Variation in the Size, Energy Content, and Biochemical Composition of Invertebrate Eggs: Correlates to the Mode of Larval Development
The egg is, perhaps, the singular, most influential cell in the life history of any marine invertebrate. Extremes in egg size are correlated with developmental mode and, as a consequence, the temporal duration of the planktonic period. Interpretation of the relationship between egg dry organic weight, energy content, or biochemical composition, and differences among taxa, ideally should include an evaluation of the structures and cellular mechanisms involved in egg production. K. J. Eckelbarger presents an interesting discussion of the role of the ovary and vitellogenic mechanisms in the evolution of invertebrate life-history patterns. The reduction in initial cytoplasm, and hence egg size, of the separated blastomeres is correlated with reduced larval size and a decreased rate of development. For planktotrophic species, however, juvenile size at metamorphosis was independent of “egg” size. Average differences in egg size, energy content, and biochemical composition are reflected in differences in developmental mode.