Federico Marangoni

Growth-Mark Formation and Chronology of Two Neotropical Anuran Species

Abstract In amphibians from tropical or subtropical regions well-expressed growth marks in bone could be expected because of the existence of strong dry/wet seasons, but little evidence is available. Additionally, temporal patterns of growth-mark formation may be a function of genetic and environmental factors. We used skeletochronology and a laboratory experiment to tease apart both causal sources, establishing direct correspondence between an observed pattern of bone growth and the actual age of Ceratophrys cranwelli and Dermatonotus muelleri from the subtropical Argentinean Chaco. Also, we describe the growth by application of the von Bertalanffy model. Growth rates decreased in both species, tending to reach asymptotic values at age 8–10 months after metamorphosis. Both species clearly exhibited haematoxylinophilic lines of arrested growth (LAG) after one year growing in captivity. These results reinforce the hypothesis that in subtropical climates the LAG formation is ultimately caused by a general intrinsic (genetic) control.

Extreme reduction in body size and reproductive output associated with sandy substrates in two anuran species

Geographic variation in body size and reproductive traits has been reported in a wide range of organisms, including amphibians. Most studies have focused on latitudinal and/or altitudinal variation where differences in temperature and duration of the growing season are the main causes for population divergence. We describe a steep variation in body size and reproductive traits in two anuran species in southwestern Spain, associated with changes in the geological substrate. Pelobates cultripes and Bufo calamita (= Epidalea calamita ) drastically reduced their size (a 71.6% and 76.1% reduction in body mass for P. cultripes and B. calamita , respectively) in just about 60 km. This extreme size reduction was more pronounced at the boundary between two different geological substrates (hercinic and sandy soil). Mean clutch mass, egg size, and clutch size were all smaller in B. calamita populations in the sandy environment. Likewise, clutch mass and egg size were both smaller in sandy P. cultripes populations. We observed a negative correlation between size-adjusted fecundity and egg size for both species, suggesting the existence of a reproductive trade-off that could explain the differences in reproductive allocation between populations and species. In P. cultripes , small-bodied populations had relatively higher fecundities and smaller eggs than large-bodied ones, whereas in B. calamita populations from the sandy area we found both populations with high fecundity and small eggs, and populations with low fecundity and large eggs. Common environmental effects associated with the sandy substrate produce a similar reduction in size in both toad species.

The Identity of Eupemphix fuscomaculatus Steindachner, 1864 (Amphibia: Anura)

Abstract Eupemphix fuscomaculatus Steindachner, 1864 was described on the basis of a single specimen collected at Caiçara, Mato Grosso, Brazil. This species, currently included in the genus Pleurodema, experienced a confusing taxonomic history and is supposedly known only from the holotype and seven specimens from Río Apa, Paraguay, collected by Alfredo Borelli in 1893–1894. Examination of Steindachners holotype and Borellis specimens revealed that they are not conspecific, E. fuscomaculatus is a junior synonym of Physalaemus biligonigerus (Cope, 1861 “1860”), and the specimens from Río Apa, Paraguay, could not be distinguished by their morphology or ploidy either from Pleurodema bibroni or P. kriegi, and are referred here as Pleurodema bibroni based on ecological considerations. Contrary to a recent proposal, the presence of vomerine teeth is not considered diagnostic for the genus Pleurodema, as they are absent in seven of the 13 species of Pleurodema examined. In addition, we propose to amend the type locality of P. biligonigerus to the surroundings of La Paz, Entre Ríos Province, Argentina.

Tolerância e sensibilidade térmica em anfíbios.

We are currently living in a scenario of climate change in which the rise of the average environmental temperatures and the increase of events of extreme temperature peaks is forecasted, among others. The study of the thermal tolerance and sensitivity is very important, particularly in amphibians, when forecasting the impact of rising temperatures on both the fauna and flora of the world. Knowing that amphibians are an essential part of the world’s terrestrial and aquatic biodiversity, and that they possess a series of ecophysiological characteristics and life history traits, which makes them very susceptible to environmental changes, it is essential to identify the species/communities that are more vulnerable to global warming.

Sexual Size Dimorphism and Age in Odontophrynus cf. barrioi (Anura: Odontophrynidae) from the Monte Desert, Argentina

Abstract Current knowledge on sexual dimorphism and population structure in the genus Odontophrynus is limited. We studied age structure, age at maturity, and longevity in Odontophrynus cf. barrioi, with skeletochronology. We also determined whether sexual dimorphism in body size exists in this species, and evaluated its relation to demographic life history traits. We found that females were larger in four variables corresponding to the morphology of the head. In addition, females of O. cf. barrioi have a longer tibia-fibula and femur than males. Nevertheless, Odontophrynus cf. barrioi shows no sexual dimorphism in snout–vent length. We suggest the possibility that sexes have different growth trajectories after the onset of reproduction, as they are exposed to different selection pressures, or even predation rate, because of size differences.

Depredación de Erythrolamprus poecilogyrus (Serpentes: Dypsadidae) por Lethocerus annulipes (Heteroptera: Belostomatidae)

Se da a conocer el primer registro de depredacion en la serpiente Erythrolamprus poecilogyrus por parte de la chinche de agua gigante Lethocerus annulipes .