Symbiotic relationships occur when two different organisms live together. We can divide these relationships in 3 types:

Mutualism: when both individuals benefit from the relationship;

Commensalism: when only one benefits from it, while the other species is not affected;

Parasitism: when not only just one specie benefits from it but also causes harm to the other one.

We, as divers, are lucky to observe many of these underwater living arrangements. Here are just two examples:

Anemone and Clownfish

Here is a classic example of mutualism. The clownfish, also known as Nemo or anemonefish, seeks shelter in the midst of the stinging tentacles of the anemone. The anemone’s poison can paralyze other fishes but the clownfish has a thick layer of mucus and is immune to it. The anemone offers protection and a safe place for the clownfish to lay its eggs. Moreover, the clownfish also gets a little bit of food, as it eats the anemone’s dead tentacles and leftovers.

But the clownfish also has a lot to offer. It helps to scare away some predators and gets rid of parasites. Scientists say that it might even help to oxygenate the anemone as it swims through it. The fish’s excrement are full of nitrogen, which contributes to the anemone’s growth.

The anemone can also host crabs and shrimps, offering protection without getting anything in return (commensalism).

Goby and Pistol Shrimp

That is a very interesting mutualistic relationship. The shrimp is almost blind, making it very hard for it to spot predators in time. In the other hand, it is a very good digger and a specialist when it comes to burrows. By contrast, the goby has an excellent eye-sight but is quite defenseless when it comes to predators. So, what a better way to survive than to combine their strengths to minimize their weaknesses?

During the day, the goby stays at the entrance of the burrow, keeping an eye out for any predators. Meanwhile, the shrimp is busy digging and improving their house. The long antenna of the shrimp is always in contact with goby’s fins. If any danger comes to sight, the goby flicks his tail in a certain way and the shrimp quickly goes back inside. If the predator gets any closer, the goby also retreats to the safety of his burrow.

When night comes, the pair goes back inside their shelter. The shrimp closes the entrance with pebbles to guarantee a good night’s sleep.

Do you want to find out more about other symbiotic relationships? Keep checking our blog, we will come back next month with more on the subject.