Practical 2 - Crustacean Feeding Strategies

Question 1

What is the difference between a male prawn and a female prawn?

Answer 1

Males have a petasma and females have a thelycum (underneath body).

Question 2

Overall body plan of a crustacean.

Answer 2

Head: 2 pairs antennae, mandible, 2 maxillae.
Thorax (or pereon) may be fused with head to form cephalothorax: 8 pairs thoracopods - 3 maxillipeds, 5 pereiopods.
Abdomen (or pleon): Up to 6 pairs pleopods (including the uropods).

Question 3

Feeding strategy: Planktonic crustacea.

Answer 3

Planktonic crustacea e.g. some copepods use mouth appendages like paddles to funnel water to the mouth.

Question 4

Feeding strategy: Barnacles and krill.

Answer 4

Barnacles use cirri (feathery thoracopods) to filter feed. Krill similar to barnacles but form a feeding basket with appendages.

Question 5

Feeding strategy: suspension feeding.

Answer 5

Some suspension feed in burrows by driving water by beating their pleopods and removing food.

Question 6

Feeding strategy: depoist feeding.

Answer 6

Deposit feeders – various methods of removing food from sediment e.g. some copepods ‘sand lick’.

Question 7

Feeding strategy: predatory.

Answer 7

Grasp prey with chelate (sometimes with mouth) – tear, grind or shear with mouthparts (mandibles mainly).
Stab or club or ambush and inject to stun/kill prey – a shock wave produced when a cheliped is snapped quickly closed (snapping shrimps).

Question 8

Feeding strategy: herbivory.

Answer 8

Macrophagous herbivores and scavengers hang on to food and bite bits off with mandibles.

Question 9

Feeding strategy: parasitic.

Answer 9

Ectoparasites (mouth parts for piercing, tearing and sucking body fluids) fully parasitic throughout host tissue absorbing nutrients directly. In some the parasite takes over complete control of the host’s body enslaving it.

Question 10

Suborder Pleocyemata. Infraorder Brachyura. ‘True’ crabs.

Answer 10

Marine, freshwater semi-terrestrial and moist terrestrial. Abdomen symmetrical, reduced and flexed beneath thorax. First pereopods are chelate and enlarged.

Question 11

Larval stages of a decapod crustacean.

Answer 11

Naupilus; Zoea; Megalopa.

Question 12

Carcinus maenas

Answer 12

Omnivore – plants and animals – eat a lot of mussels.
Third maxilliped covers the mouth.
Second and third maxilliped similar to third but smaller.
Mandibles for cutting.
Between mandibles is the mouth.

Question 13

Penaeids. Suborder Dendrobranchiata.

Answer 13

Penaeids (benthic or pelagic) and sergestid (pelagic) shrimps.
Chelae on first 3 peropods.
Animals generally >30cm long.
Some e.g. Penaeus, are of major commercial importance.
Feeding using maxillae, maxillipeds, mandible etc.