TOPIC 23: Ecdysozoa Flashcards
what is clade ecdysozoa characterized by?
by molecular phylogeny
what kind of group is clade ecdysozoa
monophyletic
what are ectodysozoans protected by
their cuticle
a tough, non-living outer layer of orgnaic material outside of the epidermis
cuticle
functions of a cuticle
- protect the animal for dessication and mechanical injury
- exoskeleton for structural support
if a cuticle is a non living outer layer, what can we infer?
that it does not grow, causing animals to moult
three layers of a cuticle
- endocuticle
- exocuticle
- epicuticle (no cuticle)
what is special about the epicuticle
its a thin, water resistant layer with not cuticle
_____ run from the epidermis to the top of the cuticle
fine ducts
how are ecdydid differ in cuticle function compared to ecdysozoa
they can regenerate their missing limbs
sclerotized meaning
hard
in anthropods, the cuticle is ___ in specific regions
sclerotized
process that corss-links chitin polymers with protiens to create a hard and rigid cuticle
sclerotization
regions where there is no sclerotization
unslcerotized
what does an unslcerotized cuticle contain?
contains unmodified chitin that is translucent and allow for movement
does moulting begin internally or externally?
internally
steps to moulting
1) ecdysozoan becomes inactive
2) apolysis: separation of the epidermis from the cuticle
3) inactive enzymatic moulting fluid fills empty space
4) growth of the epidermis
5) secretion of new cuticle
6) activation of enzymes in moulting fluid
7) shedding of old cuticle
8) sclerotization of the new cuticle
what happens to the old enzymes from the old cuticle during moulting
they get digested by the epidermis and is reused for the new cuticle
characteristics of nematodes
- simple body plan due to secondary simplication
- lack segmentation, appendages and eyes
- no circulatory system
- moult their cuticle
- have hemocoel
how is movement achieved om phylum nematoda
they move with side to side contractions of body wall muscles
