Genetic differentiation among distinct karyomorphs of the wolf fish Hoplias malabaricus species complex (Characiformes, Erythrinidae) and report of unusual hybridization with natural triploidy

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

The fish fauna in tropical rivers: The case of the Sorocaba river basin, Sao Paulo, Brazil

A survey was carried out on the fish species in the Sorocaba. River basin, the main tributary of the left margin of the Tiete River, located in the State of Sao Paulo, Brazil. The species were collected with gill nets. After identification of the specimens, their relative abundance, weight and standard length were determined. Up to the present moment there are not any studies that focus this subject in this hydrographic basin. Fifty-three species, distributed in eighteen families and six orders were collected. Characiformes were represented by twenty-eight species, Siluriformes by seventeen species, the Gymnotiformes by three species, Perciformes and Cyprinodontiformes by two species, and the Synbranchiformes by one species. Among the collected species there were two exotic. The most abundant species were Astyanax fasciatus and Hypostomus ancistroides. In relation to total weight the most representative species were Hoplias malabaricus and Hypostomus ancistroides. Cyprinus carpio, Prochilodus lineatus, Schizodon nasutus and Hoplias malabaricus were the most representative species in relation to average weight. Largest standard length were recorded for Sternopygus macrurus, Steindachnerina insculpta, Eigenmannia aff. virescens and Cyprinus carpio.

Genetic identification of interspecific hybrid of Neotropical catfish species (Pseudoplatystoma corruscans vs. Pseudoplatystoma reticulatum) in rivers of Mato Grosso do Sul State, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Identification of the molecular sex-differentiation period in the siberian sturgeon

Sexual development prior to gonadal sex differentiation is regulated by various molecular mechanisms. In fish, a molecular sex-differentiation period has been identified in species for which sex can be ascertained prior to gonadal sex differentiation. The present study was designed to identify such a period in a species for which no genetic sex markers or monosex populations are available. Siberian sturgeons undergo a slow sex-differentiation process over several months, so gonad morphology and gene expression was tracked in fish from ages 3-27 months to identify the sex-differentiation period. The genes amh, sox9, and dmrt1 were selected as male gonad markers; cyp19a1a and foxl2a as female gonad markers; and cyp17a1 and ar as markers of steroid synthesis and steroid receptivity. Sex differentiation occurred at 8 months, and was preceded by a molecular sex-differentiation period at 3-4 months, at which time all of the genes except ar showed clear expression peaks. amh and sox9 expression seemed to be involved in male sexual development whereas dmrt1, a gene involved in testis development in metazoans, unexpectedly showed a pattern similar to those of the genes known to be involved in female gonadal sex differentiation (cyp19a1 and foxl2a). In conclusion, the timing of and gene candidates involved with molecular sex differentiation in the Siberian sturgeon were identified. Mol. Reprod. Dev. 2015. © 2015 Wiley Periodicals, Inc.

Validation of absolute quantitative real-time PCR for the diagnosis of streptococcus agalactiae in fish

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Innovative molecular approach to the identification of Colossoma macropomum and its hybrids

Tambaqui (Colossoma macropomum) is the fish species most commonly raised in the Brazilian fish farms. The species is highly adaptable to captive conditions, and is both fast-growing and relatively fecund. In recent years, artificial breeding has produced hybrids with Characiform species, known as “Tambacu” and “Tambatinga”. Identifying hybrids is a difficult process, given their morphological similarities with the parent species. This study presents an innovative molecular approach to the identification of hybrids based primarily on Multiplex PCR of a nuclear gene (a-Tropomyosin), which was tested on 93 specimens obtained from fish farms in northern Brazil. The sequencing of a 505-bp fragment of the Control Region (CR) permitted the identification of the maternal lineage of the specimen, all of which corresponded to C. macropomum. Unexpectedly, only two CR haplotype were found in 93 samples, a very low genetic diversity for the pisciculture of Tambaqui. Multiplex PCR identified 42 hybrids, in contrast with 23 identified by the supplier on the basis of external morphology. This innovative tool has considerable potential for the development of the Brazilian aquaculture, given the possibility of the systematic identification of the genetic traits of both fry-producing stocks, and the fry and juveniles raised in farms.