Florencia Vera Candioti

Shape variation in lentic and lotic tadpoles of Melanophryniscus (Anura: Bufonidae)

The bufonid genus Melanophryniscus includes 26 species that are divided into three phenetic groups based on adult morphology. Larvae develop in environments such as temporary ponds, streams or phytotelms. We studied variation in external morphology related to lentic and lotic microhabitats, through landmark-based geometric morphometrics on body shape, and multivariate analysis on oral disc measurements. Results show a morphological continuum between species that inhabit lentic versus lotic water systems. Features both in body shape and oral disc coincide with previous characterizations of lentic and lotic tadpoles published elsewhere. El género de bufónidos Melanophryniscus comprende 26 especies actualmente reunidas en tres grupos fenéticos distinguidos por la morfología de los adultos. En adición, las larvas se desarrollan alternativamente en variados ambientes, tales como charcos, arroyos temporarios y fitotelmata. Estudiamos la variación morfológica externa asociada a ambientes lóticos y lénticos, mediante morfometría geométrica de landmarks sobre la forma del cuerpo, y análisis multivariado de las medidas del disco oral. Los resultados muestran un continuo morfológico entre las especies que habitan sistemas lénticos vs. lóticos. Las características corporales y del disco oral coinciden con caracterizaciones previas de renacuajos lénticos y lóticos ya publicadas.

The Tadpole and Karyotype of Rhinella achavali (Anura: Bufonidae)

Abstract We describe the external morphology, buccal cavity, chondrocranium, hyobranchial skeleton, and musculature of the tadpole of Rhinella achavali (Achavals Toad), along with its karyotype. Tadpoles were found in a small, permanent stream and were showing schooling behavior. The characterization of the proposed species groups within Rhinella cannot be currently improved using external larval morphology, as it seems to be much conserved within this genus. Buccal cavity morphology confirms the distinctiveness of the Rhinella veraguensis (Veragua Toad) group with respect to other known Rhinella. Musculoskeletal character states are similar among bufonids, although within this family the basal genus Melanophryniscus shows some distinctive states. The karyotype is composed of 22 bi-armed chromosomes, with secondary constrictions in pair 7, as found in the other species in the Rhinella marina (Marine Toad) group.

Direct-developing frogs: ontogeny of Oreobates barituensis (Anura: Terrarana) and the development of a novel trait

Within Anura, direct development involves ontogenetic changes of the biphasic ancestral pattern. The recent partitioning of the genus Eleutherodactylus, along with the proposition of the unranked taxon Terrarana, has renewed an interest to the morphological and ecological diversity among direct-developing frogs. The morphological changes during embryonic development of Oreobates barituensis is similar to those of other Neotropical direct-developing species, including the reduction or absence of several larval and embryonic characters (e.g., external gills and adhesive glands), heterochronic changes (e.g., early developing limbs and late persistence of ciliated epidermal cells), and the appearance of new structures (e.g., egg tooth). The tail achieves an extraordinary peramorphic development (encloses the entire embryo), and the location of its expanded part is interpreted as a heterotopic change resulting in a novel trait. An enveloping tail with apparently non-heterotopic fins, combined with the absence of gills, has been only reported for a species of the related genus Craugastor, and these morphologies suggest an informative perspective for the study of evolution of direct development in terraranans.

A Tale of a Tail: Variation during the Early Ontogeny of Haddadus binotatus (Brachycephaloidea: Craugastoridae) as Compared with Other Direct Developers

