Sergio D. Rosset

Review of the Geographic Distribution of Diploid and Tetraploid Populations of the Odontophrynus Americanus Species Complex (Anura: Leptodactylidae)

Abstract We review the geographic distribution of diploid and tetraploid populations of the Odontophrynus americanus species complex. Ploidy was determined using chromosome count as well as erythrocyte size. We found a complex geographic pattern of populations with different ploidy, including areas of syntopy and sympatry. The tetraploid O. americanus presents three disjunct population groups, which were isolated from one another by diploid populations. One of these tetraploid groups is distributed in central and eastern Argentina, southern Brazil, southern Paraguay, and Uruguay, with the other two population groups of the tetraploid O. americanus inhabiting southeastern Brazil, and northwestern Argentina respectively. We extend the distribution of both diploid Odontophrynus lavillai and Odontophrynus cordobae, and we present new records of three more allopatric diploid population groups, referred to here as Odontophrynus sp. Some of these population groups are associated with biogeographic regions. The karyotypes of the three currently known taxa of the O. americanus species complex are given. We report the occurrence of a naturally occurring triploid specimen and the first occurrence of B-chromosomes in the genus. Our review indicates that there is a complex distribution pattern of populations of different ploidy, including areas of syntopy and sympatry, and cytogenetic variability. This could indicate the presence of more species, occurrence of auto and allopolyploidy, and multiple origins of tetraploidy.

New Species of Odontophrynus Reinhardt and Lütken 1862 (Anura: Neobatrachia) from Brazil and Uruguay

Abstract A new species of the Neotropical frog genus Odontophrynus from coastal regions of Brazil and Uruguay is described. It is included in the americanus species group and has a diploid complement of 22 chromosomes. Odontophrynus sp. nov. is distinguished from the other species of the americanus group by having smaller size, head nearly as wide as long, skin on dorsum bearing small-sized warts, and distinct postorbital and parotoid glands that form a longitudinal ridge. Moreover, the new species has a pair of enlarged postorbital dark blotches around the afore-mentioned glandular ridge and few small-sized dark blotches on the upper lip and forelimbs. Odontophrynus sp. nov. is also characterized by nasals and frontoparietals well separated from one another, frontoparietal fontanelle exposed anteriorly, and the maxillar process of nasals slightly separated from the nasal process of the pterygoids.

Feeding in Syntopy: Diet of Hydromedusa tectifera and Phrynops hilarii (Chelidae)

Abstract Stomach contents were obtained from 25 Hydromedusa tectifera and 47 Phrynops hilarii that live in syntopy in a pampasic stream in Buenos Aires province, Argentina. Both species are arthropod consumers. Copepods, ostracods, and hemipterans are the preferred items for P. hilarii, and H. tectifera prefers copepods, ostracods, immature dipterans (mainly chironomids), and ephemeropteran larvae. Items that most contribute to the diet of both species are immature chironomids, corixids, and belostomatids. Available food varies little among seasons, being slightly lower in winter months and part of the summer. Diet diversity changes by seasonal variation of prey item abundance in the diet of both species. Diet diversity is higher for P. hilarii (more generalist and broader trophic niche) than in H. tectifera, but there is no niche overlap between them. No significant correlation between the size of turtles and length of prey items was found. There is no evidence that the long neck of H. tectifera relates to piscivorous habits, because fish are a small fraction of its diet and arthropods constitute the bulk of the ingested items.

A study on the venom of Bothrops alternatus Duméril, Bibron and Duméril, from different regions of Argentina.

We report a comparison of toxic and enzymatic activities of Bothrops alternatus venoms collected from specimens of different regions of Argentina with a pool of these same venoms. We determined lethal, hemorrhagic and pro-coagulant (plasma and fibrinogen) doses, as well as indirect hemolysis, hydrolysis of gelatin and fibrinogen. The electrophoretic pattern of the venoms and that of fibrinogen incubated with each of the venoms was studied by SDS-PAGE. The toxic activities were consistent with those reported for these venoms but with noticeable differences between samples which do not seem related to geographical or climatic characteristics. In some cases the pooled venom showed values close to the individual samples, but it was not representative since at least the half of the venoms (4/9) exhibited very different patterns of toxicity. The potency of some activities in the individual venoms ranged from much higher to much lower than those determined in the pooled venom (0.1 to 3 fold). Not all venoms exhibited thrombin-like activity but all hydrolyzed alpha and beta chains of fibrinogen; however, degradation patterns were not always similar. Variation in activities and toxicities do not seem to be related to geographical or climatic characteristics.

