Be a crustacean or eat a crustacean. The species of the Maldives mostly fall mostly into one of these two camps. And some into both. These inside out arthropods, as they are called, are a core piece of the Maldives marine life puzzle.
The ubiquitous creature of the aquatic world, crustaceans are found throughout the lakes and seas of the world. Oceans, like the warm Indian Ocean, is where the Maldives calls home along with many types of crab, shrimp and lobster.
The defining feature of a crustacean is its exoskeleton, hard outer “shell” as it is often termed. Soft and squishy on the inside and hard on the outside, they’re the opposite of spine-supported mammals. Many crustaceans shed their outer layer to grow. While most call the water home, some stick to land or a combination of both environments. The ghost crab that is seen scurrying across the white sands of the Maldives lives in the intertidal zone and digs deep burrows along open sandy beaches. If they are still you might miss them, as they camouflage with the color of the sand.
Lobsters, shrimp and prawns are commonly fished for human consumption but they are not as important as some other types in the overall food chain. Krill and a similar creature called a copepod, despite their small size, make up a significant part of the world’s biomass and a core base of the food chain.
Leggy lobsters are known the world over as a seafood delicacy. They come out at night and may be seen by divers on a night dive using their tail to skuttle backwards out of the light. Their big front claws keep divers at a distance. If you were close enough to shake a claw though it would be noticeable that the “left-handed crab” has a larger left hand claw.
Stripe-legged spiny lobsters are known in the Maldives as are the painted rock lobsters. Caves and crevices of the reef are where they hide during the day and they prefer the sandy bottoms of reefs to feed on other hard shell creatures like molluscs.
Crabs frolic between worlds – the underwater world and the terrestrial world. There are crabs a plenty in the Maldives, characterized by the hidden tail as compared to the long muscular tails of lobsters.
Hermit crabs can surprise beach goers by suddenly becoming a walking seashell, then quickly retracting their legs and bodies back inside when approached. This role as crab habitat is one reason tourists are discouraged from collecting seashells in sensitive marine environments like the Maldives. The Maldives is known for several types of hermit crab, including the red hermit crab and the dark glove hermit crab.
While hermit crabs are considered “false crabs”, with shorter back legs and a longer abdomen, “true crabs” have 4 walking legs in addition to their clawed arms at the front. In the Maldives, these are the flat rock crabs, tropical land crabs and red spotted crabs to name a few. In that space where the tide rises and falls, where the marine and terrestrial meet is where you’ll find flat rock crabs and ghost crabs. The tropical land crab goes through water to land transformation. Once it has acquired its final outer shell, it stays on land and goes back to the shores edge just to lay its eggs. On the other hand the red spotted crab is found under water hiding among the corals, one to watch out for when scuba diving.
Apart from the recognizable hardbacks of the sea, there are colorful crustaceans that inadvertently put on exciting displays. Previously thought to be phytoplankton that light up the beaches at night with their bioluminescence, the cause of this phenomenon has now been identified as a type of crustacean. Due to a different type and duration of glow, the surreal neon blue beach effect actually comes from tiny ostracod crustaceans. At 1 millimetre to 1 inch in size, these small creatures are like stars shining brighter than would seem possible. Photos of the dream-like beach have previously circulated on the internet explained as phytoplankton but are now being corrected as ostracod crustaceans, according to Cornell biology professor James Morin.
Another creature that adds colour to a diver’s experience, if spotted, is the multicolored mantis shrimp. These spindly creatures also have an otherworldly, science-fiction vibe to them. You can see one in this awesome video along with the huge variety of other marine creatures to be seen in the Maldives. This video really shows how much there is to see in just one trip!
How the tables turn
On the other hand, crustaceans are also a meal for Maldives creatures other than for human consumption. From smaller fish like snapper, wrasse and puffers to sharks and moray eels, crustaceans have the role of prey in many of their relationships. Some hermit crabs even feed on each other.
Without crustaceans on the reef, many fish would be without food and cleaners. The building blocks for a healthy marine ecosystem include crustaceans, in the Maldives and beyond.