Animals, like us, experience a deterioration of memory in old age. A new study, however, indicates that cuttlefish are the first species in which this appears not to be the case.
Building on previous research, the study was conducted by scientists from the University of Cambridge, Massachusetts' Marine Biological Laboratory, and France's University of Caen. It was conducted on 24 Sepia officinalis cuttlefish, half of which were "not-quite adult" (10 to 12 months old) and half of which were in old age (22 to 24 months old). Cuttlefish typically only live for about two years.
All of the animals were initially trained to approach a black and white flag inside their tank, when that flag was being waved. They were subsequently presented with two such flags, placed in two different locations. When they approached one of those waving flags, they were given a piece of king prawn meat. When they approached the other, they were given a live grass shrimp – a food that they very much preferred. The second flag, however, was only waved once every three hours.
After four weeks, it was found that all 24 cuttlefish became adept at establishing which flag provided which food, and was thus the better one to subsequently approach. What's more, the locations of the two flags were regularly changed, so the animals had to constantly relearn (and thus re-memorize) which was which.
The memory of specific events – such as prawn meat or live shrimp coming from a certain flag – is known as "episodic memory." In humans and most other creatures, it is believed to decrease as a part of the brain known as the hippocampus deteriorates. Cuttlefish don't have a hippocampus, so memory tasks are instead assigned to the "vertical lobe" of their brain. That lobe doesn't deteriorate until the last two or three days of their lives.
"The old cuttlefish were just as good as the younger ones in the memory task – in fact, many of the older ones did better in the test phase," says U Cambridge's Dr. Alexandra Schnell, first author of a paper on the study. "We think this ability might help cuttlefish in the wild to remember who they mated with, so they don’t go back to the same partner."
The paper was recently published in the journal Proceedings of the Royal Society B.
Source: University of Cambridge
