Swelling of wolffish, Anarhichas lupus L., eggs and prevention of their adhesiveness

Wolffish, Anarhichas lupus L. has internal fertilization. The eggs are released into water before the beginning of cleavage and stick together in clutches. To develop methods for separating eggs for subsequent incubation, changes during egg swelling and egg shell hardening were observed. Uninseminated eggs did not swell in ovarian fluid, but a perivitelline space formed in sea water because of a partial cortical reaction. In inseminated eggs kept in ovarian fluid, a cortical reaction took place and swelling was caused by elevation of the yolk membrane. Shrinkage of the yolk and absorption of water were observed after inseminated eggs were placed in sea water. Eggs swelled in ovarian fluid diluted by less than 30% sea water showed abnormal cleavage during subsequent development. An effective method for preventing egg stickiness after fertilization was to distribute them in trays with stagnant sea water for at least 5-6 h. Milk was effective for loss of egg adhesiveness at 50% concentration, but some eggs cleaved abnormally and subsequent mortality was high. The influences of ovarian fluid and milk on initial egg development with respect to peculiarities of egg swelling are discussed.