Meeting Abstract
Larvae of the sand dollar, Dendraster excentricus, have been used extensively to understand morphological responses to variation in environmental conditions. The goal of this study was to assess the physiological responses in growth and development of larvae reared at different algal concentrations. Larvae were fed 1,000 (low-fed) and 10,000 (high fed) algal cells ml-1 (Rhodomonas sp.) and rates of feeding, metabolism and growth were monitored. We hypothesized that high-fed larvae would not only grow faster than low-fed larvae, but would also have a higher metabolic growth efficiency. At 21 days of age, cumulative energy used for metabolism was 3.5 and 20 mJ for low- and high-fed larvae. Cumulative protein growth at day 21 was 35 and 813 ng protein ind-1. Total energy invested in growth was calculated as 2.2 and 51.6 mJ. Energy acquired through algal feeding, was 9.2 and 82.8 mJ. The gross metabolic growth efficiency (energy utilized for metabolism and growth standardized to energy acquired) was 62% and 86% for low- and high-fed larvae. Efficiency of protein growth was 19% and 46% for low- and high-fed larvae. Relative to changes in growth, differences in developmental rates were much more modest. By day 21 low-fed larvae were at the 6-arm stage and high-fed larvae were at the 8-arm stage. While these results support our hypothesis, they also highlight alternate strategies for growth and development available to larval forms. Exploitation of these alternate pathways likely plays a significant role in linking larval recruitment success to environmental conditions.
