Coral Reef Crustaceans

Coral reef crustaceans include such familiar animals as shrimps, lobsters, and crabs. Members of the Class Crustacea are common throughout coral reef ecosystems, and are found in all three primary coral reef zones.

Like the related arthropods such as insects, spiders, centipedes, etc., crustaceans have segmented bodies, external skeletons, and numerous, jointed limbs. However, unlike most arthropods which are strictly or mainly terrestrial, crustaceans are primarily aquatic creatures, mostly marine.

Crustaceans play a host of different roles in the ecology of coral reef communities. Some are scavengers, cleansing the reef of decaying animal remains. Others are active predators or omnivores. Many are preyed upon by coral reef fishes.

Here, we discuss the three most common types of crustaceans found in coral reef ecosystems: spiny lobsters, shrimps, and crabs.

Spiny Lobsters

Spiny lobsters (Panulirus spp.), long considered by many the premier delicacy of the tropics, are probably the best-known and most sought after of all coral reef crustaceans.

A spiny lobster peers from its daytime reef shelter. Photo: Courtesy NOAA

Spiny lobsters are much more common only at certain times of the year on both Caribbean and Indo-Pacific reefs. They are not full-time reef residents, but rather visitors that spend considerable time in deep benthic habitats distant from reefs. Nonetheless, at times their numbers in reef areas are substantial.

Typically, spiny lobsters remain safely positioned by day in cracks and crevices within the reef, with only the slowly waving antennae protruding. At night, they wander about more freely.

With high commercial value and ever-increasing fishing pressure however, seeing lobster packed reefs is no longer a common experience for coral reef explorers.

Shrimps

Shrimps are common coral reef crustaceans inhabiting most coral reef habitats. These are a diverse group of crustaceans that come in many sizes and colors.

Cleaner shrimp. © Fotolia.com

On coral reefs, some shrimp species called “cleaners” play a highly significant role in the life of the coral reef community, gaining food by removing parasites from fishes or other invertebrates.

Because of these benefits, the host grants them a special “protected” status. Even when cleaning the mouths and teeth of predators like groupers or barracudas, they are allowed to go about their business without becoming a meal themselves.

Cleaner shrimp can be distinguished from most other types of shrimps by their particularly long antennae (see photo, above). These animals are highly prized in marine aquariums.

Crabs

Crabs are ubiquitous coral reef crustaceans, occuring in all major types of habitats within the coral reef biome. Those that dwell on reefs generally remain well hidden within the reef structure by day.

Most crabs are omnivores, feeding on a wide variety of available food items, including algae, worms, mollusks, bacteria, other crustaceans, fungi, and even detritus.

Certain types of crabs may play a more prominent role in coral reef health than previously suspected. They do this by acting as “cleaners” of hard coral colonies, removing and thereby reducing the numbers of infesting parasites and other harmful organisms from the bodies of their hosts in much the same way that cleaner shrimp benefit certain fishes. In return, such crabs are provided with a readily available food source.

Crab fishing in coral reef areas has been increasingly restricted in recent years due to the ecological damage typically associated with commercial harvesting techniques.

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