The effects of energy quantity to the reproductive strategies of the sea anemone Aiptasia pulchella Carlgren 1943 Chien-Hsun Chen (Advisors: Drs. Keryea Soong, Chao-Lun Chen) Institute of Marine Biology, National Sun Yat-Sen University, Kaohsiung, 804, Taiwan, R.O.C. Thesis abstract The influences of energy quantity on the sexual and asexual reproduction and possible trade-offs between them in the sea anemone, Aiptasia pulchella were investigated. Different feeding frequencies, light intensities and presence of zooxanthellae were the treatments of energy quantity. Lacerate numbers, lacerate sizes and total weight of lacerates were used to quantify investment in asexual reproduction; oocyte sizes and gonad weights were used as the measures of sexual reproduction. The correlation between total weight of lacerates and that of gonads provided an opportunity for evidence of trade-offs between sexual and asexual reproduction. Under higher feeding frequencies, A. pulchella produced more and larger lacerates as well as larger oocytes and heavier gonads than under lower feeding frequencies. Under lower light intensities, A. pulchella produced more and heavier lacerates with than without zooxanthellae. Lacerate sizes were influenced by light intensities, presence of zooxanthellae and the interaction of the two factors. At intermediate light intensity (2000 lux), Aiptasia pulchella produced heavier gonads than at 0 lux or 10000 lux. A. pulchella produced heavier gonads with than without zooxanthellae. The oocyte sizes of A. pulchella were also influenced by light intensities, zooxanthellae and the interaction of the two. In both sexual or asexual modes of reproduction, A. pulchella performed better under higher than lower feeding frequencies. There were higher level of asexual reproduction for A. pulchella under lower light intensities with zooxanthellae. A. pulchella achieved the highest levels of fecundity, as an indication of sexual reproduction, under a light intensity of 2000 lux in individuals containing zooxanthellae. There is a positive correlation between sexual and asexual investment under different energy regimes. This is not compatible with the prediction of the trade-off hypothesis.