Replacement of dried freshwater alga Arthrospira maxima with marine diatom Schizochytrium limacinum in a diet of freshwater mussel Unio crassus (Philipsson, 1788)

Abstract

The present study was conducted to determine the possible usage of dried Schizochytrium limacinum as a replacement of Arthrospira maxima in a ration of the adult freshwater mussel (Unio crassus). The experimental diets were prepared with the different concentrations of protein-rich green freshwater algae A. maxima and docosahexaenoic acid (DHA)-rich diatom S. limacinum. Combinations were done by replacing A. maxima with 0%, 30%, 70%, and 100% of dried S. limacinum then named AM100, AM70, AM30, and AM0, respectively. These diets were used to feed 180 individuals (15 mussels/tank) of U. crassus in 12 independent glass (4 groups and 3 replicates) tanks. Live weight gain, shell dimensions, biochemical compositions, and fatty acid contents of U. crassus from whole tissue were examined before and after 30 days of feeding trial. The live weight gain was significantly higher in the AM100 (1.66 +/- 1.32 g, 5.00 +/- 3.95%) and AM70 (1.32 +/- 0.83 g, 4.05 +/- 2.56%) groups than in the (0.06 +/- 1.91 g, 0.31 +/- 5.73%) and AM0 (- 0.17 +/- 0.61 g, -0.52 +/- 1.84%) groups. We were able to detect increasing levels of DHA in the U. crassus tissues, while the given ratios of S. limacinum were increased in the diet. The results showed that S. limacinum was digested by adult U. crassus to some extent and DHA was retained in the mussel tissue. These results showed that the dependence on live algae can be decreased in the conservation effort of U. crassus by using S. limacinum in a ration.