Author:
Qjure
Book:
Qjurious
Type:
Info
Chapter:
4-522.00.00
Tunicata
English: Tunicates.
Synonym: Urochordata.
Clades: Hemichordata; Deuterostomia; Animals.
Members: Sea squirts; Sea pork.
Genera: 2300 species.
Zoology
Tunicata are underwater saclike filter feeders with incurrent and excurrent siphons; they feed by filtering sea water through pharyngeal slits. Some are sub-marine predators.
Tunicata have a notochord during their early development, but lack myomeric segmentation throughout the body and tail as adults. Tunicates lack the kidney-like metanephridial organs, and the original coelom body-cavity develops into a pericardial cavity and gonads. Except for the pharynx, heart and gonads, the organs are enclosed in a membrane called an epicardium, which is surrounded by the jelly-like mesenchyme.
Tunicates begin life in a mobile larval stage that resembles a tadpole, later developing into a barrel-like, sedentary adult form.
While most tunicates live on the ocean floor, salps, doliolids, and pyrosomes live above in the pelagic zone as adults.
Tunicates apparently evolved in the early Cambrian period, beginning c 540 million years ago. Despite their simple appearance, tunicates are closely related to vertebrates, which include fish and all land animals with bones.
Families
Ascidiacea
Appendicularia
• Larvacea
Thaliacea
• Pyrosomida
• Doliolida
• Salpida
Phlebobranchia
• Aplousobranchi
Stolidobranchia
• Molgulidae
• Styelida
• Pyuridae