Phylum Nematoda

Are nematodes pseudocoelomates? What does that mean?

Nematodes are pseudocoelomates, meaning they have a body cavity called a pseudocoelom that is not completely lined by mesodermal tissue.

How do nematodes move?

Using longitudinal muscles only, movement is thrashing or whip-like due to lack of circular muscles and cilia.

What type of muscle do nematodes have?

Only longitudinal muscles, arranged beneath the epidermis.

How does the nematode nervous system work?

Movement is controlled by the nervous system with non-contractile muscle extensions connected to the dorsal and ventral nerve cords.

Describe the general life cycle of a parasitic nematode

• Eggs pass in feces

• Embryonate and hatch in soil

• Juveniles develop into infective stage (L3)

• Penetrate skin

• Migrate to lungs → trachea → swallowed

• Mature in small intestine

• Adults produce eggs → feces

What are the infective juveniles in nematodes called?

L3 larvae (third-stage juveniles)

What disease do intestinal nematodes cause?

American Hookworm can cause anemia, fatigue, respiratory issues, dermal larval migrans.

How much blood loss is caused by American Hookworm?

Around 600mL per day

What is the genus for intestinal nematoda?

necator americanus

What is the genera for filarial nematodes?

Wuchereria, bancrofti, brugia malayi

What is the function of the hydrostatic skeleton in nematodes?

It maintains body rigidity and allows movement via pressure created by fluid inside the pseudocoelom.

What ix the main parasitic intestinal nematodes

And the disease they cause?

necator americanus and it can cause american hookworm; causes anemia, fatigue, respiratory issues, dermal larval migrans

What disease do filarial nematodes cause?

Cause lymphatic filariasis, leading to lymphedema and elephantiasis

How is Wuchereria bancrofti transmitted?

Mosquito takes up microfilariae → larvae mature in mosquito → transmitted when it bites a human

What role do nematodes play in ecosystems aside from being parasites?

Most nematodes are non-parasitic and aid in nutrient cycling by decomposing organic matter in soil.

How is nematode movement different from annelid movement?

Nematodes can only bend side-to-side due to the absence of circular muscles, while annelids use both longitudinal and circular muscles for peristaltic movement.