Rhynchocoela

Rhynchocoela is a phylum of marine invertebrates commonly known as ribbon worms or proboscis worms. These animals are characterized by a long, extensible proboscis, a muscular tube housed within a cavity called the rhynchocoel. This proboscis is used for capturing prey and can be deployed with great speed and force. The phylum comprises over 1,000 described species and is divided into two classes: anopla and enopla.

Rhynchocoelans are typically soft-bodied and unsegmented, with a complete digestive system. Their body plan includes a coelom, circulatory system, and nervous system. Many species are brightly colored, while others are more cryptic. They inhabit a wide range of marine environments, from shallow intertidal zones to the deep sea, and are found on all continents. Their diet consists mainly of small invertebrates such as polychaete worms, mollusks, and crustaceans, which they subdue with their barbed proboscis.

Reproduction in Rhynchocoela is diverse, with both sexual and asexual methods observed. Some species are hermaphroditic, while others have separate sexes. Larval stages are common, and these can be planktonic or benthic. Despite their relatively simple body plan, rhynchocoelans play important roles in marine ecosystems as predators. Their unique proboscis mechanism has also made them subjects of scientific study.