A REVISION OF ODONTOPHRYNUS BARRIOI (ANURA: NEOBATRACHIA): MORPHOLOGY, OSTEOLOGY, VOCALIZATIONS, AND GEOGRAPHIC DISTRIBUTION

Abstract The present paper provides diagnostic characters from external morphology and osteology that reinforce the specific recognition of the frog Odontophrynus barrioi, describes its advertisement and encounter calls, and extends its distribution range. Odontophrynus barrioi is distinguished from all other species of the genus principally by the large size of adults, great number of irregularly arranged postorbital and temporal glands, lack of both a light vertebral line and keratinous spines, alary process of the premaxilla short and wide, pterygoid process of the maxilla well developed, and high preorbital process of the maxilla. The advertisement call consists of a trill of a single repeated and pulsed note with a low dominant frequency. The encounter call consists of only one note of similar frequency as the advertisement call, but longer in time duration. We report new records of O. barrioi from Catamarca, La Rioja, and San Juan Provinces (Argentina), that increase considerably the range of this previously poorly known species.

Southernmost Localities of Trachemys dorbigni and First Record of Trachemys scripta elegans for Argentina (Cryptodira: Emydidae)

Abstract We report two new localities for Trachemys dorbigni that expand the southern range border for approximately 120 km. These new localities are Arroyo Buñirigo and Arroyo Zapata. Both are streams related to the Río de La Plata shoreline at Buenos Aires province, Argentina. We also record the nonnative Trachemys scripta elegans for the first time for Argentina.

Amphibia, Anura, Cycloramphidae, Odontophrynus lavillai : first record for Brazil and geographic distribution map

The Neotropical genus Odontophrynus currently consists of 11 species distributed in southern and eastern South America (Frost 2008). The widest distributed O. americanus group is constituted by diploid and tetraploid cryptic species very difficult to distinguish morphologically, which show a complex geographic pattern including areas of syntopy and sympatry (Barrio and Pistol de Rubel 1972; Rosset et al. 2006 and references therein).

Natural interspecific hybridization in Odontophrynus (Anura: Cycloramphidae)

The frog genus Odontophrynus is a composite of diploid and tetraploid populations and species that are widely distributed in South America. Some of the several genetic studies on this group report the production of artificial hybrids but only a single case of natural hybridization has been documented, in southern Brazil. In this study we report the finding of an interspecific natural hybrid specimen in central Argentina. We present morphological and cytogenetical evidence that the diploid taxa Odontophrynus cordobae and O. occidentalis are the parental species. The hybrid genome exhibited problematic pairing and segregation of homeologue chromosomes during meiosis, and the production of non-reduced gametes.

Stereotyped Defensive Behaviours in Frogs of the Genus Odontophrynus (Amphibia: Anura: Odontophrynidae)

Abstract: Observations on stereotyped defensive behaviours are presented for 7 frog species of the Neotropical genus Odontophrynus from Argentina and Uruguay. Seven stereotyped postures were observed, among which the most common observed were puffing up the body, contracting, and crouching down. Newly reported behaviours include tongue protrusion, eye protection, and some combinations of postures. We provide an account of defensive behaviours already described in Odontophrynus and discuss the correspondence between the terminology used by previous authors and recently proposed classifications. In addition, we highlight defensive mechanisms associated with the body raising posture in Neotropical anurans, which may include intimidating predators, body shape disruption, warning signaling, and exposure of skin macroglands.

The advertisement call and geographic distribution of Odontophrynus lavillai Cei, 1985 (Anura: Odontophrynidae).

Currently, the genus Odontophrynus Reinhardt & Lutken comprises 11 species distributed in southern and eastern South America. Among them, O . americanus (Dumeril & Bibron), O . lavillai Cei, O . cordobae Martino & Sinsch, and O . maisuma Rosset constitute a group of sibling diploid and tetraploid species, the O. americanus group (Rosset et al . 2006 and literature cited therein).