Annual reproductive cycles in three geographically separated populations of Patiriella regularis (Verrill), a common New Zealand asteroid

Abstract

Annual reproductive cycles and related changes in the pyloric caeca of the common New Zealand asterinid, Patiriella regularis (Verrill) were followed for sixteen months, in three geographically separated populations. These separate sub-populations showed marked differences in animal size and abundance and in reproductive development. The reproductive cycle was more clearly defined than in other asterinids studied and spawning occurred in summer (local) from January to March. The major reproductive difference between sub-populations was that the reproductive potential in two areas was more than twice that of the third. The cycle of the pyloric caeca index was pronounced in two of three sub-populations and bore an approximately inverse relationship to the reproductive cycle. In the area of low reproductive potential the pyloric caeca showed little fluctuation in size throughout the year. In order to test the contention that the reproductive potential is influenced by available food supplies a series of laboratory experiments were designed to run concurrently with the field studies. A representative sample of Patiriella taken from the area of low reproductive potential and raised for 11 months on crabs, showed reproductive potentials higher than any encountered in the field study areas at the same time, just before spawning. It is concluded that in Patiriella regularis the presence of stored food reserves in the pyloric caeca during the winter months is essential for good gonad development. Where such food reserves are absent due to shortage of suitable food in the habitat, reproductive potentials are low.