Hand-stripping of semen and semen quality after maturational hormone treatments, in African catfish Clarias gariepinus

A.T.M. Viveiros, Y. Fessehaye, M. ter Veld, R.W. Schulz, J. Komen-2002
Aquaculture, 213(1-4): 373-386
Abstract:

In the hatchery-bred African catfish, Clarias gariepinus, spontaneous semen release does not occur and hand-stripping is practically impossible. This reproductive dysfunction may be due to a lack of a pre-spawning gonadotropin (luteinizing hormone––LH) surge. To test this hypothesis, the effects of hormones that increase plasma LH levels were analyzed. Mammalian gonadotropin releasing hormone analogue (mGnRHa), mGnRHa plus pimozide, a dopamine antagonist (mGnRHa-PIM), ovaprim (salmon GnRHa plus domperidone, a dopamine antagonist), carp pituitary suspension (carp-PS), Clarias pituitary suspension and combinations of carp-PS and ovaprim were tested. Stripped fluid, when present, was compared to intratesticular semen, 12 or 24 h after injection (latency time). Plasma LH levels increased (P<0.05) 2 h after injection in all hormone treatments, compared to control fish. Stripping of a few drops of fluid, containing some viable spermatozoa, was possible in four out of five males treated with two injections of carp-PS, sampled 12 h later, and in 13 out of 24 males treated with combinations of carp-PS and ovaprim. Spermatocrit, sperm concentration and hatching rates obtained with stripped fluid, however, were very low compared to those obtained with intratesticular semen, from the same males. The number of sperm cells collected per kg body weight increased only in fish treated with two consecutive injections of carp-PS and a 12-h latency time. Treatments using single injections of pituitary suspensions and treatments with mGnRHa, mGnRHa-PIM or ovaprim did not facilitate hand-stripping of viable sperm cells, nor did they increase the number of sperm cells collected per kg. Based on these results, it is unlikely that hatchery-bred catfish males are not strippable because of a lack of an LH surge.

(Fish Culture and Fisheries Group, Wageningen Institute of Animal Sciences Wageningen University, P.O. Box 338, 6700 AH, Wageningen, The Netherlands, e-mail of A.T.M. Viveiros: ana.viveiros@ufla.br, e-mail of J. Komen: Hans.Komen@alg.venv.wau.nl)

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