Crustaceans – Arthropods

Question 1

What are the five subgroups of the Arthropoda?

Answer 1

1. Crustacea
2. Hexapoda
3. Trilobitomorpha
4. Cheliceriformes
5. Myriapoda

Question 2

What are examples of the Crustacea?

Answer 2

Crabs, shrimps, lobsters, barnacles, etc

Question 3

What are examples of the hexapoda?

Answer 3

Insects and their relatives (crustaceans?)

Question 4

What are examples of the trilobitomorpha?

Answer 4

Trilobites (extinct)

Question 5

What are examples of the cheliceriformes?

Answer 5

Spiders, scorpions and their kin

Question 6

What are examples of the myriapoda?

Answer 6

Many legged arthropods: centipedes, millipedes, etc

Question 7

How many described living species of Crustacea are there?

Answer 7

67,000 described living species

Question 8

What sizes do Crustaceans range?

Answer 8

100um – 3m

Question 9

What are the 3 unifying crustacean characteristics? (Crustacean bauplan)

Answer 9

1. 5-segmented head
2. Trunk region
3. Biramous limbs

Question 10

What does the 5-segmented head of Crustacea feature?

Answer 10

2 pairs of antennae, mandibles and 2 pairs of secondary mouthparts (maxillae)

Question 11

What does the trunk region of Crustacea feature?

Answer 11

It is usually divided into 2 magmata – thorax and abdomen

Question 12

What is true of the biramous limbs of the Crustacea?

Answer 12

• ‘Two-branches’
• Remipedia – ‘primitive’ body design
• Secondary uniramy (single branched limbs) is widespread

Question 13

What other features do Crustaceans (not all) have?

Answer 13

1. Carapace or cephalic shield (reduced in some groups)
2. Planktonic nautilus larva

Question 14

What are the 3 aspects of Crustacean diversity?

Answer 14

1. Diversity of segments in an adult of one species
2. Segment diversity between species
3. Diversity of segment morphology during ontogeny

Question 15

How many types of segments can be present an an adult of one species?

Answer 15

Up to 14 distinct types of segments

Question 16

What is true of segment diversity between species?

Answer 16

• A particular body segment takes many forms in different taxa.
• Tagmatisation can become extensive

Question 17

What is an example of tagmatisation becoming extensive?

Answer 17

In crabs/lobsters etc., thoracic segments become associated with the head, and their appendages function as accessory mouthparts – known as maxillipeds

Question 18

What is true of segment morphology during ontogeny?

Answer 18

3 pairs of setose appendages of nautilus larva become 2 pairs of antennae and mandibles

Question 19

What has a major role in the 3 aspects of Crustacean diversity?

Answer 19

Shifts in homeotic gene expression has a major role in all 3 aspects

Question 20

What are the features of planktonic nauplius larva?

Answer 20

• Median simple eye
• 3 pairs of setose appendages – which become 3 pairs of antennae and mandibles
• Suppressed in many groups which have direct development e.g. isopods and amphipods