SENSITIVE STAGES DURING EMBRYONIC-DEVELOPMENT OF WOLFFISH, ANARHICHAS-LUPUS L DETERMINING THE FINAL NUMBERS OF RAYS IN UNPAIRED FINS AND SKELETAL ABNORMALITIES

Larvae of common wolffish (Anarhichas lupus L.) obtained from eggs inc ubated at a constant temperature of 7.0 degrees C had mean numbers of rays in the dorsal, anal, and caudal fins of 74.5, 46.4, and 23.8 resp ectively; those incubated at 11.0 degrees C had 53.8, 25.7, and 25.2 r ays, respectively. Several skeletal abnormalities, including fusion of parts and abnormal structure of neural arches in the pre-urostyle are a, accompanied the reduction in numbers of dorsal and anal fin rays at 11 degrees C. To test which period of embryonic development was criti cal for determining the final numbers of unpaired fin rays and skeleta l abnormalities, the eggs were transferred from 7 degrees C to 11 degr ees C and back at different stages. Determination of the final numbers of rays in the dorsal and anal fins and most of skeletal abnormalitie s occurred mainly between 50% vascularization of the yolk sac and the beginning of formation of rays in the caudal and pectoral fins. The fi nal 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 i ncubation period and still obtain larvae without skeletal abnormalitie s, a temperature regime during embryonic development is suggested. (C) 1996 International Council for the Exploration of the Sea