Reproductive biology of Erythrolamprus jaegeri coralliventris (Serpentes: Dipsadidae) in the Brazilian Coastal Pampa.

We analyzed reproductive biology of Erythrolamprus jaegeri coralliventris, a snake from the Brazilian Pampa. Females presented larger snout-vent length than males, while no significant differences were found in tail length/snout-vent length ratios between sexes. Females attain sexual maturity in larger sizes than males. The reproductive cycle of females presented a seasonal pattern, with advanced vitellogenesis occurring from middle winter to middle spring and oviductal eggs occurring from middle winter to middle summer. The real fecundity ranged from two to eigth eggs and the expected fecundity varied from one to 12 secondary follicles. No significant correlation was found between females body size and the following parameters: real fecundity, length of the largest egg and potential fecundity. Therefore, E. j. coralliventris presents a seasonal reproductive pattern, which seems to follow the rainfall profile observed for the studied region. This may represent a strategy of energy gain associated to the reproductive cycle, considering that the food resources most explored by this species are anurans that present higher activity during rainy periods.

Diet, sexual dimorphism and reproduction of sympatric racers Philodryas aestiva and Philodryas patagoniensis from the coastal Brazilian Pampa.

Herein we investigated diet, sexual dimorphism and reproductive biology of two sympatric congeneric species at the coastal Brazilian Pampa, Philodryas aestiva and P. patagoniensis. Analysis of the stomach content of the scansorial Philodryas aestiva revealed that it feeds mainly on Anura and small mammals, while it occasionally consumes Insecta, Squamata and Aves. The more terrestrial Philodryas patagoniensis presented a broader diet, composed mainly of Anura, Squamata and small mammals. Insecta and Actinopterygii were found in lower frequencies. In females of both species, snout-vent length was significantly larger than in males, while tail length/snout-vent length ratio was significantly higher in males. Males reach sexual maturity at smaller sizes than females in both species. Fecundity was higher in P. patagoniensis (3 to 24 eggs; 15 ± 8.15) than in P. aestiva (10 to 20 eggs; X = 14.50 ± 3.53). Females of P. aestiva showed secondary follicles in all seasons while eggs occurred from middle-winter to early-summer. Secondary follicles occurred throughout the year in P. patagoniensis, but concentrated in spring. Eggs occurred in late-summer, middle-autumn and spring. Both species presented positive correlations between SVL and clutch size. Differences in analyzed traits seem to reflect divergences in species morphology and use of habitat/microhabitat.

High arsenic and low lead concentrations in fish and reptiles from Taim wetlands, a Ramsar site in southern Brazil.

The pollution caused by heavy metals and metalloids represent an emerging threat to wetlands worldwide. Herein we examined the concentrations of arsenic (As) and lead (Pb) in fish and aquatic/semi-aquatic reptiles from Taim wetlands, a Ramsar site located at the southernmost Brazilian coastal plain. A total of 82 individuals from six fish and three reptile species from varied trophic levels were analysed through furnace graphite atomic absorption spectrophotometry. Mean As concentrations (µg·g-1 dry weight) were markedly high, ranging from 13.06 ±â€¯3.18 to 19.4 ±â€¯4.04 in fish and 3.51 ±â€¯2.36 to 19.00 ±â€¯10.45 in reptiles. Mean Pb concentrations were low, ranging from 0.00067 ±â€¯0.00060 to 0.0040 ±â€¯0.00045 in fishes and 0.00103 ±â€¯0.0011 to 0.0271 ±â€¯0.0353 in reptiles. The highest As mean level was detected in the herbivore-insectivore fish Astyanax aff. fasciatus, a species of low trophic level among the analysed taxa. The highest Pb mean level was found in the broad-snouted caiman Caiman latirostris, the highest trophic level species analysed. The present study warns for the contamination of As especially in edible fish, which constitute a threat to the communities that use this resource in systems connected to Taim wetlands. As concentrations in reptiles were also higher than those reported in previous studies concerning the groups herein addressed. It is possible that the high As burdens found in the analysed species could be attributed to the use of fertilizers and pesticides in extensive irrigated rice areas located in Taim wetlands surroundings, but natural sources cannot be dismissed.

Pleistocene climatic oscillations in Neotropical open areas: Refuge isolation in the rodent Oxymycterus nasutus endemic to grasslands.

Pleistocene climatic oscillations favoured the expansion of grassland ecosystems and open vegetation landscapes throughout the Neotropics, and influenced the evolutionary history of species adapted to such environments. In this study, we sampled populations of the rodent Oxymycterus nasutus endemic to open areas in the Pampas and Atlantic Forest biomes to assess the tempo and mode of population divergence using an integrative approach, including coalescence theory, ecological niche models, and morphometry. Our results indicated that these O. nasutus populations exhibited high levels of genetic structure. Six major mtDNA clades were found, structuring these biomes into distinct groups. Estimates of their divergence times was indicated to be 0.571 myr. The high degree of genetic structure is reflected in the analyses of geometric morphometric; skull differences between lineages in the two ecoregions were detected. During the last glacial maximum, there was a strong increase in suitable abiotic conditions for O. nasutus. Distinct molecular markers revealed a population expansion over time, with a possible demographic retraction during the post-glacial period. Considering that all clades coalesce with the last interglacial maximum, our results indicated that reduction in suitable conditions during this period may have resulted in a possible vicariance associated with refuge isolation.

Reproductive biology of the Green Ground Snake Erythrolamprus poecilogyrus sublineatus (Serpentes: Dipsadidae) in Subtropical Brazil.

