous studies. According to the present phylogeny, this second lineage is formed by the P. nebulosum Clade (P. guayapae + P. nebulosum), P. marmoratum, the re-defined P. thaul Clade (P. bufoninum, P. somuncurense, P. thaul) and the P. bibroni Clade (P. bibroni, P. cordobae, P. kriegi). The reproductive modes of Pleurodema represent a unique combination of features within Leiuperinae, including three egg-clutch structures, two types of amplexus, and lack of vocalization. Also, some species of Pleurodema have been considered fossorial, because they are capable of digging with their hind-limbs and remaining in self-made burrows during dry seasons. The evolution of characters associated with reproductive biology and fossoriality is discussed in light of the obtained results.

Embryonic ontogeny of three species of Horned Frogs, with a review of early development in Ceratophryidae

Horned Frogs of the family Ceratophryidae are conspicuous anurans represented by three endemic South American genera. Most ceratophryids inhabit semiarid environments, but three species of Ceratophrys occupy tropical or temperate humid areas. Several morphological and behavioral characters of larvae and adults are conserved across the family. Based on examination of specimens and accounts in the literature, the embryonic development of C. ornata, C. cranwelli, and the monotypic genus Chacophrys are described and compared with that of species of Lepidobatrachus. Ceratophryid embryos share a suite of morphological features and heterochronic shifts during development. Most features, such as gill structure, ciliation, early hatching, and precocious differentiation of the gut and hind limbs, are shared by all the species regardless the differences in the habitats that occupy. This is consistent with previous observations of some adult characters, and likely supports the hypothesis of an early diversification of ceratophryids in semiarid environments. Other embryonic features, such as the morphology and ontogeny of the oral disc and digestive tract, are correlated with larval feeding habits and vary within the family. The evolutionary and ecological significance of some conserved characters (e.g., gastrulation pattern, Type-A adhesive glands) and other taxon-specific features (e.g., nasal appendix) remain to be explored in the group.