The filter-feeding rates and particle retention efficiencies of three species of Cyclosalpa (Tunicata

The particle retention spectra of the mucous nets of three species of salps were determined by measuring differences in grazing rates on particles of different sizes with a Coulter Count-er. It is pointed out that the only correct method for determining these spectra for an organism feeding in a closed vessel is to compare rates of clearance for each particle size class; if ratios of the quantity ingested to the initial amount ’ in each size class are used, incorrect retention spectra will be produced. Cyclosalpajoridana, Cyclosalpa afjkis, and Cyclosalpa polae can all remove particles about 4 SL. in diameter and larger with 100 % efficiency. Observed differ-ences between species in the retention characteristics of the filtration apparatus can be ascribed to differences in the sizes of the. animals. In general, smaller salps can retain a greater fraction of small particles than can larger ones. Although quantitative differences in the particle retention spectra between generations and species exist, there is little evidence that qualitative differences arc also present. Depending on the abundance of these salps, their grazing impact on particles with diameters as small as 1 p could be significant. Salps are pelagic tunicates which fee