Take a Peek at the Reef's Condo Critters
By Tammy Peluso
From the surface it's easy to see the big picture; the structure of the reef, the procession of neon-colored fish, the magnificent gardens of coral. When you freedive, you get to peek inside the inner sanctum where fish and critters sleep and hide. Within the reef's rocky maze of nooks, crannies and crevices lurk fish of assorted shapes and sizes and a legion of invertebrates such as shrimp, crabs, lobster and octopuses. Many create permanent homes they fiercely protect and guard; others boldly cruise the reef, ducking into shadowy corners when in need of temporary protection or respite.
Surprisingly, the housing situation on the reef is quite similar to our own: There are furnished apartments, fixer-uppers, trailers, motels and custom built homes. Regardless, they all provide the basic requirements: shelter, protection and proximity to food.
Many critters, such as moray eels, move into the reef as is; they just claim a crevice for their own. They don't do much redecorating but are particular about the architecture; usually choosing a roomy dwelling that has both a front and back door. During the daytime morays often stay close to home; peering from their lairs, waiting for an easy meal. At night morays roam the reef under cover of darkness; they don't see well and feed using their astute sense of smell. Most morays eat crustaceans; a few, such as the West Indian Spotted Moray (Gymnothorax moringa), eat small fish as well. Eels can be dangerous if provoked but are typically mellow and, in many cases, downright friendly. They are, however, extremely protective of their homes so it's best to stay out unless invited.
The pipes on sunken airplanes and ships are prime real estate U/W; on new wrecks the tubes are always the first to be chosen. Pipes are popular with small fish such as gobies and blennies as well as morays; they are the perfect fortress. Eventually, the pipes become covered with sponges, algae and coral, creating an ideal frame for photo subjects; close-up kits and macro lenses are perfect. When there are several eels living in proximity to each other, the eels will often switch dens or live together in the same hole.
Some shrimp, crabs and blennies are architects; they build burrows in the sand and sculpt niches in rocky crevices filled with substrate suitable for excavation, such as sand or coral rubble. One of the most creative builders is the mantis shrimp; a bizarre creature that has huge psychedelic stalked eyes, a fierce grin and a punch powerful enough to break a camera lens. They are usually found in niches along rocky bottoms or in deep sand burrows. Mantis shrimp are beautiful, dangerous and an enigma to macro photographers. Knowing where and how they live makes it a bit easier, but they are quite skittish. You need to watch from a distance till they peek out of their burrows, then sneak up on them.
Tubeworms (members of the Serpulidae family), fanworms and featherdusters (members of the Sabellidae family), come in a feathery assortment of shapes, colors and sizes; some look like miniature Christmas trees, others have frilly, fan-like layers. For protection, these worms build sturdy tubes, using lime, mucus and sand. The worms can fold their bodies into the tube like an umbrella when necessary. The worms are filter feeders and use their pretty plumes to capture plankton. They typically build their tube castles on reefs where there are strong currents. Although these colorful worms exist individually, they are often seen living in huge colonies, covering coral boulders with a lush living carpet of tiny, flower-like animals. When living together the worms are all tuned to the same frequency; if you frighten one, you scare them all. If you move too fast around a colony of tubeworms, they vanish in a colorful flash. Despite their fragile appearance, they are quite sturdy and make excellent subjects for macro photography.
Hermit crabs are vagabonds; they use empty shells for homes. They are scavengers and scour the ocean floor and reef in search of food, taking their homes with them. They are most active at night and are often seen munching in the moonlight. Hermit crabs have no hard cuticle to protect their soft abdomen and would, without the protection of a shell, be devoured easily. Some species of hermit crabs live in sheltered burrows. Hermit crabs can't move very fast so they use their shells like armor, when threatened they quickly pull inside and block the door with their largest claw. The shell keeps the hermit crab safe from most predators with some exceptions. Octopus can easily penetrate the shells with their powerful beaks; snails can inject a deadly poison; and starfish will eventually win out with patience and persistence. As they grow, hermit crabs will change homes and move into larger shells. If homes are scarce, hermit crabs have been known to forcibly evict another hermit crab.
The delicate Arrowcrab has a totally different approach. Generally, it hides during the day, often in or near the protective arms of an anemone or crinoid; at night, the Arrowcrab will often leave its sheltered den in search of food. They use their long spindly legs to scuttle across the reef top, retreating into corners when necessary. At night, Arrowcrabs are often found perched atop a coral or sponge, picking morsels from the passing current.
Getting to know the reef takes time and patience, it's best to start shallow and gradually go deeper as your skills improve. Take the time, it's a world worth knowing.