an exploration into connections between the sensory modalities of a marine predator.

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Cephalopods are known as the ‘charismatic megafauna’ of the invertebrate world. We humans are generally fascinated by their stealth, their ability to camouflage, and their massive brains. The physical form of cephalopods is so different from our own that we find them creepy and fascinating all at the same time. Their long arms, piercing jaws and gripping tentacles are the stuff of human folklore – except that there’s nothing mythical about them.
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As I mentioned above, cephalopods have substantial, mulit-lobed brains, which makes them a natural choice for studies relating to neurobiology and neuroecology. In addition to their considerable brain-power, their complex eyes provide them with a clear window into the murky depths of the aquatic realm. Cuttlefish, for example, are primarily visual predators. Although they posess the ability to detect odors they do not generally approach or orient towards particular smells. Juveniles receive no parental care and begin visually hunting 3 – 12 days after hatching. Their preferred prey is small shrimp, although they will hunt for small crabs if shrimp are unavailable.

In order to explore the connectedness between the sensory modalities of cuttlefish vision and smell, biologists conducted a series of in-situ experiments on embryonic cuttlefish. Embryos were exposed to several different olfactory stimuli during the weeks prior to hatching: shrimp (prefered prey), crabs , mussels, and a sea water control. Subsequent to hatching visual choice tests of two prey types (shrimp and crabs) with NO olfactory stimulation were performed in order to assess whether embryonic exposure to different olfactory stimulation had an effect on visual prey choice.

The results proved very interesting. Control cuttlefish (no odor exposure) preferentially attacked shrimp, as did cuttlefish that had been exposed to crab odors. Hatchlings that had been exposed to mussel odors showed no preference between either crabs or shrimp; however, those that had been exposed to shrimp odors preferentially attacked crabs. In other words, the prey preferences were reversed depending on the olfactory stimulation they received as embryos!

These experiments clearly showed that embryonic exposure to different olfactory stimulants resulted in changes to visual prey preference in newly hatched cuttlefish. A ‘cross modal effect’ is defined as information from one sensory modality (eg smell) that manifests as changes in another sensory modality (eg vision), and is clearly what is being observed here – despite the fact that exposure to the two stimulants took place over different time periods and at different developmental stages. The key question (that remains to be answered) is how information from various modalities is integrated in the cuttlefish brain.

Overall, this research represents an interesting find; however, it raises more questions than it answers (doesn’t it always?!). I’m looking forward to reading more about this work as it progresses…stay tuned!

Guibé M, Boal JG, & Dickel L (2010). Early exposure to odors changes later visual prey preferences in cuttlefish. Developmental psychobiology, 52 (8), 833-7 PMID: 21157990

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