ecdysozoans; nematodes

Question 1

what two phylums of ecdysozoans do we consider

Answer 1

nematoda and athropoda

Question 2

ecdysis means

Answer 2

shedding exoskeleton

Question 3

nematodes (roundworms) charcateristics

phylum within ecdysozoans

Answer 3

• most microscopic
• ubiquitous (found everywhere)
• interstitial dwellers (freshwater and marine sediments, soil)
• major role in ecosystems as decomposers
• many parasites
• non segmented, cylindrical body
• tapered at both ends
• ecdysis; shed cuticle at each moult
• complete gut with mouth and anus
• most dioecious, sexual reproduction, internal fertilization

Question 4

are nematodes (roundworms) segmented

Answer 4

no

Question 5

describe nematode gut

Answer 5

complete gut with mouth and anus

Question 6

describe nematode (roundworm) reproduction

Answer 6

sexual reproduction, dioecious, internal fertilization

Question 7

nematodes are _______ (in terms of germ layers)

Answer 7

triploblastic; 3 cell laters

Question 8

what is nematode body wall lined with

Answer 8

thick cuticle secreted by underlying epidermis

(hold v high internal pressure, v hard, v resilient, durable, pliable, exoskeleton)

Question 9

what is nematode body cavity

Answer 9

pseudocoelom: intermediate form of cavity, lined by mesoderm on one side only

Question 10

nematode muscles are _____

Answer 10

longitudinal

Question 11

describe nematode circulatory and respiratory system

Answer 11

• none, internal transport via body fluid

Question 12

many annuli (rings) in the cuticle but nematodes are NOT

Answer 12

segmented

Question 13

nematode excretory system

Answer 13

rather complex, rather distinct pore and canals that drain the pseudocoelomic cavity;

osmoregulatory rather than excretory (ie removes salts not nitrogenous wastes)

Question 14

nematodes moulting

Answer 14

nematodes moult to shed old exoskeleton and grow
moulting may be associated w change of environment, reproduction, behaviour of nematode

Question 15

how many larval stages do nematodes have

Answer 15

4

Question 16

egg to adult cycle

Answer 16

egg, hatch, L1, moult, L2, moult, L3, moult, L4, moult, adult

will also moult as adult

will generate new cuticle while they are in old cuticle

Question 17

movement of nematodes

Answer 17

• think hard spaghetti, only bend slightly
• muscles attached so as to flex body in one plane; dorso ventral
• muscles act on exoskeleton which is rigid, resilient and flexible
• hydro “skeleton” high internal pressure acts to bring body straight
• movement in serpentine (S shaped flexing, snake like)
• move in aquatic, interstitial or across substrates

Question 18

model organism of nematodes

Answer 18

• caenorhabditis elegans
• free-living soil nematode
• first multicellular organism to have its genome sequenced
• few cell types
• short generation time
• ancestry of each cell established

Question 19

haemonchus contortus

nematode example

Answer 19

• barbers pole worm
• blood feeder, by blood letting
• major pathogen (parasite) of sheep (a related species in cattle)
• occurs in summer rainfall areas (QLD, northern NSW)
• resistance to anthelminthics (anti-worm) treatments well entrenches
• some regions (ex south africa) can’t sustain flocks due to drug resistant strains

Question 20

life cycle of haemonchus contortus (barbers pole worm)

nematode

Answer 20

• adult worms in abomasum of sheep
• eggs pass w feces
• 1st stage larval L1 hatch-feed on bacteria in feces
• molt to L2 then L3 in feces (molt twice in feces)
• L3 migrate in moisture away from feces, climb grass blades (need moisture to move, usually from early morning dew or rainfall)
• sheep infected by eating grass w L3s

Question 21

another important nematode example that is a parasite of humans and dogs among others

Answer 21

hookworms

Question 22

dog hookworm name

Answer 22

ancylostoma caninum

Question 23

human hookworm name

Answer 23

necator americanus

Question 24

how hookworms feed

nematode

Answer 24

swim to intestinal lining, sucks plug of tissue into mouth and spits it out, sucks back in over over and over, secreting enzymes, overtime breaks down the tissue, then blood flows into hookworm, wasteful feeders

