Life history and reproduction of the amphipod Synchelidium trioostegitum (Crustacea, Oedicerotidae) on a sandy shore in Korea
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The life history and reproductive strategy of the amphipod Synchelidium trioostegitum were studied on a sandy shore at Dolsando, South Korea. Samples were taken once a month for 1 year using a 0.3-mm sledge net on the bottom in 1 m of water at spring tide low water. The highest density of S. trioostegitum occurred from February through March. Ovigerous females were recorded virtually year-round, with a particularly high proportion in fall and early spring, indicating continuous recruitment with two dominant periods. The occurrence of ovigerous females was not correlated with environmental factors, such as temperature and salinity, and no significant difference between the body lengths of females and males was observed. The mean adult body length was greater in the early spring breeding period than in the fall. Brood size and embryo volume were positively correlated with the body length of ovigerous females. Brood size significantly decreased with increases in embryonic developmental stage. Embryo volume was significantly larger in the fall than in the early spring, but brood size was significantly smaller in fall, suggesting a strategy of using the same amount of reproductive energy during breeding periods. This type of reproductive effort is different from that of other Synchelidium amphipods having the same habitat and feeding regime. Our results suggest that interspecific competition for food and territory may be important in defining the reproductive strategy.
KeywordsBody Length Brood Size Breeding Period Ovigerous Female Life History Pattern
We thank Dr. B. Sainte-Marie (Maurice Lamontagne Institute, Fisheries and Oceans Canada, Canada) and Dr. K.E. Conlan (Canadian Museum of Nature, Canada) for critical readings of the manuscript and providing valuable comments. We also thank two reviewers for their valuable comments that greatly improved the manuscript. This work has been conducted with the support through the research program of KORDI with contract Nos. PE97201 and PP06401.
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