Tm. Frost et al., A YELLOW-GREEN ALGAL SYMBIONT IN THE FRESH-WATER SPONGE, CORVOMEYENIA-EVERETTI - CONVERGENT EVOLUTION OF SYMBIOTIC ASSOCIATIONS, Freshwater Biology, 38(2), 1997, pp. 395
1. A previously undescribed symbiotic relationship is reported between
the freshwater sponge Corvomeyenia everetti, which occurs throughout
eastern North America, and a yellow-green alga. 2. Ultrastructural and
pigment analyses place the algal endosymbiont within the class Eustig
matophyceae in the division Heterokontophyta. 3. The relationship of t
he alga with C. everetti appears to be specific and it contributes sig
nificantly to the energy budget of the host. 4. Although the growth fo
rm of C. everetti is very similar to other freshwater sponges that usu
ally have green-algal symbionts, its phylogeny has been proposed to be
quite distinct, suggesting convergent evolution by both algae and spo
nges in the development of symbiotic associations in fresh water.