Common Names
Annelids are commonly referred to as segmented worms, but some specific groups have their own names. For example, earthworms belong to the class Oligochaeta, while leeches belong to the class Hirudinea. Marine annelids include a diverse range of species, often grouped under the common name polychaetes.
Characteristics
Key characteristics of Annelida include:
- Segmentation: The body is divided into segments, each with its own set of organs.
- Coelom: A fluid-filled body cavity that provides hydrostatic support and allows for organ development.
- Closed circulatory system: Blood is contained within vessels and circulates throughout the body.
- Nervous system: A well-developed nervous system with a brain and ventral nerve cord.
- Excretory system: Nephridia or metanephridia remove waste products from the body.
Environments
Annelids are found in a wide range of habitats, including:
- Marine: Many species of polychaetes live in the ocean, from the intertidal zone to the deep sea.
- Freshwater: Some species of annelids live in freshwater lakes and rivers.
- Terrestrial: Earthworms are a common example of terrestrial annelids.
References
