Nematopsis ostrearum and N. prytherchi (Eugregarinina: Porosporidae) with Special Reference to the Host-Parasite Relations

Abstract

Oysters (Crassostrea virginica) with mixed, natural, infections of Nematopsis were fed to different decapods. Nematopsis ostrearum developed in Panopeus herbstii, Eury-panopeus depressus and Eurytium limosum but not in Petrolisthes armatus, Penaeus aztecus and Menippe mercenaria. The parasites were then transmitted to oysters wherein they showed special affinity for the mantles. Nematopsis prytherchi developed in Menippe mercenaria but not in the other decapods mentioned. It was transmitted to oysters and showed special affinity for the gills. Different lots of oysters were subjected to extremely heavy experimental infections of the 2 spp. of Nematopsis. Mortality results in these mollusks were complicated by unknown factors and were neither consistent nor decisive. The question of the possible importance of Nematopsis in oyster mortalities remains unsettled. A discussion of various aspects of the host-parasite relations in the Porosporidae in particular and gregarines in general is presented and the idea is developed that the cephaline gregarines are not noted for being pathogenic.