Nurse egg feeding and energy balance in embryos of Crepidula dilatata (Gastropoda: Calyptraeidae) during intracapsular development

Abstract

On the basis of growth, nurse egg consumption and respiration rate measurements, an energy balance for encapsulated embryos of Crepidula dilatata Lamarck was established in an estuarine population in Southern Chile. Consumption of nurse egg was highest within the first weeks of life of the shelled embryos. Embryonic growth rate was high in terms of shell length and biomass, compared with literature data for pelagic larvae of related species. The hatching process began when the embryos reached shell lengths between 1100 and 1200 .mu.m (extreme values: 1075 and 1600 .mu.m). Oxygen consumption values per individual were very low and, consequently, had little influence on the energy balance. During early develompent, ingested energy met the energy costs of the embryos. The 'balance point' between ingested and consumed energy occurred at a shell length of 650 .mu.m. Above this size, energy costs greatly exceeded ingested energy; hence larger embryos use energy acquired and stored during the early first development stages. The efficiency with which stored energy was used exceeded 90% and the high (values (> 90%) for net growth efficiency (K2) demonstrate the channeling of ingested energy almost exclusively towards growth