The Suitability of Four Algal Species as Food Source for Daphnia Pulex
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The effects of four different algal species (Chlamydomonas reinhardi, Cryptomonas ovata, Asterionella formosa, and Anabaena viriabilis) on the Cladoceran Daphnia pulex. were studied on a comparative basis. Parameters stressed were growth, survivorship, and fecundity. Filtration, ingestion, and assimilation rates and assimilation efficiencies for Daphnia fed these four algal species were calculated using radiotracer experiments and were used as supportive data for the comparative life history study. Daphnia fed Chlamydomonas exhibited the highest growth rate of all samples and those fed Cryptomonas exhibited the highest reproductive rate. Animals fed Asterionella also showed relatively high values for all parameters, yet most were significantly smaller than animals fed Chlamydomonas or Cryptomonas. Animals fed Anabaena never reached reproductive maturity, died at an early age, and never reached a length comparable to Daphnia fed the other algal species. Filtration rates were relatively high for all four species of algae, and in general dropped off as algal concentration increased. The highest filtration and assimilation rates were found with Daphnia fed Asterionella and the highest assimilation efficiencies were found with animals fed Asterionella and those fed Cryptomonas. The lowest values for assimilation efficiencies were exhibited by animals fed Anabaena. It was concluded that Chlamydomonas and Cryptomonas were the best food sources, followed respectively by Asterionella and Anabaena, Anabaena having almost no nutritional value for Daphnia.