Crustacea

Question 1

Give examples of crustacea.

Answer 1

Crabs, lobsters, shrimp, barnacles and pillbugs.

Question 2

What is the difference between chelicerates and mandibulates?

Answer 2

Chelicerates lack jaws, but have chelicerae as mouthparts. Mandibulates have mandibles which are jaws.

Question 3

Give general Crustacean characteristics.

Answer 3

Nearly all aquatic. Have gills apart from hermit crabs. Small ones move by water current. Can filter feed, scavenge or predate.
Body divided into 2/3 regions. In some species head and thorax are fused into a cephalothorax.
Chitinous exoskeleton.
Carapace (fold of exoskeleton over head and thorax) may be present or absent.

Question 4

Give characteristics of the Malacostraca.

Answer 4

• Largest group of Crustaceans.

- Includes decapods (crabs and lobsters) and stomatopods (mantis shrimp).

Question 5

What is the crustacean body plan?

Answer 5

• 2 pairs of antennae (large ones for taste, touch and smell, small ones for taste, touch and balance).
• Mandibles and two pairs of maxilla on head.
• Two stalked, compound eyes, can be unstalked, reduced or lost.
• 5+ pairs of legs.
• Malacostraca appendages different from other crustaceans.
• Biramous jointed legs and second antennae.

Question 6

What do biramous and uniramous mean?

Answer 6

Uniramous - one branch.

Biramous - two branches.

Question 7

What are exopods and endopods?

Answer 7

Exopods - external branch.

Endopods - internal branch.

Question 8

Give examples of specialised crustacean appendages.

Answer 8

Claws, antennae, legs, swimmerets and mandibles.

Question 9

Give characteristics of the Decapods.

Answer 9

Largest group and largest size of crustacean.
Five pairs of walking legs.
3 pairs of maxillipeds.
Cephalothorax and abdomen.
Shrimps are scavengers.
Lobsters are nocturnal.

Question 10

Give characteristics of crabs.

Answer 10

Small abdomen and wide cephalothorax.
V shaped abdomen in males, U shape in females.
Most diverse group of decapods.
Scavenge and predate.

Question 11

How do crustaceans reproduce?

Answer 11

Right after the female moults, mating occurs.
- Fertilised egg is attached to female, carried in pleopods, amphipods and isopods brood eggs in a chamber. Some release their eggs or attach them to objects. Young are small adults or larvae.

Question 12

What is a nauplius?

Answer 12

A stage of the crustacean life cycle with a single eye, three pairs of appendages (first and second antennae and mandibles). Shrimps have a nauplius.

Question 13

Give characteristics of the Isopods.

Answer 13

Pillbugs and sowbugs.
Flat body.
Mouthparts for masticating and grinding.
Females carry young in pouch.
Several jointed limbs on thorax. 
Few parasitic.

Question 14

Give characteristics of the Amphipods.

Answer 14

Laterally compressed, no carapace.
Very small.
Detritivores or scavengers.

Question 15

Give characteristics of Euphausiacea.

Answer 15

Planktonic shrimp-like crustaceans.
Carapace.
Filter-feeder; diatoms and plankton.
Polar.

Question 16

Give characteristics of barnacles.

Answer 16

Sessile.
Suspension feeding.
Hermaphroditic.
6 naupliar stages.