| Summary: | The aim of this research project was to investigate ecological aspects of reproduction in the Antarctic brachiopod Liothyrella uva (Broderip, 1833). Previous studies on L. uva revealed a low metabolism, slow growth and longevity which, coupled with the recent discovery of sub-biennial growth rings, indicates the possibility of an unusual reproductive strategy. The reproductive cycle of L. uva is described, based on gonad section data from monthly samples collected from a population at Signy Island, Antarctica. Mean oocyte diameter (102-156μm) and the mean percent spermatozoa (27-50%) changes over a two-year period, show large inter-annual differences in reproductive activity. These data also highlight the variability of the reproductive cycle of L. uva and suggest the possibility of three reproductive cycle periodicities (continuous, annual and long-term). Brooding in L. uva was investigated in the austral summer. Brood characteristics measured included the number in each brood, size of embryo or larva, total energy content of the whole brood, energy content per gram dry mass, and energy per embryo or larva. Elemental (CHN) analysis enabled energies to be calculated from carbon values and were also obtained for the brooding female tissues. Brood energy content decreased significantly (from 49-40kJ/gDM) over the three-month period. However, energy per embryo or larva significantly increased (from 0.15J to levels around 0.40J). This was a result of the addition of new, small, highly energy dense early embryos later in the main brooding period. Larval release was studied by holding L. uva females in individual tanks. Release types and timing were highly variable both for individual L. uva and between females. Overall, the period of larval release of each female varied between less than 1 week to over 1.5 months. All developmental stages were seen from early gastrulae through to settled juveniles. Settlement in the laboratory matched that seen in a concurrent field experiment. Larvae exhibited preference for live ...
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