Midterm II (Arthropoda)

Question 1

Ecdysozoa

Answer 1

“To strip off” (AKA moult)

Question 2

The Panarthropoda

Answer 2

• with arthropods
• small coelem
• ventrolateral appendages/walking pairs
• Hemocoel and open circulatory system (Blood + lymph = hemolymph)

Question 3

Phylum Arthropoda

Answer 3

• “joint + foot”
• Over 80% of named animals
• 1.5 million + species
  What are they?
• inverted with segmented bodies, jointed limbs, and an exoskeleton made of chitin
• Marine, freshwater, terrestrial…
  Synapomorphies:
• Compoud eye
• 1 pair of antennae
• Chitinous exoskeleton with articulated appendages

Question 4

Why are they so diverse?

Answer 4

1. Exoskeleton
   - chitinous cuticle: protection + mobility
2. True segmentation and appendages
   - specialized functions; locomotion
3. Respiration -> metabolism
4. Sense organs
5. Complex Behaviour
6. Metamorphosis
   - more niches available

Question 5

Basic Terminology

Answer 5

Tagmata
- groups of segments that work together for a common function
- head, thorax, abdomen
Uniramous (one claw) vs Biramous (two claws)
- Chelicerae (fangs) vs Mandibles (chewing) (insect vs spider)

Question 6

Subphylum Chelicerata

Answer 6

• Horseshoe crabs, spiders, ticks, scorpions, sea spiders
• Two tagmata: cephalothorax and abdomen
  Appendages:
• no mandibles and no antennae
• 1 pair of chelicerae, 1 pair pedipalps (manipulate food in front of mouth), and 4 pairs of walking legs (most uniramous, some biramous)

Question 7

Subphyla

Answer 7

1. Chelicerata
2. Myriapoda
3. Crustacea
4. Hexapoda

Question 8

Subphylum Myriapoda

Answer 8

• “myriad + foot”
• Centipedes and millipedes
• Two tagmata: head + trunk
  Appendages:
• mandibles
• 1 piece of antennae
• 1-2 pairs of legs per segment (centipedes have one, millipedes will have two)
• Uniramous appendages

Question 9

Subphylum Crustacea

Answer 9

• Crusta = “shell”
• 70, 000 + species
• Mostly marine; also FW and terrestrial
• Two tagmata: Cephalothorax and abdomen (some exceptions)
  Appendages
• 2 pairs of antennae
• mandibles w 2 pairs of maxillae
• 1 pair of walking/swimming legs per segment (some absent)
• All biramous (except 1st antennae)

Question 10

Crustacean Body Plan

Answer 10

1. Carapace (dorsal head cuticle covers head and thoracic sides)
2. Cephalothorax: head (feeding and sensory) + thorax (locomotion and respiration); 13 segments
3. Abdomen: Locomotion and reproduction; 6 segments

Question 11

Internal form and function (crustaceans)

Answer 11

Open circulatory system
- pumping heart (not all)
- limbs help move hemolymph around!
Gills attached to appendages
Excretory/osmoregulation through antennal glands

Question 12

Improved sensory system (crustaceans)

Answer 12

• Advanced nervous systems
  Median eye and compound eyes
• compound eyes similar to insects’
• good at detecting motion and polarized light
  Statocysts, tactile hairs
  Chemosensory -> taste and smell

Question 13

Reproduction

Answer 13

• Most have separate sexes and internal fert
• Most brood eggs
• Larval stages (e.g., nauplii, zoeae, megalopae)

Question 14

Feeding

Answer 14

• Maxillipeds, maxillae, and mandibles = hold/manipulate/shred food
• Claws (chelipeds) and waking legs = food capture, piercing/crushing
• predators, scavengers, deposit feeders, filter feeders, and parasites!