Different life histories of the co-occurring fairy shrimps Branchipus schaefferi and Streptocephalus torvicornis (Anostraca)

摘要

Branchipus schaefteri and Streptocephalus torvicornis commonly co-occur in ephemeral ponds throughout the Mediterranean Region. We compared survivorship, growth, and reproduction. Our results show statistically significant differences in all three parameters under laboratory conditions at 25degreesC, reflecting different life history strategies between these species. Branchipus schaefferi grows quickly to 18 mm body length, producing roughly 1700 cysts during an average lifespan of 24 days, while S. torvicornis lives an average of 120 days (length 24 mm), laying 2400 cysts. This suggests that S. torvicornis is better adapted to deep longer-lived pools, whereas B. schaefferi may survive in small, more ephemeral pools as formed from spring melt water and autumn rains. While the lifespan is equal for both sexes in B. schaefferi, the males of S. torvicornis live 2.8 times longer than females (325 days versus 114) compelled into a long postreproductive period by lack of females in their environment.