Arthropoda V - Pancrustacea

Question 1

Decapoda Groups

Answer 1

Caridae - shrimp
Astacidea - crayfish & lobster
Anomura - hermit crabs, king crabs
Brachyura - true crabs

Question 2

Decapoda Characteristics

Answer 2

Well-developed carapace (covers entire thorax)
3 pairs of maxillipeds
5 pairs of pereopods

Question 3

Caridea (shrimps)

Answer 3

Delicate, slender pereopods (don’t need to be as muscular)
Large, muscular abdomen
Well developed pleopods (swimming)
Holopelagic or Pelago-benthic

Question 4

Astacidea (crayfish & lobsters)

Answer 4

More robust pereropods 
Large, muscular abdomen 
Pleopods (short swim bouts) 
Chelipeds (1st pair pereopods) 
Very calcified exoskeleton

Question 5

Brachyura (true crabs)

Answer 5

Broad, the flat cephalothorax
Heavy, robust pereopods
Chelipeds (1st pair pereopods)
Reduction of abdomen; loss of uropods
Reduction/loss of pleopods
Closed gill chambers

Question 6

True Crab Pleopods

Answer 6

Females use pleopods to hold egg masses where they brood into a later larval stage
Males have 2 pairs of pleopods
1st pair is hollow cylinders, spermatophores are placed here
2nd pair is a rod-like plunger that pushes spermatophore into female gonopore

Question 7

Anomura (squat lobster)

Answer 7

Most diverse group 
5th pair of pereopods reduced 
Muscular abdomen 
Form chelipeds
Generally benthic

Question 8

Anomura (hermit crabs)

Answer 8

Insert abdomen into gastropods shell
Asymmetric abdomen 
Reduced pleopods (none on the right side)
Uropods grip columella of shell

Question 9

Anomura (porcelain crabs)

Answer 9

3 pairs of walking legs
Reduced 4th pair, keeps gills clean
Carcinization

Question 10

Anomura (king crabs)

Answer 10

Heavily calcified exoskeleton

Carnizied

Question 11

Anomura (sand crabs)

Answer 11

Sandy habitats
Burrow using legs
2nd pair antennae for suspension feeding

Question 12

Gill Ventilation

Answer 12

In decapods with exposed gills water moves in ventrally through the openings and moves anteriorly and exits here
In decapods with closed gills (Brachyura) aperture at the anterior end, water moves in here. Moves over gills going dorsally and posterior. Move back anteriorly and out through another opening

Question 13

Gill cleaning

Answer 13

pereopod brushes in shrimp
Anomuran crabs have 5th pair pereopods are gill scrubbers
Brachyurans use epipods of the three pairs of maxillipeds as the combs to clean gills interiorly
Astacidea use setae intertwined with gills attached to walking legs, when they walk they clean the gills