The tabbie is found in many parts of North and South America. Photo: Shawn Hanrahan,
Reading aloud Butterflies can still remember their lives as caterpillars or larvae after their metamorphosis, US researchers have shown. This was unclear for a long time, because during the change from larva to mature butterfly, the entire body is almost disassembled and reassembled. In experiments, however, Douglas Blackiston, Elena Casey and Martha Weiss of Georgetown University in Washington have shown that moths trained as larvae to avoid a particular odor retained the learned behavior after pupation. Blackiston and his colleagues chose the tobacco hawk Manduca sexta as a study object. The animal of the family of the swarmers goes through five caterpillar stages, until it develops to the butterfly. For the experiment, however, only caterpillars in the last three stages were subjected to a smell training: The researchers put them in an apparatus and offered two exits, one filled with pure air, the other strongly with ethyl acetate, an adhesive smelling of adhesive, was saturated. Since the tabbie has no natural aversion to the smell, the researchers added power to the second way to shock the animals as they entered the tube. In further experiments, the caterpillars avoided the odor of ethyl acetate when confronted with it.

After pupation to the butterfly, the scientists subjected the animals to the same test and discovered that they avoided the smell of the solvent even now, but only if they had been trained in the fifth instar. The younger larvae had "forgotten" the conditioning. This could mean, the researchers say, that the memories are stored in the so-called mushroom body. This is a structure in the brain of insects that is responsible for memory and learning and consists of several lobes. The so-called gamma-Lobus develops already in the embryonic stage, but atrophies during pupation. Alpha and beta lobes, however, are formed only in the fifth caterpillar stage and remain even after the metamorphosis
intact. The researchers suggest that the young larvae therefore forgot their training with loss of gamma-lobus, whereas older ones retained the knowledge with the help of the other two praises.

Douglas Blackiston (Georgetown University, Washington) et al .: PLoS ONE, volume. 3, e1736 ddp / Livia Rasche


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