Topic 23: Ecdysozoa

Question 1

Clade Ecdysozoans

Answer 1

Sub clade of bilateria, covered by a cuticle that is periodically moulted.

Question 2

Ecdysozoan Cuticle

Answer 2

A tough, non-living, outer-layer of organic material outside the epidermis, periodically moulted (ecdysis), composed of chitin. Consists of three layers.

Question 3

Functions of the Cuticle

Answer 3

Protects against desiccation and mechanical injuries. No capacity for growth.

Question 4

Sclerotization

Answer 4

Cross linking of chitin w/ proteins to create a hardened rigid cuticle plates (sclerites).

Question 5

Steps Ecdysis/Moulting

Answer 5

1. Apolysis: the old cuticle separates from the epidermis
2. Inactive enzymes are secreted in the space
3. Epidermis grows and folds
4. New proto-epicuticle, a thin protective layer, grows on top of the epidermis.
5. Enzymes are activated, old endocuticle is digested
6. Moulting fluid reabsorbed
7. New epicuticle is completed.
8. Old cuticle is moulted
9. New layer is sclerotized

Question 6

Phylum Nematoda

Answer 6

Round worms with no segmentation, possess a hemocoel and digestive system.