Reproduction among channel catfish, blue catfish, and their F1 and F2 hybrids.

摘要

Reproductive traits of channel catfish (Ictalurus punctatus), blue catfish (I. furcatus), their F1 hybrid (channel catfish female X blue catfish male) and their F2 hybrid were examined. F2 hybrid females had a lower frequency of ovulation (P<0.05; 12.2%) than did channel catfish, blue catfish and F1 hybrid catfish (83.5, 58.4 and 56.5% respectively), when these females were induced to spawn with carp pituitary extract and were then hand-stripped. F2 hybrids that ovulated produced fewer ova per kilogram of body weight (P<0.05) (923 ova/kg) than did channel catfish, blue catfish and F1 hybrid catfish (7893, 5600 and 5676 ova/kg respectively). F1 hybrids had smaller testes per kilogram of body weight than channel catfish (P<0.05) (1.08 and 2.72 g/kgrespectively), but did not have smaller testes than blue catfish (1.71 g/kg). Channel catfish ova had better fertilization (73.6%) than did F3 hybrid ova (5.1%; P<0.05). Channel catfish ova also had the highest observed hatching percentage (41.5%). Channel catfish maternal genetic effects had a strong positive effect on fertilization percentage; channel catfish-additive genetic effects had a strong positive effect on hatching percentage. Individual epistatic recombination loss had a strong negative effect on hatching percentage. F1 hybrids rarely laid eggs when backcrossed to parent species in aquaria. F2 hybrids did not naturally spawn in open ponds, in the pens in ponds, or in aquaria. F2 breakdown was apparent, and backcrossing was naturally difficult. These reproductive problems in hybrids will make development of synthetic breeds from channel catfish and blue catfish difficult and will reduce the likelihood of introgression between the 2 species in the natural environment.