Aplidium solidum (Ritter and Forsyth, 1917)

Common name(s): Red ascidian, Sea pork

Synonyms: Amaroucium solidum Aplidium solidum
Phylum Chordata 
Subphylum Urochordata 
Order Enterogona 
Suborder Aplousobranchia 
Family Clavelinidae 
Aplidium solidum under an overhanging boulder at Cape Flattery.  Diameter about 10 cm
(Photo by:  Dave Cowles July 2008)
Description:   This compound, colonial tunicate has many individuals (zooids) all enclosed within the same gelatinous tunic.  The colony grows as a thick, gelatinous or fleshy, encrusting, often lumpy sheet or slab which is at least 5 mm thick but does not have a stalk.  The zooids are arranged in systems--individual zooids have their oral apertures separately at the surface, but the atrial apertures of multiple zooids all open together into the same cavity with a single, larger opening.  The overall colony color is red, pinkish, or pale and may be encrusted with sand (but is usually sand-free).  The separate oral siphons of the zooids are usually red or orange-brown.  The pharynx of zooids has 12-16 (usually 13-15) rows of stigmata.  Colonies may be up to 5 cm thick.  Colony diameter to 20 cm.

How to Distinguish from Similar Species: Aplidium californicum also forms a gelatinous or fleshy colony with zooids in systems but the zooids are tan, yellowish, or orange-brown and usually have less stigmata on the pharynx. Archidistoma molle can be reddish or pink (with red dots) but the zooids are not in systems and the colony tends to be globular in form.

Geographical Range:  Southern British Columbia to San Diego, CA

Depth Range:  Intertidal to 40 m

Habitat:  Rocks and pilings in areas with current.

Biology/Natural History:   In California, colonies of this species can grow to 7 cm diameter in 3 months.  The larvae are brooded in the atrial cavity in spring and summer.

The symbiotic copepod Arthurhumesia canadensis may be present inside the zooids.  The amphipod Polycheria osborni is also a rare symbiont.  The nudibranch Hermissenda crassicornis often feeds on the zooids.



Dichotomous Keys:
  Kozloff, 1987, 1996
  Carlton, 2007

General References:
  Harbo, 1999
  Kozloff, 1993
  Lamb and Hanby, 2005
  Morris et al., 1980

Scientific Articles:

Web sites:

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

Authors and Editors of Page:
Dave Cowles (2008):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)