Comparison of larval bioenergetics of two marine gastropods with widely differing lengths of planktonic life, Thais haemastoma canaliculata (Gray) and Crepidula fornicata (L.)

Abstract

Larvae of many shallow-water near-shore tropical gastropod species appear to have planktonic durations of several months or more and therefore may have great dispersal capabilities. To investigate physiological factors possibly related to length of planktonic life, this study documented the larval bioenergetics and carbon budgets for one such teleplanic (long-distance) species, Thais haemastoma canaliculata (Gray), in comparison with the relatively short-lived larvae of the temperate species, Crepidula fornicata (L.). Growth, ingestion, and respiration rates were measured in the laboratory during the first 4 wk of larval life for T.h. canaliculata and the first week of larval life of C. fornicata, up to shell lengths of ≈900 and 700 μm, respectively. Larvae of both species were reared at 24°C on a diet of Isochrysis sp. (clone T-ISO) at 18 × 10 4 cells · ml −1. Tissue growth increased at a constant rate for C. fornicata, but at an exponential rate for T.h. canaliculata. Ingestion rates (cells eaten · larva −1 · h −1) for C. fornicata were ≈1.25× higher than rates for T.h. canaliculata at equivalent shell lengths. Respiration rates (μl O 2 consumed · larva −1· h −1) for T.h. canaliculata were generally 1.25 × higher than rates for C. fornicata at similar shell lengths. Estimated assimilation efficiencies were similar for both species and declined during development (from 44 to 28% for C. fornicata and from 33 to 25% for T.h. canaliculata). However, while gross and net growth efficiencies (growth · ingestion − · 100% and growth (growth + respiration) −1 100%) declined during larval development for C. fornicata, growth efficiencies were constant or increased during early development for T.h. canaliculata.