Meeting Abstract

P1.49  Saturday, Jan. 4 15:30  Differences in feeding performance between larvae that capture particles using different mechanisms PERNET, B; California State University, Long Beach bruno.pernet@csulb.edu

Feeding larvae of marine invertebrates capture particles by such mechanisms as reversal of cilia in a single band (e.g., echinoderms) or trapping particles between two parallel bands of cilia beating in opposite directions (e.g., many annelids). The consequences of alternative feeding mechanisms for performance are unclear, because planned comparisons of feeding among larvae are rare. In an effort to answer a simple question – are different feeding mechanisms associated with differences in feeding performance? – we are examining feeding over ontogeny in diverse larvae. Here I report on studies of plutei of the echinoderm Dendraster excentricus and trochophores of the annelid Hydroides gracilis. For each species, clearance rates on uniformly-flavored polystyrene spheres 0.45-30 µm in diameter were estimated from ingestion rates across ontogeny, at constant temperature. Plutei consumed spheres ≤3 µm in diameter at very low rates, and had their highest clearance rates on 10-30 µm spheres. The length of cilia in the feeding band did not increase over ontogeny, and band length-specific clearance rate (~2 ml/d/mm) was roughly constant over ontogeny. Trochophores had their highest clearance rates on 6-15 µm spheres, and captured very few spheres ≥20 µm in diameter; however, they captured the smallest spheres (0.45 and 1 µm) at rates much higher than those of plutei. In trochophores, specific clearance rate increased over ontogeny, in part due to increases in the length of prototrochal cilia. Clearance rates estimated here are as high or higher than those obtained using other methods (e.g., direct observation, depletion of particles in suspension), suggesting that simple ingestion rate methods provide useful estimates of larval feeding abilities for comparative studies.