Week 10, Arthropoda Flashcards
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).
How many pairs of legs do members of the Hexapoda subphylum have?
Three.
True or False?
Hexapoda have antennae
True.
True or False?
Chelicerata have antennae
False.
True or False?
Myriapoda often have wings.
False.
(Hexapoda often have wings. Myriapoda includes centipedes (Chilopoda) and millipedes (Diplopoda))
True or False?
Isopoda are an order of Hexapoda
False.
(Isopoda are an order of Crustacea, and include slaters and pillbugs)
True or False?
Slaters and pillbugs are members of the Hexapoda subphylum
False.
(They are a member of the Crustacea subphylum)
True or False?
Isopoda are mostly aquatic
True.
True or False?
Isopoda expel their waste as urine
False
(They conserve water by releasing it directly into the air as ammonia)
True or False?
Slaters and pillbugs aren’t generally problems in the garden
True.
(They’re primarily detritivores, however they will occasionally feed on young seedlings, but the damage is usually minimal.)
What is interesting about the way Isopods moult?
They moult half of their exoskeleton at a time. The posterior half is moulted first, then the anterior half 2 or 3 days later.
What are landhoppers?
→ Members of the Amphipoda class (Crustacea phylum).
→ Common under stones (they require a moist, humid environment)
→ Eat decaying plant material
→ Jump around when disturbed
Describe some biological and morphological features of Chilopoda (centipedes)
→ 1 pair of legs per body segment
→ Mostly nocturnal
→ Generalist predators
- mostly of collembola (springtails), diptera (flies and mosquitoes), spiders, and mites
→ Use venom located in specialised appendages (first pair of legs) to immobilise prey
→ Lack a waxy coating of their cuticle, meaning they lose water easily and as such require moist microhabitats
→ Excrete nitrogen waste in water (urine)
What is the main difference between anamorphic and epimorphic development in Chilopoda (centipedes)?
Anamorphic development:
→ Legs added during moults
Epimorphic development:
→ Born with all legs
How do Diplopoda aid in building soil fertility?
Most are detritivores, and their main agroecological role is to break up dead plant material into smaller pieces, thus increasing the surface area for bacteria and fungi to feed on.
True or False?
The first segment of Diplopoda has no legs.
True
True or False?
ALL of the segments of Diplopoda have two pairs of legs
False.
(The first segment has none, and the following 3 segments only have one pair each.)
True or False?
Diplopoda reproduction is asexual
False.
(Millipedes reproduce sexually.)
True or False?
Certain species of Diplopoda look very similar to Isopoda.
True.
(Pill millipedes look very similar to pillbugs. They can even roll themselves into a ball in the same way.)
How can you tell the difference between a pill millipede (Diplopoda) and a pillbug (Isopoda)
Apart from the difference in the number of legs/segment, isopoda have 3 main body sections (head/cephalon, pereon, and pleon), which have different spacing between the ‘plates’. The spacing of the exoskeleton plates is wider at the pereon (in the middle), and shorter/tighter together towards the tail-end (pleon). Millipede exoskeleton segments are more uniform in their shape and size.
Why are Portuguese millipedes (for example) less active in summer?
They rely heavily on water availability, which is reduced in summer.
When is the peak ‘seasons’ for diplopoda?
- Autumn
- Spring
