Coral Reef Cleaner Fish
Pacific Ocean Wrasse Dances to Attract Clients
Striped Cleaner Wrasses (Labroides dimidiatus) are the best known of many types of cleaner fish that advertise their services on coral reefs. Big fish (many of which are predatory and would normally eat smaller fish) allow these little helpers to swim all over them and even to enter their mouth and inspect their gills. The cleaners eat the parasites and both parties gain from the relationship.
Cheat Pretends to be Cleaner Wrasse
The Sabre-toothed Blenny (Aspidontus taeniatus) looks very much like the Striped Cleaner Wrasse, and it even performs a very similar dance to attract larger fish. When the unsuspecting giant is waiting patiently to be cleaned the Blenny dashes in and bites off a chunk of its flesh. After this experience the larger fish will usually view all cleaners with some suspicion, often attacking blennies in future.
Benefits of Parasite Removal Outweigh Occasional Injury
Obviously it is important that most ‘client’ fish have a good experience, so the relative numbers of mimics (the blennies) must remain small. If there were more blennies than wrasses the larger fish would rapidly learn to ignore the advertising dances and simply eat the cleaners as well as the blennies. There is a complex balance of advantages to be considered here – the advantage to the large fish of parasite removal must outweigh the disadvantage of being duped occasionally and suffering minor injury.
Evolution of Cleaning Behaviour
Many species of small reef fish have become specialists at parasite removal, and all have distinctive markings and behave in ways to attract client fish. Those in the Atlantic are not closely related to the ones found in the Pacific, but they look similar because they have evolved to live in very similar ways (convergent evolution). Coral Reefs are ancient habitats and there has been sufficient time for very complex relationships to develop between the animals that live there. It is difficult to imagine what the ‘first steps’ might have been – maybe the opportunistic removal of external parasites lurking on the safer parts of the future ‘clients’? Cheats always prosper - so it is less difficult to see how the blennies fit in!
Cleaner Shrimps
The Pacific Cleaner Shrimp (Lysmata amboinensis), also known as the Skunk Cleaner Shrimp, feeds on all sorts of small free-living invertebrates as well as fish parasites. This means that it can be safely kept in a reef tank. Unfortunately this is not the case for the Striped Cleaner Wrasses, they have become so specialised that they only eat fish parasites, and in the confines of a small tank (with insufficient ‘clients’) they simply starve to death.
