Untitled Quiz

Nematodes, also known as roundworms, are long, thin, and often thread-like.
Their heads are small, with only small sense organs. Their bodies taper at both ends.
A diverse group, about 15,000 species exist.
Most nematodes are less than 5cm long and many are microscopic.

Nematodes use their pseudocoelom as a hydrostatic skeleton. This fluid-filled cavity provides support.
Their bodies have a thick cuticle made primarily of collagen. This tough exterior resists high hydrostatic pressure.
Longitudinal muscles are beneath the epidermis. These muscles aren't arranged in antagonistic pairs, the cuticle plays this role. Muscle contractions on one side of the body are transmitted through the hydrostatic skeleton, causing the cuticle on the other side to stretch and contract respectively.

Nematodes have a complete digestive system: mouth, muscular pharynx, intestine, rectum, and anus.

Most male nematodes are smaller than females. Males have tails.
Fertilization is internal.
Juveniles develop through multiple stages, each involving molting or cuticle shedding.

These nematodes live in the sea, freshwater, and soil.
They are found in every environment and mostly inhabit the interstitial spaces of sediments and soils.
The majority are carnivorous, but some feed on algae, fungi, or plant roots, especially roots.
Some are pests, piercing root cells and sucking out contents.
Globally, they destroy approximately 12% of cash crops.

Many species attack animals and plants.
Examples of parasitic nematodes include ascarids, hookworms, Guinea worms, trichina worms, pinworms, and filarial worms.

A large roundworm found in humans.
Globally, about 1.4 billion people are infected.
They live in the small intestine.
Females can be a foot long and produce hundreds of thousands of eggs daily.
Infection occurs through ingestion of uncooked food or via soiled fingers.
Ingested eggs hatch in the small intestine, migrate to the lungs, break out of the alveoli, ascend the trachea, then are swallowed and settle in the small intestine.
In the intestines, Ascaris lumbricoides can cause abdominal pain and allergic reactions, and possibly cause complete intestinal blockage.
Larval migration is more lethal than presence of adult worm in the intestine.

Small. The common species is only about 11mm long.
Named for the dorsal curve in their anterior end.
Feed on blood and heavy infections cause severe anemia.
Suck more blood than they use.
Have sophisticated anti-clotting factors to avoid blood clot formation during ingestion.
Do not permanently attach in one spot but move around the gut before reattaching to feed.
The life cycle of hookworms is similar to that of ascarids.
Infections start when larvae penetrate human skin.
Larvae travel to the lungs, are coughed up and swallowed, and finally reach the intestines.
Can cause debilitating anemia, stunting growth, and general lack of energy

Infections (Dracunculiasis) are now confined to sub-Saharan Africa.
Infection occurs when drinking water containing crustaceans.
Larvae consume copepods and undergo two molts inside.
Humans drink unfiltered water containing copepods with larvae; larvae release when copepods die.
Immature worm penetrates the gut wall and wanders through the body, maturing and growing.
Mating occurs, then the male worm dies and the female migrates under the skin, usually in the legs.
After a year, the female worm moves to the skin surface, causing painful blisters.
Sufferers immerse their feet in water, rupturing the blisters, and allowing the female worm to lay eggs, restarting the life cycle.
Removal is done by winding the worm out slowly on a stick over weeks.
A broken worm leads to a serious bacterial infection.
Preventing people from walking in drinking water sources and boiling or filtering water before drinking help reduce infections/avoid infections.
Campaign coordinated by the U.N. and Carter Center has been tremendously successful, reducing infections to approximately 11,000 by 2006, from millions in 1986

Tiny nematode causing the potentially fatal disease trichinosis.
Infection typically is from eating undercooked pork.
Trichinella lives in cysts that form in the muscle cells of host.
When the cyst hatches, the larvae burrows through the gut wall, where immature females live and produce young.
These juveniles travel to the circulatory system, then to muscle cells.
The juvenile penetrates the muscle cell and the cell repairs itself, forming a cyst around the cell.
This process manipulates the host's DNA to cause the production of collagen.
This host manipulation keeps the parasite alive until ingested by another host.
Adults typically do not persist long in the gut before being expelled by the immune system.
Common in wild animals like foxes, wolves, and bears. Smaller mammals, like skunks, raccoons and rats, that share environments with pigs are the main source of pig infection.
Pigs become infected by eating infected animals.
In humans, few parasites cause little to no symptoms, but heavy infections can cause intense muscle pain and even death.