. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. P. CALOW AND J. B. JENNINGS The cestodes are somewhat atypical, when compared with the other ento- symbiotes, in that they have relatively high and variable calorific values (Table I). The latter probably result from variability in lipid contents; high lipid levels have been reported in Hymenolepis diminuta by Webb and Mettrick (1973) but much lower levels are recorded for several other cestodes (Smyth, 1966). In H. diimnuta gravid proglottids contain a higher proportion of lipid than do immature and mature ones (Fairbairn,
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. P. CALOW AND J. B. JENNINGS The cestodes are somewhat atypical, when compared with the other ento- symbiotes, in that they have relatively high and variable calorific values (Table I). The latter probably result from variability in lipid contents; high lipid levels have been reported in Hymenolepis diminuta by Webb and Mettrick (1973) but much lower levels are recorded for several other cestodes (Smyth, 1966). In H. diimnuta gravid proglottids contain a higher proportion of lipid than do immature and mature ones (Fairbairn, Wertheim, Harpur and Schiller, 1961; Mettrick and Cannon, 1970) and this is reflected in their high calorific value (Table II). If the cestode strobila is viewed as a series of progressively maturing reproductive units, though, rather than as a single individual, it becomes legitimate to compare only the immature and mature proglottids with the whole individuals from other flatworm groups. The gravid proglottids contain the products of reproduction and are more comparable, therefore, to the cocoons of free-living flatworms. The im- mature and mature proglottids have calorific values closer to those of other ento- symbiotes than does the whole cestode (Table II) and so conform more closely to the basic evolutionary trend in the phylum. TABLE II Calorific values (kcal/g ash-free dry wt.), Joule equivalents and ash contents in Hymenolepis diminuta kcal/g ash-free dry wt ± 95% conf. interval kj/g ash- free dry wt Ash % dry wt ± 95% conf. interval Number of mea- surements Whole worm ± ± 10 Immature proglottids Mature proglottids Gravid proglottids ± ± ± ± 1 8 10 f = insufficient material for replicates. The link between calorific value, fecundity and mode of life would seem, there- fore, to be amply demonstrated in the Platyhelminthes. The precise nature of this link is at fi
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