Internal Oral Features Research Articles

THE TADPOLE OF THE CASQUE-HEADED FROG, APARASPHENODON BRUNOI MIRANDA-RIBEIRO (ANURA: HYLIDAE)

The tadpole of Aparasphenodon brunoi is described and illustrated for the first time (external morphology and internal oral features) from Maricá, State of Rio de Janeiro, Brazil. Characters of this tadpole include: body representing 30% of total length; eyes lateral; spiracle single, sinistral, with opening directed upward and backward; anal tube median; dorsal fin originating at the mid-third of body; caudal tip extended into a flagellum; oral disc anteroventral; and labial tooth row formula 2(2)/6(1). In general, body and tail brown. Tail with transverse dark brown stripes. Morphological comparisons were made with tadpoles of eight other pond and stream-dwelling casque-headed treefrog species of the genera Argenteohyla, Osteocephalus, and Trachycephalus. The tadpoles of the subspecies of Argenteohyla possess characteristics that may indicate full specific rank of these taxa, so that the taxonomic status of these subspecies should be revaluated. Considering that high number of tooth rows is usually associated with stream dwellers, the presence of this characteristic in A. brunoi tadpoles (a pond-dweller) may represent retention of an ancestral lotic pattern. Furthermore, the number of tooth rows in the posterior labium of A. brunoi corroborates the putative morphological synapomorphy of the tribe Lophiohylini (presence of at least four posterior labial tooth rows in the larval oral disc).

The tadpole of Physalaemus fuscomaculatus (Anura: Leptodactylidae), with a description of internal oral morphology

The external morphology and internal oral features of Physalaemus fuscomaculatus (Steindachner, 1864) tadpoles are described and compared with other species in the Physalalemus biligonigerus group (Lynch, 1970). Tadpoles of P. fuscomaculatus have a morphology similar to other species within this group and closely resemble those of P. santafecinus Barrio, 1965 and P. biligonigerus (Cope, 1861). The tadpole of P. fuscomaculatus differs from those of the biligonigerus group by the following characters: i) proportionally shorter tail compared to total length, ii) presence of two narrow ventral gaps on marginal papillae of the oral disc; iii) upper jaw sheath Mshaped; iv) presence of two lingual papillae; v) two to three prepocket papillae, and vi) three to five pustulations anterior to each buccal pocket. This is the first record of Physalaemus fuscomaculatus in southeastern Brazil.

Anatomical features of Leiopelma embryos and larvae: Implications for anuran evolution

A controversial issue in anuran systematics is the relationship of Leiopelma to other anurans because recent phylogenetic constructions imply different relationships among the basal frogs. Of particular evolutionary interest is whether early development of Leiopelma resembles an ancestral salamander-like larva, an anuran tadpole, or neither. In the 1950s, Neville G. Stephenson hypothesized that direct development is the primary mode of development in amphibians, based on the fact that Leiopelma spp. lack a free-living (=feeding) larval stage. Although this hypothesis has not been generally accepted, it has not been formally refuted. We review Stephenson's work on Leiopelma and examine the anatomy of embryos/"larvae" of the four extant Leiopelma species for evidence of vestigial larval features that might refute the "direct-developing ancestor" hypothesis. We describe internal oral features in early developmental stages of Leiopelma and compare Leiopelma with a closely related basal anuran, Ascaphus, to assess whether their early developmental stages share any derived features. In Leiopelma hochstetteri, embryos/larvae have open gill slits and some faint rugosities around one gill slit that may be vestiges of gill rakers or filters. They also have more intestinal loops, indicative of an elongated alimentary tract, at earlier rather than late embryonic/larval stages. Collectively, these features support the view that the ancestor of Leiopelma had a free-swimming, free-feeding, aquatic larva. The palatoquadrate of Leiopelma archeyi reorients approximately 40 degrees from a more horizontal to a more vertical position through embryonic/"larval" development. This amount of cranial remodeling is intermediate between that seen in salamanders (17-27 degrees) and that reported for Ascaphus (64 degrees ) and other basal frogs (71-78 degrees) at metamorphosis. We found no internal oral features that Leiopelma shares specifically with Ascaphus. However, Leiopelma embryos have a ventrally positioned mouth and a downturned rostrum, characteristic of Ascaphus and other stream-adapted tadpoles.

