Meeting Abstract

S3.5  Monday, Jan. 4  Swimming embryos point to planktonic performance standards for early-developmental motility MCDONALD, K. A.*; GRUNBAUM, D.; Smithsonian Tropical Research Institute; University of Washington, School of Oceanography mcdonaldk2@si.edu

Cilia perform critical swimming, feeding, and sensory functions in planktonic invertebrate larvae. Development and phylogeny constrain larval form, but evidence for the independent evolution of complex ciliary structures (for instance, opposed bands) suggests that functional analysis of swimming and swimming/feeding structures may reveal more about performance requirements than developmental constraints. Ecological performance standards could also apply to the earliest free-living stages. Though earliest motile stages are simple swimming ‘blobs,’ species already differ in parameters of size, shape, ciliary length, and patterning/extent of ciliation. These morphological differences could contribute to significant differences in performance, and thus transport and mortality. Consistently high performance achieved despite differences in these characteristics could indicate that swimming is under strong selection from earliest development. We developed a hydrodynamic model of embryonic swimming, parameterizing swimmers as ciliated ellipsoids. Model predictions were tested against experimental results for swimming in thirteen broadcast-spawning species. In ten species, predicted actual and neutral-weight swimming speeds conformed well to measured results, indicating that embryo size and density are sufficient to predict swimming performance without detailed knowledge of ciliation. Experimental results showed a strong decrease in density with size across species, but little trend in swimming speed with size, suggesting that diverse species trade off density against speed at first swimming. Together, modeling and experimental work indicate that swimming performance ‘standards’ apply from the time of first motility.