PUGNOSE EELS, SIMENCHELYS-PARASITICUS (SYNAPHOBRANCHIDAE) FROM THE HEART OF A SHORTFIN MAKO, ISURUS-OXYRINCHUS (LAMNIDAE)

A 395 kg shortfin mako, Isurus oxyrinchus (Lamnidae) landed at Montauk , New York in June of 1992 was found to contain two dead, but otherwis e healthy appearing pugnose eels, Simenchelys parasiticus (Synaphobran chidae) within the lumen of its heart. The path along which the eels m ade their way into the shark's heart was not found. Histological exami nation of the shark's heart revealed the presence of medial hyperplasi a and hypertrophy of small arterioles, multifocal arteriosclerosis, an d relatively high numbers of capillaries per unit area. These phenomen a were not observed in similar sections taken from hearts of six uninf ected mako sharks. The stomachs of both eels were filled with blood, s uggesting that they had been within the shark at least long enough to feed. Consideration of this new record along with the literature suppo rts a trophic designation of facultative endoparasite for the species Simenchelys parasiticus.