Nematodes Flashcards
What are nematodes grouped in?
The ecdysozoa
What type of coelom do nematodes have?
Pseudocoelomates - only one layer of mesoderm
Give some features of nematodes
Have a cuticle made of collagen
Undergo four moults during life
3rd larvae stage is known as dauer stage (free-living form and the most infective stage in parasitic form)
Covered in glycocalyx - protects from outer environment and bactera (it is secreted from cuticles)
Often grow when they moult - SOME can grow without moulting
Only have longitudinal muscles and no circular
No circulatory or respiratory system - relies on diffusion
Excretory canals - for water removal
Simple gut
Dioecious and have internal fertilisation (some hermaphrodites)
Some have buccal cavity modifications (stylet to stick into plants, teeth to latch onto host)
Oesophagus that is under high pressure
Sensory sensilla
Give some features of nematode reproduction
Males are usually smaller
Male seek out females
Use spicules to transfer sperm
Fertilisation happens in the uterus
Females can eject sperm from unwanted males
Give some features of parasitic nematodes
Parasitism has evolved several times
Radiation accompanied the evolution of flowering plants, insects and amniotic vertebrates
Parasitic as juveniles, adults or both
One or more intermediate hosts
Give the life cycle of a pin worm
Only human - human and has no intermediate host
Pinworm is in the human gut (often infants)
Impreganted female migrates to the host anal region at night
Zygotes released on the host, bedclothes and into airborn dust
Eggs mature to infective stage
Eggs enter new host by ingestion
Eggs hatch in intestine
Larvae mature
Cycle repeats
Give the life cycle of a hook worm
Human - human with no intermediate host
Adults live in intestines and feed on blood
Mate
Eggs are passed through faeces into soil
Develop into dauer-like stage and seek out host on vegetation
Burrows through skin of the host and into the bloof system
Goes into the lungs
Gets coughed up and swallowed by the host for the cycle to repeat
Give the life cycle of a guinea worm
Infeceted human host from contaminated water
Larvae released when copepods die and these penetrate host stomach and intestinal wall
Mature and reproduce
Fertilised female worm migrates to the surface of the skin and causes a blister
Discharges larvae
People tend to cool blisters in the water
Female worm emerges from skin and release larvae into the water
Larvae consumed by crustacean/copepods
Develop into dauer-like stage in copepod
Human drinks contaminated water with copepods
Give the life cycle of filarial nematode
Nematodes mate in lymphatic glands of a human
Release larvae into the peripheral blood system - matches to when mosquito is active
Mosquito takes up larvae
Forms dauer stage
Mosquito can then infect another (or even the same) human for the cycle to repeat
Can block lymphatic system to leaks into tissues - this casues swelling/elephantiasis
