Nematodes

Explain why nematodes must undergo ecdysis (molting) during their development.

• To remove parasites from their surface

• To change from aquatic to terrestrial forms

• The inflexible cuticle restricts growth, so it must be shed and replaced as the animal increases in size

• To reproduce sexually instead of asexually

How do the amphid structures help distinguish between the two major classes of nematodes?

• Secernentea have spiral amphids for water detection, while Adenophorea have pocket-like amphids for soil detection

• The different amphid shapes reflect their evolutionary divergence and different sensory needs

• Only parasitic species have amphids, so their presence indicates the class

• Amphid shape determines whether the species can infect humans

Compare the transmission strategies of Necator americanus and Wuchereria bancrofti. Why do they use different methods?

• Necator uses skin penetration because it needs to reach blood vessels, while Wuchereria uses mosquitoes because it affects the lymphatic system

• Their different transmission methods reflect adaptation to different environmental conditions and host behaviors

• Necator is smaller so it can penetrate skin, while Wuchereria is larger and needs a vector

• The transmission method depends on the final location in the host body

Analyze why Trichinella spiralis has a different infection strategy compared to intestinal nematodes like Ascaris.

• Trichinella targets muscle tissue for reproduction, requiring meat consumption rather than fecal-oral transmission

• Trichinella is smaller and cannot survive in the intestinal environment

• Trichinella evolved from a different ancestor than other nematodes

• Trichinella only infects carnivorous animals

Discuss the role of the cuticle in nematodes and how it affects their survival in various environments.

• The cuticle is only important during the larval stages

• The cuticle allows for gas exchange, which is crucial for survival

• The cuticle is primarily for locomotion and does not affect survival

• The cuticle provides structural support and protection against desiccation