The author of The Eastern Evil
Cuttlefish is a common mollusk in the ocean, because it will spray ink on the enemy when it encounters a strong enemy, and then wait for an opportunity to flee, so it is also called "squid". According to studies, the color of the body surface of cuttlefish changes with its mood changes, because there are many pigmented small sacs in the skin of cuttlefish. In addition, cuttlefish have also been found to be an animal with superior memory, and the human memory gradually weakens with age, while the cuttlefish's memory seems to be able to remain until old age.
On August 17, the Royal Society Journal b published a paper on the study of cuttlefish's memory ability, which pointed out that researchers found through experiments that cuttlefish's memory does not deteriorate with age, which also makes cuttlefish the only animal with this ability. So what kind of experiments did the researchers conduct on cuttlefish? Why does cuttlefish's memory last so long?
The paper pointed out that researchers from the University of Cambridge in the United Kingdom, the Woods Hole Marine Biology Laboratory in the United States and the University of Caen in France joined forces to conduct experiments on 24 common cuttlefish, and the experimental subjects were divided into 10 to 12 months old group and 22 to 24 months old group, the former age group of cuttlefish is not yet mature, and the latter age group is close to twilight. The researchers aimed to verify how long cuttlefish's memory can be maintained and whether it declines with age.
After a group discussion, the researchers decided to conduct a "episodic memory test" on cuttlefish. They first fed two groups of cuttlefish of different ages by placing a black flag and a white flag in the tank, then placing the king shrimp that cuttlefish did not like to eat at the black flag and the grass shrimp that the cuttlefish preferred to eat on the white flag. The experimenters provided feeding every 3 hours, and the position of the black and white flags was set randomly at each time, and the experimental process lasted for one month.
If cuttlefish have a good episodic memory, then no matter how the position of the black and white flag changes, they can remember through a month of training that the white flag has placed delicious grass shrimp, and the white flag has placed the unpalatable king shrimp, and only by judging the color and position of the flag can get better food. A month later, the researchers tested two groups of cuttlefish and found that older cuttlefish found grass shrimp at a higher rate than younger cuttlefish.
This means that older cuttlefish maintain that memory after forming a specific memory of food, and their memory does not decline significantly even as they age. Conversely, the memories formed by young cuttlefish are not strong. The study found that the lifespan of cuttlefish is generally only about 2 years, which means that 22 to 24 months of cuttlefish can still maintain memory ability in the last moments of life, which is surprising to researchers.
The opposite of the cuttlefish being able to maintain memory for a long time is human beings, people with age, the memory is generally gradually declining, to the old age stage of many specific events occurred when and where can not remember, let alone let the elderly recall what last Monday dinner ate. Modern medical research believes that the decline in hippocampal function in the brain has led to the decline of this "episodic memory" in humans.
Surprisingly, the plot memory ability of cuttlefish can not only be maintained until old age, but also deteriorate until the last two or three days of life, is this also related to the hippocampus? The researchers anatomically analyzed the old cuttlefish and found that there is no hippocampus in its brain, but a "vertical lobe" that is responsible for learning and memory functions. That is, the hippocampus is the main cause of episode memory decline.
So what is the use of this super memory ability of cuttlefish? Scientists say cuttlefish's memory is especially important for reproduction. Unlike other animals, cuttlefish do not begin to reproduce until the end of their lives, so they develop deep memories after a single breed, which helps them to reproduce more widely.
Since we talk about cuttlefish, let's talk about another problem, how to distinguish between cuttlefish and octopus. Both animals are molluscs common in the ocean. And the two are very similar in form, so that many people think that octopus is cuttlefish, cuttlefish is octopus, in fact, they have certain differences in appearance and structure. The first is the difference in the number of brachiopods, the octopus is called "octopus" because it has 8 brachiopods, while the cuttlefish has 10 brachiopods.
So if you don't know cuttlefish and octopus, you can tell which cuttlefish and which is an octopus by counting the number of brachiopods. The second is the difference in appearance and shape, the body of the octopus is sac-shaped, like a ball; the body of the cuttlefish is relatively flat and wide. The head of the octopus is short and round, and the head of the cuttlefish is long and round.