Abstract The New World direct-developing frogs (Brachycephaloidea = Terrarana) comprise nearly a thousand species that share direct development among other putative synapomorphies, yet embryonic development in this group has been thoroughly described in only about 20 species. Here we describe the early ontogeny of the craugastorid Haddadus binotatus, making special emphasis on tail structure and development, and its differences and similarities with that of other terraranans. The morphological changes during embryonic development of H. binotatus and those of other Neotropical direct-developing species are alike, with some variation including the absence of external gills, timing of limb differentiation, and tail configuration. The tail with a rotated core axis and lateral and asymmetric fins that cover the posterior half of the embryo represents an outstanding case of developmental repatterning. We present some interpretations of the evolution of the tail and its three major aspects, the rotation of the core axis, and the origin and extensions of the fins, and pinpoint that those mechanisms underlying fin development should be fairly plastic, allowing the ontogenetic and evolutionary variation within the Brachycephaloidea clade. Resumen Las ranas de desarrollo directo del Nuevo Mundo (Brachycephaloidea = Terrarana) incluyen cerca de mil especies que comparten el desarrollo directo entre otras sinapomorfías putativas; sin embargo el desarrollo embrionario en este grupo ha sido descripto en no más de 20 especies. Aquí describimos la ontogenia temprana del craugastórido Haddadus binotatus, con especial énfasis en la estructura y el desarrollo de la cola y sus diferencias y similitudes con la de otros terraranas. Los cambios morfológicos durante el desarrollo embrionario de H. binotatus son similares a los de otras ranas neotropicales con desarrollo directo, con algunas variaciones que incluyen la ausencia de branquias externas, los tiempos de diferenciación de las extremidades y la configuración de la cola. La cola con su eje rotado y aletas laterales y asimétricas que cubren la mitad posterior del embrión representa un caso excepcional de cambio en los patrones del desarrollo. Aquí presentamos algunas interpretaciones sobre la evolución de la cola y sus tres aspectos principales: la rotación del eje y el origen y extensión de las aletas, y señalamos que los mecanismos que subyacen al desarrollo de la aleta parecen ser lo suficientemente plásticos como para permitir la variación ontogenética y evolutiva presente en el clado Brachycephaloidea.

The Stream Tadpoles of Rhinella rumbolli (Anura: Bufonidae)

Abstract:  The Rhinella veraguensis group is likely a paraphyletic assemblage that contains 16 species of Andean toads. To date, descriptions are available for larval stages of only three species, all of which possess a distinct sucker in the abdominal region. In this study, we describe the tadpoles of Rhinella rumbolli, a medium-sized Salta Toad typical of forest streams in northwestern Argentina. Thirty-three larvae (Gosner Stages 32–36) were processed for studies of the external morphology, buccal cavity, and musculoskeletal system. These larvae show a mosaic of features, some typical of the genus and some others unique to the R. veraguensis group. Several character states are specific to R. rumbolli, namely the lack of an abdominal sucker, 2–4 lingual papillae, and the absence of adrostral cartilages. Some traits are frequent in other stream tadpoles such as the muscular tail, large oral disc with complete labial rows, and the wide and robust anterior neurocranium. Bufonid tadpoles exhibit an extraordinary variation in ecology, such as preferred microhabitat, and the diversity within the family is exemplified within the genus Rhinella. Further comparative morphological and developmental studies, framed in the context of phylogenetic hypotheses, are needed in order to explore the pattern variation in different clades and to discuss character evolution and form–function relationships.

The Adhesive Glands during Embryogenesis in Some Species of Phyllomedusinae (Anura: Hylidae)

Abstract. Among anuran embryonic structures, the adhesive (cement) glands appear posterolaterally to the stomodeum and produce a mucous secretion that adheres embryos to surfaces in and out of the egg. In this paper, we study the ontogeny of the adhesive glands in five species of Phyllomedusa representing the two main clades recognized in the genus, plus embryos of Agalychnis aspera and Phasmahyla cochranae. Clutches were collected in the field, and embryos were periodically fixed to obtain complete developmental series and then studied with a stereomicroscope, scanning electron microscopy and routine histological techniques. Structural variations include glands absent (in P. cochranae and Phyllomedusa boliviana), functional club-shaped glands (morphogenetic Type C in Phyllomedusa sauvagii, Phyllomedusa iheringii, and Phyllomedusa tetraploidea), and an unusual Type C-like pattern in Phyllomedusa azurea, characterized by large, oblong glands in a horseshoe-like disposition around the oral disc. This latter gland configuration is similar to that of A. aspera. Interspecific variations also include the arrangement and regression pattern of the secretory region, which are in turn different from those of Type C glands in other clades. To interpret the origin and evolution of gland developmental patterns in the group, we still need information on gland occurrence and development in the basal genera of Phyllomedusinae (Phrynomedusa and Cruziohyla) and in the basal taxa of the two major clades of Phyllomedusa.

