Production of Transgenic Channel Catfish.

Abstract

The channel catfish industry has experienced tremendous growth over the last several years. This growth has triggered more intensive culture practices resulting in disease outbreaks and devastating mortalities. Medicated feeds and vaccination have been of limited use. This research presents studies on techniques to produce disease resistant channel catfish by gene transfer. The gene used was the cecropin B gene from the giant silkworm moth Hyalophora cecropia, controlled by an acute phase response (APR) promoter also from H. cecropia. The objectives of this study were to: (1) determine if an early maturing population of catfish from Lake Maurepas, Louisiana, could he used as a model fish for genetic research; (2) develop techniques for the collection of unfertilized catfish eggs; (3) determine the effect of electroporation of eggs on the resulting embryos, and (4) develop screening methods of embryos to determine the percentage transgenic fish. The early maturing channel catfish population from Lake Maurepas, Louisiana was determined to be a normal population of channel catfish in all respects other than maturing at an early age and small size, and spawning later in the year when compared to other populations of channel catfish in southern Louisiana. An alternative channel catfish spawning method in which females are grouped rather than paired with males is described. The proportion of successful spawns for paired females (41%) was not significantly different (P = 0.64) from that of the grouped females (58%). Percent fertilization was significantly different (P = 0.02) for eggs stripped from paired females (43 $\pm$ 37%) and grouped females (16 $\pm$ 20%). The grouped method has promise if timing for collection of high quality eggs can be determined. The effect of electroporation of unfertilized eggs on fertilization and hatching rate was significant $(P < 0.0001).$ However, there was no effect (P = 0.32) on percentage of fry surviving to 2 weeks after fertilization. Methods for the isolation of potentially transgenic treatment groups prior to screening were developed. The polymerase chain reaction was used to screen embryos for the presence of the cecropin gene which was evident in 47% of the embryos tested.