Genotype-environment interactions for survival at low and sub-zero temperatures at varying salinity for channel catfish, hybrid catfish and transgenic channel catfish

Organisms exposed to sub-zero temperatures are at risk of freezing damage. Fingerling channel catfish, Ictalurus punctatus, hybrid catfish (channel catfish female x blue catfish, Ictalurus furcatus, male), channel catfish transgenic for the goldfish glutamate decarboxylase 65 gene driven by the carp beta-actin promoter (beta A-GAD65), and channel catfish transgenic for the catfish growth hormone gene driven by the antifreeze protein promoter (AFP-ccGH) were compared for survival at different temperatures (9.0 degrees C, 6.0 degrees C, 3.0 degrees C, 1.0 degrees C, 0.5 degrees C, 0 degrees C, and -0.5 degrees C) at different salinities (0 ppt, 2.5 ppt, 5 ppt, and 7.5 ppt). The two transgenes were of interest as growth hormone not only affects growth, but also affects osmoregulation, and GAD65 construct could alter gonadotropin with the potential consequence that GnRH affects growth hormone production. Survival was 98-100% for all genetic groups at all salinities between 0 degrees C and 9.0 degrees C. However, large differences were observed at -0.5 degrees C. At 0 ppt salinity, 100% of AFP-ccGH transgenic (T) fingerlings survived, but survival of all other genetic groups was 0-2%. Raising salinity to 2.5 ppt at sub-zero temperature had a strong positive impact on survival as survival rates of AFP-ccGH (T), AFP-ccGH control (C), channel catfish, beta A-GAD65 (T), beta A-GAD65 (C) and hybrid catfish were 100, 100, 98, 76, 100 and 18%, respectively. Increasing salinity further to 5 ppt decreased overall survival, although it was still higher than at 0 ppt. Survival rankings were altered, with means for beta A-GAD65 (T), beta A-GAD65 (C), AFP-ccGH (T), AFP-ccGH(C), channel catfish and hybrid catfish of 69, 0, 15, 22, 0 and 0%, respectively. Mortality was 100% in all genetic groups at -0.5 degrees C and 7.5 ppt demonstrating significant interaction between temperature and salinity. Negative heterosis was observed for the hybrids at low temperature at the respective salinities. (C) 2016 Elsevier B.V. All rights reserved.