Visually cued animals that inhabit the deep sea must signal to one another in order to facilitate group behaviors, yet the capacity and mechanisms for information transfer in such a dimly lit habitat are largely uninvestigated. By examining in situ behavioral footage of the Humboldt squid, Dosidicus gigas, we demonstrate the potential for a deep-living social animal to visually convey and receive large quantities of information by combining complex pigmentation patterning with whole-body luminescence. Our findings reveal a capability for information sharing comparable to advanced forms of animal communication known from well-lit habitats. This may have important implications for ecosystem processes, as information sharing between abundant predators is involved in energy and nutrient transfer throughout the world’s oceans.

Abstract

Visual signals rapidly relay information, facilitating behaviors and ecological interactions that shape ecosystems. However, most known signaling systems can be restricted by low light levels—a pervasive condition in the deep ocean, the largest inhabitable space on the planet. Resident visually cued animals have therefore been hypothesized to have simple signals with limited information-carrying capacity. We used cameras mounted on remotely operated vehicles to study the behavior of the Humboldt squid, Dosidicus gigas, in its natural deep-sea habitat. We show that specific pigmentation patterns from its diverse repertoire are selectively displayed during foraging and in social scenarios, and we investigate how these behaviors may be used syntactically for communication. We additionally identify the probable mechanism by which D. gigas, and related squids, illuminate these patterns to create visual signals that can be readily perceived in the deep, dark ocean. Numerous small subcutaneous (s.c.) photophores (bioluminescent organs) embedded throughout the muscle tissue make the entire body glow, thereby backlighting the pigmentation patterns. Equipped with a mechanism by which complex information can be rapidly relayed through a visual pathway under low-light conditions, our data suggest that the visual signals displayed by D. gigas could share design features with advanced forms of animal communication. Visual signaling by deep-living cephalopods will likely be critical in understanding how, and how much, information can be shared in one of the planet’s most challenging environments for visual communication.