Meeting Abstract

118.6  Tuesday, Jan. 7 11:30  Shifts in the Expression of Developmental Regulatory Genes Involved in the Evolution of a Novel Life History Difference WYGODA, J.A.*; BYRNE, M.; MCCLAY, D.R.; WRAY, G.A.; Duke University; University of Sydney; Duke University; Duke University jaw61@duke.edu

Developmental mode can influence dispersal, gene flow, speciation and extinction rates in marine taxa and thus can have important consequences for micro- and macroevolutionary processes. While the ancestral developmental mode of sea urchins is indirect through a feeding larval stage (planktotrophic), non-feeding development (lecithotrophic) has evolved independently multiple times. In order to identify evolutionary changes in gene expression underlying this ecologically significant shift in life history, we used Illumina RNA-seq to measure expression dynamics across 6 developmental stages in three sea urchin species: the lecithotroph Heliocidaris erythrogramma, the closely related planktotroph Heliocidaris tuberculata (3 myr), and an out-group planktotroph Lytechinus variegatus (50 myr). Our analyses draw on a well-characterized developmental gene regulatory network (GRN) in sea urchins to understand how the ancestral developmental program was altered during the evolution of lecithotrophic development. Our results suggest that changes in gene expression profiles were more numerous during the evolution of lecithotrophy than during the persistence of planktotrophy, and this contrast is even stronger when only GRN genes are considered. We found evidence for both conservation and divergence of GRN linkages in H. erythrogramma, as well as significant changes in the expression of genes with known roles in patterning the larval skeleton and gut, which are greatly modified in lecithotrophs. Collectively, these results indicate that the transition from planktotrophic to lecithotrophic development involved a surprising number of changes to key developmental processes over a short evolutionary timescale.