The social status of the male Nile tilapia (Oreochromis niloticus) influences testis structure and gene expression

• DOI: 10.1530/rep-11-0292
• Publication Date: 2011-10-27T00:59:44Z
• Authors: Frank Pfennig; Thomas Kurth; Stefan Meißner; Andrea Standke; Markus Hoppe; Freia Zieschang; Christine Reitmayer; Andy Göbel; Georg Kretzschmar; Herwig O Gutzeit
• Keywords: Fish Proteins; Male; 0303 health sciences; Behavior, Animal; Eye Color; Pigmentation; Gene Expression; Leydig Cells; Cichlids; Real-Time Polymerase Chain Reaction; DEAD-box RNA Helicases; 03 medical and health sciences; Social Dominance; Proliferating Cell Nuclear Antigen; Testis; Animals; Steroid 11-beta-Hydroxylase; Female; Testosterone; Spermatogenesis; Territoriality

Dominant and territorial behaviour are known social phenomena in cichlids and social stress influences reproduction and growth. The gonadotropic hormones trigger spermatogenesis and subordinate males have typically lower levels of gonadotropins than dominant males. In this study, we compared testis morphology and gene expression of dominant and subordinate Nile tilapia males (d- and s-males) in socially stable communities. The d-males had the highest gonadosomatic index but they were not the largest animals in the majority of studied cases. Long-term d-males showed large groups of Leydig cells and hyperplasia of the tunica albuginea due to numerous cytochrome-P450-11β-hydroxylase (Cyp11b) expressing myoid cells. Increased Cyp11b expression in d-males was reflected by elevated 11-ketotestosterone plasma values. However, immunofluorescence microscopy and expression analysis of selected genes revealed that most s-males conserved their capability for spermatogenesis and are, therefore, ready for reproduction when the social environment changes. Moreover, in s-males gene expression analysis by quantitative RT-PCR showed increased transcript levels for germ line-specific genes (vasa,sox2anddmc1) and Sertoli-specific genes (amh,amhrIIanddmrt1) whereas gene expression of key factors for steroid production (sf1andcyp11b) were reduced. The Nile tilapia is a promising model to study social cues and gonadotropic signals on testis development in vertebrates.