By Jamie Yoshida
Cephalopods are considered to be the most advanced of the molluscs in terms of speed, intelligence and sensory ability. Out of all the cephalopods, focus will be shifted to one species in particular, the cuttlefish. These marine critters belong to the family Sepiida, which belong to the phylum Mollusca. They are closely related to other members of the phylum Mollusca, which include octopuses and squid (Dees. 1961). Cuttlefish inhabit shallow temperate ocean waters and are found along the coasts of Africa, Asia, Australia, the Mediterranean and Western Europe (Dees. 1961). Although these creatures may appear similar to their close relatives, cuttlefish have a distinguishing and unique feature that is exclusive to their species. The cuttlebone is composed of aragonite and includes several other features; is highly porous and serves as an internal shell, which provides buoyancy (Allmon. 2008). Diets consist of shrimp, fish, crabs, small molluscs, worms and other cuttlefish (Zumholz. 2006). Predators include sharks, fish, seals, dolphins and larger cuttlefish (Costa et al. 2005).
Out of all the invertebrates, cuttlefish have been shown to have the largest brain-to-body size ratios (Wells. 1962). Although brain size is not always correlated with intelligence, cuttlefish have been shown to have a capacity for learning (Alves et al. 2007). As defined by Kamil (1987) intelligence is “encompassing those processes by which animals obtain information about their environment, retain it, and use that information to make decisions during their behavioural activities” (p. 273). This learning capacity or in other words, animal cognition is often what is referred to when studying animal intelligence. Cuttlefish have managed to demonstrate their level of intelligence by exhibiting various forms of learning; including visual, cognitive and associative methods (Alves et al. 2007). They have also illustrated advanced navigational and communication abilities, learning capacity and mating techniques.
Camouflage between interspecific species is nothing new within the animal kingdom. Despite being colour blind, cuttlefish and other cephalopods have demonstrated the ability to communicate using various colour patterns that are dependent on environmental textures (Mathger et al. 2008). Cuttlefish have highly advanced visual and sensory organs, which allow for the regulation and expression of visual features, including textures, spots and lines (Kelman et al. 2008). With a total of 40 chromatic components, chromatic behaviour can be used to coordinate and produce a particular pattern colouration to suit a particular situation, ranging from courtship rituals to camouflage from predators ((Kelman et al. 2008). This behaviour is neurally controlled as opposed to hormonal (Wardill et al. 2012). Visual strategies utilized by this species have shared similarities to human object recognition (Kelman et al. 2008).
Cuttlefish have managed to evolve and develop an alternative mating strategy that often gives smaller males the upper hand. Sexual mimicry utilized by cuttlefish is a demonstration that size isn’t always an advantage. Due to a much higher male to female ratio, there is high mating competition (Hanlon et al. 2005). Smaller males, under normal circumstances would be at a mating disadvantage against larger males. This dimorphic difference has lead to the development of the ability to “impersonate” the appearance of a female in an attempt to deceive other cuttlefish guarding potential mates (Hanlon et al. 2005). Males hide their sexually dimorphic fourth arm and imitate moulted skin patterns (Norman et al. 1999). These crafty creatures even go as far as shaping their arms to mimic the same posture as egg laying females! Females more often choose those cuttlefish that exhibit this visually deceiving mating technique.
There is evidence suggesting that cuttlefish have demonstrated the use of spatial skills. They are able to understand their environment to maximize hunting efficiency and return safely to their den. Several experiments have been conducted in order to find out exactly how much spatial knowledge cuttlefish possess. An experiment conducted by Alves et al. (2007) was set up which involved training cuttlefish to solve a spatial task with distal cues within a T-maze. The final results yielded all cuttlefish successfully reaching the learning criteria within 3-10 trials. Performance increased throughout the trails, with the number of correct choices made also increased (Alves et al. 2007). This is a strong indication that cuttlefish do possess some understanding of spatial skills and their surrounding environment.
Alves, C., Chichery, R., Boal, J. G., & Dickel, L. (2007). Orientation in the cuttlefish Sepia officinalis: response versus place learning. Animal cognition, 10(1), 29-36.
Catalani, J. A. (2008). Cephalopod intelligence. American Paleontologist, 16(3), 35.
Costa, P. R., Rosa, R., Duarte-Silva, A., Brotas, V., & Sampayo, M. A. M. (2005). Accumulation, transformation and tissue distribution of domoic acid, the amnesic shellfish poisoning toxin, in the common cuttlefish, Sepia officinalis. Aquatic toxicology, 74(1), 82-91.
Dees, L. T. (1961). Cephalopods: Cuttlefish, Octopuses, Squids. US Department of the Interior, Fish and Wildlife Service, Bureau of Commercial Fisheries.
Hanlon, R. T., Naud, M. J., Shaw, P. W., & Havenhand, J. N. (2005). Behavioural ecology: transient sexual mimicry leads to fertilization. Nature, 433(7023), 212-212.
Kamil, A. C. (1994). A synthetic approach to the study of animal intelligence. Behavioural Mechanisms in Evolutionary Ecology (ed. LA Real), 11-45.
Kelman, E. J., Osorio, D., & Baddeley, R. J. (2008). A review of cuttlefish camouflage and object recognition and evidence for depth perception. Journal of Experimental Biology, 211(11), 1757-1763.
Norman, M. D., Finn, J., & Tregenza, T. (1999). Female impersonation as an alternative reproductive strategy in giant cuttlefish. Proceedings of the Royal Society of London. Series B: Biological Sciences, 266(1426), 1347-1349.
Wardill, T. J., Gonzalez-Bellido, P. T., Crook, R. J., & Hanlon, R. T. (2012). Neural control of tuneable skin iridescence in squid. Proceedings of the Royal Society B: Biological Sciences, 279(1745), 4243-4252.
Wells, M. J. (1962). Brain and behaviour in cephalopods. Stanford University Press.
Zumholz, K., Hansteen, T. H., Klügel, A., & Piatkowski, U. (2006). Food effects on statolith composition of the common cuttlefish (Sepia officinalis). Marine Biology, 150(2), 237-244.