Age-specific energetics of reproduction in Nucula turgida (Leckenby and Marshall) a bivalve with lecithotrophic larval development

Summary

Nucula turgida is a protobranch bivalve of the shallow sublittoral which produces, for a bivalve, unusually large eggs with a high lipid content to sustain the lecithotrophic development of the larvae. Males and females have similar reproductive investments, and the most noticeable feature of their output is the proportional increase in reproductive output as the animals age. Reproduction, as a proportion of the assimilation (Rep/C), was around 0.17 at population level but ranged from 0.055 in the 3 + year class to 0.54 in the 7 + year class. Similarly, C(=1 − [(A − G/R]) where A is assimilation, G gonad production and R is respiration, which appeared to be almost perfectly balanced at population level (C= −0.05) in fact varied from very conservative (C= −1.63) at 3 + to very “reckless” at 7+ (C=0.57). Using age-specific data, more accurate estimates can be made of future recruitment, and by back-calculation the survival rate from spawning to appearance in the benthos can be calculated.