ecdysozoa Flashcards
what is the process of ecdysis?
molting the cuticle to grow
what is the cuticle?
a non-living outer layer of skin
what is the cuticle made of?
chitin
what are properties of the cuticle?
frequently sclerotized (hardened), but only in particular regions.
unsclerotized cuticle in between are flexible, which allows for movement
the cuticle has several layers, both living and non-living. what are all of the layers?
epicuticl
exocuticle
endocuticle
epidermis
what is the living layer of the cuticle? what is its function?
the epidermis is composed of living cells that secrete substances to the cuticle
what are the properties of the non-living cuticle?
endocuticle - within
exocuticle - outside
epicuticle - upon
what is the process ecdysozoians undergo?
molting - apolysis
what does apolysis mean?
shedding one layer of the cuticle
how does an ecdysozoian molt?
- inactive molting fluid is secreted by the epidermis
- the thin protective layer is deposited
- epidermis separates from the endocuticle
- new cuticle begins to form, thin protective layer precludes digestion
- activation of enzymes in the molting fluid make the endocuticle digested
- liquified oviducts are taken up by the epidermis
- sclerotized exocuticle is not digested
- new cuticle is ‘wrinkled’ giving it a greater surface area
- molting fluid is reabsorbed
- epicuticle is laid down
- exocuticle and epicuticle is shed through the process of ecdysis
- differentiate into exocuticle and endocuticle
why are animals that have molted larger than before?
because the new cuticle expands
how do they sclerotize (harden) their new cuticle?
secretions transported by the ducts
what is an old cuticle called?
exuviae
from the ecdysozoa species comes what animal and species?
nematodes
what are some characteristics of the phylum nematoda?
most are small
no segmentations
no appendages
no eyes
blunt at one end, pointy at the other
open circulatory system (no blood vessels)
complete digestive system (mouth and anus)
two sexes
direct development
do nematodes have to molt their non-living cuticle?
yes!
nematodes are eutelic. what does this mean?
once they hatch, growth occurs by each cell growing, not by addition of more new cells