Internal Oral Morphology of Tadpoles of Dermatonotus muelleri and Elachistocleis bicolor

-The internal oral morphology of tadpoles of Dermatonotus muelleri and Elachistocleis bicolor were analyzed using scanning electron and stereoscopic microscopy. Similarities between these larvae include the architecture of the buccal roof and floor: wide and almost flattened surfaces; unperforated internal nares appearing as circular depressions; absence of infralabial and lingual papillae; presence of massive, triangular postnarial papillae; and absence of other papillae posterior to the median ridge. Differences include a raised glottis placed in the center of the buccal floor arena in D. muelleri, and the number of the lateral papillae positioned at each side of the prenarial arena. We suggest that the oral flaps and the roof papillae play a significant role in the capture of food particles by establishing the inflow of alimentary water, and aggregating food particles and mucus inside the buccopharyngeal cavity. Microhylid tadpoles have a stable pattern of body size and shape, and oral and buccopharyngeal features, which may reflect ecological and functional constraints relative to the morphology of other suspension feeding anuran larvae. Although there is some information on the interal oral morphology of larvae of several species of the extremely diverse Microhylidae (over 280 species distributed in 10 subfamilies; Duellman, 1993), there are only eight descriptions of the oral cavity (e.g., Wassersug, 1980; Inger, 1985; Wassersug and Pybur, 1987; Chou and Lin, 1997). There is only one such description for a neotropical representative of this family, namely the peculiar tadpoles of Otophryne robusta (Wassersug and Pyburn, 1987). Our investigation focused on the two southernmost species of neotropical microhylids, Dermatonotus muelleri and Elachistocleis bicolor, whose larvae have received attention by many authors. Both species have lentic, suspension feeding, Type II tadpoles (Altig and Johnston, 1989). The external larval morphology of D. muelleri was characterized by Vizotto (1967) and Lavilla (1992), who also described the structure of the chondrocranium and visceral skeleton. The tadpole of E. bicolor was described by Williams and Gudynas (1987). Lavilla and Langone (1991, 1995) analyzed the ontogenetical peculiarities of the proctodeal tube and spiraculum of this species, as well as the structure of the cephalic skeleton. Wild (1995) reported a phylogenetic analysis of all New World microhylid genera which included tadpole features of the genera Dermatonotus and Elachistocleis, but nothing concerning internal oral morphology. Herein we present descriptions of the internal oral features of the tadpoles of Dermatonotus muelleri and Elachistocleis bicolor MATERIALS AND METHODS All tadpoles were captured from the wild and preserved in 10% formalin. Oral and buccopharyngeal features were observed using stereoscopic and scanning electron microscopy (SEM) following the techniques proposed by Wassersug (1976) and Echeverria (1992). Once dissected, buccal structures were critical-point dried and coated with gold-palladium for SEM. Video records of some of the SEM are kept at the VIDEO collection in the research laboratory of DDE. Drawings of the buccal surface were made with a camera lucida, after staining structures with 2-3 drops of Carazzi's hematoxylin. Terminology is that of Viertel (1982) for the buccopharyngeal cavity and Gosner (1960) for tadpole stages. Portions of the anterior gut of two individuals of each species were dissected for qualitative examination of their contents. For light microscopy (LM) observation, the gut was dehydrated, cleared, and embedded in paraffin (56-58 C); longitudinal and transverse sections (4 ,um) were stained with PAS or a modified version of Masson's trichrome (Martoja and Martoja-Pierson, 1970). Tadpoles were deposited in the personal collection of DDE, Department of Biological Sciences of Facultad de Ciencias Exactas y Naturales (FCEN).

A survey of internal oral features of Leptodactyloid larvae (Amphibia: Anura)

A survey of internal oral features of Leptodactyloid larvae (Amphibia: Anura)

Morphological correlates of subaerial existence in leptodactylid tadpoles associated with flowing water

Tadpoles of the Brazilian leptodactylid frog genera Cycloramphus and Thoropa are characterized by having extremely depressed bodies and elongated, nearly finless tails. In this paper we describe internal oral features of Cycloramphus duseni, Thoropa miliaris, and Thoropa petropolitana larvae. These tadpoles are similar internally. Although they are considered "stream adapted" by some authors, they are found on steep, wet, rocky surfaces often near, but not directly in, streams. Internally they differ from typical stream larvae in having less buccal papillation, having an exposed glottis, and lacking secretory ridges on the branchial food traps. These are features that they share with other subaerial tadpoles, be they semiterrestrial or arboreal. Elongated tadpoles associated with streams appear more adapted for avoiding currents than living within them. Extreme elongation in tadpoles characterizes a fossorial way of life.