Meeting Abstract
The success over evolutionary time of lineages with colonial organizations (e.g. cnidarians) is substantial. Coloniality has only evolved in a few lineages however, suggesting specific selection pressures that favor this life history mode. To test hypotheses for why coloniality may have evolved, we are examining gene expression and physiological energetic differences between solitary and experimentally manipulated colonial morphotypes of the starlet sea anemone, Nematostella vectensis. Coloniality may confer specific reproductive advantages, such as increases in the quantity or quality of offspring, when compared with solitary individuals. Offspring of better quality may be produced, for example, when mothers provision eggs with biochemical constituents with greater organic content and/or per unit energy, such as lipid and protein. We measured per egg levels of maternal provisioning using standard colorimetric assays of total lipid and protein content for eggs produced by solitary and two-headed (colonial) morphotypes of N. vectensis. Our results from these assays reveal significant differences between morphotypes in per-egg organic and energetic contents and densities. Our results indicated that one-headed individuals produced eggs that were significantly more energy-rich. Alternatively, two-headed individuals produced significantly more and larger eggs, each containing significantly less lipid and protein. We will discuss these results in light of their effects on offspring quality, development, and growth, as well as their implications for the selection pressures favoring the evolution of coloniality.
