Nemertean

Nemertean refers to a phylum of unsegmented worms known as Nemertea. These marine invertebrates are commonly called ribbon worms or proboscis worms. A defining characteristic of nemerteans is their eversible proboscis, a muscular tube that can be rapidly projected from the mouth to capture prey. This proboscis is housed within a fluid-filled cavity called the rhynchocoel. Nemerteans exhibit a wide range of body forms, from slender and elongated to more flattened shapes. They possess a complete digestive system with both a mouth and an anus. Their coloration can vary greatly, with many species displaying vibrant hues. Nemerteans are found in diverse marine environments, from intertidal zones to the deep sea, and some species also inhabit freshwater or terrestrial habitats. They are carnivorous, feeding on a variety of small invertebrates such as crustaceans, mollusks, and other worms. Reproduction in nemerteans can be sexual, with external fertilization being common, or asexual, through fragmentation. Their nervous system is relatively simple, featuring a brain and longitudinal nerve cords. Some nemerteans are known to produce toxins, which they use for defense or to subdue prey. The phylum Nemertea contains several thousand described species, and ongoing research continues to reveal new information about their biology and ecological roles.