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Animal and Vet Biology (Wk 5) Lecture 2 (Phylum Nematoda: Roundworms…
Animal and Vet Biology (Wk 5) Lecture 2
Body cavities
Acoelomate
No body cavity e.g. Phylum latyhelminthes
Coelomate
Fluid filled cavity that lies between the gut and body wall. Lined by mesoderm on both sides
Benefits
Seperate control of organs eg body musculture and gut
circulatory system
greater body complexity
independent movement of body wall and enclosed organs
waste removal
function as hydrostatic skeleton
storage area for egg and sperm
Lophotrochozoan Phyla
Molluscs - non segmented
Chitons, Gastropod, bivalves, cephalopods
snail =ventral nerve cord, surrounds gastro intestinal tract, sensory structures, have shell, formation of gills
Annelids - segmented
Segmented worms
Leeches, fire worms, earthworms, tree worm
segmentation = better control of body sections and diversifiction of function
Phylum Acanthocephala
Group for organisms-realated to rotifers
use arthropods as intermediate host
Macracanthorhynchus hirudinaceus
Inserts into intestinal lining
Use pigs as definitive host
Lifecycle
Proboscis penetrates intestinal lining
lives within intestine
reproduce
eggs pass with faeces
ingested by beetle larvae
pigs eat beetle or beetle larvae
process starts again
Ecdysozoans
shedding exoskeletons
includes nematodes and arthopods
Phylum Nematoda: Roundworms
Fresh water and marine sediment, soil (mainly crawling in surface between sand grains etc) dwellers
Major role in ecosystems as decomposers
Many parasites
Non-segmented, cylindrical body tapered both ends
Shed cuticle as each moult
Microsopic and everywhere!!
Most dioecious (both sexes), sexual reproduction, fertilisation internal
Features
Triploblastic three cell layers
Body wall lined by thick cuticle secreted by underlying epidermis
Body cavity = pseudocoelom
Body with longitudinal muscles only
No respiratory or circulatory system, internal transport via body fluid
Covered by exoskeleton (cuticle) quite hard and is secreted by the epidermis
Have mouth and anus
nerve ring gives rise to sensory structures = blind but bilaterally symmetrical and therefore have locomotion
Moulting
Nematodes moult to shed old exoskeleton and grow
Moulting may be associates with change of environment, reproduction, behaviour of nematode
larvae hatched from egg of nematode = needs to grow
Is restricted by cuticle = in order to grow further it must moult
Process =Hatch then they are larva then they moult
Movement in nematodes
Muscles act on exoskeleteon which is rigid, resilient and flexible
movement in serpentine
moves through substrates
First multicelular organism to have its genome sequnced
short generation time
Parasites
Haemonchus contortus
Blood feeder through blood letting
Major parasite of sheep
occurs in summer rainfall areas
showing strong resistance to anti-worm treatmenrs
Life cycle
Worms living stomach of sheep
Eggs pass with faeces
Larva 1 feed on bacteria in faeces
Moult to L2 and L3 in faeces
L3 migrate to climb grass blades
Sheep eats grass = infected with L3
Hookworms
Nermatodes with prominant mouth region
Parasites of human and animals
Dog and human hookworms
Suck blood relatve to body size
Very wastefu feeders = can cause enmaemia
lifecycle
live in gastrointestina tract
eggs pass through faeces
develop in faeces
climb onto grass blades
Can penetrate through the skin iof their host
Ascarids
Large intestinal worms
Causes disease by occluding intestine and because of aberrant migration in host
Females lay VERY resistant eggs
Out compete host for food in large populations
In humans, pigs, horses, dogs
Horses life cycle
eggs ingested by horse
larvae hatches in small intestine
burrows into wall of small intestine
Migrates till it find blood vessel = finds lungs
Moves through from lungs to trachea and back to SI
Adult are the in small intestine, passes through faeces process begins again
Parascaris
lung effects
loss of energy
colic
Pinworms
Live in large intestine
Dog Heartworm
Right side of heart and pulmonary artery
Lifecycle
Adults worms live in blood system
Gets carried by mosquitos from dog to dog
females lay larvae, into bloodstream
Larvae eaten or drank by mosquito and they migrate to the salivary glands
Plant parasitic nematode
Many nematodes attack plants
Nematodes are soil dwellers
Live in abundance in soil
attach to the roots
can be devastating
Mechanical and chemical injury
Secondary infections at wound site
enhance infections at wound site
enhance secondary disease organisms
plants lose ability to withstand water stressed
Ectopararsotes
endoparasites = migrated into plant
attach to cells within he plan
changes structure of plant
females become large worm = extends out from roots
males are free from migratory and will attach to the demale
Nematomorpha
Horse hair worms
Larvae parasitic -
Near dead inscet
Parasitic in insects, when ready to produce, induce insect t go to water, parasite will burst out of insect to get to water
Infect a range of insects
Mass of worms