Group Ecdysozoa

Question 1

How many phyla is this group made out of? and what are the two main ones?

Answer 1

8 phyla

1. Nematoda
2. Arthropoda

Question 2

What is the main characteristic present in the phyla in ecdysozoa?

Answer 2

they go through ecdysis, which is the process of molting the cuticle (non-living outer layer of skin) in order to grow

Question 3

What is sclerotization?

Answer 3

their cuticle is sclerotized –> hard

• only some parts of it are sclerotized and they are called sclerites
• theres unscleritized cuticle in between them so it allows the animal to move

Question 4

What is an epidermis?

Answer 4

its below the cuticle and its living cells that secrete substances to make the cuticle

Question 5

What are 3 non-living layers of the cuticle?

Answer 5

1. endocuticle (endo=within)
2. Exocuticle (exo = outside)
3. Epicuticle (epi = upon)

• endo is the largest one and epi the small last layer of the cuticle

Question 6

When does moulting start?

Answer 6

it starts before there is external evidence of skin sheddnig

Question 7

What are the 10 steps in Moulting?

Answer 7

1. Apolysis occurs –> Epidermis separates from endoocuticle
2. Inactive moulting fluid is secreted by epidermis
3. a thin protective layer is deposited between moulting fluid and epidermis
4. The enzymes in the moulting fluid activate and the endocuticle is digested and liquefied products are taken up by epidermis (sclerotized exocuticle is not digested)
5. At the same time as this, a new undifferentiated layer of cuticle deposited beneath protective layer and the protective layer keeps it form being digested
6. moulting fluid is reabsorbed
7. epicuticle (wax layer) is laid down
8. Ecdysis: shed old exocuticle and epicuticle and swallow air or water to help split old skin
9. New cuticle expands and the newly moulted animal is larger than ever
10. New cuticle sclerotized by secretions transported in the canals and differentiate into exo and endocuticles