Crab

Crab species scuttle across sandy beaches, rocky tide pools, coral reefs, and deep-sea vents. Their bodies are protected by a hard exoskeleton made of chitin and minerals, which they molt as they grow. Five pairs of legs include a set of claws for defense, feeding, and communication. Because elbows bend sideways, crabs often move laterally, allowing fast escapes into burrows or crevices. Gills hidden beneath the shell stay moist so some land crabs can breathe air for hours while hunting or migrating.

Crabs play cleanup crew for coastal ecosystems. Many species sift sand for detritus, scrape algae from rocks, or crack open mussels with their claws. Ghost crabs dig deep burrows that aerate beaches and provide shelter for other creatures. Fiddler crabs wave oversized claws to attract mates and stir mud flats, releasing nutrients for marsh plants. In mangrove forests, tree-climbing crabs munch fallen leaves, returning nutrients to the soil.

Life cycles often involve dramatic migrations. Horseshoe crabs, technically distant relatives, crawl onto beaches under spring moons to lay eggs that feed migrating shorebirds. Blue crabs move from estuaries to salty coastal waters to release millions of larvae that drift with currents before returning upriver. After molting, crabs hide until the new shell hardens, making them temporarily vulnerable.

Humans rely on crabs for food, bait, and cultural festivals. Sustainable fisheries set size limits and release egg-bearing females to protect future generations. Scientists tag crabs to learn how warming oceans and sea-level rise affect their ranges. Aquariums teach visitors how to handle crabs gently by grasping the back of the shell rather than swinging them by claws.

Protecting crabs means safeguarding coastal habitats. Wetland restoration, living shorelines, and restrictions on beachfront lighting help hatchlings navigate. Reducing plastic pollution prevents crabs from getting trapped in debris. Classroom projects that build model crab traps or monitor tide pools encourage students to appreciate these sideways walkers that keep shorelines healthy.