In Dauin we are privileged to be right next to some of the best muck-diving in the world. What is “muck diving”? It’s diving over underwater landscapes which look unspectacular at first sight, but reveal amazing rare and unusual marine life upon a closer look. While we have dive sites with really nice corals in Dauin, some of our best dive spots feature mainly … sand! Occasionally, a sole anemone sits in those sandy planes, or a discarded rope is draped over a hump in the sand. Around these sessile organisms or human artifacts lives an amazing fauna of small animals. Among the most spectacular species of this fauna are the crustaceans: shrimps, crabs, squat lobsters and their relatives.
In an often featureless underwater landscape, there are a few different strategies for surviving as a relatively slow, and small (and tasty!) crustacean.
Some of them expertly camouflage themselves, and make themselves virtually invisible. The saw blade shrimp is one good example, matching the color and shape of the black coral fingers on which it lives.
I claimed that this shrimp is “virtually invisible” – how did I still find it? I know from experience that it lives on this type of coral, so I was looking very carefully. And, I have much bigger eyes and a bigger visual brain than the fishes which would want to eat this shrimp. For some clueless snapper or grouper, the saw blade shrimp would indeed be close to completely invisible!
This Halimeda crab does the same thing, but different: it looks exactly like the Halimeda algae among which it lives. To find these you, again, have to know precisely what you are looking for. The crabs don’t even move that much, making their detection even harder.
Another strategy for crustaceans to survive is to be translucent, or almost translucent. Lots of shrimp live in the sand with bodies devoid of color pigments. These two are good examples; the second shrimp took the additional safety measure of hiding in a beer bottle.
My Anemone is My Fortress
Still other crustacenas use stingy anemones as their home base, and avoid capture in this way. If you hover carefully next one of to the many anemones in Dauin, you will be able to discover a very diverse selection of shrimp and crabs. This porcelain crab never occurs outside of anemones. Note: porcelain crabs are not actually crabs! They are more closely related to squat lobsters.
And it’s not just anemones which crustaceans like to hide in. Many bigger invertebrates serve as their homes. This hermit crab hides in a small hole in an encrusting hard coral. Also quite a safe place.
This squat lobster hides in a crinoid (a feather star) for its whole life. And it matches its host’s color and pattern so well!
Find yourself a Goby
And there is one more really unique strategy, which allows small shrimp to live in sandy planes … to team up with a small marine fish, a goby. In this symbiosis, the shrimp digs a burrow which is used by both animals, while the goby, with much better eyesight, serves as a watchman at the entrance of the burrow. You need to swim calmly to be able to observe this symbiosis, but it’s worth the effort!
I am amazed how diverse this crustacean fauna is, and how interesting the behavior of these animals is. Come dive with us and check it all out!