The Chambered Nautilus (Nautilus pompilius) is one of 6 extant species of nautilus, the closest living relative of coleoid cephalopods (octopuses, squid, and cuttlefish). Considered by many to be living fossils, nautiluses have experienced little morphological change over millions of years and are more similar to ancient cephalopods than modern coleoid cephalopods. Nautiluses have numerous notable differences with coleoid cephalopods, including an external shell, much longer lifespan, and a uniquely simple eye structure. 

Coleoid cephalopods utilize a lens to focus light onto their retina, this camera-type eye is a classic example of convergent evolution with vertebrates. However, nautiluses have a unique, pinhole eye structure. Lacking both a lens and a cornea, light passes through a pupil that is open to the environment. Due to this simple eye structure, nautiluses are considered to have visual acuity of a fruit fly. This is a striking contrast to coleoid cephalopods which rely on their acute vision for hunting, communication, and aspects of camouflage.

Sketch and fact contributed by Claire Jones. Claire is a master’s student in the Animal Biology Graduate Group and is a member of the UC Davis Center for Animal Welfare. Their research interests include cognition, welfare, and visual perception and they are currently investigating how differential access to vertical space at a young age impacts the development of depth perception in egg-laying hens. 

Sources:

Saunders, W. B., & Landman, N. (Eds.). (2009). Nautilus: The Biology and Paleobiology of a Living Fossil, Reprint with Additions (Vol. 6). Springer Science & Business Media.

Serb, J. M., & Eernisse, D. J. (2008). Charting evolution’s trajectory: using molluscan eye diversity to understand parallel and convergent evolution. Evolution: Education and Outreach, 1(4), 439-447.