COWART, J.D.: Sometimes It’s Good to Taste Bad: Palatability of Pteraster tesselatus (Echinodermata: Asteroidea) Adults and Offspring

This study investigated secondary metabolites as chemical defenses in Pteraster tesselatus adults and offspring. Members of the Pterasteridae rapidly secrete copious amounts of mucus over their aboral surface when attacked. This mucus secretion is an effective anti-predator mechanism and may contain saponin or saponin-like compounds. In addition, most Pterasteridae brood direct developing offspring within a specialized brood chamber called the nidamental chamber. Pteraster tesselatus is unique because it has re-evolved pelagic development. When P. tesselatus re-evolved pelagic development, the offspring were once again exposed to pelagic predators. The offspring of P. tesselatus are large (1.0 to 1.4 mm in diameter), energy rich, positively buoyant, bright orange, lack morphological defenses, and are unpalatable to two species of northern pacific fish, Oligocottus maculosus (p<0.001) and Gasterosteus aculeatus (p<0.001). I hypothesized that the feeding deterrent properties of P. tesselatus adults and offspring are the result of secondary metabolites as chemical defenses. To test this hypothesis, I conducted a series of feeding bioassays on adult body wall and ovary extractions using O. maculosus as a generalist predator. Results support my hypothesis by showing that adult body wall and ovary extractions are unpalatable to O. maculosus. Although relatively unstudied, patterns of adult and larval chemical defenses may provide insights into the evolution of complex life cycles and of differing modes of development among marine invertebrates.