First record of Chaunus achavali ( Anura , Bufonidae ) from Rio Grande do Sul , Brazil , with a key for the identification of the species in the Chaunus marinus group

The bufonid toad Chaunus achavali, a recently described species known only from Uruguay, is recorded for Brazil. This species is morphologically similar to C. ictericus and C. arenarum, and several individuals were labeled in Brazilian scientific collections under these taxa. A lectotype of C. arenarum is designated. Additional field notes on C. achavali and a key for the identification of the species in the Chaunus marinus group are presented.

During fieldwork in the Municipality of Candiota, south of state of Rio Grande do Sul, Brazil (DI-BERNARDO & KWET, 2002;DI-BERNARDO et al., 2004), we collected several specimens of an unidentified species of Bufo.These specimens, superficially similar to C. arenarum and C. ictericus, were preliminary determined as Bufo sp.(aff.arenarum) in KWET (2001), and as Bufo sp. in DI-BERNARDO et al. (2004).A single individual belonging to the same taxon was later collected in the Municipality of Quinze de Novembro, and another specimen was photographed in the Municipality of Agudo, both localities situated in central Rio Grande do Sul.Additional specimens labeled under the names C. arenarum or C. ictericus, were identified in the collections of Universidade Federal do Rio Grande do Sul, Universidade Federal de Santa Maria, and Museu de Ciências Naturais da Fundação Zoobotânica do Rio Grande do Sul.To confirm the species identity, we re-examined all individuals and compared them with the type material of Chaunus achavali and C. arenarum, and with additional specimens of C. arenarum and C. ictericus.Our comparison revealed that the unidentified specimens collected by us belong to Chaunus achavali.The aim of this publication is: (1) to report the first record of Chaunus achavali for Brazil; (2) to present life history notes of this poorly known species; (3) to remark on the type specimens of Chaunus arenarum; and (4) to provide an artificial key for the identification of adult toads in the Chaunus marinus group, based on external morphology.
In order to designate a lectotype for Chaunus arenarum, we examined the type material present in the Museum für Naturkunde, Berlin.Measurements of these specimens were taken to the nearest 0.1 mm using digital calipers.Additional material, including type specimens of Chaunus achavali, C. arenarum and C. jimi, and specimens of C. ictericus, C. marinus, C. rubescens, and C. schneideri, were compared in order to construct an identification key to the species in the C. marinus group.First record of Chaunus achavali (Anura, Bufonidae) from Rio Grande...

RESULTS
Morphology.For our comparisons, we studied the type material of Chaunus arenarum, which has never been examined since the original description of this species.In the ZMB collection, we found three syntypes, out of seven specimens mentioned by HENSEL (1867).These three specimens are in a rather good condition and were originally catalogued under ZMB 6779.Now they are housed under three separate numbers: ZMB 6779, ZMB 57370 and ZMB 57371 (Figs.2-7).To prevent taxonomic problems in the future, we herein designate ZMB 6779, the largest specimen, as the lectotype of C. arenarum, and ZMB 57370 and 57371 as paralectotypes (see Table I for measurements of these three type specimens).
Our morphological comparison between C. arenarum, including living specimens, and the recently collected material from Candiota and Quinze de Novembro revealed that they belong to distinct species (Figs. 4, 5).The differences, e.g., in shape of parotoid glands (inner margin concave in C. achavali and sinuous in C. arenarum), development of cranial crests (sharper in C. achavali), development of toe membranes (bigger in C. achavali), and general dorsal coloration (light cream, sometimes yellowish-gray in C. arenarum versus dark brown, ferruginous in C. achavali) are significant and sometimes already visible in juveniles (Figs. 6,7).A comparison with the other two species of the C. marinus group known from Rio Grande do Sul, C. schneideri (Fig. 8) and C. ictericus (Fig. 9), also demonstrated clear morphological differences, e.g., presence of paracnemic (tibial) glands in C. schneideri (absent in C. achavali), well developed, subtriangular parotoid glands in C. schneideri and C. ictericus (small and cylindrical in C. achavali), and less developed foot web in C. schneideri and C. ictericus (well developed in C. achavali).On the other hand, when comparing our specimens with C. achavali we did not find differences, meaning they are  First record of Chaunus achavali (Anura, Bufonidae) from Rio Grande... Field notes.During our fieldwork in Candiota, Chaunus achavali was occasionally observed in or near small forest streams, in elevations around 160 m a.s.l.The first seven specimens (MCP 3936,3937,3938,3939,3940,3941,3973, all adults except MCP 3941) were collected on 21th December 1999, in activity at night, most of them out of water, along the margins of a small stream (G.F. Pontes, pers.com.).Most adult individuals were found perched on tree-trunks, about 20-50 cm above the water surface, and some specimens under stones.One male was sitting in the water.Despite the concomitant presence of adult males and females at the same site, we did not hear advertisement calls, and did not find eggs or tadpoles.The MCP 3941 is figured here (Fig. 7) to illustrate the different dorsal coloration of living juveniles.Whereas adults of C. achavali (Fig. 5) are uniformly brownish or reddish, ferruginous on dorsum, juveniles possess a conspicuous pattern of orange and creamcolored blotches, which are irregularly arranged in several longitudinal lines.Other two individuals (MCP 4095 and 4374), with well developed nuptial pads, were collected in October 2000 and January 2001, in water collections with pH = 9.00 and pH = 6.82, respectively.Three juveniles (MCP 4466,4467 and 4468) were collected in 12th January 2001, inactive under stones, between 17h and 18h 30min.
The specimen from Quinze de Novembro (MCP 5687) was found on 14th February 2002 at day, sitting in the water at the margin of a small stream, near Santa Clara do Ingaí.The specimen photographed in Agudo (Fig. 11, not collected) was found in 6th January 2001 at morning, walking over rounded, river-rolled stones, at the left margin of the Jacuí river.

