EFFECT OF FOOD CONCENTRATION AND GENOTYPE ON HARD-PART MORPHOLOGY OF THE MARINE BRYOZOAN, ELECTRA PILOSA (L.)

Evaluation of hard-part morphology as a function of available food concentrations offers a new interpretation of the controls of the phenotype in marine bryozoans. Morphometric measurements of the bryozoan Electra pilosa (L.) allows for partitioning of the effects of genotype and variable food concentrations on five morphologic characters: opesial width (OW), opesial length (OL), zooecial width (ZW), zooecial length (ZL), and zooecial area (ZA). Three genotypes with clonal replicates were grown in six separate tanks within a common waterbath. The bryozoans were fed three different concentrations of the cryptophyte Rhodomonas sp. The data set consists of five measurements from five individual zooids from each replicate colony. The morphometric data were analyzed using three-way full-factorial ANOVA. Genotype, food concentration, tank, and interactions between them were the factors considered. Results show that food is highly significant for all characters (p < 0.001) and accounts for >20% of the total variance among each character excluding ZA. Genotype is highly significant for OW, OL, ZL, and ZA, and is significant (0.05 > p >0.001) for ZW. Genotype accounts for >20% of the total variance for ZL and ZA. The tank factor and interactions with tank account for very small amounts of variance. However, some characters within the tank factor still had significance. The genotype x food interaction and the genotype x food x tank interaction were significant (0.05 > p >0.001). Contrary to previous studies, these results show that food is an important factor in the hard-part morphology of Electra pilosa. Implications from this study extend into areas of paleoclimate research, which employ zooid size as a proxy for seasonality.