Brooding behaviour and larval development in the new zealand chiton onithochiton neglectus de rochebrune (Mollusca Polyplacophora)

The chiton Onithochiton neglectus is widespread throughout New Zealand, occurring under boulders down to at least 20 m depth. Several populations in the vicinity of Leigh, on the northeastern coast of the North Island, were monitored for 2 years. Brooding individuals were found in many of these samples, and on present evidence, brooding apparently occurs in all seasons except winter (June to August). Female O. neglectus brood their eggs in the pal- lial grooves, the number of eggs varying widely from several hundred to several thousand. The embryos from several brooders were collected and reared in the laboratory. These were then used to describe the developmental stages of O. neglectus. Embryos undergo most of their development inside a capsule (chorion), but are released after 12-15 days as well developed trochophores which retain some swimming ability. Settlement occurs within hours of hatching, and is almost immediate if a suitable substratum is available.