ON THE MORPHOLOGY AND LIFE HISTORY OF PHOCANEMA DECIPIENS (KRABBE, 1878) MYERS, 1959 (NEMATODA:ANISAKIDAE)

Abstract

Phocanema (synonyms: Porrocaecum, Terranova) decipiens is described in detail and its probable life cycle outlined. Eggs deposited in salt water develop and hatch in 7 to 14 days at between 10 °C and 24 °C, even after previous freezing. Temperatures over 24 °C are lethal. Larvae fed to a large variety of invertebrates passed quickly through their intestines still alive; fed to fish, they disappeared within 24 hours but in one case a larva was found ensheathed in the intestine. No larvae were found in 'wild' invertebrates although many were infected with free-living nematodes. It is concluded that, while numerous invertebrates may act as 'transport' hosts for the larva to a fish, none acts as a true intermediate host. While larvae infective to seals occur commonly in the muscles of cod, a large variety of other fish are also infected and are a more probable source of infection. Development to maturity in the seal takes approximately three weeks, and it is probable that the main source of the infection in the Gulf of St, Lawrence is the harp seal, although harbor and grey seals also contribute to it.