The Leathery Tunicate - Styela plicata
Brian Jones, Senior Aquarist
 

	Leathery Tunicate

This spring, a mysterious, brownish-orange growth was commonly seen on dock pilings in the area.  This harmless animal is a type of sea squirt called the leathery tunicate.   There are hundreds of different kinds of tunicates in the world’s oceans, including solitary species and those that live in colonies.  Though the leathery tunicates are often found living very close to each other, it is technically a solitary species.  As with barnacles, the tunicates will cram themselves together on the available structure. 

The adult tunicate pumps about 1 gallon of water each hour, capturing plankton (tiny plants and animals) for its meals.  Two pacemakers alternate the flow of blood (typically green) through the tissue, each one operating while the other re-charges.  Interestingly, the body structure is largely composed of cellulose, a fibrous substance normally found in plants.  

The larval tunicate has a characteristic it shares with vertebrates (including fish and humans), called a notochord.  Rather than developing into a backbone, the larval tunicate notochord is absorbed into the body tissue as the larva attaches to a structure and starts developing. 

Though these animals are often seen as a nuisance, fouling docks, piers and boat hulls, a closer examination shows a very interesting, and often overlooked, example of local marine life.