The Natural History, Life History and Ecology of the two British species of "Asterina"

Emson and Crump (1978) realised that British Asterina exhibit two discrete types of reproductive behavior and this led, in 1979, to the recognition that two species were present -- A. gibbosa and A. phylactica . Subsequent papers have clarified the degree of overlap and separation between the two species to such an extent that it is now possible to review their biology. The crucial differences between them, in terms of habitat partitioning where they are sympatric, seem to result from differences in behaviour, and especially from their responses to light. But in fact the whole life strategies of A. gibbosa and A. phylactica are different. In addition to the fact that A. phylactica broods the eggs and developing juveniles whereas A. gibbosa does not, A. phylactica matures earlier and has a shorter life span. Although the species appear to be morphologically similar and may be found together exploiting a similar food supply, it is shown in this paper that their ecological niches are quite different.