Transcriptomic Profiling and Microsatellite Identification in Cobia (Rachycentron canadum), Using High-Throughput RNA Sequencing.

Cobia (Rachycentron canadum) is a marine teleost species with great productive potential worldwide. However, the genomic information currently available for this species in public databases is limited. Such lack of information hinders gene expression assessments that might bring forward novel insights into the physiology, ecology, evolution, and genetics of this potential aquaculture species. In this study, we report the first de novo transcriptome assembly of R. canadum liver, improving the availability of novel gene sequences for this species. Illumina sequencing of liver transcripts generated 1,761,965,794 raw reads, which were filtered into 1,652,319,304 high-quality reads. De novo assembly resulted in 101,789 unigenes and 163,096 isoforms, with an average length of 950.61 and 1,617.34 nt, respectively. Moreover, we found that 126,013 of these transcripts bear potentially coding sequences, and 125,993 of these elements (77.3%) correspond to functionally annotated genes found in six different databases. We also identified 701 putative ncRNA and 35,414 putative lncRNA. Interestingly, homologues for 410 of these putative lncRNAs have already been observed in previous analyses with Danio rerio, Lates calcarifer, Seriola lalandi dorsalis, Seriola dumerili, or Echeneis naucrates. Finally, we identified 7894 microsatellites related to cobia's putative lncRNAs. Thus, the information derived from the transcriptome assembly described herein will likely assist future nutrigenomics and breeding programs involving this important fish farming species.

Aluminum at environmental concentrations affects the sperm quality of the freshwater teleost Astyanax altiparanae: An in vitro study.

Aluminum (Al) is present in rivers and reservoirs in concentrations above that is allowed by regulatory agencies (e.g. 0.5 mg L-1 Al), which can impair fish reproduction. The present study evaluated the in vitro effects on the sperm of Astyanax altiparanae upon Al exposure at different concentrations (0, 0.05, 0.1, 0.3, and 0.5 mg L-1) with various exposure periods (50 s, 10 min, and 30 min). The following biomarkers were evaluated: membrane vitality, DNA fragmentation, morphology, kinetics (10 s and 30 s after sperm activation), and sperm mitochondrial activity. Al damages the membrane vitality of gametes at 0.3 and 0.5 mg L-1 after 50 s of exposure. After 30 min of exposure, there was a decrease in membrane vitality at 0.1 and 0.5 mg L-1, and the membrane vitality decreased with increased exposure time. Within 30 s after sperm activation, Al (0.3 and 0.5 mg L-1) reduced sperm motility by more than 50% at the longest exposure time, while at 0.1 and 0.5 mg L-1, Al exposure reduced motility over time. The average path speed (VAP; 10 s post-sperm activation) was reduced at longer exposure times at 0.05 and 0.5 mg L-1 of Al. Increased exposure time had deleterious effects on mitochondrial activity at the highest concentrations tested. Al did not damage DNA and sperm morphology. In conclusion, Al negatively influences the sperm quality of A. altiparanae with a potential effect of exposure time and increasing concentrations.

Effects of GnRH and the dual regulatory actions of GnIH in the pituitary explants and brain slices of Astyanax altiparanae males.

The pituitary gonadotropins, Fsh (follicle-stimulating hormone) and Lh (luteinizing hormone), regulate testicular development and functions in all vertebrates. At the pituitary, different signaling systems regulate the synthesis and secretion of the gonadotropins, such as the hypothalamic neuropeptides GnRH (gonadotropin-releasing hormone) and GnIH (gonadotropin-inhibitory hormone). While GnRH exerts stimulatory roles, the actions of GnIH remain controversial for many teleost species. Therefore, the aim of this study was to evaluate the in vitro effects of chicken GnRH2 (cGnRH2) and zebrafish GnIH-3 (zGnIH-3) on the male gonadotropin and GnRH system expression using pituitary explants and brain slices from a neotropical species with economical and ecological relevance, Astyanax altiparanae. Our results showed that in males, cGnRH2 increased fshb and lhb mRNA levels in the pituitary explants. Interestingly, zGnIH-3 has no effect on basal gonadotropin expression, however zGnIH-3 decreased the cGnRH2-induced fshb and lhb transcripts in male pituitary explants. In the male brain slices, zGnIH-3 showed stimulatory effects, increasing gnrh2 mRNA levels. Overall, our results suggested that GnIH seems to have dual regulatory actions on gonadotropin and GnRH2 expression of A. altiparanae males. This study provided basic information on endocrine regulation of A. altiparanae reproduction, and the obtained results will expand our knowledge, improving the reproductive management of this economically important freshwater species.