Nemertea

Definition

Nemertea, also known as ribbon worms, is a phylum of invertebrate animals characterized by their long, slender bodies and unique proboscis used for capturing prey. These worms exhibit a variety of body forms and sizes, ranging from a few millimeters to several meters long, and are primarily found in marine environments, although some inhabit freshwater and terrestrial habitats. The members of this phylum showcase diverse reproductive strategies and possess a closed circulatory system, which sets them apart from other invertebrates.

5 Must Know Facts For Your Next Test

1. Nemerteans have a closed circulatory system that allows for efficient transport of nutrients and gases throughout their bodies, which is more advanced than the open circulatory systems found in many other invertebrates.
2. They exhibit a range of feeding behaviors, using their proboscis to hunt small prey like crustaceans, mollusks, and even other worms.
3. Some species of nemerteans are known for their remarkable regenerative abilities, allowing them to regrow lost body parts.
4. Reproduction in nemerteans can be sexual or asexual; some species produce free-swimming larvae while others develop directly.
5. The nervous system of nemerteans is more complex than that of flatworms, featuring a pair of cerebral ganglia and longitudinal nerve cords.

Review Questions

• How does the structure and function of the proboscis in nemerteans contribute to their feeding strategy?
  • The proboscis in nemerteans plays a crucial role in their feeding strategy by allowing them to capture prey efficiently. This specialized structure can be extended rapidly to ensnare small organisms, such as crustaceans or mollusks, using mucus or venom. The ability to immobilize prey with a venomous gland enhances their hunting success and allows them to thrive in various environments.
• Discuss the significance of the closed circulatory system in nemerteans compared to other invertebrate phyla.
  • The closed circulatory system in nemerteans is significant as it enables more efficient transport of oxygen and nutrients compared to the open circulatory systems found in many other invertebrates. This system allows for better regulation of blood flow and pressure, which supports their active predatory lifestyle. It also facilitates larger body sizes and more complex organ systems by ensuring that all tissues receive adequate supplies for metabolism.
• Evaluate the evolutionary adaptations that have enabled nemerteans to successfully inhabit diverse environments such as marine, freshwater, and terrestrial ecosystems.
  • Nemerteans have developed several evolutionary adaptations that allow them to thrive in various environments. Their versatile proboscis enhances their hunting efficiency across different habitats. The presence of a closed circulatory system supports larger body sizes and active lifestyles. Additionally, some species exhibit adaptations for surviving desiccation when transitioning between aquatic and terrestrial habitats. These features contribute to their ecological success and highlight their adaptability within the broader context of Lophotrochozoa.

Related terms

Proboscis: An elongated feeding structure used by nemerteans to capture prey, extending out of the body and often equipped with a venomous gland.

Coelom: The body cavity found in many animals, including nemerteans, which provides space for the development of internal organs and allows for complex bodily functions.

Lophotrochozoa: A superphylum that includes various invertebrate groups such as flatworms, rotifers, and nemerteans, characterized by specific developmental stages including a lophophore or trochophore larva.