Differentially expressed genes in the pituitary of the Amazonian fish Arapaima gigas

Arapaima gigas, known as pirarucu, is one of the largest tropical freshwater fish and an icon fish species of the Amazon. Many studies on reproduction of A. gigas have been developed but a significant gap persists. To analyze the gene expression profile of A. gigas from wild stocks, four cDNA libraries from pituitary of young and adults of males and females were developed. Among the differentially expressed genes, 97 genes related to several physiological functions were identified, especially related to growth and reproduction. The main ones were activin receptor IIB, estrogen receptor, follistatin, growth hormone receptor isoform 1, luteinizing hormone receptor, pituitary adenylate cyclase-activating polypeptide, prolactin receptor, somatostatin receptor type 1 subtypes A and B. Gene expression in A. gigas differs strongly between adult and young, but presents high similarity between male and female. EST collections obtained in this study represent an important resource to better understand the mechanisms involved in the growth, cell development, reproduction and sexual differentiation of this species. In addition, the present set of results contributes towards improvement of breeding management of this important fish species for world aquaculture.    Key words: cDNA library, gene expression, Amazonia, pirarucu.