Cuttlefish avoid snacking to leave room for their favourite meals, it has emerged from new University of Cambridge research. On realising that shrimp – their preferred food – will be available in the evening, they will eat fewer crabs during the day.
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“It was surprising to see how quickly the cuttlefish adapted their eating behaviour,” said first author of the study Pauline Billard. “In only a few days they learned whether there was likely to be shrimp in the evening or not. This is a very complex behaviour and is possible only because they have a sophisticated brain.”
When the researchers reliably provided one shrimp every evening, the European common cuttlefish (Sepia officinalis) became more selective in eating crabs through the day. When provided with evening shrimp on a random basis, they quickly became opportunistic, increasing their daytime crab intake.
By learning and remembering patterns of food availability, the cuttlefish optimise their foraging activity not only to guarantee that they eat enough but also to ensure that they eat more of their preferred foods.
To assess these preferences, the researchers tested 29 cuttlefish by putting crab and shrimp an equal distance away from them at the same time, five times daily for five days. All went for the shrimp.
Cephalopods and vertebrates diverged in evolutionary terms around 550 million years ago, yet the organisation of their nervous systems is remarkably similar, say the researchers.
“This flexible foraging strategy shows that cuttlefish can adapt quickly to changes in their environment using previous experience,” said Prof Nicola Clayton, who led the study. “This discovery could provide a valuable insight into the evolutionary origins of such complex cognitive ability.”
The French National Research Agency-funded study is published in Biology Letters.
In further cephalopod brainpower revelations, this time from Australia's University of Queensland, it seems that squid brains are almost as complex as those of dogs.
To understand cephalopods’ ability to instantly camouflage themselves, Dr Wen-Sung Chung and Professor Justin Marshall from the university’s Queensland Brain Institute carried out the first mapping of squid brains in 50 years, using MRI techniques.
They examined the bigfin reef squid (Sepioteuthis lessoniana).
“This is the first time modern technology has been used to explore the brain of this amazing animal, and we proposed 145 new connections and pathways, more than 60% of which are linked to the vision and motor systems,” said Dr Chung.
He said that cephalopods, which include octopus, cuttlefish and squid, had complex brains “approaching that of a dog and surpassing mice and rats, at least in neuronal number. For example, some cephalopods have more than 500 million neurons, compared to 200 million for a rat and 20,000 for a normal mollusc”.
Examples of complex cephalopod behaviour include the ability to camouflage themselves despite being colour-blind, count, recognise patterns, problem-solve and communicate using a variety of signals (to which now add meal-planning).
The study noted new networks of neurons governing behaviour such as locomotion and “countershading camouflage” – when squid display different colours on the top and bottom of their bodies, so that they blend into the background whether viewed from above or below.
The team now wants to establish why different cephalopod species have evolved different brain subdivisions.