I studied anatomy, gut content, and the relationship among these traits in a set of anuran tadpoles. Larval stages (mainly Gosner stages 31–36) of nineteen species from various lentic environments were selected. Morphological characters from the skeleton, musculature, oral apparatus and buccopharyngeal cavity were recorded, and a gut content analysis was performed, with emphasis on food size distribution. Ordination techniques were applied in order to find patterns of similarity in morphology and gut content. Canonical ordination methods were used to investigate the relationship among gut content, morphology, and phylogeny in the species considered. The results show that several skeletal, muscular, and buccal characters are relatively maintained within genera. Other features, which have appeared independently in different lineages, reflect convergence phenomena in some cases related to ecological aspects. The configuration of the hyobranchial skeleton, the development of the buccal floor depressor and levator muscles, and mouth gape width correlate with prey size. In some species, morphology is clearly related with feeding. Tadpoles that ingest large food particles relative to their body length present morphological traits attributable to macrophagy. Taxonomically unrelated tadpoles of Dendropsophus nanus, D. microcephalus and Ceratophrys cranwelli possess hyobranchial skeletons with robust, rostrocaudally long ceratohyals and reduced branchial baskets with short ceratobranchials devoid of lateral projections and spicules. Lepidobatrachus llanensis tadpoles have laterally extended ceratohyals which, along with the lateral extension of the jaws, result in a very wide oral apparatus and an ample buccopharyngeal cavity that allows the tadpole to ingest large and whole prey; the branchial basket, although its ceratobranchials lack lateral projections and spicules, is slightly reduced in area. The four species mentioned have a noticeable development of the buccal floor depressor muscles, and buccal cavities with scarce filtering and entrapping structures. In Elachistocleis bicolor, Dermatonotus muelleri, Chiasmocleis panamensis, and Xenopus laevis tadpoles, the branchial basket occupies >70% of the total hyobranchial skeleton area, and the hypobranchial plates are highly reduced; the buccal floor levator muscles are well-developed, with an increased site of attachment on the ventral expansion of the lateral process of the ceratohyal; the scarcity of the filtering structures in the buccopharyngeal cavity are balanced with the great development of the branchial filters and secretory zones; all these features relate to a diet based on small particles not significantly different from those of most other species; however, experimental studies show that species with similar hyobranchial apparatus and muscles are the most efficient when retaining minute particles. Finally, a large group of species present generalized morphological characters, such as a branchial basket occupying about 50% of the total hyobranchial apparatus, intermediate values of mouth gape width and buccal floor levator / depressor muscles ratio, and abundant filtering structures in the buccopharyngeal cavity; these species feed frequently on food particles between 1–30% of the tadpole body length; however, in some of the species, macrophagous diets are also reported in the literature, indicating that this morphology is flexible in more ample prey size ranges.

Vera Candioti, M.F. 2004. Morphology and feeding in tadpoles of Ceratophrys cranwelli (Anura: Leptodactylidae). -Acta Zoologica (Stockholm) 86 : 1-11This paper provides data on the skeleton, musculature, buccal apparatus, buccopharyngeal cavity and diet of Ceratophrys cranwelli tadpoles, and attempts to contribute to the knowledge of relations between morphology and ecology in anuran larvae. Both in morphological characters and feeding habits, these tadpoles are very similar to other species within the genus. They possess many of the structural features usually found in predaceous tadpoles: strong, keratinized jaw sheaths and keratodonts, reduced buccal papillation, high values of in-lever arm proportion and buccal floor area, well-developed ceratohyals, and hypertrophied jaw muscles. Food sources consist of other tadpoles, microcrustaceans, larvae of insects, plant fragments, as well as rotifers and microalgae. As facultative carnivores, they are likely to play an important role in regulating the aquatic communities of the ephemeral ponds where they develop.

We describe the bufonid gastromyzophorous tadpoles of Rhinella quechua from montane forest streams in Bolivia. Specimens were cleared and stained, and the external morphology, buccopharyngeal structures, and the musculoskeletal system were studied. These tadpoles show a combination of some traits common in Rhinella larvae (e.g., emarginate oral disc with large ventral gap in the marginal papillae, labial tooth row formula 2/3, prenarial ridge, two infralabial papillae, quadratoorbital commissure present, larval otic process absent, mm. mandibulolabialis superior, interhyoideus posterior, and diaphragmatopraecordialis absent, m. subarcualis rectus I composed of three slips), some traits apparently exclusive for the described species of the R. veraguensis group (e.g., second anterior labial tooth row complete, lingual papillae absent, adrostral cartilages present), and some traits that are shared with other gastromyzophorous tadpoles (e.g., enlarged oral disc, short and wide articular process of the palatoquadrate, several muscles inserting on the abdominal sucker). In the context of the substantial taxonomic and nomenclatural changes that the former genus Bufo has undergone, and despite the conspicuous morphological differences related to the presence of an abdominal sucker, the larval morphology of R. quechua supports including it in the genus Rhinella and placing it close to species of the R. veraguensis assemblage.

