Steroid profiles during oocyte maturation and lhrha-pimozide induced ovulation in the asian catfish, Clarias Batrachus (L)
2000
Nayak, P.K. | Singh, B.N. | Ayyappan, S. (Central Institute of Freshwater Aquaculture, Kausalyaganga (India))
Plasma sex steroid profiles were studied during the reproductive phase (vitellogenesis and spawning phase) and the luteinizing hormone-releasing hormone analogue (LHRHa) and pimozide (PIM) induced ovulation in Asian catfish, Clarias batrachus. The levels of estradiol-17á (e2) and estrone (E1) rapidly increased reaching a peak during the vitellogenic phase, while a decline was marked during the spawning phase coinciding with the rise of 17x - hydroxy progesterone (17xP) and 17x-20á -dihydroxy progesterone (17x-20áP). The testosterone (T) levels increased in vitellogenic phase in plasma and the elevated levels maintained till fish spawned. Administration of LHRHa/PIM evidently induced ovulation in Asian Catfish. LHRHa/PIM caused an increase in plasma testosterone and 17xP levels at 6 h, while peak levels 17x20á P were attained at 12 h possibly coinciding with occurrence of germinal vesicle breakdown of oocytes. Fish checked for ovulation by hand stripping released copious streams of transparent greenish brown eggs at 18-21h. The post ovulation stage was marked by decreasing trend in the 17x-20á P levels. The decline of 17xP and T levels in plasma with concomitant increase of 17x-20á P during the final oocyte maturation and ovulation could suggest that the latter functioned as the maturation inducing steroid (MIS) in the Asian Catfish.
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