Class Pycnogonida Sea Spiders

The body shape and gangling legs of sea spiders call to mind their terrestrial namesakes. Most of the thousand species live in shallow benthic zones at higher latitudes. They are predominantly predators of hydroids, bryozoans, and polychaetes, but some consume microorganisms, algae, and even detritus. Food is either macerated with chelae or externally predigested and then sucked into the digestive tract with a proboscis.

Sea spiders have a barely perceptible head and a body comprising four pairs of long legs joined by a narrow, segmented trunk. Most are small (1—10 mm), but some deep-water behemoths reach 6 cm in body length with a 75-cm leg span. Their eyes are mounted on an tubercle to give them a 360° arc of vision.

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