Neuropeptide Y (NPY) induces gonad reversal in the protogynous bluehead wrasse, Thalassoma bifasciatum (Teleostei: Labridae).
Female-to-male sex transformation in the protogynous marine fish Thalassoma bifasciatum is the culmination of a neuroendocrine cascade triggered by social and behavioral cues. We have previously shown that the hypothalamus and pituitary gland, key components of the neuroendocrine axis, play a significant role in gender reversal of this species. However, nothing is known about the possible involvement of other brain factors with the hypothalamo-pituitary gland axis in this fish. One such factor, neuropeptide Y (NPY) has been shown to effect a direct or indirect control of GtH-II release in gonochoristic teleosts. In view of this finding, we have investigated the role of NPY on sex reversal in T. bifasciatum. Females (n = 38) were injected intraperitoneally thrice weekly with NPY at a dose of 0.02 microgram/gbw dissolved in 0.6% saline. Controls (n = 48) received equal volumes of saline. Fish were sacrificed at 1, 4, 6, and 8 weeks. By the end of 8 weeks, 81.6% of the NPY-treated fish showed signs of gonad reversal ranging from early (n = 25) to mid- (n = 3) and late stage (n = 3). Furthermore, the effects of NPY appeared to be dependent on duration of treatment. At 6 and 8 weeks, the ovaries of four and three fish, respectively, were markedly degenerated. Our findings shed new light on the neuroendocrine control of sex reversal in T. bifasciatum and in hermaphroditic forms in general.
Kramer
C R
CR
Biology Department, College of Staten Island, New York 10314, USA.
Imbriano
M A
MA
D000818:Animals; D005260:Female; D005399:Fishes / Q000502:physiology*; D006066:Gonads / Q000187:drug effects* / Q000473:pathology; D057850:Hermaphroditic Organisms; D007274:Injections, Intraperitoneal; D009478:Neuropeptide Y / Q000494:pharmacology*; D009490:Neurosecretory Systems / Q000502:physiology; D010053:Ovary / Q000187:drug effects / Q000473:pathology; D019849:Sex Determination Processes
D009478:Neuropeptide Y