Effects of acidification on the isotopic ratios of Neotropical otter tooth dentin.

RATIONALE: Stable carbon and nitrogen isotope ratios are widely used in ecological studies providing important information on the trophic ecology and habitat use of consumers. However, some factors may lead to isotopic variability, which makes difficult the interpretation of data, such as the presence of inorganic carbon in mineralized tissues. In order to remove the inorganic carbon, acidification is a commonly used treatment. METHODS: The effects of two methods of acidification were tested: (i) dentin acidification with 10% HCl using the 'drop-by-drop' technique, and (ii) dentin acidification in an 'HCl atmosphere', by exposing the dentin to vaporous 30% hydrochloric acid. Results were compared with untreated subsamples. The stable carbon and nitrogen ratios of untreated and acidified subsamples were measured using an elemental analyzer coupled to an isotope ratio mass spectrometer. RESULTS: The nitrogen isotopic ratios were statistically different between the two acidification treatments, but no significant changes in carbon isotopic ratios were found in acidified and untreated samples. CONCLUSIONS: The results indicated that acidification had no effect on carbon isotopic ratios of Neotropical otter tooth dentin, while introducing a source of error in nitrogen isotopic ratios. Therefore, we conclude that acidification is an unnecessary step for C and N stable isotope analysis.

The partitioning of food resources between two rodents in the subtropical region of southern Brazil.

The capybara (Hydrochoerus hydrochaeris) and nutria (Myocastor coypus) are herbivorous semi-aquatic rodents. Although these rodents occur in sympatry in southern South America, little is known about how the two species interact in relationship to food resources. In this context, the aim of this study was to analyze the food resource overlap, the feeding strategy and the diversity of the diet of capybaras and nutria. A micro-histological analysis of feces was used to study the diets. A total of 48 plant species belonging to 10 families were identified in the diet of H. hydrochaeris, and a total of 49 species belonging to 14 families were identified in the diet of M. coypus. According to the Amundsen graphical method, both rodents adopted a specialized strategy for feeding on Poaceae and a generalized strategy for other families. The results of a multivariate analysis of the dietary data showed significant differences between the two rodent species and among the seasons. These differences between diets may be related to the different proportions of each food item eaten. However, the dietary overlap between the two rodents in the Taim wetland was high, suggesting that partitioning of other resources ensured the coexistence of the species.

The partitioning of food resources between two rodents in the subtropical region of southern Brazil

ABSTRACT The capybara (Hydrochoerus hydrochaeris) and nutria (Myocastor coypus) are herbivorous semi-aquatic rodents. Although these rodents occur in sympatry in southern South America, little is known about how the two species interact in relationship to food resources. In this context, the aim of this study was to analyze the food resource overlap, the feeding strategy and the diversity of the diet of capybaras and nutria. A micro-histological analysis of feces was used to study the diets. A total of 48 plant species belonging to 10 families were identified in the diet of H. hydrochaeris, and a total of 49 species belonging to 14 families were identified in the diet of M. coypus. According to the Amundsen graphical method, both rodents adopted a specialized strategy for feeding on Poaceae and a generalized strategy for other families. The results of a multivariate analysis of the dietary data showed significant differences between the two rodent species and among the seasons. These differences between diets may be related to the different proportions of each food item eaten. However, the dietary overlap between the two rodents in the Taim wetland was high, suggesting that partitioning of other resources ensured the coexistence of the species.

Feeding ecology of the Neotropical otter Lontra longicaudis in the Lower Arroio Grande River, southern Brazil.

