Meeting Abstract

133.4  Monday, Jan. 7  Allometry indicates giant eyes of Giant Squid are not exceptional SCHMITZ, L*; MOTANI, R; OUFIERO, CE; MARTIN, CH; MCGEE, MD; GAMARRA, AR; LEE, JJ; WAINWRIGHT, PC; Claremont McKenna, Pitzer, and Scripps Colleges; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis; Univ. of California, Davis lschmitz@kecksci.claremont.edu

The eyes of giant and colossal squid are among the largest eyes in the history of life, yet it is poorly understood how their eye size compares to that of squid and other aquatic organisms when scaling effects are considered. We performed a large-scale comparative study that included 88 squid species and 237 species of acanthomorph fish. While squid have larger eyes than most acanthomorphs, a comparison of relative eye size among squid suggests that giant and colossal squid do not have unusually large eyes. It is probable that the giant eyes of giant squid result from a phylogenetically conserved developmental pattern manifested in very large animals. It was recently proposed that sperm whale predation is the main driver of eye size evolution in giant squid, based on an optical model that suggested optimal performance in detecting large luminous visual targets such as whales in the deep sea. We revised the constants used in the model and conclude that large eyes perform equally well in detecting point targets and large luminous targets in the deep sea. Whatever the cause of large eyes, they appear to have several advantages for vision in the reduced light of the deep mesopelagic zone.