FOOD QUALITY OF GELATINOUS COLONIAL CHLOROPHYTES TO THE FRESH-WATER ZOOPLANKTERS DAPHNIA-PULICARIA AND DIAPTOMUS-OREGONENSIS

1. The capacities of the gelatinous colonial chlorophytes Pandorina morum and Sphaerocystis schroeteri to sustain survival and reproduction in the calanoid copepod Diaptomus oregonensis and the cladoceran Daphnia pulicaria were evaluated quantitatively. Control groups of animals were fed equivalent biovolumes of Cryptomonas reflexa, which is known to favour high levels of survival and reproduction. 2. On a biovolume basis, all three algae sustained equal survival of Daphnia, but Cryptomonas and Pandorina allowed longer survival of Diaptomus than did Sphaerocystis. 3. Both animals produced significantly more offspring clutch(-1) and more total offspring on Cryptomonas than on either chlorophyte. Both animals produced more total offspring on Pandorina than on Sphaerocystis. 4. The interclutch duration for Daphnia was significantly longer on Pandorina than the other algae, and the interclutch duration for Diaptomus was longer on Pandorina than on Cryptomonas. 5. Daphnia utilized the gelatinous chlorophytes more effectively than did Diaptomus.