Long-legged Spider Crab

Overview

The Long-legged Spider Crab (Macropodia rostrata) is a small, slender crustacean easily recognized by its exceptionally long, thin legs and pear-shaped, triangular carapace. Often referred to as a "decorator crab," it frequently attaches pieces of algae to its body to blend seamlessly into its surroundings, providing both protection from predators and a stealthy advantage when hunting.

Appearance

This species typically reaches a modest size, with a carapace length generally under 30 mm. Its body and legs range in color from greyish-yellow to reddish-brown, sometimes featuring white markings. The rostrum is divided into two distinct lobes, and the overall appearance is often described as fuzzy or hairy due to the algae it collects for camouflage. When removed from the water, it may appear as a crumpled, twig-like structure.

Distribution & Habitat

Macropodia rostrata is widely distributed across the northeastern Atlantic, from Norway down to Morocco, and is common throughout the Mediterranean Sea. It inhabits a variety of environments, including kelp forests, seagrass meadows, muddy sand, and rocky areas covered in algae. While it can be found in the intertidal zone, it is often more common in deeper subtidal waters, particularly in the southern parts of its range.

Biology & Behavior

These crabs are slow-moving and rely heavily on their camouflage to avoid detection. Underwater, they exhibit a unique, bicycle-like swimming motion. They are opportunistic and vulnerable to predation, which drives their habit of decorating themselves with local vegetation to mimic seaweed stems.