Observations on the Fatty Constituents of Marine Plankton

To determine what may be, in the natural habitat of the plankton, the possible source and supply of vitamins A and D, collections of diatoms and of zooplankton were made from Port Erin in the spring and summer of 1928. The dried plankton was treated in Soxhlets with light petroleum, and precautions were taken to ensure against irradiation, against overheating and against oxidation through access of air. Feeding tests for vitamin A were supplemented by observations upon the colour reaction with antimony trichloride and by spectroscopic examination. It is shown that the phytoplankton oil is more potent than the zooplankton oil in its growth-promoting action and this is correlated with a greater richness in carotene releated lipochrome pigments. Vitamin A as such is apparently absent from both phytoplankton and zooplankton. The possible relation of vitamin A to other pigments of vegetable and animal origin and its possible derivation from them are discussed briefly. In testing for vitamin D, the degree of healing was determined both by histological (line test) and by X-ray examinations. In daily doses of 50 mg. phytoplankton oil showed no antirachitic activity but zooplankton showed slight activity. The bearing of these results with those of other investigatiors is discussed and it is suggested that the small amount of vitamin D which appears to be present in these animals results from their irradiation while in surface waters, rather than from a prolonged diet of phytoplankton.