ABSTRACT
The reproductive biology of a population of the cidarid echinoid Goniocidaris umbraculum (Hutton)occurring on the outer continental shelf off Otago has been examined. Regular determination of the gonad index and histological examination of sectioned gonads show a clearly defined reproductive cycle. Gonads reach the peak of development in June–July each year and spawning is completed by August–September. Oocytes take two years to complete their development within the ovaries. Gonad indices of males are consistently higher than females. After spawning developing eggs are retained on the peristome, which sinks to accommodate up to 60 embryos brooded for approximately 8 weeks. The evolution and ecological significance of brooding in Gc.iiocidaris umbraculum is discussed.
