The traditional appearance of the sea spider is that of long legs and a small body. Across the many species of sea spider, the leg count varies from 4 – 6 pairs. Sea spiders operate without the respiratory system that we are used to. Instead, they use their legs to take in vital gasses, such as oxygen. They also utilize a proboscis, which enables them to digest soft-bodied invertebrates via a sucking mechanism. Some species of sea spiders are so tiny that the muscles on their exoskeleton are made of just a single cell. The legs of sea spiders also contain their guts and genitals, which makes them very unique.