Physiological ecology of Adalaria proxima (Alder et Hancock) and Onchidoris muricata (Müller) (Gastropoda:Nudibranchia). III. Energy budgets

Gross energy budgets are presented for (immature) juvenile and (reproducing) adult stages of the nudibranch molluscs Adalaria proximo (Alder et Hancock) and Onchidoris muricata (Müller). Measurements of growth, respiration and reproduction in seven individuals of each species are compared and contrasted with estimates of consumption. Assimilation efficiencies of both species were low compared with those for other species of gastropod. Respiratory costs for reproducing A. proximo were approximately equal to those for juveniles of both species, however, a significant decline in respiratory cost was observed between the juvenile and adult stages of O. muricata. This was reflected in the net reproductive efficiency which was accordingly greater in O. muricata than in A. proximo. On a daily basis, somatic tissue degrowth was of greater importance in maximising the reproductive output of A. proximo than of O. muricata. Degrowth contributed almost 19% of the daily energy flux to reproduction in A. proximo whereas the equivalent value for O. muricata was only 8%. A significant correlation was obtained between spawning rate and juvenile growth rate in O. muricata. No such association was observed for A. proximo although adult degrowth rate was closely (but not significantly) correlated with spawn production rate. These patterns are discussed with reference to the evolution of different larval types in these species.