Arthropods (Chelicerates, Myriapods, Crustaceans) Flashcards
What are the characteristics of the Clade Ecdysozoa?
1) Have a outer body covering called cuticle
2) Molt a cuticle
3) Coelomate and Pseudocoelomate body plans
4) Most constrained Metazoan body plans
What are the characteristics of the Phylum Nematoda?
1) Most constrained body plan - hydrostatic pressure
2) Elastic cuticle contains pseudocoel under pressure
3) Only longitudinal muscles - move thru tight spaces
4) Free-living and parasitic
What is the body plan of Phylum Nematoda?
Highly constrained (all look identical)
- Must swallow against hydrostatic pressure
- No respiratory structure limits size (long and skinny)
How does the body plan of Nematodes affect reproduction?
Mostly dioecious with internal fertilization
-Form shelled eggs internally allows embryo to form its own high pressure
How do Nematode parasites differ from Platyhelminthes parasites?
Platyhelminth absorb food through their tegument
Nematode parasites must swallow their food because their cuticle is a barrier
What are some examples of nematode parasites?
- Intestinal roundworms
- Hookworm (burrow through feet)
- Filarial worms (elephantitis)
- Guinea worms (driven to extinction by humans)
What is the life cycle of the Guinea worm?
1) Human drinks contaminated water w/ coepepods
2) Coepepods die and release guinea worm larvae
3) Fertilized female worm migrates to skin, causes blister, and discharges larvae
4) Larvae are ingested by coepepod
How many germ layers do Nematodes have?
Triploblastic but pseudocoelomate
What is the mode of locomotion for Nematodes?
Longitudinal muscles work against pseudocoel to move in tight spaces, write when not in tight spaces
What is the cuticle used for in the Phylum Arthropoda?
As an exoskeleton
What is the Arthropod cuticle made of?
chitin and protein
How does the Arthropod cuticle grow?
Ecdysis
How are Arthropod jointed appendages attached?
With muscles attaching from inside to exoskeleton
How do terrestrial Arthropods breathe?
Respiratory system of internal tracheids with openings called spiracles
-this restricts size of arthropods
What are the three layers of the Arthropod cuticle made of?
Mostly chitin and protein
How is the growth of Arthropods characterized?
Growth is discrete (not continuous) step function
How is ecdysis controlled in Arthropods?
Hormonal control
Explain the Ecdysis process in Arthropods.
Basement membrane secretes new cuticle from inside out
- Epidermis eats old exoskeleton
- Rest of Exoskeleton separates
How do Arthropods move their limbs?
from the inside-out with muscles acting on the exoskeleton
What are apodemes?
Where the muscles attach to inside arthropods
-allow the flexion of articulated jointed appendages
What kind of body plan do arthropods have?
Metameric body plan of repeated segments
- each segment has repeated ganglia to control motion of paired appendages
- Most species have segments combined to form tagmata
What kind of nervous system do arthropods have?
Mostly ventral nervous system
How do arthropods digest their food?
Only midgut is absorptive - exoskeleton covers most of gut
What kind of circulatory system do arthropods have?
Open circulatory system - hemocoel is present
