ABSTRACT
Populations of Ocyurus chrysurus were compared genetically and morphometrically along the West Atlantic coast to test the null hypothesis of population homogeneity in the area. Brazilian populations were found to be differentiated in shape (canonical variates analysis; F[48,515] = 10.84, p < 0.0001). Analyses of mitochondrial DNA sequences (663 bp of the control region) did not show any differences between Brazilian populations but could detect differences between Brazilian and Caribbean (Belize) populations. The samples from Pernambuco differed significantly from the other Brazilian populations in allozyme frequencies (11 loci; F ST = 0.167; p < 0.05), but this may have resulted from the small number of samples analysed for that population. Sequence variation of Belize samples departed from neutral expectations (Fu's FS = -8.88; p < 0.001). A mismatch distribution analysis points to an ancient population expansion in that area. We conclude that the genetic data do not allow the rejection of the null hypothesis of panmixia for Brazilian yellowtail snapper populations which should be treated as a single genetic stock, with a latitudinal gradient on their morphology which probably results from phenotypic plasticity. On the other hand, there is a severe restriction to gene flow between O. chrysurus populations from the Caribbean and from the southwestern Atlantic.
Subject(s)
Animals , DNA, Mitochondrial , Fishes/genetics , Base Sequence , Genetic Variation , Genetics, Population , PhylogenyABSTRACT
We tested the zinc-finger sex chromosome-linked genes Zfx/Zfy and the sex-determining region Y (Sry) genes for gender determination of biopsy samples from marine and riverine tucuxi dolphins (Sotalia guianensis and S. fluviatilis). We also evaluated the performance of these genes with decomposed carcasses, for which sexing cannot rely on the direct examination of the reproductive tract. Both systems proved reliable for sexing 46 fresh and decomposed samples, making them especially useful when biopsy darting is coupled with photo-identification studies.
ABSTRACT
Penaeid shrimps are important resources for worldwide fisheries and aquaculture. In the Southwest Atlantic, Farfantepenaeus brasiliensis, F. paulensis, F. subtilis, Farfantepenaeus sp. and Litopenaeus schmitti are among the most important commercially exploited species. Despite their high commercial value, there is little information available on the different aspects of their biology or genetics and almost no data on their stock structure. We used allozymes to estimate variability levels and population genetic structure of F. brasiliensis, F. paulensis, L. schmitti and the recently detected species Farfantepenaeus sp. along as much as 4,000 km of Brazilian coastline. No population heterogeneity was detected in F. brasiliensis or L. schmitti along the studied area. In contrast, F ST values found for Farfantepenaeus sp. and F. paulensis indicate that the populations of those two species are genetically structured, comprising different fishery stocks. The largest genetic differences in F. paulensis were found between Lagoa dos Patos (South) and the two populations from Southeast Brazil. In Farfantepenaeus sp., significant differences were detected between the population from Recife and those from Fortaleza and Ilhéus.
Subject(s)
Animals , Decapoda , Genetics, Population , Penaeidae , Brazil , HeterozygoteABSTRACT
The sea-bob shrimp, Xiphopenaeus kroyeri, is one of the most important economic marine resources along the entire Brazilian coast. Nevertheless, despite its economic importance, no studies have examined the population genetics of this species. In this paper, we used ten allozyme loci to study the pattern of genetic structuring in X. kroyeri along the southeastern Brazilian coast. Seven of the ten analyzed loci were polymorphic, yielding observed heterozygosity values higher than those reported for other penaeid shrimps. The population from São Paulo was significantly different from the other two populations (Rio de Janeiro and Espírito Santo), which, in turn, seem to form a single panmitic unit. Therefore, our results clearly indicate that conservation policies for this species should consider the São Paulo population as an independent stock from those of Rio de Janeiro and Espírito Santo.
Subject(s)
Animals , Genetics, Population , Isoenzymes , Penaeidae/genetics , Brazil , Crustacea , Polymorphism, GeneticABSTRACT
In this paper we use allozyme analyses to demonstrate that individuals in Anthopleura krebsi aggregates are monoclonal. Additionally, sympatric samples of the red and the green colour-morphs of A. krebsi from Pernambuco, Brazil were genetically compared and no significant differences were observed between them (gene identity = 0.992), indicating that they do not belong to different biological species. All individuals within aggregates of the green colour-morph were found to be identical over the five polymorphic loci analysed. Such results would be extremely unlikely (P < 10(-11)) if the individuals analysed had been generated through sexual reproduction, thus confirming the presence of asexual reproduction in this species.