Here’s a short video from Nature that isn’t based on a single research paper, but on the continuing work of Redouan Bshary, a biologist in Switzerland who studies interspecific communication and behavior in fish. The article itself, a summary of Bshary’s work written by Alison Abbott, is called “Animal behaviour: Inside the cunning, caring and greedy minds of fish“, and deals largely with the relationship between cleaner wrasses and their “cleanees.”
It turns out that this relationship is far more complex than the simple symbiotic relationship I’ve always taught (“cleaneee gets dead skin and parasites removed, cleaner gets a meal”). There is cheating by the cleaners, punishment by those fish who get a bum job of cleaning, and all kinds of complex social dynamics.
The video accompanying the article, however, deals with a different interspecies relationship—that between groupers and moray eels who seem to hunt “cooperatively”:
Now from the video alone, it looks as if the grouper is getting all the benefits, using the moray eel to flush prey for him (note that this also involves the moray leaving the safety of its den in the reefs). The experiments shown at the end demonstrate learning ability in groupers, but one question is missing in all this: What does the moray get out of it? This behavior would not evolve (or persist, if it’s not genetically based) if both species didn’t derive some benefit from it. My immediate reaction would be that the moray gets some noms, too, but this isn’t mentioned in the video, which seems to show that all the benefits devolve to the grouper. A better video would explain the benefits to both partners.
One alternative, which I find unpalatable and not biologically sound, is that the groupers are enslaving the morays as sort of a hunting d*g, to flush prey for them. In this scenario the moray gets nothing. However, in nature we don’t see this kind of slavery very often, though it’s the norm for humans and their d*gs.