Relationships between sex and the size and number of forebrain gonadotropin- releasing hormone-immunoreactive neurones in the ballan wrasse (Labrus berggylta), a protogynous hermaphrodite

• Published in: Journal of comparative neurology (1911) Vol. 410; no. 1; pp. 158 - 170
• Main Authors: Elofsson, Ulf O. E., Winberg, Svante, Nilsson, Göran E.
• Format: Journal Article
• Language: English
• Published: New York John Wiley & Sons, Inc 19.07.1999
• Subjects: Animals; Cell Count; Cell Nucleus - metabolism; Cell Size - physiology; Female; Fishes - anatomy & histology; Fishes - metabolism; Fishes - physiology; gonadotropin-releasing hormone; Gonadotropin-Releasing Hormone - metabolism; Hermaphroditic Organisms; Immunohistochemistry; labridae; Labrus berggylta; Male; Marine; monandry; Neurons - cytology; Neurons - metabolism; Prosencephalon - cytology; Prosencephalon - metabolism; sex change; Sex Characteristics; Sex Determination Processes - physiopathology; teleost; Tissue Distribution - physiology; monandry; sex change; MONOPTERUS-ALBUS ZUIEW; MALE G; labridae; SPAWNING BEHAVIOR; teleost; ENDOCRINE CHANGES; LUTEINIZING-HORMONE; gonadotropin-releasing hormone; MALE MASU SALMON; ONCORHYNCHUS-MASOU; HAPLOCHROMIS-BURTONI; PLATYFISH XIPHOPHORUS-MACULATUS
• ISSN: 0021-9967; 1096-9861; 1096-9861
• DOI: 10.1002/(SICI)1096-9861(19990719)410:1<158::AID-CNE13>3.0.CO;2-P

This study is the first to examine the brain gonadotropin‐releasing hormone (GnRH) cell population phenotype in a protogynous and monandric sequentially hermaphroditic fish. Male ballan wrasse (Labrus berggylta) had on average higher numbers of GnRH‐immunoreactive (GnRH‐ir) cells within the brain preoptic area (POA) than females, a difference not found in GnRH‐ir cells in other brain regions. Furthermore, in males, but not females, the number of these POA GnRH‐ir cells correlated with body size. Maturational state (prespawning or postspawning) had marked effects on mean profile sizes (but not numbers) of both GnRH‐ir cell bodies and cell nuclei, even when existing differences in body size and allometric relationships had been taken into account. Postspawning males tended to have larger GnRH‐ir profiles in all brain regions relative to both prespawning males and females. Moreover, the GnRH‐ir cell number in POA, and the cell body profile size in both POA and at the level of the anterior commissure, correlated with gonad size in spermiated prespawning males, indicating a relationship between both size and number of GnRH cells and male gonadal development. These results suggest that temporary changes in the size of brain GnRH‐ir neurones are coupled to the male spawning cycle, and that permanent POA GnRH‐ir cell number changes are involved in the process of sex change in sequential hermaphrodites. However, smaller males had no more preoptic GnRH‐ir cells than equally sized females, which may argue against a proximate inducing role of GnRH cell number changes in naturally occurring sex reversal. J. Comp. Neurol. 410:158–170, 1999. © 1999 Wiley‐Liss, Inc.