Hm. Reiswig et A. Ricciardi, REEXAMINATION OF CORVOSPONGILLA-NOVAETERRAE (PORIFERA, SPONGILLIDAE),AN ENVIRONMENTALLY RESTRICTED FRESH-WATER SPONGE FROM EASTERN CANADA, Canadian journal of zoology, 71(10), 1993, pp. 1954-1962
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.