Meeting Abstract
Major transformations in body shape punctuate the evolutionary history of ray-finned fishes. Eel-like or torpedo-shaped fishes emerge, sometimes rapidly, from lineages that are otherwise made up of fusiform or shorter-bodied species. These transitions in shape may result from different combinations of changes in anatomical features spread across the body, but it is unknown whether these changes emerge in a correlated manner or if they accrue in series over time. In this study, we measure dimensions of the body, skull, and vertebral regions for species of blenniiform fishes and use phylogenetic methods to identify exceptionally rapid evolution of elongated body shape in a blenniiform subclade that includes the pikeblenny (Chaenopsis alepidota) and arrow blenny (Lucayablennius zingaro). Major shape transformation began in the shared ancestral lineage of these species (i.e., their stem lineage) as the skull elongated and body depth decreased. After splitting from this ancestor, these species continued to elongate, but they followed different evolutionary trajectories. Transformation in the arrow blenny was achieved by elongating the head, whereas the pikeblenny lengthened the caudal region by greatly increasing vertebral numbers. Overall, our results reveal a major body shape transformation—eel-like blennies—that arose because of cascading anatomical changes spread across multiple ancestral lineages, perhaps as a result of adoption of a novel ambush-style predation followed by divergence in dietary niche.
