ecdysozoans; nematodes Flashcards
what two phylums of ecdysozoans do we consider
nematoda and athropoda
ecdysis means
shedding exoskeleton
nematodes (roundworms) charcateristics
phylum within ecdysozoans
- 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
are nematodes (roundworms) segmented
no
describe nematode gut
complete gut with mouth and anus
describe nematode (roundworm) reproduction
sexual reproduction, dioecious, internal fertilization
nematodes are _______ (in terms of germ layers)
triploblastic; 3 cell laters
what is nematode body wall lined with
thick cuticle secreted by underlying epidermis
(hold v high internal pressure, v hard, v resilient, durable, pliable, exoskeleton)
what is nematode body cavity
pseudocoelom: intermediate form of cavity, lined by mesoderm on one side only
nematode muscles are _____
longitudinal
describe nematode circulatory and respiratory system
- none, internal transport via body fluid
many annuli (rings) in the cuticle but nematodes are NOT
segmented
nematode excretory system
rather complex, rather distinct pore and canals that drain the pseudocoelomic cavity;
osmoregulatory rather than excretory (ie removes salts not nitrogenous wastes)
nematodes moulting
nematodes moult to shed old exoskeleton and grow
moulting may be associated w change of environment, reproduction, behaviour of nematode
how many larval stages do nematodes have
4
egg to adult cycle
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
movement of nematodes
- 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
model organism of nematodes
- 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
haemonchus contortus
nematode example
- 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
life cycle of haemonchus contortus (barbers pole worm)
nematode
- 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
another important nematode example that is a parasite of humans and dogs among others
hookworms
dog hookworm name
ancylostoma caninum
human hookworm name
necator americanus
how hookworms feed
nematode
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
hookworm (nematode) life cycle
- 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
ascarids (nematode)
- 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
what are the ascarid names of pigs, humans, horses and dogs
- pigs: ascaris suum
- humans: ascaris lumbricoides
- horses; parascaris equi
-dogs; toxocara canis
looking at horse ascarid: parascaris equi
life cycle
- 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
looking at horse ascarid: parascaris equi
how do they effect equine host
- lung effects due to migrating larva, can lead to pneumonia
- loss of energy
- colic
- intestinal perforation
- intestinal obstruction
another example of nematodes: pinworms
- 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
pinworm name in horses and humans
- horses: oxyuris equi
- humans: enterobius vermicularis
dog heartworm; name and where they occur
nematode
dirofilaria immitis
- adult worms; right side of heart and pulmonary artery
(also occurs in cats)
life cycle of dog heartworm (dirofilaria immitis)
nematode
- 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
Lymphatic filariasis; wuchereria bancrofti
- 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
Trichinella spiralis; nematode
- 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
Trichuri trichiura; nematode
- Whipworm
- Common parasite of animals and humans
Plant parasitic nematodes
- 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
Types of plant parasites
Ectoparasites
Migratory endoparasites
Sedentary endoparasites
Sedentary semi-endoparasites
Heterodera glycines
Soybean cyst nematode
Infect root of hosts
Phylum nematomorpha
- 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
