SEX EFFECTS ON GROWTH RESPONSE TO GROWTH HORMONE (GH) INSERTION FOR TWO GH CONSTRUCTS IN CHANNEL CATFISH, Ictalurus punctatus, AT TWO AGES  

Nermeen Y. Abass*, and Rex A. Dunham
 
School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, AL 36849, USA
 School of Fisheries, Aquaculture and Aquatic Sciences, Auburn University, AL 36849, USA .
Department of Agricultural Botany, Faculty of Agriculture Saba-Basha, Alexandria University,
Egypt
Nyy0001@auburn.edu

More than 925 million people are suffering from chronic hunger in the world and the majority of hungry people live in developing countries. Fish are an important source of animal protein and nutrition for people worldwide. Gene transfer represents a potential solution to develop the fast- growing, high-performance. Catfish is the primary aquaculture species in the United States. Growth hormone (GH) has been considered as a candidate gene for growth and development in teleost fish.

Channel catfish, Ictalurus punctatus, GH cDNA driven by the ocean pout Zoarces americanus antifreeze protein promoter (opAFP-ccGH) or rainbow trout Oncorhynchus mykiss metallothionein promoter (rtMT-ccGH) were transferred to the channel catfish, I. punctatus, via electroporation. GH transgenic (P1) were mated to produce the F1 generation. The present study was designed to compare the growth performance of male and female transgenic channel catfish GH cDNA of both promoter types and their non-transgenic full-siblings in earthen ponds at different ages.  

Body weight among the transgenic individuals and their full siblings was different at all ages. Catfish transgenic for opAFP-ccGH grew 1.67-2.8 fold larger than their full siblings and those transgenic for rtMT-ccGH grew 1.51-3.16 fold larger than their full siblings. Significant differences in body weight between the sexes were found at 12 and 36 months. Body weight of the males was significantly higher compared with those of the females at 12 months of age (P < 0.001) However, body weight of the females was significantly higher compared with those of the males at age 36 months (P < 0.0001). The body weight of 36-month-old transgenic opAFP-ccGH females (2110±880 g), was 1.20 times higher than that of the males (1760±600 g). However, the body weight of transgenic rtMT-ccGH females (2340±470 g), was 1.31 times higher than that of the males (1780±570 g). In the case of non-transgenic GH siblings males grew faster than females at 12 and 36 months (P < 0.001). Apparently, elevation of growth hormone levels or associated epistasis alters sexually dimorphic growth after sexual maturation.