Ecdysozoan Phyla and Nematodes

Learning Outcomes

• Identify common features of Ecdysozoans.
• Describe the structure and significance of the cuticle in nematodes.
• Explain the life cycle of filarial worms.
• Discuss the ecological roles of nematodes.

Features of Ecdysozoans

• Characterized by the process of ecdysis (molting) to grow.
• Cuticle present in many species, often composed of chitin or collagen.
• Important ecological functions in various communities.

Phylum Nematoda (Roundworms)

• "Roundworms" lacking circular muscles; unsegmented body.
• Pseudocoelomate structure with a layered collagenous cuticle.
• Absent cilia; have renette cells for excretion.
• Taxonomy remains unsettled; ubiquitous and abundant in diverse ecosystems.

Nematode General Anatomy

• Cuticle:
  • Layered and noncellular; provides resistance and support.
  • Allows wave-like movement due to the absence of circular muscles.
• Digestive System:
  • Simple with the reproductive system involved in gamete exchange.
  • Sperm deposited, leading to fertilization in the ovaries.

Nematode Excretory System

• Comprises glandular and tubular structures.
• Simple nervous system connected to excretory function.
• Excretion involves diffusion across glands into the pseudocoelomic fluid; varies based on the environment.