Arthropods (Chelicerata)

Question 1

what is the name of the first segment on an arthropod (prostomium)?

Answer 1

acron

Question 2

what is the name of the last segment on an arthropod (pygidium)?

Answer 2

telson

Question 3

what are some differences between annelids and arthropods?

Answer 3

annelid
- has coelomic spaces in each segment
- longitudinal and circular muscles
- closed blood vasculature
- hydrostatic support

arthropod
- limited number of small coeloms, mostly hemocoel
- bundles/bands of muscles
- one dorsal vessel that dumps blood into hemocoel
- cuticular support

Question 4

what are the layers of an arthropod cuticle?

Answer 4

topmost = epicuticle (waxy lipid based, may have seta sticking out)
procuticle (middle portion) = exocuticle (protein based with pigments) and endocuticle (calcium carbonate based)

Question 5

what glands in the epidermis contribute to the cuticle?

Answer 5

• trichogen gland: forms seta projections
• dermal gland: replenishes epicuticle by secreting new material

Question 6

what is ecdysis?

Answer 6

molting
- costs lots of energy, makes organism vulnerable but can clean exterior and allow for reproduction

Question 7

describe the pathway of blood in an arthropod

Answer 7

• heart
• arteries
• hemocoel
• vessels (systemic) and gills (pulmonary)
• ostia
• heart again

Question 8

what two “groups” are within Arthropoda?

Answer 8

Mandibulata and Chelicerata

Question 9

Chelicerata
what classes are within Chelicerata?

Answer 9

Arachnida, Pycnogonida (sea spiders), Xiphosura (horseshoe crabs)

Question 10

which groups have biramous legs?

Answer 10

Trilobitomorpha and Mandibulata have them, Chelicerata do not

Question 11

where are the mouthparts on different arthropods?

Answer 11

Trilobitomorpha = segment 2
Mandibulata = segment 3
Chelicerata = segment 1

Question 12

how do the number of body sections differ between arthropods?

Answer 12

Trilobitomorpha and Mandibulata = 2-3 tagmata (head, abdomen, thorax)
Chelicerata = 1-2 tagmata

Question 13

Chelicerata
how does respiration differ between Xiphosura and Pycnogonida?

Answer 13

Pycnogonida = no gills, respiration done through leg appendages
Xiphosura = book gills

Question 14

Chelicerata
how do the body plans differ between Xiphosura and Pycnogonida?

Answer 14

Xiphosura:
- large mantle shell covering entire dorsal body
- book gills
- long telson

Pycnogonida:
- respiration done on leg appendages
- no telson

Question 15

Chelicerata
what structure was adapted to give spiders silk threads?

Answer 15

metanephridia

Question 16

Chelicerata
how many segments do arachnids have?

Answer 16

6 anterior, 5-6 posterior