E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Ascidia paratropa (Huntsman, 1912)
Glassy Tunicate
Family: Ascidia
 

© Derek Holzapfel  Email the photographer   (Photo ID #15930)

E-Fauna BC Static Map
Distribution of Ascidia paratropa in British Columbia
Details about map content are available here.

Introduction


There are 50-or so species of sea squirts or tunicates (Class Ascidiacea) along the British Columbian coast, but probably less than 20 of these are common. However, the relatively large size of some of the solitary forms, their overall diversity of shapes and colours, their unusual life styles, and their evolutionary relationships to vertebrates, make them invertebrates of great interest. They come in two main forms, solitary and colonial, with the latter being separated into social and compound types. Solitary forms are the most visually obvious and these make up most of the species presently represented on E-Fauna BC. They are attached by one end, often from a stalk, and have a body encased in a protective outer covering or tunic drawn into two prominent siphons. The tunic is non-living and made up of a cellulose-like substance that is often extremely tough in texture. Compound colonial forms grow in flat, plating colonies that can be easily differentiated from sponges by their usually smooth, slippery texture. The two colonial types, social and compound, are comprised of small units or zooids, each functionally equivalent to what has been described for solitary forms, but differing in the extent to which the zooids are fused together.

The evolutionary link to vertebrates and other chordates comes in the possession of pharyngeal gill slits, notochord, and hollow dorsal-tubular nerve cord in the "tadpole" larva. All but the gill slits are lost during metamorphosis of the larva to adult form. The familiar expression, "For Man was once a leather bottel", derives from these evolutionary characters.

Whether solitary or colonial, the pattern of water circulation for feeding and respiratory purposes is similar. Seawater enters via branchial siphons and exits via atrial siphons. Within the body the water is sieved through a barrel-like structure known as the branchial basket, where food particles are removed and consumed. As the waste water exits, it carries feces and other wastes and, in season, reproductive products. Foods eaten include particulate organic matter and a variety of small planktonic organisms, including many invertebrate larvae. Any junk material taken in can be forcibly expelled or back-flushed via the branchial siphon by rapid muscle contraction; hence the name "sea squirt".

For information on the different types of tunicates with details on feeding, reproduction, and defenses see A Snail's Odyssey.

Note Author: Tom Carefoot, Department of Zoology, University of British Columbia

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
UnlistedUnlistedUnlistedUnlisted
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Range and Status Information Links

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2019. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 22/11/2019 4:04:33 AM]
Disclaimer: The information contained in an E-Fauna BC atlas pages is derived from expert sources as cited (with permission) in each section. This information is scientifically based.  E-Fauna BC also acts as a portal to other sites via deep links.  As always, users should refer to the original sources for complete information.  E-Fauna BC is not responsible for the accuracy or completeness of the original information.


© E-Fauna BC: An initiative of the Spatial Data Lab, Department of Geography, UBC