Lecture 18 Flashcards
Ectdysozoa characteristics
moult cuticle in order to grow (ectdysis)
ectdysis
entire cuticle shed at once
4 main phyla of ectdysozoa
- onychophora (110)
- tardigrada (800)
- nematoda (25 000)
- arthropoda (1 million)
epidermis
below cuticle, living cells that secrete substances that become cuticle
3 layers of cuticle
- epicuticle (includes layer of waxes)
- exocuticle
- endocuticle
sclerites
hardened plate-shaped regions
moulting 10 steps
- apolysis
- inactive moulting fluid secreted by epidermis
- thin protective layer deposited between moulting fluid and epidermis
- enzymes activated, endocuticle digested
- new undifferentiated layer of cuticle deposited under protective layer (greater surface area, wrinkled)
- moulting fluid reabsorbed
- epicuticle laid down
- old exocuticle and epicuticle moulted (ectdysis)
moulting 10 steps
- apolysis
- inactive moulting fluid secreted by epidermis
- thin protective layer deposited between moulting fluid and epidermis
- enzymes activated, endocuticle digested
- new undifferentiated layer of cuticle deposited under protective layer (greater surface area, wrinkled)
- moulting fluid reabsorbed
- epicuticle laid down
- old exocuticle and epicuticle moulted (ectdysis - may swallow water or air)
- new cuticle expanded
- exocuticle sclerotized
phylum onychophora
velvet worms, tropical terrestrial
phylum onychophora
velvet worms, tropical terrestrial, Cambrian ancestors were marine
haemocoel
no closed blood vessels, organs bathed in haemolymph, pumped by open-ended tubelike heart
onychophora morphology
- soft-bodied, segmented
- lobopods
- little cephalization
- haemocoel
- single pair of sensory antennae on head
- exchange gases using tracheal system
7.
onychophora morphology
- soft-bodied, segmented
- lobopods
- little cephalization
- haemocoel
- single pair of sensory antennae on head
- exchange gases using tracheal system
tracheal system
stigmata lead to tracheae which terminate in many fine tubes, O2 and CO2 diffuse
stigmata aka spiracles
openings in sides of onychophoran body