THE NUTRITIONAL INADEQUACY OF <i>CHLORELLA</i> AND <i>CHLAMYDOMONAS</i> AS FOOD FOR <i>DAPHNIA PULEX</i>1

Abstract

Daphnia pulex failed to reproduce normally when fed either Chlorella pyrenoidosa or Chlamydomonas reinhardtii cultured and suspended in defined inorganic media. Lifespan was shorter, ovulation was reduced, and a large percentage of ovulated eggs failed to complete embryonic development. The same algal culture suspended in “biologically conditioned water” supported a normal lifespan and ample but not maximal reproduction. The active factors are heat‐stable. Several organic compounds were tested to find a substitute for aquarium water. Calcium pantothenate (300 mg/liter) improved survival and reproduction significantly, but for only one generation; alanine, glucosamine, and carnatine were not significantly beneficial. CaC1 2 improved survival and reproduction of two succeeding generations. Despite increases in the amount of calcium added, Daphnia cultures could not be maintained indefinitely on Chlamydomonas suspended in a defined salt solution. The algae appear to be deficient in meeting the nutritional requirements of Daphnia pulex, especially with respect to reproduction. Their proper utilization seems to depend on factors supplied by other organisms, probably bacteria, and probably provided in the water from natural sources used in most experiments.