Ascidia
Ascidiacea, commonly known as sea squirts or tunicates, are a class of marine invertebrate animals. They are filter feeders that belong to the subphylum Tunicata, within the phylum Chordata. Ascidiacea are sessile, meaning they attach themselves to a surface and remain fixed in place, and they are found in a wide range of marine environments worldwide.
Characteristics
Ascidiacea are characterized by their sac-like bodies, which are typically covered in a tough, leathery outer tunic made of cellulose. They have two siphons, an incurrent siphon that draws in water and an excurrent siphon that expels water. They possess a simple circulatory system, a well-developed digestive system, and a nervous system that is concentrated in a single ganglion.
Environments
Ascidiacea are found in a variety of marine habitats, including intertidal zones, shallow waters, and deep-sea environments. Some species are solitary, while others are colonial, forming large clusters.
Common Names
Ascidiacea are commonly referred to as sea squirts because when they are disturbed, they expel a jet of water through their excurrent siphon. They are also sometimes called tunicates, due to their leathery tunic.
References
* [Sea Squirt](https://en.wikipedia.org/wiki/Sea_squirt)* [Ascidiacea](https://www.britannica.com/animal/Ascidiacea)