Boltenia villosa (Stimpson, 1864)

Common name(s): Spiny-headed tunicate, hairy sea squirt, stalked hairy sea squirt, bristly tunicate

Phylum Chordata
 Subphylum Urochordata
  Class Ascidiacea
   Order Stolidobranchia
    Family Pyuridae
Boltenia villosa from subtidal near Rosario.  Marks in background are mm, with cm noted.
(Photo by: Dave Cowles, July 2006)
Description:  A solitary ascidian with an opaque tunic that is covered with spinelike projections.  Attached to the substrate by a stalk, which may be short or long. The tunic is reddish-orange or tan, with orange to red siphons.  The siphons can be hard to see.  Up to 10 cm tall (especially if on a long stalk), diameter about 2.5 cm.

How to Distinguish from Similar Species:  The only other solitary ascidians with an opaque tunic and with spinelike projections have no distinct stalk and the projections have side branches arranged in circles.

Geographical Range:  Southern Alaska to San Diego, CA.  Most common on outer coasts.

Depth Range:  Low intertidal to 100 m

Habitat:  Attached to hard substrates in water with good circulation

Biology/Natural History:  This species concentrates vanadium in its body tissues (500-750 ppm by dry weight, excluding the tunic).  These are some of the highest levels of vanadium concentration seen in tunicates.  Diet includes crustacean nauplii, mollusc veligers, and eggs.  Predators include the seastars Dermasterias imbricata and Orthasterias koehleri, and the predatory Oregon triton snail Fusitriton oregonesis .  Sometimes contains the symbiotic crab Pinnotheres pugettensis or the several species of copepods.  Gametes are ripe year-round, but mainly in the summer.  Fertilization is external.  Settle 6 hours to 5 days after hatching.

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Dichotomous Keys:
  Flora and Fairbanks, 1967
  Kozloff 1987, 1996
  Smith and Carlton, 1975

General References:
  Gotshall, 1994
  Kozloff, 1993
  Morris et al., 1980
  O'Clair and O'Clair, 1998
  Sept, 1999

Scientific Articles:

Zeng, Liyun, Molly W. Jacobs, and Bill J. Swalla, 2006.  Coloniality has evolved once on Stolidobranch ascidians.  Integrative and Comparative Biology 46:3 pp 255-268

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:

This closeup of the individual above shows the siphons partly open.

Stalked individual
This small stalked individual, only 1 cm long, is attached near the apex of an occupied Oregon triton shell. Photo by Dave Cowles, July 2020

Authors and Editors of Page:
Dave Cowles (2006):  Created original page