Meeting Abstract
Cephalopods generally have large, well-developed eyes, but the sizes of these eyes relative to body mass vary across ontogeny and phylogeny. Eye size is a crucial determinant of visual capability, as a larger eye can improve both sensitivity and resolution and ultimately determines visual range. However, eyes are metabolically expensive and the neural processing associated with vision imposes a significant energetic cost. Large eyes may also be targets for predators. Thus, the environment and visual needs of an organism will determine the cost-benefit balance for eye size. Light in the ocean decreases with depth, making the deep sea a particularly interesting environment in which to investigate eye scaling. Most vertebrates show negative intraspecific allometry, where relative eye size decreases throughout growth within a species, as well as negative interspecific allometry, where relative eye size is smaller in larger-sized species. Eye allometry in cephalopods, however, has not been well-studied. Here, we examine how eye diameter scales with body mass and length throughout growth, and how eye size compares among different species of deep-sea cephalopods occupying different depth regimes. We measured eye diameter, lens diameter, dorsal mantle length, and mass in a variety of species housed in the cephalopod collection at the Smithsonian’s National Museum of Natural History. We found variation in intraspecific scaling relationships, with deepwater cephalopods often exhibiting close to isometric eye scaling. We will discuss interspecific variation in allometric patterns, relationships with biome, depth and vertical migration, and ultimate implications for visual ranges of deep-sea cephalopods.
