| Abstrakt: |
The embryonic development, early growth and survival of pure and reciprocal hybrid crosses of Sharptooth Catfish Clarias gariepinusand Sampa Heterobranchus longifiliswere studied. The morula and blastula stages occurred 5 and 10 min earlier, respectively, in pure crosses (at 4 h, 10 min and 5 h after fertilization, respectively) than in hybrids. Timing of gastrulation in pure strain H. longifilisand the ? H. longifilis× ? C. gariepinuscross was earlier (9 h) than in pure strain C. gariepinusand ?C. gariepinus× ? H. longifilis(9 h, 25 min), but similar timings were recorded during the somite stages (18 h). Hatching started at 23 h in H. longifilis, at 23 h, 10 min in C. gariepinus, and at 23 h, 15 min in the hybrids. Yolk absorption was complete in 4 d, but exogenous feeding began on the third day (72 h) when larvae weighed 0.7± 0.01 mg (mean ± SE). After 4 weeks of feeding ad libitum with shell-free Artemia, pure crosses of both species grew better than the hybrids, and C. gariepinusrecorded the highest weight (83.33 mg). The hybrids, however, showed significantly higher survival than did the pure strains. |
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