In scallops, muscle contractile activity is mainly supported by ATP, which is derived from arginine phosphate breakdown (Bailey et al.
Thus, both functional and environmental hypoxic conditions are supported by similar metabolic pathways, with both muscle arginine phosphate and glycogen as the main supporting energy substrates.
Because arginine phosphate is the main source of ATP for muscle contraction and metabolism during exposure to environmental hypoxia, we expected a stronger effect on the maximum number of claps of the scallops in trial I.
The maximum number of claps (or muscle contractions) executed by scallops depends on their muscle arginine phosphate content (Bailey et al.
Thus, we presume that scallops exposed to short-term hypoxic cycles could likely maintain their metabolism and capacity to restore arginine phosphate, at least in part, to minimize the hypoxic effects on escape capacity.
The proportion of recovery claps or clapping rates under normoxic conditions depends on the muscle's capacity to recuperate the arginine phosphate pool through aerobic glycolysis--namely, by glycogen catabolism (de Zwaan et al.
In most groups of animals, sudden onset, high power requirements are largely met by anaerobic glycolysis and the depletion of high-energy phosphate storage compounds such as arginine phosphate or creative phosphate (McArdle et al.
In spiders, a similar pattern is associated with accumulation of anaerobic byproducts and depletion of arginine phosphate (Prestwich 1983a, b, 1988b).
Phasic contractions are primarily supported by generation of ATP from arginine phosphate through the arginine kinase reaction, with only 30% of the ATP used during exhaustive escape responses arising from anaerobic glycolysis and octopine generation (de Zwaan et al.
Contractions by the striated adductor muscle primarily use ATP generated from arginine phosphate by the arginine kinase reaction (Chih & Ellington 1983, Thompson et al.