Unit 9 - Ecdysozoa Flashcards
ecdysis
Unifying characteristic: shedding/molting of the cuticle
Nematoda
- 25,000 species
- Thread-like
- Found everywhere
Ecdysozoa
- includes: Nematodes, Nematomorpha, Kinorhyncha, Tardigrada, and Arthropoda
- all have cuticle that is molted
Acoelomate, pseudocoelomate, or eucoelomate?
Pseudocoelomates
Hydrostatic pressure
Very high pressure in body cavity
Collagen
Structural protein that makes up the cuticle
Cuticle
- Has a distinct criss-cross pattern of collagen
- has to be shed for growth to occur
Muscle arms
extensions of muscle cell that connect to nerve cords
opposite of normal pattern
Complete or incomplete gut?
Complete
Digestive system
- Mouth
- Muscular pharynx
- Non-muscular intestine
- Anus - waste is projected due to pressure in the body
Nematoda sperm
- Non-flagellated sperm, instead are ameoboid cells that move with pseudopodia
Ascaris life cycle
- Eggs swallowed -> juveniles hatch in small intestine and burrow through intestinal wall and into blood -> heart -> lungs -> trachea -> stomach -> adults move to small intestine -> eggs are released in feces -> eggs swallowed
Necator
- Hookworm
- Plates for feeding
- Burrows through skin
Trichinella
- Trichina worm
- In meat, raw/under cooked
- produce live offspring
Enterobius
- Pinworm
- Eggs ingested
- Adults found in large intestine
- Eggs laid around the anus at night
- most common in US
Filarial Worms
- Transmission: mosquitoes, black flies
- Live in the lymphatic system
Nematomorpha
- called horsehair worms
- juveniles are parasitic on arthropods
- adults are free living in aquatic or moist habitats
Clade Panarthropoda
Three phyla: Onychophora, Tardigrada, and Anthropoda
Hemocoel
Cavity lined with extracellular matrix, not lined with mesoderm
Circulatory system
Open, but have some vessels and a heart
Phylum Tardigrada
- Water bear
- 900 species
- Small, less than a mm
- Habitat is moist, but sometimes dries out
- Have four pairs of short, stubby, unjointed legs
- Have a pointy straw used to suck fluid during feeding
Cryptobiosis
- Found in tardigrada
- Secretive life
- Suspended animation
- Metabolism shuts down in poor conditions and can then turn back on
Ecdysozoan Phylogeny
- Details are iffy, a lot of relations are undetermined
- Nematoda and Nematomorpha sister groups
- Panarthropoda
Eutely
Trait that some nematodas have: a fixed number of cells at maturity
Nematode reproduction
dioecious
internal fertilization
males have copulatory spicules
Kinorhyncha
- “movable beak”
- marine worms
- live mostly in sediment
