Subphylum Chelicerata

Question 1

What are the tagma of this subphylum?

Answer 1

1. Prosoma

2. Opisthosoma

Question 2

What is the 1st pair of appendages and their function?

Answer 2

Chelicerae (feeding)

Question 3

What is the 2nd pair of appendages and their function?

Answer 3

Pedipalps-varies depending on class

Question 4

Describe chelate appendages

Answer 4

Distal article acts as opposable thumb, operated by antagonistic muscles
Penultimate article forms other part of this claw, but doesn’t move

Question 5

What are the three main classes of chelicerates?

Answer 5

1. Merostoma (horseshoe crabs)
2. Arachnida (spiders, ticks, scorpions)
3. Pycnogonida (sea spiders)

Question 6

What are the tagmata of merostoma?

Answer 6

1. Prosoma
2. Opisthosoma
3. Telson

Question 7

Is the telson a true metamere?

Answer 7

NOOOOOOOOOOOOOOOOOO

Question 8

Name the appendages of the prosoma of horseshoe crabs and their function in order from anterior to posterior

Answer 8

1. Chelicerae (bring food to mouth)
2. Pedipalps (catch food) with gnathobase
3. Walking leg with gnathobase
4. Walking leg with gnathobase
5. Walking leg with gnathobase
6. Walking leg

Question 9

What are the appendages of the opisthosoma in merostoma?

Answer 9

1. Genital operculum

2-6 book gills

Question 10

What are book gills? What is their advantage?

Answer 10

Made of gill lamellae: delicate folds of thin exoskeleton -increase SA for gas exchange

Question 11

How were book gills modified for terrestrial gas exchange in arachnids?

Answer 11

Became internalized book LUNGS in deep in pocketing of body wall

Question 12

How does excretion of nitrogenous waste occur in arachnids?

Answer 12

The low pH of the gut causes urate to precipitate to uric acid crystals which can be excreted via the anus without much water.

Question 13

What are the openings to book lungs called in scorpions?

Answer 13

Spiracles

Question 14

What is the purpose of pectines in scorpions?

Answer 14

Have a high concentration of mechanosensory bristles to detect prey.

Question 15

What do the chelicerae do in scorpions?

Answer 15

Chelate for food manipulation

Question 16

What do the pedipalps do in scorpions?

Answer 16

Elongated and chelate for prey capture (grasping and tearing)

Question 17

What is a unique part of the scorpion?

Answer 17

The telson with the venom gland

Question 18

What do the chelicerae do in spiders?

Answer 18

They are non-chelate fangs

Question 19

What do the pedipalps do in spiders?

Answer 19

Tap for mechano sensing and transfer sperm in males

Question 20

What allows the opisthosoma of spiders to move to spin webs?

Answer 20

The thin pedicel

Question 21

What is something unique to a spider’s opisthosoma?

Answer 21

The spinnerets. Many spigots released silk, this hardens in contact with the air and the spiders weaves it into silk.

Question 22

What are the functions of spider silk? (5)

Answer 22

1. sperm transfer
2. egg cases
3. prey capture
4. aqualung in aquatic spiders
5. ballooning behavior in some juveniles

Question 23

How are tick mouthparts modified?

Answer 23

Chelicerae: slice hole in body of host
Pedipalps: support other appendages
Hypostome: anchors tick while taking blood meal

Question 24

What is unique about the opisthosoma in Pycnogonida?

Answer 24

Reduced to a little nub with the anus on it

Question 25

How many prosomal appendages do pynogonids have? What are they called

Answer 25

7 total

1. Chelicerae (non-chelate)
2. Pedipalps (sensing)
3. Ovigerous leg
4. Walking
5. Walking
6. Walking
7. Walking

Question 26

What is unique about how pycnogonids feed?

Answer 26

Use a proboscis which is a sucking tube for feeding

Question 27

What are the ovigerous legs used for?

Answer 27

Males use to brood egg mass on their ventral side