Reproductive investment reduces recuperation from exhaustive escape activity in the tropical scallop Euvola zizac

In scallops, mobilization of reserves from the adductor muscle to support m aintenance and reproductive activity may impinge upon a major role of the a dductor muscle, the movement of the valves during swimming and escape respo nses. The tropical scallop Euvola ziczac (Linnaeus 1758) invests energy res erves to different degrees during its two periods of reproduction each year . We evaluated the impact of reproductive investment on the escape response s (clapping capacity and recovery after exhaustive exercise) of E. ziczac s ampled at different reproductive stages (immature, mature, spawned) during the two reproductive periods in 1997. We compared the escape response capac ities with the levels of muscle energetic reserves (glycogen, proteins, and arginine phosphate) and muscle metabolic capacities [activity of the glyco lytic enzymes: glycogen phosphorylase (GP), pyruvate kinase (PK), phosphofr uctokinase (PFK), octopine dehydrogenase (ODH), arginine kinase (AK), and t he mitochondrial enzyme, citrate synthase (CS)I. Gonad size, gamete volume fraction, and levels of gonadal protein and lipid were greater for mature s callops during the first than during the second reproduction. Numbers of cl aps during escape responses (49-57) and levels of muscle arginine phosphate remained similar throughout the different reproductive stages in both repr oductive periods. In contrast! recovery was slowed during gonadal maturatio n in both reproductive periods and during spawning in the first reproductio n. Scallops generally took more time to regain their initial clapping capac ity during the first (25-40 min) than during the second reproduction (20-30 min). Muscle glycogen decreased markedly during both gonadal maturation an d spawning in both reproductions; whereas, muscle proteins decreased only i n the first reproduction. The levels of most enzymes decreased during gonad al maturation in both reproductions, and also after spawning, particularly during the first reproduction. We concluded that gonadal maturation and spa wning did not decrease clapping capacity of E. ziczac, but decreased its ca pacity to recover from exhaustive exercise most likely due to decreased lev els of energetic reserves and a reduced metabolic capacity of the adductor muscle. Moreover, these effects were probably stronger during the first cyc le because of the greater reproductive investment coincident with decreased food availability.