Reproduction of the Diadematidae sea urchin Centrostephanus rodgersii in a recently colonized area of northern New Zealand

Reproduction of the sea urchin Centrostephanus rodgersii at the Mokohinau Islands (northeast New Zealand) was studied in terms of the gametogenetic cycle and sex ratio, and larval range of thermal tolerance was determined. A comparison with the reproductive patterns in populations located in New South Wales (NSW), the historical range of the species, and Tasmania, where the species has only recently arrived (approximate to 50-60 years ago), was made. Results indicate that C. rodgersii in New Zealand is capable of growing gonads, completing a gametogenetic cycle and producing viable gametes. The timing of this process is similar to the population in Sydney (central NSW), where spawning is probably triggered by the winter solstice and lasts from July to September. The sex ratio was skewed towards females (1.6 females for each male), which may be indicative of the recent arrival of the species in New Zealand. Larvae obtained from this population were able to develop at a measurable rate after 72 h only between 16 degrees C and 25 degrees C. Ambient temperatures during spawning at the Mokohinau Islands (15.7-16.8 degrees C) appear to be at the lower end of the range of temperatures suitable for early larval development.