Eupsophus calcaratus, a leptodactyloid frog from the austral Andean forests of Argentina and Chile, has endotrophic, nidicolous tadpoles. We studied a metamorphic series from Stages 31 to 46 of Gosner's developmental table (1960). Other than the scarce pigmentation, proportionately large eyes, and massive developing hindlimbs, the remaining external characters are similar to those of generalized, exotrophic larvae. At the same time, internal morphology does not reveal any character state attributable to the endotrophic-nidicolous way of life; conversely, structures such as the hyobranchial skeleton and the mandibular cartilages are similar to those of exotrophic-macrophagous tadpoles. The metamorphic process is characterized by the delayed development of diverse structures (e.g., ethmoid region, palatoquadrate, and hyobranchial apparatus), and the retention of some larval characters (e.g., parietal fenestrae, overall absence of ossification) with the absence of development of some "juvenile" characters (e.g., adult otic process, several bones) in metamorphosed individuals. These heterochronic processes and truncation of larval development are related to a shorter larval life (when compared to other species of the austral Andean region) and to the small size at metamorphosis.

No abstract

After the description of the chondrocranium, hyobranchial apparatus, associated musculature, buccal apparatus, buccopharyngeal cavity, digestive tract, and gut contents, it was possible to define the feeding modes of Scinax nasicus and Hyla nana tadpoles (Gosner Stages 31-36). Scinax nasicus larvae are "typical" microphagous tadpoles, with keratodonts and robust rostrodonts appropriate for rasping surfaces and mincing of food particles; the buccopharyngeal cavity is equipped with filtering structures and has a conspicuous glandular zone and a highly developed branchial basket. In contrast, H. nana tadpoles have a modified buccal apparatus; the reduction of the buccopharyngeal and branchial basket structures, together with the high lever-arm ratio and the great development of the depressor muscles of the buccal floor are indicative of macrophagous feeding.

Labial teeth of anuran tadpoles are keratinized structures derived from the activity of a single epidermal cell of the oral labia; they are not homologous with adult anuran teeth, nor with teeth of other vertebrates. The present study comprises a first approach for studying labial tooth shape variation that will be useful for future studies of comparative development and the functional mechanics of feeding structures. We examined interspecific shape variations in the labial teeth of anuran tadpoles and searched for correlations of these variations with ecomorphological guilds and phylogeny. Species ordination shows that important variations at various taxonomic levels are related mainly to the general curvature of the tooth axis, the angle between the labial tooth base and tip, head length and curvature, and sheath width. The teeth of most basal taxa are broad-based and curved, although some broad-based teeth also characterize some phthanobatrachian species. Teeth of hyloids and ranoids differ in the oral angle, overall curvature, and sheath width. A phylogenetically independent ecomorphological effect is significant only for lotic suctorial and gastromyzophorous guilds; teeth in these forms have short, thick and curved heads, wide sheaths, and generally acute oral angles. The lack of a significant correlation between labial tooth shape and trophic guilds suggests that labial tooth harvesting ability has a wide latitude that could be particularly functional only under specific circumstances.

Vera Candioti, M.F., Nuñez, J.J. and Ú beda, C. 2011. Development of the nidicolous tadpoles of Eupsophus emiliopugini (Anura: Cycloramphidae) until metamorphosis, with comments on systematic relationships of the species and its endotrophic developmental mode. -Acta Zoologica (Stockholm) 92: 27-45.Species of Eupsophus are unique within Alsodinae in having nidicolous tadpoles. They are characterized by traits typical of generalized exotrophic (e.g., oral disc and spiracular tube) and endotrophic larvae (e.g., scant pigmentation and large hind limbs). The larval morphology and development of E. emiliopugini, including external, buccal, and musculoskeletal features, is described herein. Like the larvae of other alsodines, these larvae have four lingual and four infralabial papillae, quadratoethmoid process, and an m. rectus cervicis with a double insertion. Among the traits exclusive to the genus are: the absence of the pseudopterygoid process and quadrato-orbital commissure; presence of the m. subarcualis rectus I with two slips; and presence of the m. subarcualis rectus II-IV inserting on Ceratobranchial II. The development and metamorphosis of Eupsophus include some characters that develop later (e.g., degeneration of mouthparts and chondrocranium with minimum calcification), characters that develop earlier (e.g., hind-limb appearance and jaw and suspensorium ossification), and characters that develop at the same time (e.g., most external features and cranial muscles) than in most exotrophic species. Some distinctive characters (third lower labial ridge absent, general configuration of the hyobranchial skeleton, skeletal development with retention of larval traits) resemble those of other endotrophic species, and the precocious ossification of jaws and suspensorium is shared with several direct-developing species among recent amphibians.