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Data and code from: Solo culture of echinoid larvae allows quantification of genetic and maternal contributions to food-conditioned phenotypic plasticity in ciliated band length

Johnson, Darren1; Pace, Douglas1; Pernet, Bruno1

Published Sep 11, 2026 on Dryad. https://doi.org/10.5061/dryad.4f4qrfjv2

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Abstract

The feeding larvae of many echinoderms develop long ciliated bands (which serve as food-capturing structures) when reared in low-food environments, and short ciliated bands when reared in high-food environments. This response has been studied for ~40 years, but because of limits to sample size imposed by traditional culture methods, the shape of the reaction norm is poorly characterized, and the extent to which reaction norm characteristics are determined by additive genetic variance and maternal effects is poorly understood. We used a paternal half-sib mating design and a novel method of rearing larvae individually to describe the shape and inheritance of the reaction norm in larvae of the sand dollar Dendraster excentricus. Each of 20 males was mated to two unique females, and offspring from all crosses were fed the alga Rhodomonas sp. at concentrations ranging from 1000-10,000 cells mL-1 for four days. The experiment thus started with a total of 400 larvae, 10 from each of 40 families (20 sires crossed with 40 dams). Mortality and other losses meant that the final dataset included 332 larvae. At 5 days post-fertilization, we measured larval midline body length, mean postoral arm length, and ciliated band length. We then used an animal model analysis to estimate genetic and maternal effect contributions to variation in CBL reaction norms. The mean reaction norm was non-linear, with a ~17% decline in ciliated band length from 1000 to ~6000 cells ml-1 but little change at higher food levels. Additive genetic variation in elevation and shape explained ~18% of observed variation in reaction norms, while maternal effects explained ~13% of observed variation. The same analysis conducted on postoral arm length showed similar results. The reaction norm for larval phenotypic plasticity in D. excentricus thus seems likely to be moderately responsive to natural selection. The culture method introduced here may be useful in describing and analyzing reaction norms in diverse marine invertebrate larvae.