The tadpole of Hypsiboas leptolineatus ( Braun and Braun , 1977 ) , a species in the Hypsiboas polytaenius clade ( Anura ; Hylidae )

The larval morphology of Hypsiboas leptolineatus was studied. The tadpole has an ovoid body in lateral view, wider than deep; snout rounded with dorsal reniform nostrils; spiracle sinistral with lateral wall attached to body; anal tube dextral; tail fins convex with acuminate tip; oral disc ventral; labial tooth row formula is 2(2)/3(1); moderately developed beaks with serrated jaw sheaths. These external oral features are compared with those of the known tadpoles in the Hypsiboas polytaenius clade. The oral cavity was studied using an electron microscope. Life history aspects are commented.

Hypsiboas leptolineatus has been described from southern Brazil by Braun and Braun (1977).Kwet (2001) studied reproductive aspects and vocalization patterns of this species, but its tadpole remains unknown.Within the H. polytaenius clade, external tadpole morphology has been described for H. polytaenius (Heyer et al., 1990), H. goianus and H. cipoensis (Eterovick et al., 2002).In our article, we describe the larval morphology of H. leptolineatus and compare it with morphological characteristics of these previously described tad-poles.The morphology of the internal oral cavity of H. leptolineatus is also described.

Material and Methods
Tadpoles were collected at the Centro de Pesquisa e Conservação da Natureza Pró-Mata, Municipality of São Francisco de Paula, Serra Geral region in the State of Rio Grande do Sul, between 1995 and 1997 by A. Kwet.The larvae were stored in 70% alcohol and deposited in the SMNS collection (Staatliches Museum für Naturkunde Stuttgart) (see Appendix 1).External measurements were made to the nearest 0.01 mm using a stereoscopic microscope and internal features were analysed by a scanning electron microscope.Tadpoles were staged according to Gosner (1960).The terminology for describing external features follows Altig and McDiarmid (1999) and, regarding internal oral structures, Wassersug (1976Wassersug ( , 1980)).(Braun and Braun, 1977)

Tadpole description
Description based on 17 tadpoles in stages 25-37 (Table 1).Body ovoid in lateral view, wider than deep, 32% of total length (Figure 1); snout rounded in lateral view; nostrils dorsal, reniform, closer to eye than to tip of snout; distance between nares 55% of interorbital width; spiracle sinistral, lateral wall attached to body; anal tube dextral, right wall displaced anteriorly and dorsally; tail approximately 68% of total length; tail fins convex, height approximately 20% of its length; tail fin with acuminate tip; fin origin slightly anterior to base of the tail muscle.Oral disc ventral, width 36% of body width, with lateral folds (Figure 2); labial tooth row formula (LTRF) 2(2)/3(1); labial teeth small, closely positioned; teeth smaller in A2 than A1, and in P3 than P2; a row of marginal papillae around the whole oral disc, except for a rostral gap; a row of sub-marginal papillae laterally and ventrally; beak moderately developed; upper jaw sheath concave, lower jaw sheath U-shaped, both serrated.
In preserved specimens, body colour greyish to brownish, with notable dark patches and small dots uniformly distributed on dorsum.Tail yellowish, with a blackish to brownish line on the medium portion of the tail muscle.Brownish spots scattered on superior portion of tail.Tail fins transparent.Gut visible through belly skin.Some larvae with darker coloration and greyish to brownish tail fins, dark brownish dorsum and tail muscle.

Oral cavity
Buccal roof elongated with prenarial and postnarial arenas clearly visible (Figure 3a).Prenarial arena with   a V-shaped ridge, with a depression at central portion, placed on the middle width of the arena.Narial valve projection obliquely oriented, with posterior wall higher than anterior wall.Two pronounced lateral ridge papillae, one at each side, and smaller pointed papillae present.Median ridge approximately 75% of total width of buccal area.U-shaped buccal roof arena delimited by finger-like papillae with variable length, containing numerous small pustulations.Lateral walls of buccal roof arena with a row of papillae on each side and pustulations.Glandular zone concentrated centrally.Dorsal velum clearly delimited.Buccal floor triangular, with a semicircular posterior limit (Figure 3b).Two compressed infralabial papillae with ramifications on borders.Two equally sized lingual papillae, symmetrically arranged in the middle of tongue.Two diagonal rows of papillae at each side of buccal floor arena.Small pustulations covering the arena.Ventral velum clearly visible.
The distribution ranges of the species in the H. polytaenius clade seem to be geographically separated.Hypsiboas leptolineatus is the only species occurring in southern Brazil, in higher regions of the Rio Grande do Sul and Santa Catarina states (Cruz and Caramaschi, 1998;Kwet and Di-Bernardo, 1999).Hypsiboas goianus occurs in central-western Brazil, in the Goiás and Distrito Federal states and in the southwest of the state of Minas Gerais.Hypsiboas cipoensis and H. polytaenius might have an allopatric distribution in southeastern Brazil.Whereas H. cipoensis inhabits the higher regions of Serra do Cipó, H. polytaenius is found on lower parts of the Serra do Mar and the Serra da Mantiqueira (Cruz and Caramaschi, 1998).
The adults of H. leptolineatus inhabit open areas, where they are frequently found in the proximity of small streams and ponds (Kwet, 2001).Only limited data on the tadpole ecology of H. leptolineatus and the other known species of the H. polytaenius group are available.Tadpoles of H. leptolineatus were observed throughout the year at the bottom of water bodies among stones (Kwet and Di-Bernardo, 1999).Tadpoles of H. cipoensis were observed in small streams and backwaters (Haddad et al., 1988;Eterovick et al., 2002), whereas H. polytaenius tadpoles were found on the floor of permanent or temporary ponds (Cardoso et al., 1989;Heyer et al., 1990).The tadpoles of H. goianus live at the bottom of small streams surrounded by forest vegetation (Eterovick et al., 2002).All these observations about substrate utilization indicate that the tadpoles in this clade belong to the benthic morphotype.

Figure 3 .
Figure 3. Section of the oral cavity of Hypsiboas leptolineatus: a) the buccal roof of the mouth; and b) the buccal floor (bar = 0.5 mm).