Question 25

hookworm (nematode) life cycle

Answer 25

- start in intestine, sexual reproduction - egg released into feces - larva hatches in feces, feeds on bacteria in feces - migrates across grass/soil, sits on grass, waits to be ingested - migrate through blood vessels, reach the lungs, burst from blood vessels of lungs into lumen on lungs, get up to throat, get swallowed down

Question 26

ascarids (nematode)

Answer 26

- large intestinal worms in mammals - cause disease by occluding intestine and because of aberrant migration in host (trying to escape dewormer) - compete with host for food - females lay desiccation resistant eggs, do not hatch in environment

Question 27

what are the ascarid names of pigs, humans, horses and dogs

Answer 27

- pigs: ascaris suum - humans: ascaris lumbricoides - horses; parascaris equi -dogs; toxocara canis

Question 28

looking at horse ascarid: parascaris equi life cycle

Answer 28

- in horses adult parasite takes up to 12 weeks to develop, lives in small intestine, sexual reproduction, produce many many offspring - eggs in feces - eggs can survive on pasture for years - eggs will mature but not to hatch - eggs ingested by horse, usually foal - larva hatches in small intestine - larva burrow into walls of small intestine, finds blood vessel - lungs; burst into alveoli - somehow get up to trachea then swallowed

Question 29

looking at horse ascarid: parascaris equi how do they effect equine host

Answer 29

- lung effects due to migrating larva, can lead to pneumonia - loss of energy - colic - intestinal perforation - intestinal obstruction

Question 30

another example of nematodes: pinworms

Answer 30

- small worms in rectum of mammals - not pathogenic, feed on bacteria within host - in large intestine, can migrate and cause issues but don't usually - become problematic when migrate out of host through anus, causes intense irritation, common in kids

Question 31

pinworm name in horses and humans

Answer 31

- horses: oxyuris equi - humans: enterobius vermicularis

Question 32

dog heartworm; name and where they occur nematode

Answer 32

dirofilaria immitis - adult worms; right side of heart and pulmonary artery (also occurs in cats)

Question 33

life cycle of dog heartworm (dirofilaria immitis) nematode

Answer 33

- adult worms in pulmonary artery of dog - adult worms produce infective stage; microfilaria L1st still encased in sheath (egg shell) - microfilaria (larva) in blood, ingested by nosquito - mosquiro vector transmits heartworm w blood meal - microfilaria develop to L3s in muscle - migrate of salivary glands and mosquito mouthparts

Question 34

Lymphatic filariasis; wuchereria bancrofti

Answer 34

- Worms sit in lymph ducts and block lymph flow; enlarge limbs, causes intense pain and secondary infection - Elephantiasis; not a common phenomenon; grossly enlarged limbs by parasites - Good strategies for disease minimization so not as common

Question 35

Trichinella spiralis; nematode

Answer 35

- Parasite than involves predation of host, transmitted from mammal to mammal by mammals eating eachother - Adults in intestine of host, offspring in muscle, new host infected by eating that muscle - The worm that would be virus; invades cells - Only worm species that becomes an intracellular parasite - Larva in nurse cell in skeletal muscle - Adult in intestine - Is able to change the cells in which it lives, ex gets contractile cell and makes it become a nurse cell; able to take over cell

Question 36

Trichuri trichiura; nematode

Answer 36

- Whipworm - Common parasite of animals and humans

Question 37

Plant parasitic nematodes

Answer 37

- Many nematodes attack plants - Nematodes soil dwellers - Attach to roots - Some migrate to other regions of plants - Can be devastating to agriculture - Mechanical and chemical injury - Secondary infections at wound site - Enhance secondary disease organisms - Plants lose ability to withstand water stresses

Question 38

Types of plant parasites

Answer 38

Ectoparasites Migratory endoparasites Sedentary endoparasites Sedentary semi-endoparasites

Question 38

Heterodera glycines

Answer 38

Soybean cyst nematode Infect root of hosts

Question 39

Phylum nematomorpha

Answer 39

- Horsehair worms, often seen animal animal drinking troughs - Can be very large - Quite common, NOTHING to do with animals however, parasites of INSECTS - Breed in freshwater locations - Larvae parasitic; drives insects to water when adult and escape into water - Adults mate in large aggregations: “gordioidea” ; gordian knot, the worms form like a mass of worms in a knot - Insects infected when drinking water - When worms mature they induce host to go to water and burst from insects body