Ascidian cannibalism correlates with larval behavior and adult distribution

In the San Juan Islands, Washington, solitary ascidians that occur in dense monospecific aggregations demonstrate gregarious settlement as larvae, whereas species that occur as isolated individuals do not. All gregarious species reject their own eggs and larvae as food, but nongregarious species consume conspecific eggs and larvae. Moreover, the rejection mechanism is species-specific in some cases. Correlation analysis suggests that species specificity of the rejection response has a basis in siphon diameter, egg density, and larval size, but not in number of oral tentacles, or tentacle branching. One strongly cannibalistic species, Corella inflata Huntsman, avoids consuming its own eggs and newly released tadpoles by a unique brooding mechanism that involves floating eggs, negative geotaxis after hatching, and adult orientation.