Sensitive stages during embryonic development of wolffish,Anarhichas lupusL. determining the final numbers of rays in unpaired fins and skeletal abnormalities

Abstract

Larvae of common wolYsh (Anarhichas lupus L.) obtained from eggs incubated at a constant temperature of 7.0)C had mean numbers of rays in the dorsal, anal, and caudal fins of 74.5, 46.4, and 23.8 respectively; those incubated at 11.0)C had 53.8, 25.7, and 25.2 rays, respectively. Several skeletal abnormalities, including fusion of parts and abnormal structure of neural arches in the pre-urostyle area, accompanied the reduction in numbers of dorsal and anal fin rays at 11)C. To test which period of embryonic development was critical for determining the final numbers of unpaired fin rays and skeletal abnormalities, the eggs were transferred from 7) Ct o 11 )C and back at diVerent stages. Determination of the final numbers of rays in the dorsal and anal fins and most of skeletal abnormalities occurred mainly between 50% vascularization of the yolk sac and the beginning of formation of rays in the caudal and pectoral fins. The final number of caudal fin rays was determined between the latter stage and formation of rays in the dorsal and anal fins. To reduce the egg incubation period and still obtain larvae without skeletal abnormalities, a temperature regime during embryonic development is suggested. ? 1996 International Council for the Exploration of the Sea