Ref ID : 763
George William Salt; Comparisons of the diets and reproductive performances of two sympatric rotifers, Asplanchna girodi and Asplanchna priodonta. Freshwater Biology 22:417-430, 1989
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1. Diet composition and the production of embryos were measured in Asplanchna girodi and Asplanchna priodonta collected through 3 years in the Sab Joaquin-Sacramento delta of California. The two species are sympatric in low to moderate densities for 5 months of the year. 2. Despite marked differences in the structure of the trophi, both species consumed the same array of prey species. Percentage composition of the diet varied both intra- and interspecifically. The food niches of the two species appear to differ little from one another. 3. Individuals of Asplanchna girodi had a mean number of prey in the gut per individual than did those of A. priodonta, due to their larger size. Per unit volume, each species prey gathering performance was the same. Asplanchna priodonta produced more embryos per calculated unit volume of prey ingested than did A. girodi. 4. During spring, when both species were present in the plankton, A. priodonta did not capture size Class 2 and 5 animals (volumes 0.09-1.0 um3 x 10E6 and 3.0-3.5 um3 x 10E6 respectively) nor large Synchaeta. Both these prey classes were in the diet during the summer and autumn months. Several hypotheses are examined as possible explanations for this phenomenon.