We investigated reproductive features of the dipsadid snake Erythrolamprus poecilogyrus sublineatus in the southernmost Brazilian coast, a subtropical region characterized by well-marked seasons. Females are significantly smaller than males, have a shorter tail, and reach sexual maturity at later times along their development. In contrast to tropical subspecies, E. p. sublineatus females presented a seasonal pattern, with secondary follicles occurring from late winter to early autumn and egg production restricted to the whole spring and early summer. Males presented seasonal variation in testes volume (increase in autumn and decrease in winter) while no significant seasonal variation was found in ductus deferens width. The number of oviductal eggs varied from two to nine, thus, real fecundity is also inferior than that observed in tropical E. poecilogyrus forms. Considering the thermal requirements for reproduction, it is possible that the colder climatic conditions of the southern Brazilian coast have shaped the seasonal reproductive pattern in E. p. sublineatus. The shorter body size of this subspecies may also represent a conditioning factor of low fecundity.

Reproductive biology of the Green Ground Snake Erythrolamprus poecilogyrus sublineatus (Serpentes: Dipsadidae) in Subtropical Brazil

ABSTRACT We investigated reproductive features of the dipsadid snake Erythrolamprus poecilogyrus sublineatus in the southernmost Brazilian coast, a subtropical region characterized by well-marked seasons. Females are significantly smaller than males, have a shorter tail, and reach sexual maturity at later times along their development. In contrast to tropical subspecies, E. p. sublineatus females presented a seasonal pattern, with secondary follicles occurring from late winter to early autumn and egg production restricted to the whole spring and early summer. Males presented seasonal variation in testes volume (increase in autumn and decrease in winter) while no significant seasonal variation was found in ductus deferens width. The number of oviductal eggs varied from two to nine, thus, real fecundity is also inferior than that observed in tropical E. poecilogyrus forms. Considering the thermal requirements for reproduction, it is possible that the colder climatic conditions of the southern Brazilian coast have shaped the seasonal reproductive pattern in E. p. sublineatus. The shorter body size of this subspecies may also represent a conditioning factor of low fecundity.

Geographic variation in skull shape of the water rat Scapteromys tumidus (Cricetidae, Sigmodontinae): isolation-by-distance plus environmental and geographic barrier effects?

The geographic variation in skull size and shape of the swamp rat Scapteromys tumidus was examined in samples from eight geographic clusters in almost of its distribution in southern Brazil and Uruguay. For analysis we used two-dimensional geometric morphometric methods for dorsal, ventral and lateral views of the skull. The geometric descriptors showed no significant differences in skull size between geographic clusters, while differences in shape were highly significant. We found a significant and moderate correlation between geographic and morphological distances, corroborating the isolation-by-distance model. Samples from the Rio Grande do Sul central coastal plain were the most differentiated, segregating completely from all other samples in canonical variate analysis for the dorsal view. The most visible variable regions in skull were the zygomatic arch (mainly the squamosal root of zygomatic) and the lateral braincase borders. Once correlation between geographic and morphological distances were not strong, it is possible that other factors (environmental heterogeneity and/or geographic barriers) may are acting in S. tumidus skull differentiation.

Feeding ecology of Erythrolamprus jaegeri jaegeri (Günter, 1858) and Erythrolamprus poecilogyrus sublineatus (Cope, 1860) in the coastal zone of Subtropical Brazil (Serpentes, Dipsadidae).

The snakes Erythrolamprus jaegeri jaegeri and Erythrolamprus poecilogyrus sublineatus are sympatric and syntopic in the coastal region of southern Brazil. Herein, we analyzed the diet composition to evaluate the niche breadth and the prey selection by both species. We examined 192 specimens, and analysis of stomach contents revealed that both species predominantly consume anurans. However, the diet of E. j. jaegeri consists mainly of fish and amphibians, whereas that of E. p. sublineatus is broader, including fish, amphibians, reptiles and mammals. The Standardized Levins Index presented lower values for E. j. jaegeri (BA = 0.17) than for E. p. sublineatus (BA = 0.61), evidencing specialist and generalist strategies for each species, respectively. Regarding prey selection, E. p. sublineatus presented a larger snout-vent length, head, mouth and lower jaw than E. j. jaegeri and fed on larger prey. In addition, positive correlations between the size and weight of predators and prey were confirmed in both species. The results show the development of different mechanisms for co-occurrence of the two species, such as prey selection by size, such that the size of the predator is related to the size of their prey, or by developing different strategies to decrease niche overlap between species.

The ichthyofauna of limnic systems in Quaternary deposits of extreme southern Brazil.

The Quaternary in the state of Rio Grande do Sul (RS), southern Brazil, is geologically represented by the coastal plain and was originated by successive events of Pleistocene-Holocene marine transgressions and the occurrence of alluvial deposits. This paper aimed to characterize the fish assemblage occurring in a swampy Quaternary area adjacent to Lagoa Pequena, a lacustrine system connected to the west margin of the Laguna dos Patos estuary. A checklist is also provided of the ichthyofauna so far recorded in limnic systems of Quaternary deposits in the state of Rio Grande do Sul. A total of 42 species was recorded, distributed in nine orders, 18 families and 31 genera. Characidae and Cichlidae were the most representative families, comprising 15 and 4 species respectively. A bibliographic revision associated to our sample data revealed the occurrence of 156 species in limnic systems inserted in RS Quaternary deposits (114 limnic, 15 marine/estuarine/limnic, ten marine/estuarine, nine estuarine/limnic and eight marine). Characiformes and Siluriformes are the most diverse orders, corroborating the Neotropical pattern. Seven species can be considered endemic to RS Quaternary deposits.