BI0004 - Lecture 5 - Parasitology and Mutualism
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What is parasitology?
What do parasites have?
- Gaining nutrition at the expense of a host (who gets no return).
- Keeps the host alive (at least for a while).
They have; a complex lifecycle; specific adaptations to living on/in the host; ways of avoiding adverse reactions from the host.
What are monophagous parasites?
Parasites which feed off one species or closely-related species of host.
What are polyphagous parasites.
Parasites which feed off many species of host.
What are microparasites?
- Microscopic parasites.
- Pathogenic bacteria; Protists; some fungal spores
What are macroparasites?
- Parasites visible with the naked eye.
- Fungae, plants, animals.
What are endoparasites?
Parasites which live inside the host
What are ectoparasites?
Parasites which live on the host (outside)
What physical adaptations do endoparasites have?
- Barbs, suckers, hooks, and teeth for fixing to host organs.
- Strong epidermis to avoid host attack.
What reproductive adaptations do endoparasites have?
Continuous reproduction - leads to high numbers of offspring.
What lifecycle adaptations do endoparasites have?
- They often have many stages of development specifically designed to allow them to survive in different intermediate hosts throughout their life cycle.
- e.g. different structure in Faeces > snail > Fish > Mammal > Faeces
What diseases to endoparasites cause, and what treatments are there?
- Weight loss
- Immune Reactions
- Chemical treatments
- Pharmaceutical treatments
What physical adaptations do ectoparasites have?
Claws, suckers, hooks, and barbs for fixing to hosts whilst feeding.
What host-seeking adaptations do ectoparasites have?
- Thermotaxis - bed bugs
- Chemotaxis - mosquitoes
What is the lifecycle of extoparasites?
Tends to be egg to adult form, getting bigger as it does so. Not drastic differences in different stages.
What diseases do ectoparasites cause, and what treatments are there?
- Skin lesions,
- Loss of blood,
- Infectious disease
- Loss of money
- Heat treatment
- Chemical treatment
- Freezing treatment
What is a plant holoparasite?
A parasite which gains all its nutrition from the host
What is a plant heteroparasite?
- Gains at least some nutrition from photosynthesis?
- e.g. Ivy
What is an epiparasite?
- A parasite which feeds on another parasite.
- e.g. type of fly.
What is a kleptoparasite?
- A parasite which steals food from another.
- e.g. hyenas.
What are social parasites?
- They are parasites which take over an aspect of the host's lifecycle.
- e.g. cuckoo pretending to be another bird's offspring.
- e.g. Large blue butterfly - get ants to look after its larvae.
What is the impact of parasites?
- Reduced fitness
- Parasitic castration
- Behavior change
- Physical pathology
What is ascariasis?
Where is it most common?
- Intestinal worms.
- Up to 10% of the population of the developing world is infected
- 45% of Latin America
- 95% in parts of Africa
- Children are infected more often than adults. 3-8.
- Infection is more likely to be more serious if nutrition is poor.
- Caused by eating uncooked food grown in contaminated soil, or irrigated by inadequately treated wastewater.
What are the symptoms of Ascariasis?
- Bloody sputum
- Low fever
- Passing worms in stool
- Shortness of breath
- Skin rash
- Stomach pains
- Vomiting worms
- Worms exiting nose or mouth
How does Ascariasis spread when in body?
- Larvae hatch in intestine and burrow through gut wall.
- Migrates to the lungs through blood
- Breaks into alveoli and travels up trachaea
- Coughed up and swallowed
- Passes though to intestine and matures into adult worms.
- live for 1-2 years
What is malaria?
- Malaria is a mosquito-borne infectious disease of humans and other animals caused by parasitic protozoans (a type of unicellular microorganism) of the genus Plasmodium.
- Commonly, the disease is transmitted via a bite from an infected female Anopheles mosquito, which introduces the organisms from its saliva into a person's circulatory system.
- In the blood, the protists travel to the liver to mature and reproduce. Malaria causes symptoms that typically include fever and headache, which in severe cases can progress to coma or death.
- The disease is widespread in tropical and subtropicalregions in a broad band around the equator, including much of Sub-Saharan Africa,Asia, and the Americas.
What is a parasitoid?
They gain nutrition at the expense of a host (the host gets no return)
But they kill the host fairly quickly
What is an example of a parasitoid?
- Parasitoidal wasps
- Lay its larvae into a living host.
- The larvae grow.
- They break out of the host.
- They often change the host's behaviour - e.g. getting them to defend the larvae from predators.
- Pathogenic bacteria
- Grow colonies inside the living host
- Burst cells
- Pathalogical damage leads to death.
What is mutualism?
- There is mutual benefits, no overall cost for either.
- Can be defensive - ants eating aphids - or dispersive - bees drinking nectar.
What is commenalism?
- Two organisms, only one has benefits.
- e.g. barnacles on whale.
- e.g. remora fish on shark eating leftover.
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