. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 310 W. B. STICKLE ET AL in response to normoxic seawater after 12-h exposure to anoxic seawater (Fig. 6B, C), are probably related to the feeding history of the snails. Feeding rate is the primary bioenergetic component to become variable in gradients of environmental factors, and certain individuals cease feeding altogether under stressful conditions (Stickle, 1985). Small oyster drills, such as those used in this study, are particularly sensitive to the selection of opti- mum-sized bivalve prey, because prey size can limit
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 310 W. B. STICKLE ET AL in response to normoxic seawater after 12-h exposure to anoxic seawater (Fig. 6B, C), are probably related to the feeding history of the snails. Feeding rate is the primary bioenergetic component to become variable in gradients of environmental factors, and certain individuals cease feeding altogether under stressful conditions (Stickle, 1985). Small oyster drills, such as those used in this study, are particularly sensitive to the selection of opti- mum-sized bivalve prey, because prey size can limit the ingestion rate, and hence the energy budget of the preda- tor (Garton, 1986). T. haemastoma prefers a number of different prey items (Butler, 1953), the importance of which may vary with the size of the snail. Oyster drills also exhibit a large specific dynamic action effect, ele- vated metabolic rates associated with digestion of food, in normoxic seawater, anoxic seawater, and when ex- posed to the air (Stickle el a/., 1986). All of these factors probably contributed to the variability in individual met- abolic rates which resulted in two apparent patterns of response in the recovery of oyster drills from 12 h of an- oxia. The metabolic rate depression of T. haemastoma ex- posed to anoxia (Table II) suggests a switch to the rela- tively more efficient succinate and propionate pathways in the molluscs, compared with the well developed, but less efficient, classical glycolysis system in the crusta- ceans(Gade, 1983; Gnaiger, 1983a, 1987; and deZwaan and Thillart, 1985). During initial exposure to environ- mental anaerobiosis, the biochemically estimated ATP turnover rate may drop to about 10% of aerobic resting rates in crustaceans, and the reductions may be even larger in molluscs (deZwaan and Thillart, 1985). During the initial exposure to anoxia, when aspartate is still the precursor of succinate in the molluscs, the rate is three to five times higher than the subsequen
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
