Showing papers by "David Beach published in 1973"
TL;DR: It is concluded that polyunsaturates may be passed intact from one trophic level to another in marine food chains, and that tapeworms can be used to monitor lipids in the food chains in which the hosts participate.
Abstract: Callibothrium verticillatum, a cestode from the spiral intestine of the dogfish, Mustelus canis, incorporated a characteristic polyunsaturated fatty acid of marine organisms (22:6 03) without conversion or degradation. The tapeworm was incubated in vitro with [14C] 22:6 w3. Its labeled lipids were fractionated and their radioactivities assayed by column and thin-layer radiochromatography nlethods. Triglyceride (50% of dpm collected) and unesterified fatty acids (28%) were the most radioactive fractions. Sterol ester, wax ester, diacylglyceryl ether, diglyceride, monoglyceride, cardiolipin, phosphatidylethanolamine, phosphatidylserine, and phosphatidylcholine also were radioactive. 22:6 ca3 and the other fatty acids of the tapeworm were collected by preparative gas-liquid radiochromatography from the total fatty acids, hydrogenated total fatty acids, triglyceride fatty acids, and unesterified fatty acids. Only 22:6 w3 was radioactive. Lipids were 25% of the dry weight of C. verticillatum. The major lipids were triglyceride (54 wt% of total) and phosphatidylcholine (25%). The polyunsaturated fatty acids of the neutral lipids were mostly eicosenoic (20:5 w3 was 25% of total), and of the polar lipids were docosenoic (22:6 w3 was 30%). The fatty acid composition of the tapeworm, the contents of the spiral intestine, and the fluids and tissues of the dogfish were strikingly similar. It is concluded that polyunsaturates may be passed intact from one trophic level to another in marine food chains, and that tapeworms can be used to monitor lipids in the food chains in which the hosts participate. Polyunsaturated C20 and C22 fatty acids are characteristic components of the storage and membrane lipids of most marine organisms; for example, planktonic unicellular algae (except blue-greens and the Chlorophyceae) (Kates and Volcani, 1966; Ackman et al., 1968; Chuecas and Riley, 1969; Holz, 1969; Lee and Loeblich, 1971), benthic multicellular algae (except Chlorophyceae) (Wagner and Pohl, 1965; Chuecas and Riley, 1966; Pohl et al., 1968; Radunz, 1968; Jamieson and Reid, 1972), protozoa (Uronema sp., Labyrinthula sp.) (Harrington, G. W., and Holz, G. G., Jr., unpublished), phycomycete fungi (Ellenbogen et al., 1969), invertebrates (Ackman and Eaton, 1966, 1967; Ackman et al., 1970; Culkin and Morris, 1970a, b; Lee et al., 1971), and vertebrates (Kayama et al., 1963a, b; Ackman, 1967; Ackman et al., 1971; Malins and Wekell, 1970). They are synthesized de novo by the photosynthetic planktonic and benthic algae. Marine animals incorporate them intact from their diet, and also biosynthesize them by elongating and desaturating C18 acids such as 18:2 o6, 18:3 w3, and 18:4 o3. Some invertebrates may obtain C20 and C22 polyunsaturates and/or their precursors from seawater directly Received for publication 20 March 1973. through their body surfaces (Testerman, 1972). Heterotrophic algae, protozoa, and the fungi may supply themselves with the C20 and C22 polyunsaturates by de novo synthesis, by direct incorporation from the environment, and by elongation and desaturation of the Cis fatty acids. The most typical marine polyunsaturates are o)3 eicosapentaenoic and docosahexaenoic acids with methylene-interrupted double bonds of the cis configuration; i.e., all-cis, 5,8,11,14, 17-20:5 and 4,7,10,13,16,19-22:6 (Ackman, 1964; Hinchcliffe and Riley, 1971). The cestodes of sharks contain these fatty acids (Buteau et al., 1969, 1971) and it has been assumed that they acquire them from their immediate environment, the contents of the spiral intestine. We have tested the possibility of direct incorporation, by exposing a tetraphyllidean of sharks to [14C] 22:6 o3 and then performing a radiochemical analysis of the lipids of the tapeworm to determine the distribution of the polyunsaturate. Cestodes were chosen as particularly favorable material for an experiment on direct incorporation of 22:6 oj3 since they neither oxidize nor biosynthesize fatty acids de novo (Meyer et al., 1966).
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