Structural and Heterochronic Variations During the Early Ontogeny in Toads (Anura: Bufonidae)

Abstract:  In recent decades, a renewed interest in comparative studies of embryonic ontogeny in anurans is taking place. Toad embryos are often employed as model organisms, and scarce attention has been put on interspecific variations. In this work we analyze the development of transient embryonic and larval structures in 21 species in five genera of Bufonidae. These species vary in their ovipositional mode and the type of environments where the embryos and tadpoles develop, including ponds, streams, and axils of leaves of terrestrial or epiphytic plants. Comparative anatomical studies and sequence heterochrony analyses show that primary morphological variations occur in the morphology at the tail-bud stage, the arrangement and development of the external gills, adhesive gland type and division timing, growth of the dorsal hatching gland on the head, configuration of the oral disc, emergence and development of the hind limbs, and presence of the abdominal sucker. Some of these transformations are best explained by phylogeny (e.g., early divergent taxa of bufonids have embryos with kyphotic body curvature, Type C adhesive glands, and a very small third pair of gills). Other traits might be correlated with reproductive modes (e.g., phytotelmata embryos hatch comparatively late and show an accelerated development of hind limbs). Because these actual variations are not well studied (e.g., less than the 10% of the known diversity of bufonids has been studied from this perspective), comprehensive analyses are required to interpret character evolution and the relationship with reproductive modes within the family.

Internal Larval Morphology of Two Species of Shining Leaf Frogs (Anura: Phyllomedusidae: Phasmahyla)

Abstract. We describe the buccal cavity and chondrocranial morphology of Phasmahyla cruzi tadpoles in comparison to P. guttata. We also provide a review of some characters for larval phyllomedusids and discuss some evolutionary aspects related to the funnel-mouthed configuration. Our discussion highlights that several characters evolved independently in several taxa with umbelliform oral discs. Nevertheless, we suggest that the dorsal orientation of the suprarostral cartilage and the presence of a prenarial ridge on the buccal roof may represent synapomorphic character states for the genus Phasmahyla.

Cranial anatomy of the amazing bromeliad tadpoles of Phyllodytes gyrinaethes (Hylidae: Lophyohylini), with comments about other gastromyzophorous larvae

The ecomorphological guild “gastromyzophorous” joins tadpoles that inhabit flowing water and have an abdominal sucker which is employed to adhere to substrates. Historically, gastromyzophorous larvae were known in the Bufonidae and Ranidae, but a new sucker-bearing hylid tadpole was recently described from phytotelmons in Brazilian forests. We describe the larval internal anatomy of Phyllodytes gyrinaethes and ask whether its exceptional external morphology is accompanied by derived anatomical internal features that can be related to the special habitat. We also compare it to the anatomy of sucker-bearing tadpoles from other families with a focus on characters exclusive of each lineage and the shared, convergent features. The skeleton of P. gyrinaethes is highly modified relative to that of pond-type hylines and shows a profound restructuring of the oral region, palatoquadrates, and the branchial baskets. Among the muscles, besides the overall reduction in the branchial musculature, the most unusual feature in this species are the enormous, anteriorly oriented mm. levatores mandibulae externus profundus that likely produce the abduction of the two halves of the snout. The presence of the abdominal sucker is coupled with changes in some muscle trajectories and hypertrophy of the subhyoid ligaments, and the sucker connectivity differs in some aspects compared with those of bufonids and ranids (e.g., the presence of massive mm. diaphragmatopraecordialis parallel to the sucker plane). P. gyrinaethes tadpoles, with their combination of both rare and unique morphological features plus their confined microhabitat with exceptional functional and ecological requirements, represent an extreme morphotype within Hylidae and anuran tadpoles in general.