Cyst production in the fairy shrimp, Streptocephalus proboscideus (Anostraca) in relation to algal and loricated rotifer diet

Adult fairy shrimps, Streptocephalus proboscideus (Frauenfeld, 1873) reared separately using algae (Scenedesmus acutus Meyen), a large loricate rotife r (Brachionus calyciflorus Pallas, 1766) and mixtures of algal and animal d iets (1:1 ratio on a dry weight basis) at a rate of 17 mu g DW ml(-1) day(- 1) produced a mean number of 184 +/- 38, 111 +/- 14, and 160 +/- 14 cysts p er brood, respectively. Of these, the rotifer-only diet was significantly i nferior to both other food types. Measurements of cyst volume revealed an e ffect of food type. With all three types, S. proboscideus produced cysts in the size range of 3.0-9.0 x 10(6) mu m(3). However, sizes smaller than 3.0 -9.0 x 10(6) mu m(3) occurred in algae-fed anostracans and those larger tha n 3.0-9.0 x 10(6) mu m(3) in rotifer-fed individuals. When the mean cyst pr oduction was expressed in terms of volume instead of numbers, there was a s uggestion that the mixture of algae and rotifers was the superior combinati on, while females reared on rotifers produced a significantly (38%) lower t otal cyst volume. Hatchability of cysts, either dried or un-dried, was not significantly different between treatments.