MOLECULAR-FORMS OF GNRH IN 3 MODEL FISHES - ROCKFISH, MEDAKA AND ZEBRAFISH

Three species of fish have become important in the study of reproducti on and development. Rockfish are a model for developmental studies of live-bearing perch-like fish, whereas medaka and zebrafish are models for developmental and genetic studies. The forms of GnRH are identifie d in the brains of each of these fish and in the pituitary of the rock fish to investigate the role of GnRH in reproduction. Here, we report that grass rockfish (Sebastes rastrelliger) have three forms of GnRH i n brain extracts as determined by HPLC elution position and RIA. These forms are identified as sea bream GnRH, chicken GnRH-II and salmon Gn RH. In contrast, only two forms of GnRH were detected in brain extract s of medaka (Oryzias latipes) and zebrafish (Brachydanio rerio): salmo n GnRH and chicken GnRH-II. Rockfish is distinct from medaka and zebra fish in that the most abundant form of GnRH in the rockfish pituitary is sea bream GnRH, whereas this form is absent in the other two fishes . The identification of sea bream GnRH in the rockfish brain and pitui tary extracts indicates that the phylogenetic emergence of sea bream G nRH is earlier than the order Perciformes.