One of the most common fish seen around Koh Tao is the Goby. The Goby itself is one of the smallest vertebrates in the world – some of the smallest species do not grow larger than 1cm in length – however some Gobies we have on the dive sites around Koh Tao can grow up to 10cm in length. They can be seen on many of Koh Tao’s dive sites, lying in the sand always having their faithful companion by their side, the Burrowing Shrimp.
A Symbiotic Relationship
The burrowing shrimp is a small crustacean that accompanies the Goby and there are many beneficial reasons why. The Shrimp itself acts as a builder in this symbiotic relationship, whereas the Goby acts as a guard thus the reason it is often known as a Watchman Goby.
Symbiosis literally means “living together” and is perfectly demonstrated by the Watchman Goby and burrowing shrimp. A symbiotic relationship is a relationship where two organisms work together or sometimes against each other to keep a sustainable life.
There are three different kinds of symbiotic relationship; mutualism, commensalism and parasitism. These different symbiotic relationships can be seen around Koh Tao’s dive sites and you can learn more during the PADI Underwater Naturalist Specialty diver course.
A mutual relationship is where both parties gain benefits from helping each other, whereas a communalistic relationship is where one party benefits and the other is unaffected. A parasitic relationship is where one party gains and the other one loses out.
A Safe Alliance
The way the Goby and the Shrimp live together harmoniously has developed over millennia. The Shrimp unfortunately has impaired vision which makes it very susceptible to numerous predatory fish so the Shrimp found a safe haven living alongside the Goby.
The shrimp burrows small holes into the sand so that they both can live together and as the shrimp has bad vision, the Goby acts as guard protecting him. The shrimp has long antenna that are constantly in contact with the Goby, so if the Goby sees a predator or a diver approaching he will quickly swim back into his home and the receptors in the antenna alert the shrimp to return inside as well. The Goby also catches most of the food and the shrimp benefits from this as well.
The Gobies live in an Alpha Male dominated manner. The Alpha Goby being the only male that mates with the females, thus passing down the alpha male genes to the next generation and keeping the Goby population strong. The other males struggle for food and look after the eggs inside the burrows.
Before mating, the male maintains the burrow and the female feeds more to build up sufficient energy required for the mating process. After the eggs have been laid inside the burrow the male Goby waits outside, guarding the burrow whilst funneling water down to the eggs to provide them with more oxygen. There is then a role reversal as the female maintains the rest of the burrow.
Gobies have an average lifespan of ten years, although this is generally a little longer around Koh Tao due to water temperature being a little warmer than average. The goby matures in around three to six months and lives alongside the shrimp for the duration of its life.
So keep your eyes out the next time you are diving and you may just see this unlikely pair lying in the sand helping each other out.
Author: Luke Smith (PADI MSDT #333122)