DISCUSSION
In his description of Chaunus arenarum, HENSEL (1867) mentioned seven specimens, which he had collected " bei der Stadt Rio-Grande do Sul" (= near the city of Rio Grande do Sul [Brazil]).This type locality was later specified as " Rio Grande, Rio Grande do Sul Brazil" by BOKERMANN (1966).FROST (2004) noted that the deposit location of type specimens was not designated but that the syntypes are probably in the ZMB collection, Berlin.Actually, we localized a jar with three type specimens in the Berlin collection, herein designating ZMB 6779 as the lectotype of Chaunus arenarum (Hensel, 1867).The remaining four type specimens could not be located.
Up to date, Chaunus achavali was only known from six localities in the Departamentos of Treinta y Tres, Tacuarembó, Artigas, and Rivera, in northeastern Uruguay (MANEYRO et al., 2004) Little is known about the life history of C. achavali.MANEYRO et al. (2004) reported small streams in hill regions as the most occupied habitat of this species.This agrees with our observations in Rio Grande do Sul.Whereas most toads of the genus Chaunus are terrestrial or fossorial, and breed in lentic aquatic environments (mainly species in the C. marinus group, pers.obs.), we observed adults of C. achavali perching on fallen tree trunks and branches near (just above) or inside streams and rivers.The well-developed webbing between toes (see Fig. 11) appears to be an adaptation for better dislocation in lotic waters.The dorsal skin of males with nuptial pads exhibited cornified skin tubercles.These tubercles are interpreted as a secondary sexual characteristic of adult males, as described for other bufonid species (DUELLMAN & TRUEB, 1994).This characteristic was very conspicuous in individuals collected during the end of Spring and the first Summer months, enforcing the idea that C. achavali has a seasonal reproductive activity, with its peak during the warm season.Although we could not directly observe calling or breeding activity, we found a gravid female (MCP 4375) in January.However, advertisement calls and tadpoles of this species are still unknown.We have worked for a long time in Candiota (more than two years), searching for anurans mainly in ponds and other lentic bodies of water.In such places, we found calling males, eggs, tadpoles or juveniles of all the 22 recorded species (DI-BERNARDO et al., 2004), with the exception of C. achavali.We think it is plausible to assume here that C. achavali do not use lentic collections of water, living and breeding in streams and rivers.(CEPB), Sonia T.Z.Cechin (ZUFSM), and Rainer Günther (ZMB).Reuber Brandão and Natan Maciel kindly took measurements from the types of Chaunus jimi.Glaucia Pontes provided some field notes.We acknowledge Dr. M. B. Martins (MCN) for valuable help in the handling of the manuscript as for give us the basis of Figure 1.The " Candiota Project", which gave the opportunity for collecting many of the Chaunus achavali specimens from First record of Chaunus achavali (Anura, Bufonidae) from Rio Grande... Brazil, was financed by CNPq/PADCT/CIAMB (Process CIAMB # 01/97-03/02).MD is partially financed by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (Process CNPq # 307.992/2004-7), and RM has a doctoral fellowship from Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES).

Fig. 11 .
Fig. 11.Specimen of Chaunus achavali photographed in its place of finding (margin of the Jacuí river) in Agudo, Rio Grande do Sul (not collected).Note the well-developed webbing between toes.Photo: M. Borges-Martins.
. Our new records from the neighboring Brazilian State of Rio Grande do Sul extend the geographic range of this species about 382 km NE from previous cited localities.The record from Quinze de Novembro represents the northernmost and also the highest (374 m a.s.l.) locality known to date for this species.Due to its small distribution range, MANEYRO & LANGONE (2001) classified C. achavali (as Bufo sp.) as potentially threatened in Uruguay.Data are still insufficient to assess the distribution range and threat category of this species in Rio Grande do Sul, but C. achavali may have a wider distribution than presently acknowledged, being sometimes mistaken for C. arenarum or C. ictericus.The key to adult toads in the B. marinus group presented here should allow a correct identification of this species.