Smelling to Survive by Bill S. Hansson

Author:Bill S. Hansson
Language: eng
Format: epub
Publisher: Legend Press

Doomed, not doomed?

Another deadly threat to flies (or rather their larvae) is the parasitic wasp. These tiny insects inject their eggs into the fly larva, which becomes a living food storage for the growing wasp larva. Technically, as the wasp larva kills the fly larva, it is not a true parasite, as they would live off the host but not kill it off. In fact, it is a parasitoid that clearly causes the demise of its host.

In nature, parasitoids have infected up to 80 per cent of fly larvae. They are doomed. As you can imagine, the pressure on the fly to develop countermeasures is therefore huge. We discovered one that is based on smell. The fly has developed another ecologically labelled line through its olfactory system that specifically detects the sex pheromone of the parasitoid.

When the fly smells the parasitoid odour it flies away. Amazingly, the larva has the same reaction. When its tiny smell organ picks up the same odour, it starts wiggling and wriggling and moving away, in the process making it hard for the parasitoid female to inject her egg.

Conventional wisdom has it that olfactory neurons in antennae and noses express one single odour-detecting receptor. In the adult fly, the parasitoid detector has broken this rule. We discovered that two different receptors, each detecting the pheromone odours of two different fierce enemies, are found in the same neuron. This points to an interesting fact. One and the same channel can be used to detect odours that have the same negative significance to the fly. The fly does not care which species, whether it’s A or B, that is killing its larvae. It just knows that it had better quickly buzz off somewhere else.13

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