OBSERVATIONS ON THE BIOLOGY OF MAORICOLPUS-ROSEUS (QUOY-AND-GAIMARD) (PROSOBRANCHIA, TURRITELLIDAE) FROM NEW-ZEALAND AND TASMANIA

Maoricolpus roseus lives in high to moderate abundances in New Zealand , where it appears to prefer areas of coarse or at least firm substrat es, moderate to strong currents, depths of 1-130 m and temperatures of 8-20-degrees-C. Its abundance in New Zealand seems to be positively c orrelated with availability of suspended food, negatively correlated w ith suspended terrigenous sediment, and not strongly correlated with d egree of coastal upwelling. Substrate firmness may also be important i n controlling its distribution and/or abundance. Some individuals have been observed alive in an unusual vertical orientation in crevices in rocks, but the significance of this orientation is unclear. Following its introduction into Tasmania by unknown means early in this century , M. roseus has increased dramatically in abundance, probably due to a lack of appropriate predators. In New Zealand, it is preyed upon by t eleosts and starfish, whereas in Tasmania, mortality appears to be due mostly to storms. The oxygen isotopic profiles of M. roseus shells re flect seasonal temperature changes during the life of the animal. Comp arison with a previous study on Turritella gonostoma from the Gulf of California suggests that M. roseus grows more slowly.