Aspects of the Sensory Ecology of Cephalopods

Abstract

This chapter views cephalopod sensory capabilities in the context of behavioral ecology. Some extensive field studies and controlled laboratory experiments have recently shed new light on (1) camouflage and defence, (2) foraging and feeding, and (3) reproductive behavior.There have been excit- ing discoveries on mechanisms and functions of vision and olfaction. Cephalopods (excluding Nautilus) are highly visual animals, have keen visual acuity, and see well under highly varying light conditions. Nearshore cephalopods, such as the cuttlefish, have remarkable abilities to camouflage themselves on diverse substrates using visual cues alone. None of these cues include color because cuttlefishes are color-blind, and monochromatic vision may be the norm for many cephalopods. Cuttlefishes respond to the size, contrast, number, and area of light objects in the background to switch on disruptive coloration. Polarization sensitivity (PS) enables squid and cuttlefishes to detect transparent as well as silvery- reflecting prey more effectively, and they may use PS for intraspecific communication. Foraging octopuses use visual cues to camouflage themselves, but when movement negates camouflage, they become highly conspicuous, change appear- ance with remarkable frequency, and even mimic fishes. In the sea, hearing is a better long-distance sensor for predator detection: Cephalopods have low-frequency sensitivity and a lateral line (analogous to fishes) that may perform this func- tion. Olfaction may play a role in mate choice of squid and cuttlefishes. In male squid, contact chemoreception of egg capsules stimulates highly aggressive behavior on spawning grounds. Octopuses seem capable of detecting food odor at a distance, and olfaction may improve predation on crabs by cuttlefishes. Nautilus olfaction is used for distant food odor detection and location, and perhaps for mate choice. Future emphasis on an integrative approach to the sensory ecology of cephalopods is likely to explain many other facets of their complex behavior.