REEXAMINATION OF CORVOSPONGILLA-NOVAETERRAE (PORIFERA, SPONGILLIDAE),AN ENVIRONMENTALLY RESTRICTED FRESH-WATER SPONGE FROM EASTERN CANADA

Corvospongilla novaeterrae (Potts, 1886) (Demospongiae, Spongillidae) is known only from a few acidic lakes on the eastern coast of Canada. It is considered by some to be a sexual hybrid and thus an invalid spe cies. This assumption is based upon an erroneous interpretation of C n ovaeterrae's highly variable gemmoscleres and the abundant of foreign spicules (predominantly those of Duosclera mackayi) in the type specim ens. We have examined a new specimen from Nova Scotia that has no fore ign spicules and fits the original species description. We evaluate th ree hypotheses concerning this species' status: (1) it is a hybrid of Corvomeyenia everetti and another species; (2) it is an unusual ecomor phic form of C. everetti resulting from atmospheric inputs of sea salt s; (3) it is a valid Corvospongilla species, closely related to C. sec kti, C. volkmeri, and C boehmi. Corvospongilla novaeterrae's morpholog ically variable gemmoscleres are quite similar to those of C. seckti, C volkmeri, and C boehmi, and appear to be evolutionary transients bet ween birotulates and amphioxea (as in Radiospongilla and Pectispongill a). Other characters linking C novaeterrae with other Corvospongilla s pecies include (i) large gemmules (diameter > 1000 mum) with simple mu ltiple foramina, (ii) a weakly developed or absent pneumatic layer, (i ii) the size and shape of the birotulate microscleres, and (iv) the pr edominantly rod-shaped, tangentially arranged gemmoscleres. Evidence s upports the acceptance of C novaeterrae as a valid, environmentally re stricted species.