Week 10, Arthropoda
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Describe the general characteristics and biology of arthropods
→ They have an exoskeleton, which is usually hard → Their bodies are segmented → Their appendages are jointed (arthon = joint, pod = foot) → Through evolution their appendages became specialised • locomotion (walking, jumping, flying, swimming) • sensory perception - feeding - mating
What is “ecdysis”?
Moulting to shed an exoskeleton
What is hemolymph?
Analogous to blood in animals. → circulates throughout the body cavity → doesn’t transport gases → enters the heart through pores that are valves → heart pumps from tail → head
Describe the makeup and function of an arthropod’s exoskeleton.
→ Protect the arthropod’s body → Composed of layers of proteins and chitin (a polysaccharide) → Can be thick and hard, or thin and flexible at the joints → Impermeable to water and many chemicals → Needs to be moulted/shed (ecdysis) in order for the arthropod to grow
Describe some features of the Crustacea subphylum
→ 2-3 main body segments → antennae → ≥ 3 pairs of legs → mostly aquatic → e.g. prawns, crabs, pill bugs
Describe some features of the Myriapoda subphylum
Two main classes: Chilopoda (centipedes) → One pair of legs per body segment → Odd number of pairs of legs → Predominantly carnivorous → Largest terrestrial invertebrate predators Diplopoda (millipedes) → Two pairs of legs on most body segments → Mostly detritivores (dead plant material) → Distinct head with chewing mouthparts → Terrestrial
Describe some features of the Chelicerata subphylum.
→ Includes horseshoe crabs and arachnids → One or two main body segments → 6 pairs of appendages • Chelicerae (pincer-/claw-like appendages near their mouths) • Pedipalps (pincers on scorpions, sensory appendages on arachnids) • 4 pairs of legs → Terrestrial and aquatic
Describe some features of the Hexapoda subphylum.
→ Includes insects, ∴ important for agriculture → 3 main body segments (head, thorax, abdomen) → Antannae → Three pairs of legs → Many have two pairs of wings → Mostly terrestrial
True or False? Crustacea have 2 or 3 body segments
True.
True or False? Crustacea have antennae
True.
How many pairs of legs do arthopods in the Crustacea subphylum have?
Equal to or greater than 3
Arthropods in the Myriapoda subphylum have sucking mouthparts
False; they have chewing mouthparts.
Give 2 examples of Myriapoda
→ Centipedes (Chilopoda) → Millipedes (Diplopoda)
What does the ‘Chilo’ and ‘Diplo’ prefixes represent for the two main classes of Myriapoda?
The number of pairs of legs per body segment. • Chilopoda (centipedes) = 1 pair/segment • Diplopoda (millipedes) = 2 pairs/segment
True or False? Diplopoda are predominantly carnivorous
False. Millipedes are mostly detritivores.
True or False? Chilopoda are predominantly carnivorous
True. Chilopoda = centipedes
True or False? Centipedes have 2 pairs of legs/body segment (i.e. are members of the Diplopoda class)
False. Centipedes (Chilopoda) only have one pair of legs/segment
True or False? Millipedes have 2 pairs of legs/body segment (i.e. are members of the Diplopoda class)
True.
Arachnids are members of the Hexapoda subphylum
False. (They’re members of the Chelicerata subphylum)
What are Chelicerae?
Pincer-/claw-like appendages near the mouths of arthropods in the Chelicerata subphylum (e.g. arachnids).
How many pairs of legs do arthropods in the Chelicerata subphylum have?
Four
What are pedipalps, and which arthropod subphylum has them?
Pedipalps are appendages near the heads of Chelicerata (e.g. arachnids). In spiders they’re sensory appendages, in scorpions, they’re their pincers.
How many body segments do members of the Chelicerata subphylum have?
One or two.
How many body segments do members of the Hexapoda subphylum have?
Three (head, thorax, abdomen).