The present study was based on the analysis of spraints (n = 294) collected between December 2005 and November 2007. The importance of each type of prey was determined by absolute and relative frequency. Niche breadth was also estimated. The results were reported as mean (± SD) of relative frequencies. Fish were the main prey found in spraints (57.8 ± 7.0%). Fish from Callichthyidae family were the main prey, followed by Cichlidae, the species Hoplias malabaricus and the family Characidae. The frequencies of other fish and taxa were lower than 13.9% (absolute frequency) and 5.6% (relative frequency). Despite significant seasonal variations, (P = 0.001), niche breadth values were low in all seasons (0.39 ± 0.11). Therefore, Lontra longicaudis presented a narrow niche breadth as a result of consistent fish predation. Based on these data, fish with rapid movement presenting territorial behavior and benthic fish with slow movements are the most consumed. Seasonal fluctuations are caused by the increase of secondary prey in the diet during some seasons.

In vitro assays for vesper mice (Calomys laucha) sperm using heterologous substrates from nonrodent species.

Small vesper mice (Calomys laucha) may be considered as an animal model for in vitro fertilization studies, but limited data about in vitro evaluations of their sperm quality and fertility are available. The in vitro penetration (IVP) assay is used to estimate potential sperm fertility for many mammal species, but it still requires reduction in cost and labor. This study tested improvements in the IVP assay for C. laucha sperm using swine oocytes and perivitelline layers (PVL) of chicken eggs as substrates, and evaluated associations among C. laucha sperm quality, IVP, and in vivo fertility after natural mating. In the IVP assay, gametes coincubation was carried out flat-bottomed wells with M2, in water bath at 37°C for 2 hr. C. laucha sperm presented motility, normal morphology, membrane integrity, and acrosome integrity equal to 90.6 ± 5.6, 90.2 ± 6.6, 88.7 ± 9.6, and 90.5 ± 11.5%, respectively. The IVP rate was 39.8% in swine oocytes and 87.5% in the inner PVL. Considering in vivo fertility as the gold standard, the IVP assay in swine oocytes presented a sensitivity of 16.0% and specificity of 83.3%. The sensitivity of the IVP assay in the inner PVL was 84.0%, but the specificity was not determined because there were no true negative results. Sperm membrane integrity was correlated with parturition after natural mating (r = 0.38, P<0.01) and litter size (r = 0.54; P<0.0002).The IVP assay using swine oocytes as substrates can be performed in nearly 2 hr without gametes' coincubation in CO(2).

Feeding habits of coypu (Myocastor coypus Molina 1978) in the wetlands of the Southern region of Brazil

The aim of this study was to determine the diet of coypu (Myocastor coypus) in two areas (Santa Isabel do Sul wetlands - Area 1, and Santa Marta Farm - Area 2) in the Southern region of Brazil, using microhistological analyses of feces. Twenty-four plant species were identified from collected feces samples. Among the identified species, nine are common in the animals' diet in both areas; the presence of Oriza sativa was not detected in any of the samples. Among the identified species, 84 percent and 54 percent of the coypu's diet from Areas 1 and 2, respectively, are aquatic plants. Poaceae family was most common, being found in 82 percent of the samples from both areas. Paspalum disthichum (Area 1) and Panicum tricholaenoides (Area 2) were the most frequent species on the coypu's diet. The diet comparison for both areas indicates that feeding habits vary depending on the type of habitat, environmental conditions and food availability. The absence of rice in our analysis may be an indication for the preservation of native areas around watercourses, so as to prevent coypu from invading irrigated crops.

O objetivo deste estudo foi determinar a dieta do ratão-do-banhado (Myocastor coypus), em duas regiões (áreas alagadas em Santa Isabel do Sul - Área 1 e Fazenda Santa Marta - Área 2), na região sul do Brasil, utilizando microhistological análises de fezes. Foram identificadas 24 espécies de plantas nas amostras de fezes coletadas. Entre as espécies identificadas, nove são comuns a dieta dos animais de ambas as áreas, não sendo detectada a presença de Oriza sativa em nenhuma das amostras. Entre as espécies identificadas, 84 por cento e54 por cento da dieta do ratão-do-banhado, nas Áreas 1 e 2 respectivamente, são plantas aquáticas. A família Poaceae foi a mais abundante, sendo encontrada em 82 por cento das amostras de ambasas áreas. Paspalum disthichum (Área 1) e Panicum tricholaenoides (Área 2), foram as espécies mais frequentes na dieta do ratão-do-banhado. A comparação da dieta de ambas as áreas mostrou que a alimentação varia dependendo do tipo de habitat, condições ambientais e de disponibilidade alimentar. A ausência de arroz na nossa análise pode ser um indicativo de que a preservação de áreas nativas ao redor de cursos d'água, evita que o ratão-do-banhado utilize as culturas de arroz.

Feeding habits of coypu in the wetlands of the Southern region of Brazil.

The aim of this study was to determine the diet of coypu (Myocastor coypus) in two areas (Santa Isabel do Sul wetlands - Area 1, and Santa Marta Farm - Area 2) in the Southern region of Brazil, using microhistological analyses of feces. Twenty-four plant species were identified from collected feces samples. Among the identified species, nine are common in the animals' diet in both areas; the presence of Oriza sativa was not detected in any of the samples. Among the identified species, 84% and 54% of the coypu's diet from Areas 1 and 2, respectively, are aquatic plants. Poaceae family was most common, being found in 82% of the samples from both areas. Paspalum disthichum (Area 1) and Panicum tricholaenoides (Area 2) were the most frequent species on the coypu's diet. The diet comparison for both areas indicates that feeding habits vary depending on the type of habitat, environmental conditions and food availability. The absence of rice in our analysis may be an indication for the preservation of native areas around watercourses, so as to prevent coypu from invading irrigated crops.

Lactational transfer of PCBs and chlorinated pesticides in pups of southern elephant seals (Mirounga leonina) from Antarctica.

Seven pairs of southern elephant seals (Mirounga leonina) pups and their dams were sampled during the late weaning season among a breeding population of seals on Elephant Island in Antarctica. The blubber of the pups and the milk and blubber of their dams were analyzed for lipid-normalized concentrations of PCBs and organochlorines compounds in order to evaluate the lactational transfer of these contaminants. The lipid-normalized concentrations in these tissues were in the ppb range (i.e., ngg(-1) lipid). The levels of contaminants in southern elephant seals were low in comparison with residues that have been reported in pinnipeds from the northern hemisphere. The relative tissue concentrations of the analytes measured followed the pattern: SigmaDDT>mirex>SigmaPCB>Sigmachlordane>HCB>heptachlor epoxide>dieldrin>methoxychlor>SigmaHCH>other organochlorines. The very high DDE/SigmaDDT ratio (0.91) in the blubber of dams and pups was an indicative of long-term, extremely distant pollution. On the other hand, the relatively high levels of some other organochlorine pesticides (e.g. mirex, heptachlor epoxide, dieldrin, methoxychor) may reflect the continued use of these insecticides in developing countries located in the southern hemisphere. For most of the analytes measured, the lipid-normalized concentrations were lower in pup blubber and in the milk than in the maternal blubber. Lactational transfer rates were dependent on the logK(ow) (octanol/water partition coefficient) values of the analytes measured, less lipophilic compounds being more readily transferred to the pups by the lactational route.

Residues of persistent organochlorine contaminants in southern elephant seals (Mirounga leonina) from Elephant Island, Antarctica.

Contamination of blubber tissues by organochlorine pesticides (OC) and PCBs was assessed in female and male pups and juveniles, as well as in adult females and subdominant adult males of the Southern elephant seal, Mirounga leonina, from Elephant Island in the Antarctic Peninsula. All residues of persistent organochlorine contaminants analyzed were found in blubber samples, except for beta-HCH, endosulfan II, endrin, heptachlor, and aldrin. The relative concentrations of the analytes detected were sigmaDDT > sigmaPCB > sigmachlordane > mirex > dieldrin > HCB> sigmaendosulfan > methoxychlor > sigmaHCHs > other OC pesticides. OC and PCBs concentrations were 1 or 2 orders of magnitude lower than those found in pinnipeds from northern hemisphere. The ratio sigmaDDT/sigmaPCB was higher in southern elephant seals. The relative importance of some OC residues indicates that pesticides used either currently or in the recent past in countries in the southern hemisphere are the sources of contamination in the Antarctic region. Data showed that concentrations of contaminants generally increased from pups < juveniles < adults and suggested that pups accumulated contaminants through transfer from the mother seals via transplacental and lactational routes.

Serum immunoglobulin G concentration in Southern elephant seal, Mirounga leonina (Linnaeus, 1758), from Elephant Island (Antarctica): sexual and adrenal steroid hormones effects.

Serum immunoglobulin G (IgG; indirect enzyme-linked immunosorbent assay), as well as sexual and adrenal steroid hormones' concentrations (radioimmunoassay) were determined in 63 (male and female) Southern elephant seals (Mirounga leonine) at different developmental stages (weaned pups, juveniles and adults). In females, IgG values (mean+/-S.D.) were higher (P<0.05) in adults (15.9+/-6.5mg ml(-1)) than in juveniles (7.9+/-4.0mg ml(-1)), but similar to weaned pups (12.0+/-5.0mg ml(-1)). Estrogen concentration was higher (P<0.05) in adults than in the weaned pups. In females, a significant (P<0.05) correlation (R=0.4) between serum IgG level and progesterone concentration was observed. In males, testosterone concentration was higher (P<0.05) in adults than in the juveniles and weaned pups. Aldosterone and cortisol concentrations were higher (P<0.05) in weaned pups (1056.0+/-643.1pmol 1(-1) and 272.7+/-110.0 nmol 1(-1), respectively) than in the juveniles (638.6+/-579.7pmol1(-1) and 152.9+/-97.3nmol 1(-1), respectively) and adults (386.5+/-209.1pmol (-1) and 145.7+/-67.3nmol 1(-1), respectively). These findings indicate that weaned pups are subjected to a higher natural stressful condition in the field. Despite this, humoral immunity, measured through IgG concentration, is not impaired in weaned pups.

Movement of southern elephant seals (Mirounga leonina L.) from Elephant Is. South Shetlands, Antarctica

O presente estudo descreve os movimentos de dois exemplares de elefante-marinho do sul (Mirounga leonina) durante a fase pelágica de seu ciclo de vida. Os exemplares foram capturados no verão austral de 1999 na Ilha Elefante (61º13'S, 55º23'W), Antártica, e monitorados por aproximadamente 9 meses. Cada exemplar foi instrumentado com um medidor de tempo e profundidade de mergulho via satélite (Sattelite Time Depth Recorder, STDR mod. ST-6PPT, Telonics®, EUA) com uma antena VHF acoplada ao instrumento, montado num molde de tela e resina, fixado com cintas plásticas, e colados na pelagem dorsal do animal com resina plástica. Para a instrumentação o animal era capturado com rede de contenção e imobilizado quimicamente com anestésico dissociativo (Zoletil 50®- 1mg/kg). Um dos indivíduos (23842), deslocou-se da Ilha Elefante (61.2ºS 55.3ºW) até a Ilha Rei George (62.2ºS 58.1ºW) em fevereiro quando perdemos contato com o instrumento. Já o indivíduo 23843 permaneceu nas águas ao redor da Ilha Elefante (61.2ºS 54.4ºW a 61.6ºS 55.4ºW) por grande parte do ano (janeiro à setembro), quando começou a deslocar-se para SW. Este indivíduo foi re-avistado na temporada de 1999/2000 quando o instrumento foi recuperado. Os deslocamentos registrados podem estar relacionados com o estágio de desenvolvimento de cada indivíduo. O presente estudo demonstra a viabilidade de estudos de monitoramento de elefantes-marinhos das Ilhas Shetlands do Sul, Antártica, através de telemetria por satélite e a necessidade da continuidade destes estudos num maior número de indivíduos para uma descrição mais detalhada dos padrões de migração, distribuição e forrageio apresentados.