Midterm II (Non-arthropod ecdysozoa)

Question 1

Phylum Nematoda

Answer 1

• “thread”; roundworms; <5 cm
• around 30,000-1 000 000 spp!
• V. abundant all over world; high human impact
• solid/oceans/FW/polar/mountains/plants/animals
• Most important of all parasitic animal groups
• Ecto- and endoparasites: plants and animals; crops
• Adapted mouth parts (hooks, etc.)
• Reproduction (100 000s of eggs)

Question 2

Nematoda morphology

Answer 2

• Thick cuticles (collagen) = defense and support
• Fluid-filled pseudocoelom functions as a hydrostatic skeleton
• No circular muscles (4 quadrants extend to pseudocoelem; antagonistic muscle support from cuticle)
• Thrashing motion in water, more controlled in soil

Question 3

Examples of common nematode parasites

Answer 3

1. Intestinal Roundworm (Ascaris)
   - up to 1 billion people infected!
2. Hookworm (blood suckers)
   - around 650 million people infected
3. Pinworms
   - don’t need an intermediate host
   - most common nematode parasite of developed countries
4. Filarial worms
   - arthropod transmission
   - around 200 million people infected

Question 4

Caenorhabditis elegans

Answer 4

• free-living, non-hazardous/infectious/pathogenic/parasitic
• around 1mm; lives in soil/rotting vegetation; feeds on bacteria and yeast
• One of most important experimental biological models
• All 959 cells traced from zygote to adult
• Entire nervous system known
• Genome entirely mapped and all 19 820 genes sequenced

Question 5

Phylum Nematomorpha

Answer 5

• “thread + form”; horsehair worms
• up to 1 m long!
• around 320 species; live in wet/moist areas
• Pseudocoelomates
• Semi-parasitic (via eating/drinking water)
  
  • adults free-living
  • parasitic in arthropods as juveniles
• Paragodius obamai: parthenogenetic
• Intermediate (halted) and definitive host for development; bit free-living reproduction
• Encysts on vegetation or in intermediate host

Question 6

Parnarthropoda -> Phylum Onychophora

Answer 6

• “claw + to bear”; velvet worms
• around 200 species
• 500 million yr history in fossil record. originally marine
• Tropical and subtropical leafy habitats (high moisture)
• Caterpillar-like; 0.5-15 cm
• Mostly predators (insects/snails/worms) w slime
• Soft cuticle - repels water (“velvet”)
• 14-43 pairs of unjointed legs w pad and 2 claws

Question 7

Panarthropoda -> Phylum Tardigrada

Answer 7

• “slow + step”; moss piglets, water bears!
• Marine, freshwater, damp terrestrial (mosses, lichens)
• around 1150 species; < 1 mm
• 8 unjointed legs w claws
• Pair of sharp stylets (some) and sucking pharynx
  
  • piercing and sucking plant juices or other small invertabrates
• Parthenogenetic or sexual
• Cryptobiosis!!