Project description:Pirarucu (Arapaima gigas, or A. gigas) is a native fish species to Amazon basin and, economically important in the Brazilian Amazonian for its great potential to aquaculture. In the natural environment the A. gigas is captured only in the sustainable development reserves of the State of Amazonas by applying a system of rotation in fishing in order to avoid overfishing of this important fishing resource. The reproductive biology of A. gigas has long been intriguing; however, very little is known about the molecular pathways underlying their sexual differentiation and determination. Using the SOLiD sequencing platform, a total of 432,058,560 short sequencing reads were produced. An average of ~30% of sequencing reads could be mapped to Asian arowana reference cDNAs. 305 genes showed higher expression in female brain against 8 gene with higher expressing in male brain. In gonad, there are 120 genes higher expressed in female against 10 gene higher expressed in male.
Project description:BACKGROUND:Arapaima gigas (Schinz, 1822) is the largest freshwater scaled fish in the world, and an emerging species for tropical aquaculture development. Conservation of the species, and the expansion of aquaculture requires the development of genetic tools to study polymorphism, differentiation, and stock structure. This study aimed to investigate genomic polymorphism through ddRAD sequencing, in order to identify a panel of single nucleotide polymorphisms (SNPs) and to simultaneously assess genetic diversity and structure in wild (from rivers Amazon, Solimões, Tocantins and Araguaia) and captive populations. RESULTS:Compared to many other teleosts, the degree of polymorphism in A. gigas was low with only 2.3% of identified RAD-tags (135 bases long) containing SNPs. A panel of 393 informative SNPs was identified and screened across the five populations. Higher genetic diversity indices (number of polymorphic loci and private alleles, Shannon's Index and HO) were found in populations from the Amazon and Solimões, intermediate levels in Tocantins and Captive, and very low levels in the Araguaia population. These results likely reflect larger population sizes from less urbanized environments in the Amazon basin compared to Araguaia. Populations were significantly differentiated with pairwise FST values ranging from 0.086 (Amazon × Solimões) to 0.556 (Amazon × Araguaia). Mean pairwise relatedness among individuals was significant in all populations (P < 0.01), reflecting a degree of inbreeding possibly due to severe depletion of natural stocks, the species sedentary behaviour and possible sampling biases. Although Mantel test was not significant (P = 0.104; R2 = 0.65), Bayesian analysis in STRUCTURE and discriminant analysis of principal components (DAPC) showed populations of Amazon and Solimões to be genetically differentiated from Araguaia, with Tocantins comprising individuals from both identified stocks. CONCLUSIONS:This relatively rapid genotyping by sequencing approach proved to be successful in delineating arapaima stocks. The approach and / or SNP panels identified should prove valuable for more detailed genetic studies of arapaima populations, including the elucidation of the genetic status of described discrete morphotypes and aid in delivery of conservation programs to maintain genetic diversity in reservoirs across the Amazon region.