Relative investment in offspring by sessile Rotifera

Correlations of egg and body volumes of 65 species of oviparous Rotifera fr om the three families of sessile rotifers (Atrochidae, Collothecidae, Flosc ulariidae) were determined from size measurements documented in the literat ure and from unpublished data (RLW). While egg volume (EV) of amictic (subi taneous) eggs increased as a function of body volume (BV) in these families , relative egg volume (REV) decreased with increasing BV indicating that re lative investment per offspring is less in larger-bodied species. Regressio n coefficients for REV as a function of BV for these families were signific antly different from each other and that of the strictly planktonic species studied by Walz et al. (1995). Thus, our statistical analysis indicates th at relative investment per offspring was greatest in planktonic species, in termediate in Flosculariidae, and lowest in Collothecidae. These results su ggest that the sessile families do not follow the standard pattern of EV pr edicted for planktotrophic and lecithotrophic larvae as is found in many ma rine benthic invertebrates.