Ascidiology, also known as tunicate biology, is the study of ascidians, a group of marine invertebrates also called sea squirts. However, there are other terms that can be used as synonyms for ascidiology, such as urochordate biology, which refers to the phylum that ascidians are a part of - Urochordata or Tunicata. Another synonym is didemnid biology, which focuses specifically on the almost 200 species of ascidians in the family Didemnidae. Some researchers also use the term tunicate ecology when studying the interactions between ascidians and their environment. Ultimately, these synonyms all describe different aspects of the study of sea squirts and the role they play in marine ecosystems.