Heteronemertea
Heteronemertea is a diverse class of ribbon worms within the phylum Nemertea, which are often referred to as “ribbon worms” or “proboscis worms.” They are exclusively marine, with a significant portion found in coastal environments. Notably, Heteronemertea is characterized by having a proboscis, an eversible organ used for capturing prey, which is housed within a specialized chamber called the rhynchocoel.
Characteristics
Heteronemertea are typically characterized by the following:
- Proboscis: An eversible organ used for capturing prey, housed within a specialized chamber called the rhynchocoel.
- Rhynchocoel: A fluid-filled cavity that houses the proboscis, which is connected to the body cavity by a canal called the proboscis sheath.
- Cerebral organs: Sensory organs located near the brain, which are involved in chemoreception and mechanoreception.
- Digestive tract: A complete digestive tract with a mouth, pharynx, intestine, and anus.
- Nervous system: A ladder-like nervous system with a brain located in the head and nerve cords extending along the body.
- Circulatory system: A closed circulatory system with blood vessels and a heart.
- Reproductive system: Most Heteronemertea are dioecious (separate sexes), and fertilization is usually external.
Environments
Heteronemertea are found in a variety of marine habitats worldwide, including:
- Intertidal zones: Found in the area between high and low tides, exposed to the air and water at different times.
- Subtidal zones: Located below the low tide mark, constantly submerged.
- Deep sea: Found at depths exceeding 200 meters, with some species living in abyssal plains.
- Coral reefs: Highly diverse ecosystems often hosting a variety of Heteronemertea species.
References
For more information on Heteronemertea, consult the following reliable sources: