Latin American Journal of Aquatic Mammals (LAJAM)
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A Tale of Two Dolphins: Introduction to the Special Volume on the Biology and Conservation of Neotropical Dolphins of the Genus Sotalia
No full textA Tale of Two Dolphins: Introduction to the Special Volume on the Biology and Conservation of Neotropical Dolphins of the Genus Sotali
Occurrence of chlorinated pesticides and polychlorinated biphenyls (PCBs) in Guiana dolphins (Sotalia guianensis) from Ubatuba and Baixada Santista, São Paulo, Brazil
No full textOrganochlorine pesticides and polychlorinated biphenyls (PCBs) were determined in the blubber of six Guiana dolphins (Sotalia guianensis) from the coast of the state of São Paulo, Brazil. PCBs were at the highest levels on a lipid-weight basis (25.87 to 66.03μg g-1), followed by DDTs (16.91 to 55.91μg g-1), mirex (0.24 to 1.87μg g-1), chlordanes (0.11 to 0.49μg g-1), hexachlorobenzene (HCB) (0.07 to 0.17μg g-1), heptachlor epoxide (0.05 to 0.16μg g-1) and hexachlorociclohexane (HCHs) (0.03 to 0.21μg g-1). The presence of PCBs in Guiana dolphins suggests input from the Cubatão industrial complex – the largest in Brazil. The mean p,p’-DDE/3DDT ratio was approximately 0.8 and is indicative of previous DDT application in the study area. The occurrence of HCB and HCHs can be attributed to industrial effluents and dumping on the borders of the Santos-São Vicente estuarine complex
Cervical ribs and cleft arches in Brazilian Sotalia guianensis: contribution to comparative studies of skeletal morphology in northern and southeastern specimens
No full textThe Guiana dolphin, Sotalia guianensis (Van Bénéden, 1864), is a delphinid species found along the Brazilian coast. Morphological and genetic data point to the existence of different biological populations of the species within this portion of the range. The present paper compares the frequencies of developmental anomalies in two skeletal collections from geographically distant areas. The vertebral column of 43 specimens from Marajó Bay, located on the Pará State coast, and 20 specimens from the central-north coast of the Rio de Janeiro State were analyzed. The only anomalies found were cervical ribs and cleft neural arches, both located on the seventh cervical (C7) vertebra. Cervical ribs were found in 12% of the Pará specimens and in 45% of the Rio de Janeiro specimens; according to the Fisher’s Exact Test the difference was significant at a confidence level of α = 0.01, thus confirming that the series belong to different populations. The frequencies of cervical ribs observed in the present study were also compared to the frequencies of the same anomaly found in S. guianensis from the Ceará and Santa Catarina states, Brazil, and in tucuxi (S. fluviatilis) from the Brazilian Amazon. Although the results can be partially explained by demographic and evolutionary models for Sotalia, they may be affected by differences in the composition of the collections and in diagnostic methods/criteria used by different authors. Regarding the presence of cervical ribs, Amazon tucuxi were significantly different from the Rio de Janeiro and Pará series, as well as other marine series, as previously stated in the literature. The difference in the frequency of cleft neural arches in specimens from Rio de Janeiro and Pará was also significant, but no comparison could be conducted with other series due to lack of published material. A metric technique to discriminate transverse processes with and without fused cervical ribs is proposed as a methodological contribution for diagnosing the described anomaly
Morphology of the Guiana dolphin (Sotalia guianensis) off southeastern Brazil: growth and geographic variation
No full textThe objective of this study was to analyze the morphology of Guiana dolphin (Sotalia guianensis) to evaluate the existence of geographical variation along southeastern Brazil. Body length and 39 cranial variables were measured of specimens stranded or accidentally captured to consider ontogenetic and geographic variations. The areas studied were Espírito Santo (ES; 18°30’S-20°40’S), northern Rio de Janeiro (NRJ; 21°35’S-22°25’S), southern Rio de Janeiro (SRJ; 23°00’S-23°07’S) and São Paulo (SP; 23°30’S-25°30’S). Body length at age zero predicted by a non-linear Gompertz model for the Guiana dolphin was 148.3cm for area ES, 108.97cm for area NRJ, 98.4cm for area SRJ and 90.9cm for area SP. Asymptotic values were reached at about six years of age for total body length and cranial variations. These results indicate that Guiana dolphins reach adult size and sexual maturity simultaneously at six to seven years of age, when specimens cease to grow. The growth pattern for body and skull size indicated that there is variation between geographic areas. Guiana dolphins found in São Paulo are smaller than those analyzed in northern Rio de Janeiro and Espírito Santo, which implies a different growth rate. A canonical discriminant analysis of the cranial metric characters indicated significant differences between the four geographic areas. Differences between areas NRJ, SRJ and SP were responsible for 54% (axis 1) and 34% (axis 2) of the variation, respectively. The third axis depicted a difference between the area ES and the others. A partial overlap between geographic areas was observed in the projection of the species on the canonical axes, suggesting parapatry. Geographic variation recorded in this study is likely to be related to environmental adaptations. One of the areas that could play a role in the distribution of Guiana dolphin in the surveyed area is the central coast of Rio de Janeiro, which is characterized by the absence of river discharges, a narrowing of the continental shelf and upwelling influence that might be limiting the species occurrence in this area
Proposed English common name for the neotropical delphinid Sotalia guianensis (P.-J. Van Beneden, 1864)
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Initial description of Major Histocompatibility Complex variation at two Class II loci (DQA-DQB) in Sotalia fluviatilis and Sotalia guianensis
No full textGenes of the major histocompatibility complex (MHC) play a key role in the initiation of immune response in jawed vertebrates. Variation at MHC loci can be used as an indicator of the genetic ‘health’ of natural populations and offer insight into potential susceptibility to epizootics. Here we present the first characterization of the sequence variation at two MHC class II loci (DQA and DQB) in the neotropical coastal (Sotalia guianensis) and riverine (Sotalia fluviatilis) dolphins, using cloning and direct sequencing of amplified genomic DNA. Four DQA and four DQB alleles were identified in 33 and 32 Sotalia samples, respectively, and high nucleotide diversity among these alleles was detected, similar to the findings described for other cetacean species. Positive selection was evidenced by an excess of dn/ds at the Peptide-Binding-Region of the DQB of Sotalia. The presence of common alleles at both loci in S. fluviatilis and S. guianensis are consistent with trans-species mode of evolution in the MHC. In contrast to observed low levels of mtDNA diversity at the population level, there was an apparent lack of reduction of DQA and DQB allelic variation in the Brazilian Coast population unit. This suggests either present or past balancing selection acting to maintain MHC variation in this population unit
Ecology and conservation status of tucuxi (Sotalia fluviatilis) in the Pacaya-Samiria Reserve, Peru
No full textThe distribution, relative abundance, group size, reproductive seasonality, and conservation status of tucuxi (Sotalia fluviatilis) were investigated in Peru’s Pacaya-Samiria National Reserve from 1996 to 2000. Data collection consisted of boat-based surveys of dolphins and habitat, necropsies, photo-identification of individual dolphins, and interviews with local people. Mean encounter rates were between 0.01-0.80 tucuxi/km in rivers, and 0.05-2.17 tucuxi/km2 in lakes, and were within the ranges reported for riverine tucuxi throughout their distribution. Encounter rates were highest in confluences, intermediate in lakes, and lowest in rivers. Encounter rates increased with river width. Most tucuxis were seen within 100m from shore in large rivers, and large groups were associated with confluence areas and mid-channel islands. Within lakes, tucuxis were associated with areas of deeper water. Tucuxis were not found in waters <3m depth in rivers, or <1.8m depth in lakes. Seasonal differences in encounter rates did not exist in lakes and rivers. In confluences tucuxis occurred in highest densities during low water, and lowest densities during high water. Diurnal patterns of occurrence were not observed. Tucuxis were seen most often as singles or pairs, although groups as large as 13 were observed. Significant seasonal differences in group size were not detected. Neonate tucuxi were observed in all seasons, with a slight peak in encounter rates during high water. Abundance estimates were affected by survey methods, and strengths and weaknesses of various methods are discussed. Photo-identification rates were low, and this method did not yield information about tucuxi site fidelity, movement patterns, social structure, or population size. Local people in the Reserve did not seem to have the same myths and general apprehension about tucuxis as for the other sympatric dolphin, Inia. There was no evidence that tucuxi were poisoned by fishermen, unlike Inia. Potential threats to tucuxi in this region were entanglement in fishing gear, mercury in migratory fish from gold mining elsewhere, oil spills, ship strikes, and disturbance from boats. Only one dead tucuxi was encountered, and had been entangled in a turtle net. Tucuxi teeth were found for sale in local markets