A Qualitative Model of the Interaction of Sexual Behavior and Hormone Gene Transcription in Male Blue Gourami during Reproduction

Abstract

In the present study, a model is suggested to describe hormone control in male blue gourami (Trichogaster trichopterus) along the gonadotropic brain-pituitary- gonad axis (BPG axis) and the hypothalamic-pituitary-somatotropic axis (HPS axis). This model is based on the cloning and transcription of genes encoding hormones of the two axes involved in spermatogenesis during blue gourami reproduction. Gene transcription is affected by environmental, biological, and behavioral factors. Mature males were examined in two different stages—nonreproductive in high-density habitats and reproductive in low-density habitats. Based on gene transcription, gonadotropin-releasing hormone 1 (GnRH1) was involved in controlling spermatogenesis (spermatogonia to spermatids) via the BPG axis in nonreproductive and reproductive stages by controlling follicle-stimulating hormone (FSH), 11-ketotestosterone (11KT) and 17β-estradiol (E2). However, GnRH3 had a larger effect during the reproductive stage via the BPG axis (spermatids to sperm) on luteinizing hormone (LH), 11KT, and 17α-hydroxyprogesterone (17P). At the same time, the HPS axis was involved in spermatogenesis via pituitary adenylate cyclase-activating polypeptide (PACAP) and its related peptide PRP (formerly known as GHRH-like peptide) in the brain, and growth hormone (GH) in the pituitary affected synthesis of insulin-like growth factor 1 (IGF1) in the liver.