Tardigrades and Pentastomids

Abstract

Eucoelomata in which:-

• 1. The body is not clearly differentiated into regions, although there is some evidence of metamerism.

• 2. There is no definite head.

• 3. The gut is straight and the anus is terminal.

• 4. The nervous system consists of pre-oral ganglia joined by circum-oesophageal commissures to a double ventral nerve cord which has four ganglia along its length.

• 5. Sense organs consist of eye spots, bristles and spines.

• 6. The cuticle is non-chitinous.

• 7. There are four pairs of short unjointed legs, each with terminal claws.

• 8. Muscles of the body wall are single and smooth; they occur in bands.

• 9. The body cavity is a fluid-filled pseudocoelom.

• 10. Excretory organs are Malpighian tubules.

• 11. There is no blood vascular system.

• 12. The products of the gonads are shed through the terminal part of the intestine.

• 13. The sexes are separate.

• 14. The immature stage resembles the adult.