Pretty Fly for a Cayman Guy

A while ago, a friend of mine suggested that I get in contact with the Blue Iguana Recovery Program to study those intriguing animals. A few days ago, he sent a request for me to write about another animal from his home island¹. And since I’m always ready to take suggestions, here’s a disgusting, semi-parasitic fruit fly from the Cayman Islands.

Image by Hampton Carson. Please note the white, seed-looking things around the crab's eye--those are the eggs.

Drosophila endobranchia has no common name, though if it did, it would probably be something such as the “Cayman Islands Land Crab Fly.” It is, from birth, completely attached to the land crabs found there. The eggs are laid around the eye of the crab. Once hatched, the larvae make their way to the gills, where they have a veritable feast on the microorganisms living there. Afterwards, they wander to the mouth, where they will grab whatever bits of food they can from the crab. When they’ve had their fill, they fall to the ground and pupate. Don’t think they’ve left the crabs alone, though, because, after pupating, they hitch rides on the crab’s backs until they lay the eggs.

What makes them interesting (or, at least, what this article found interesting, I think it’s pretty neat too), is that there are three separate species of Drosophila in three different locations that have given up the usual fruit fly method of eating bacteria off rotten fruit, and have taken to stealing from land crabs. The strangest part about this is they evolved these methods completely separately from each other. One is from an island in the Indian Ocean, while the others (including D. endobranchia) live in the Caribbean, and each of their life histories are different enough to show that they evolved independently.

I can’t find them on any endangered species list, but with the small size of their habitat, which is frequently being taken over by resorts, I wouldn’t be surprised if their numbers were dwindling. Also, my friend is working with a man who likely knows more about Cayman Island ecology than anyone. If he thinks they’re endangered, I’d take his word for it.

¹The entire message was:
Re: Your endangered species blog.
Drosophila endobranchia
Whaddya say?