Reproductive development of the barnacle Chthamalus malayensis in Hong Kong: implications for the life-history patterns of barnacles on seasonal, tropical shores |
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Authors: | Yan Yan Benny K K Chan Gray A Williams |
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Institution: | (1) Department of Ecology & Biodiversity, The Swire Institute of Marine Science, The University of Hong Kong, Pokfulam Road, Hong Kong, China;(2) Present address: Research Centre for Biodiversity, Academia Sinica, Taipei 115, Taiwan, China |
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Abstract: | Hong Kong, lying just below the Tropic of Cancer (22°17′N, 114°09′E), experiences a strongly seasonal environment, with a
cool almost temperate winter and a hot, tropical, summer. Histological sectioning of the gonads of the high-shore barnacle,
Chthamalus malayensis Pilsbry, showed a seasonal trend in the development of its reproductive organs. Four stages of female gonad development were
identified according to the cell types present: post-spawning, resting, growth and mature stages. The female gonad was mature
from April to November, which was related to seawater temperatures, and entered a resting phase from December to March. Although
the male gonad showed a seasonal developmental trend and reached maximum maturity in summer, the seminal vesicles were full
of spermatozoa and functional throughout the year. The reproductive season of this species is therefore solely dependant upon
the maturity of the female gonad. The estimated maximum number of broods per year was up to 10 and the maximum number of eggs
produced per brood can reach 3,000 eggs. The minimum size for female gonad maturity was 6 mm rostro-carinal diameter (RCD)
at which size, the barnacles were ~6-month old. Sperm production occurred at a smaller size (2 mm=2-month old). Compared with
Chthamalus montagui and Chthamalus stellatus from temperate regions, C. malayensis produced a greater number of broods per year, had a longer reproductive period and faster gonad development. Chthamaloid
barnacles in tropical regions may, therefore, invest more energy per year in reproduction during their life span. Contrary
to the seasonal gonad developmental pattern of C. malayensis in the present study, however, C. malayensis in Singapore (which experiences only slight seasonal variation) had mature female and male gonads throughout the year, further
supporting the strong role of climatic conditions effecting the reproductive biology of barnacles. |
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