Temperature Affects Brain and Pituitary Gene Expression Related to Reproduction and Growth in the Male Blue Gouramis, Trichogaster trichopterus

This study examined the effect of temperature on reproduction and growth-related factors in blue gourami males under nonreproductive and reproductive conditions. Males that were maintained under nonreproductive conditions did not build nest and the gonado-somatic index (% GSI) was significantly higher in fish maintained at 27 degrees C compared with fish maintained at 23 degrees C. The relative mRNA levels of brain gonadotropin-releasing hormone 3 (GnRH3), pituitary adenylate cyclase-activating polypeptide (PACAP), insulin-like growth factor-1(IGF-1), pituitary beta-luteinizing hormone (beta LH), and prolactin were significantly higher when the fish were maintained at 27 degrees C than at 231 degrees C or 31 degrees C. beta-Follicle-stimulating hormone (beta FSH) mRNA levels were significantly lower when maintained at 31 degrees C than at the other temperatures. Nests were observed only in males under reproductive conditions. In these fish, higher mRNA levels of GnRH3, PACAP, beta FSH, bLH and prolactin were detected at 27 degrees C, and higher mRNA levels of IGF-1 were detected at 23 degrees C, when compared with other temperature of maintenance or with fish that did not build nest. In conclusion, we propose that temperature has more effect on the transcription of genes, associated with reproduction, than on those pertaining to growth. J. Exp. Zool. 315:203-214, 2011. (C) 2011 Wiley-Liss, Inc.