NADELSPORA-CANCERI N G, N-SP, AN UNUSUAL MICROSPORIDIAN PARASITE OF THE DUNGENESS CRAB, CANCER-MAGISTER

The microsporidium Nadelspora canceri n.g., n. sp., is described from the striated musculature of the Dungeness crab (Cancer magister) in Or egon, USA. The needle-shaped spores were rounded anteriorly, tapered t o a posterior point and measured 7.1-11.8 x 0.2-0.3 mu m in fixed prep arations. The extremely narrow spore diameter prevented observation of morphological details at the light microscopic level and ultrastructu ral details of mature spores were difficult to resolve. Meronts were n ot observed and the monokaryotic merozoites and sporonts were not cont ained within either parasitophorous or sporophorous vesicles. Sporonts were disporoblastic and gave rise to monokaryotic sporoblasts that be came narrow and elongate as they developed into immature spores with a developing polar filament. The nucleus was not clearly resolved in ma ture spores and may have been surrounded by the lamellar polaroplast. The polar filament was of nearly uniform diameter throughout most of i ts length and ended abruptly about three-fourths of the distance from the anterior end of the spore. Unusual spherical non-membrane bound gr anules surrounded the polar filament in a spiral arrangement. The new microsporidium resembles members of the family Mrazekiidiae, but diffe rs in lacking a diplokaryon at any stage. It is probably most closely related to Baculea daphniae from which it differs primarily by spore s hape and size. The familial relationships of the genus Baculea have no t been determined and it is proposed to include it with Nadelspora in the new family Nadelsporidae.