Gobie

When we think of coral reefs we usually picture the scene we are all familiar with, corals with fish swimming around, maybe hiding in or swimming amongst the coral, just like clown fish swimming protectively around their anemone. And these interactions between animals seem commonplace to us but these can be so vital to the life of a reef. One of these crucial, yet often overlooked, interactions is between the small staghorn coral, Acropora nasuta, and the gobies, G. histrio, which live in it. Due to global warming there has been an increase in toxic seaweed algae that is spreading over reefs in the Caribbean and Pacific. The toxic algae can spread over adult corals and kill larval corals as well, resulting in dying reef systems. Already, one study has show n, that there has been up to an 80% decline in living coral in the Caribbean and up to 50% in the Pacific. But the small staghorn corals have evolved a defense system against these impeding algae. Within 15 minutes of the algae coming into contact with the coral, the coral sends out chemicals to signal the fish that live around them. The chemicals have no effect on some fish but the gobies around the coral respond to the chemicals by eating the algae until it no longer touches the coral, which protects the coral. Not only is this in itself an amazing example of coevolution, but it also demonstrates mutualism because the gobies benefit from eating the toxic algae as well. The goby skin secretes toxins, which inhibit their attackers directly following an attack that many fish can hardly swim upright. This defense mechanism allows the gobies to escape. There is research that suggests that these gobies ingest the toxic algae and may sequester the toxins to then be used for their own defense. These interactions demonstrate the recycling of resources in reef systems and also the incredible ability of organisms to evolve for specific roles in their environment. Reefs rely on a balance of all the players on the reef to maintain its health and these gobies are just one small part of this delicate equilibrium.