Sea spiders
There is some disagreement as to how sea spiders should be classified, but for a long time they have been considered arthropods. They are marine animals, and are found in all of the oceans and at both poles. Pycnogonida means “with many knees”, and refers to the many segments that make up the legs.
Sea spiders have four pairs of legs for walking, and their leg spans and body lengths vary greatly. A medium-sized sea spider may have a leg span of 5-7 cm, while the very largest species, such as the Colossendeis colossea, can have leg spans of 70 cm. The species are classified on the basis of characteristics such as their claws (chelifores), their proboscis (an elongated appendage with a mouth at the end of it) and their antennae (palps) (Figure 1). For example, some species have claws and antennae,…
