Phocanema decipiens: Molting in seals

Infective larvae of the anisakine nematode Phocanema decipiens from the muscle of Atlantic cod (Gadus morhua) were fed to harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus). During maturation in the stomach of seal hosts, P. decipiens molted twice; these molts are the third and fourth of its life cycle. The third molt occurred between the second and fifth days of infection. The third stage, i.e., infective larva entering the third molt, had a cuticular tooth ventral to the mouth; the fourth stage larva emerging from the third molt had three bilobed lips with dentigerous ridges. The fourth molt occurred between the 5th and 15th days in seals. A female nematode emerging from the fourth molt possesses a vulva and a vagina; a male possesses caudal alae, pre- and postanal papillae. Significant morphometric changes in nematodes were associated with both molts. Females and males of P. decipiens reached maturity after 15 to 25 days in seals. Ova were detected in the feces of the seal hosts as early as the 16th day.