Class Pycnyogonida - sea spiders

Characteristics

1) Range from few millimeters long and larger.

2) Small, thin bodies and usually four pairs long, thin walking legs.

3) Somites can be reduplicated. This is unique.

4) Subsidiary pair of legs (ovigers) in males, used to carry developing eggs.

5) Equipped w/ chelicerae and palps.

Structure

1) Mouth located tip long suctorial proboscis used to suck juices from soft-bodied animals.

a) Tubular sucking or feeding organ w/ mouth at end.

2) Most have four simple eyes

3) Circulatory system is limited to simple dorsal heart

4) Excretory and respiratory systems are absent

5) Long, thin body and legs provide large surface in proportion to volume, that is sufficient for diffusion of gases and wastes.

6) Due small size, digestive system extends into legs and most gonads are found there.