Protein metabolism in lecithotrophic larvae (Gastropoda : Haliotis rufescens)

Rates of protein depletion, synthesis, and turnover were measured in larvae of the abalone Haliotis rufescens as an approach to understanding macromol ecular metabolism during lecithotrophic development. Protein content decrea sed linearly during development to metamorphic competence, with 34% of the initial protein in eggs depleted during the 8-day larval life span. Fractio nal rates of protein synthesis (percentage of total body-protein synthesize d per day) decreased during development, from 40% (1-day-old trochophore la rva) to 14% (7-day-old veliger larva). Separation of proteins by one-dimens ional gel electrophoresis showed that protein pools in larvae are dominated by two high-molecular-weight protein classes (88 and 121 kDa). When the pr oteins of 1- and 3-day-old larvae were labeled with a mixture of S-35-methi onine and cysteine, the pattern on two-dimensional gels showed that the tur nover process (protein synthesis and degradation) involved hundreds of diff erent proteins. The energy gained from loss of protein could account for 20 % of the protein turnover rates for trochophore larvae and 79% of the lower turnover costs for late-stage veligers. Lecithotrophic larvae of H. rufesc ens maintained high biosynthetic activities, with up to 40% of their whole- body protein being turned over each day. Such dynamic processes during deve lopment of nonfeeding larvae would contribute significantly to maintenance metabolism.