Reproductive patterns in the Antarctic brachiopod Liothyrella uva |
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Authors: | K Meidlinger P A Tyler L S Peck |
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Institution: | (1) Southampton Oceanography Centre, European Way, Southampton SO14 3ZH, Hants, England, GB;(2) British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 OET, England, GB |
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Abstract: | The reproductive cycle of the Antarctic articulate brachiopod Liothyrella uva (Broderip, 1833) is described from monthly samples collected between September 1985 and July 1987 from a population at Signy
Island, Antarctica. Spermatogenesis and oogenesis are described for the first time in this species. Surface dried-tissue masses
for a standard individual (41 mm shell length) were calculated for the digestive diverticula, gut, lophophore and gonad from
monthly dissections of 15 brachiopods. Seasonal patterns, with summer peaks, were observed in the digestive diverticula and
gut. The lophophore and gonad masses did not exhibit seasonal trends. Females showed a sharp decrease in proportion of large
oocytes between October and November in 1986, suggesting spawning during this period. There was no similar decrease during
the same period in 1985. Mean percent spermatozoa measurements revealed a large increase in November 1985 and a rapid decline
in December 1985. This suggested a large spawning event for males in 1985 which was not repeated the following year. These
data indicate large inter-annual differences in reproductive activity as well as differences between males and females. They
also suggest the possibility of sperm storage by females. Brood characteristics were also highly variable. The smallest brooding
female was 31.5 mm in length. Some females brooded more than one developmental stage simultaneously, and variation in brood
size (numbers of embryos or larvae held in the lophophore) and brood composition between individuals was high. All samples
collected throughout the 2 yr period contained some females with broods. The data suggest that the reproductive strategy of
L. uva is highly plastic, and that there may be three reproductive periodicities on seasonal, annual and inter-annual time scales.
Received: 16 May 1997 / Accepted: 2 March 1998 |
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