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Hilary Term 1 > The Ecdysozoa > Flashcards

The Ecdysozoa Flashcards

1
Q

The Ecydysozoa are nested within the

A

Bilateria

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2
Q

Give the Ecdysozoan Classes

A
  • Nematodes
  • Nematomorphs
  • Tardigrades
  • Onychophora
  • Arthropods
  • Priapulids,
  • Kinorhynchs
  • Loriciferans
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3
Q

Which are the ‘wormy’ Ecdysozoan Classes

A
  • Nematodes
  • Nematomorphs
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4
Q

What are the ‘leggy’ Ecdysozoan Classes

A
  • Tardigrades
  • Onychophora
  • Arthropods
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5
Q

What do the Ecdysozoa have in common?

A

cuticle moulted as animal grows

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6
Q

Describe the Ecdysozoa

A
  • stiff (rigid or bendy) cuticle evolved early on this branch
  • moulting allows growth despite cuticle that can’t stretch much
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7
Q

Describe the evolutionary constraints of a stiff cuticle

A

problems for locomotion

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8
Q

Describe the Nematoda

A
  • roundworms
  • stiff cuticle: not stretchy
  • cuticle, epidermis, body-wall muscles, pharynx muscles, ventral nerve cord, lateral cord, gonodcuct, oocyte,
  • no segmentation
  • coelom with very high liquid pressure
  • helical collagen fibres in cuticle
  • can’t expand/contract body regions
  • characteristic thrashing motion
  • e.g. “Vinegar eels”- coelom with very high liquid pressure
  • helical collagen fibres in cuticle
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9
Q

Describe Vinegar eels

A
  • Turbatrix aceti
  • live in vinegar, gone-off cider etc
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10
Q

Explain the thrashing motion of nematodes

A
  • only L, not C muscle
  • stiffness allows both sides to antagonise one another
  • coelom forms semi-rigid, liquid skeleton
  • gives ‘round’ shape
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11
Q

How do Nematoda manage their through-gut?

A
  • muscles at anus control open/close
  • muscular, triradiate pharynx (sometimes called stoma) at mouth
  • pumps food in, up to 4 pulse/second
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12
Q

Give an example of the Nematoda

A
  • Enoplus
  • 3 teeth
  • 6 inner labia papillae
  • 10 cephalic setae
  • viewed under SEM
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13
Q

Describe Nematoda springiness

A
  • specialised cuticle
  • several layers
  • helical collagen fibres compress and bend: extend the muscles
  • permeable to water and gases
  • moulted x4
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14
Q

Describe the Nematode specialised cuticle from top to bottom

A
  • 3 fibrous layers
  • basal lamina
  • epidermis
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15
Q

Summarise Nematoda locomotion

A
  • sinous body waves
  • good through soil, fruit or body tissues
  • bad swimmers
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16
Q

Give an example of Nematode ecology

A

parasitism

17
Q

Describe Ascaris suum and lumbricoides

A
  • intestinal roundworm
  • in pig or human respectively
  • single host
  • infection by ingestion of eggs in soil
  • eggs passed in pig/human faeces
  • juveniles migrate through liver and lungs back to intestine
18
Q

Describe Onchocerca volvulus

A
  • 2-host life cycle
  • in lymphatic system
  • causes inflammation
  • damages skin, eye lens and retina
  • causes river blindness
  • transmitted by blackflies in flowing water
19
Q

What are some ways in which humans use nematodes?

A
  • pesticides
  • modelling (Caenorhabditis elegans)
20
Q

Describe Phasmarhabditis hermaphrodita

A
  • used as a pesticide (slug control)
  • no risk of bioaccumulation and secondary poisoning
21
Q

Describe C. elegans

A
  • first animal to have its genome completely sequenced (1998)
  • eutelic
  • genes 959 in the adult hermaphrodite; 1031 in the adult male
  • connections of every neuron mapped (302 neurons)
  • model system in cell biology and disease genetics
  • apoptosis discovery
22
Q

eutely

A

cell lineage and fate of every cell known

23
Q

Describe Nematoda in soil

A
  • ~ 300 million tonnes of nematodes in top soil layers of earth
  • ~ 600 million tonnes of humans on the planet
24
Q

Describe the Nematomorphs

A
  • horsehair worms
  • probably sister phylum to Nematodes
  • unsegmented
  • only longitudinal muscles
  • moulted cuticle
  • very long
  • reduced, non-functional gut
  • e.g. Gordius robustus
25
Q

Describe the life history of the Nematomorphs

A
  • adults free-living in water (don’t feed)
  • juveniles parasitic in arthropods
26
Q

Give an example of a Nematomorphic life style

A
  • free-living adults breed in water
  • nematomorph larva forms cyst inside mayfly nymph
  • mayfly hatches (with parasite inside)
  • cricket eats mayfly where larva develops
  • cricket wanders erratically back to water via nematomorph-mediated neuromodulation
27
Q

Describe the Tardigrada

A
  • cuticle, moulted
  • stumpy non-jointed legs
  • live in moss/water
  • abundant
  • tiny
  • anhydrobiotic

Hilary Term 1 (61 decks)

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