Metabolic Energy Costs of Development in Feeding and Non-Feeding Larvae

University Of Delaware, Newark DE

Investigators

Abstract

The energetics of larval development has received considerable attention in life-history models. Numerous theoretical considerations of the allocation of maternal energy to offspring have been published to describe the important implications of egg-size for determining the size and age of the larvae-juvenile at metamorphosis. However, the maternal allocation of energy to eggs is only one half of the developmental energetics equation. The other half is the actual amount of energy that a larva will utilize as it develops from an embryo to a juvenile, and this aspect of developmental energetics has received far less attention in the literature. The key to understanding the selective advantages or disadvantages of allocating lots of energy to a few big eggs (producing a large non-feeding larvae), or very little energy to lots of little eggs (producing a small feeding larvae), lies in an accurate assessment of the energy costs of development of each of these larval forms within a specific environment. The comparison of developmental energetics between different larval forms can be easily confounded by the phylogenetic distance between different larvae. However, a few invertebrate species produce multiple developmental forms and provide an ideal system for comparative developmental energetics. This project focuses on describing the energy costs of development in the feeding and non-feeding larvae of a single species, the spionid polychaete Streblospio benedicti. An investigation of the metabolic energy costs of development in the polychaete Streblospio benedicti will address four levels of biological function that determine energy utilization during larval development: developmental mode (feeding and non-feeding), individual variability (genotype), environmental variability (temperature and food), and protein metabolism (proteomics). Understanding these four determinants of developmental energy costs will provide a comparative framework for considering the selective advantages and disadvantages of feeding and non-feeding larval forms in current life-history models that incorporate estimates of larval metabolic requirements into the estimates of larval age and size at metamorphosis. This project will produce the first examination of a discrete biochemical mechanism (protein turnover) to account for differences in energy metabolism during development (both in terms of individual and envirom-nental variability) and potentially indicate an underlying genetic component of metabolic regulation involved in the evolution of feeding and non-feeding modes of development in marine invertebrate larvae.