I work at the Marine Education Centre located in Diani, Kenya which has several exhibits packed with information on marine ecosystems and biodiversity, including large exhibits on sea turtles, cetaceans, and whale sharks, all of which are found along Kenya’s coastline. As a matter of fact, we have a whole room dedicated to whale sharks! One of the displays in the whale shark room is of a whale shark with an entourage swimming below it. So, it doesn’t come as a surprise that the most asked question by guests, be it children or adults, is whether the entourage is baby whale sharks. Many times, guests are intrigued when we tell them that they are not pups but are in fact fish that have formed a type of relationship with the whale shark. I often go ahead and do a comparison that is much more relatable to them; birds that love hanging out on the heads or bodies of many land animals, for instance cows or even elephants, which are constantly seen nibbling on parasites. So is the case for a whale shark and remora fish, commonly called the sucker fish. They form a commensalism type of relationship which is just one of the many relationships out there in the blue.
The big blue supports a variety of relationships/associations, some of which are important for the health and survival of species. These relationships are categorized as mutualistic, commensal, or parasitic. The relationship that we are interested in for this blog is the mutualistic symbiotic relationship, which brings us to today’s topic, a closer look at cleaner symbiosis in Kenya’s coral reefs. It’s not uncommon to find cleaner symbiosis in tropical countries such as Kenya due to high parasite load. Cleaner symbiosis is a mutualistic relationship where both partners ecologically benefit from each other. Small cleaner fish feed on the parasites they find on the bodies of larger animals, which improves their health, and in return the cleaner fish get fed! I like to think of it as a grooming service for the client, kind of like when you and me visit the spa!
You remember the character Jacques from Finding Nemo? He had to stop cleaning the tank when all the occupants were plotting an escape. Jacques was a cleaner shrimp whose role was cleaning all the algae growing in the tank by feeding on it! Occasionally, diving on coral reefs in Kenya brings you eye to eye with ‘Jacques’ the cleaner shrimp (Lysmata amboinensis), also known as the Red Skunk Cleaner Shrimp because of the distinct pair of bright red stripes that outline the single white stripe running down its back. Cleaner shrimp are marine tropical crustaceans that live at cleaning stations and provide cleaning services to different species of reef fish, referred to as clients. The cleaning service involves removing ectoparasites or dead tissue found on the client fish bodies! This activity controls the client parasite load, which leads to improved survival and health of the client!
Cleaner shrimps are the kings of mutualism on coral reefs where they are often spotted on rocks or live coral, waiting for the client fish to stop by for a cleaning service. It is such an active cleaner that many fish value its service enough to allow the shrimp to clean inside their mouths! Even though the client fish can be large predators, like eels and groupers, they wouldn’t dare snack on the cleaner shrimp because they have figured out that having parasites removed is much better for their health than snacking on the little shrimp. The shrimp also eat the mucus and parasites around the wounds of injured fish, which reduces infections and aids in healing! How cool is that! Next time you come across these little helpers during your dive, try and put your hand down to get a free manicure as they pick the dead skin from your fingers! It doesn’t get cooler than that!
Sea turtles get cleaned too! Green sea turtles and hawksbill turtles tend to have algae growing on their shell and the underside of their flippers and neck. They also have small parasites attached to the skin between their scales. The mutual beneficial relationship occurs when certain reef fish species feed on the algae and parasites attached to the turtle forming a cleaner symbiosis relationship. Cleaner fish in this instance may be wrasses and gobies, but even surgeonfish and other herbivores feeding on the algae! The best-known cleaner fish on most coral reefs is the Bluestreak Indo-Pacific cleaner wrasse (Labroides dimidiatus). They clean almost any other fish species, from parrotfish to large groupers and other bigger predators like the cleaner shrimps mentioned above. They even swim into the open mouth of groupers, picking up parasites and food remains found between the grouper’s teeth, they actually work as a kind of ‘dentists’! When the grouper has had enough cleaning, it partially closes its mouth to signal the cleaner wrasse to leave its mouth and swim out. This cleaning ritual was a sensational discovery in the first days of diving in Indo-Pacific tropical coral reefs. Many pioneers of scuba diving wrote about the cleaner wrasse in their books, Hans Hass, Irenäus Eibl-Eibesfeldt, Jacques-Ives Cousteau, just to mention a few.
In Galu, a favourite diving site in Diani, there are two cleaning stations. These cleaning stations are a hotspot for divers simply because they are magical to watch. More often than not there will be a number of large sea turtles just floating motionless in the water column with their flippers stretched, enjoying some quality spa time. Other times, the turtles will lay on top of the coral to rest while being cleaned. According to sea turtle biologists the behaviour of turtles floating motionless in the water column is a signal to the local reef fish that they want to be cleaned. It’s not often that you come across a group of turtles at once, so when you get to see them on a cleaning station, that’s a jackpot!
Remember, next time you approach a cleaning station you should observe from a distance otherwise you might be disrupting an ongoing cleaning service!