Reproductive periodicity in Evechinus chloroticus in the Hauraki Gulf |
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| Authors: | MM Walker |
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| Institution: | 1. Department of Zoology , University of Auckland , Private Bag, Auckland, New Zealand;2. Department of Zoology , University of Hawai'i , 2538 The Mall, Honolulu, HI, 96822, U.S.A. |
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| Abstract: | Test diameter and gonad volume were recorded over 1 year for bimonthly samples of Evechinus chloroticus (Valenciennes) from each of 3 subtidal populations 10 km apart in the Hauraki Gulf. Histological analysis was used to relate cellular events during gametogenesis to the annual cycle of change in gonad size. Mean gonad sizes of the different sea urchin populations were compared by analysis of covariance. Gametogenesis began in the spring, and major spawning occurred in mid to late summer. The proportion of the gonads taken up by nutritive phagocyte cells increased from autumn to spring. During proliferation and growth of gametes the nutritive phagocytes declined in abundance and globulation, suggesting that reserves stored in these cells were transferred to developing gametes. Gonad size doubled during gametogenesis, declined after spawning, and remained low in autumn and winter. Differences in gonad size between populations were significant during most of the year, and were most pronounced in mid summer. Although synchronous gametogenesis occurred in the 3 populations studied, spawning occurred at different times. This suggested that spawning in this species was induced by factors acting either within sea urchin populations or over distances of a few km or less. |
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| Keywords: | Evechinus chloroticus gonads histology gametogenesis spawning population sampling Hauraki Gulf Echinometridae phenology Rangitoto Island Noises Islands Crusoe Island seasonal variation reproduction kina echinoderms |
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