Origin of vitamin D in cod-liver oil: vitamin D content of zooplankton

Abstract

THE abundance of the fat-soluble vitamins A and D in the liver of the cod has led many investigators to examine the food supplies of the cod for the source of these vitamins. In the case of vitamin A these researches have been successful. Drummond and Zilva [1922] searching for the ultimate source of vitamin A in nature found that the marine diatom, Nitzschia closterium, was capable of synthesising a fat-soluble growth factor. Jameson et al. [1922] also demonstrated that N. closterium could synthesise this factor under controlled conditions in the laboratory, but Leigh-Clare [1927], while confirming the synthesis of vitamin A by this organism, was unable to prove the presence of vitamin D in' such cultures. Thus while the diatom might be the ultimate source of vitamin A in the food of the cod, it was extremely improbable that it could be the source ofAs the cod is a deep-water fish, it is unlikely that any synthesis of vitamin D in the cod itself can take place by the action of ultraviolet irradiation, since such irradiation has been shown to be reduced to 1 % of its sub-surface value at a depth of 1 1-2*2 m. and to 0-001 % at 2-9-5-5 m. [Atkins and Poole, 1933].Bills [1927] has suggested that the cod might be able to synthesise vitamin D in its liver by some process as yet undetermined, since no rich source of the vitamin has been found in its food, but Hess et al. [1932] were unable to show any increase of vitamin D in the livers of fish which had received ergosterol intramuscularly or by mouth. Drummond and Hilditch [1930], in examining the relative vitamin values of cod-liver oils from various sources, also investigated the food supplies of the fishing grounds and reported that there was no significant content of vitamin D in the zooplankton (copepods, etc.) and only very little in the small fish on which the cod was known to feed. In the same year and later, Drummond and Gunther [1930; 1934] tested extracts of zoo-and phyto-plankton, prepared as described by Collin et al. [1934] and showed that vitamin D was probably absent from the phytoplankton but present in the zooplankton extract, to the extent of less than 100 "Coward" (International) units per ml. (equivalence of extract in terms of original matter not stated), by giving small doses to rats in curative tests. They suggested that the zooplankton might derive the vitamin D from irradiation while in surface waters, rather than from ingestion of phytoplankton. Belloc et al. [1930] tested the antirachitic potency of the sterols of plankton. They found that the sterols obtained by the saponification of the oils extracted from copepods were antirachitically active without previous irradiation, but that the sterols from ctenophores required to be treated with ultraviolet light before they had any activity. The crystalline sterol from copepods was active in doses of 0-01 mg., but no figures are given by means of which this potency can be correlated with the amount of original material from which the sterol was derived.

Vitamin D: an ancient hormone

“…The function that vitamin D and its precursors play in these primitive organisms is unknown. However, it seems clear that the large concentrations of vitamin D 3 in the liver and fatty tissues of fish originate at least in part from these food sources (5). Although fish skin has been shown to produce vitamin D 3 (2), the efficiency of production is low, and given that most fish live at depths that would preclude exposure to UVB (little UVB penetrates below 1 m of water), their endogenous production of vitamin D 3 is probably negligible.…”

Evolution and Function of Vitamin D

“…Drummond and Gunther (1930) found little vitamin D in phytoplankton, but were able to find some in zooplankton and small fish that cod fish ate. Copping (1934) found antirachitic activity in dried copepods that were harvested from the North Atlantic.…”

The significance of vitamin D for fish: a review

“…Drummond & Gunther (1930, 1933) were the first to suggest that zooplankton could be the origin of an antirachitic factor. Copping (1934) demonstrated that zooplankton contains high concentrations of vitamin D and thus could serve as dietary source of the vitamin. Zooplankton and phytoplankton contain two forms of vitamin D in high concentrations: vitamin D 2 and D 3 (Rao & Raghuramulu 1996b; Mattila et al 1997).…”