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UBC Theses and Dissertations

Aspects of the reproductive biology of Strombus gigas Egan, Brian Denis


Shell morphology changes relating to sexual maturity and the reproductive cycle of Strombus gigas were studied at a single site within the Barrier Reef lagoon of Belize, Central America. Monthly samples, from July 1981 to June 1983, of transverse tissue sections, through the digestive gland and gonad, were fixed for examination by light microscopy. Sections from all areas of the gonad were used to develop a sexual maturity scale that would permit the maturity of a specimen to be determined from the condition of a single tissue sample. The effectiveness of the technique described, for use in other meso- or neogastropods, is dependent on simultaneous maturation throughout the gonad and on an even distribution of reproductive structures within. Sexual maturity in S. gigas (as defined by the development of mature gametes) first occurs when individuals have a flaring shell lip-thickness of approximately 4 mm. Sexual maturity is reached approximately 1 year after maximum shell length is reached and approximately 6 months after development of the flaring lip, at an age of roughly 4 years. Ninety four percent of the population studied attained the legal shell length, in Belize, of 175 mm. The time delay between attaining legal length and becoming sexually mature means that there is a period, for 94% of the population, when they may be legally harvested before becoming sexually mature. Reproductive activity occurs year-round in the population studied. An annual pattern of activity was not apparent through inspection of the data alone. No statistical correlation was found between gonadal activity and average monthly air temperature or monthly rainfall.

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