Week 10, Arthropoda

Question 1

Describe the general characteristics and biology of arthropods

Answer 1

→ 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

Question 2

What is “ecdysis”?

Answer 2

Moulting to shed an exoskeleton

Question 3

What is hemolymph?

Answer 3

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

Question 4

Describe the makeup and function of an arthropod’s exoskeleton.

Answer 4

→ 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

Question 5

Describe some features of the Crustacea subphylum

Answer 5

→ 2-3 main body segments

→ antennae

→ ≥ 3 pairs of legs

→ mostly aquatic

→ e.g. prawns, crabs, pill bugs

Question 6

Describe some features of the Myriapoda subphylum

Answer 6

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

Question 7

Describe some features of the Chelicerata subphylum.

Answer 7

→ 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

Question 8

Describe some features of the Hexapoda subphylum.

Answer 8

→ 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

Question 9

True or False?

Crustacea have 2 or 3 body segments

Answer 9

True.

Question 10

True or False?

Crustacea have antennae

Answer 10

True.

Question 11

How many pairs of legs do arthopods in the Crustacea subphylum have?

Answer 11

Equal to or greater than 3

Question 12

Arthropods in the Myriapoda subphylum have sucking mouthparts

Answer 12

False; they have chewing mouthparts.

Question 13

Give 2 examples of Myriapoda

Answer 13

→ Centipedes (Chilopoda)

→ Millipedes (Diplopoda)

Question 14

What does the ‘Chilo’ and ‘Diplo’ prefixes represent for the two main classes of Myriapoda?

Answer 14

The number of pairs of legs per body segment.

• Chilopoda (centipedes) = 1 pair/segment
• Diplopoda (millipedes) = 2 pairs/segment

Question 15

True or False?

Diplopoda are predominantly carnivorous

Answer 15

False.

Millipedes are mostly detritivores.

Question 16

True or False?

Chilopoda are predominantly carnivorous

Answer 16

True.

Chilopoda = centipedes

Question 17

True or False?

Centipedes have 2 pairs of legs/body segment (i.e. are members of the Diplopoda class)

Answer 17

False.

Centipedes (Chilopoda) only have one pair of legs/segment

Question 18

True or False?

Millipedes have 2 pairs of legs/body segment (i.e. are members of the Diplopoda class)

Answer 18

True.

Question 19

Arachnids are members of the Hexapoda subphylum

Answer 19

False.

(They’re members of the Chelicerata subphylum)

Question 20

What are Chelicerae?

Answer 20

Pincer-/claw-like appendages near the mouths of arthropods in the Chelicerata subphylum (e.g. arachnids).

Question 21

How many pairs of legs do arthropods in the Chelicerata subphylum have?

Answer 21

Four

Question 22

What are pedipalps, and which arthropod subphylum has them?

Answer 22

Pedipalps are appendages near the heads of Chelicerata (e.g. arachnids).

In spiders they’re sensory appendages, in scorpions, they’re their pincers.

Question 23

How many body segments do members of the Chelicerata subphylum have?

Answer 23

One or two.

Question 24

How many body segments do members of the Hexapoda subphylum have?

Answer 24

Three (head, thorax, abdomen).

Question 25

How many pairs of legs do members of the Hexapoda subphylum have?

Answer 25

Three.

Question 26

# True or False? Hexapoda have antennae

Answer 26

True.

Question 27

# True or False? Chelicerata have antennae

Answer 27

False.

Question 28

# True or False? Myriapoda often have wings.

Answer 28

False. ## Footnote (Hexapoda often have wings. Myriapoda includes centipedes (Chilopoda) and millipedes (Diplopoda))

Question 29

# True or False? Isopoda are an order of Hexapoda

Answer 29

False. ## Footnote (Isopoda are an order of Crustacea, and include slaters and pillbugs)

Question 30

# True or False? Slaters and pillbugs are members of the Hexapoda subphylum

Answer 30

False. ## Footnote (They are a member of the Crustacea subphylum)

Question 31

# True or False? Isopoda are mostly aquatic

Answer 31

True.

Question 32

# True or False? Isopoda expel their waste as urine

Answer 32

False ## Footnote (They conserve water by releasing it directly into the air as ammonia)

Question 33

# True or False? Slaters and pillbugs aren't generally problems in the garden

Answer 33

True. ## Footnote (They're primarily detritivores, however they will occasionally feed on young seedlings, but the damage is usually minimal.)

Question 34

What is interesting about the way Isopods moult?

Answer 34

They moult half of their exoskeleton at a time. The posterior half is moulted first, then the anterior half 2 or 3 days later.

Question 35

What are landhoppers?

Answer 35

→ Members of the Amphipoda class (Crustacea phylum). → Common under stones (they require a moist, humid environment) → Eat decaying plant material → Jump around when disturbed

Question 36

Describe some biological and morphological features of Chilopoda (centipedes)

Answer 36

→ 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)

Question 37

What is the main difference between anamorphic and epimorphic development in Chilopoda (centipedes)?

Answer 37

**Anamorphic development:** → Legs added during moults **Epimorphic development:** → Born with all legs

Question 38

How do Diplopoda aid in building soil fertility?

Answer 38

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.

Question 39

# True or False? The first segment of Diplopoda has no legs.

Answer 39

True

Question 40

# True or False? ALL of the segments of Diplopoda have two pairs of legs

Answer 40

False. ## Footnote (The first segment has none, and the following 3 segments only have one pair each.)

Question 41

# True or False? Diplopoda reproduction is asexual

Answer 41

False. ## Footnote (Millipedes reproduce sexually.)

Question 42

# True or False? Certain species of Diplopoda look very similar to Isopoda.

Answer 42

True. ## Footnote (Pill millipedes look very similar to pillbugs. They can even roll themselves into a ball in the same way.)

Question 43

How can you tell the difference between a pill millipede (Diplopoda) and a pillbug (Isopoda)

Answer 43

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.

Question 44

Why are Portuguese millipedes (for example) less active in summer?

Answer 44

They rely heavily on water availability, which is reduced in summer.

Question 45

When is the peak 'seasons' for diplopoda?

Answer 45

1. Autumn 2. Spring