Aplidium californicum (Ritter & Forsyth, 1917)

Common name(s): California sea pork, sea pork

Synonyms: Amaroucium californicum Aplidium californicum
Phylum Chordata 
Subphylum Urochordata 
Order Enterogona 
Suborder Aplousobranchia 
Family Polyclinidae 
Photomicrograph of Aplidium californicum, found on dock at Fidalgo Marina.  The buccal siphons of many individual zooids can be seen scattered across the surface.  At the top right is the common opening to the atrial siphons of several local zooids.
(Photo by: Dave Cowles, July 2009 )
Description:   This colonial, encrusting tunicate forms lumpy incrustations usually 1-3 cm thick.  Most zooids are arranged in systems (groups) in which each zooid has its own opening for its oral (buccal) siphon at the surface of the colony but the atrial siphons connect to internal canals in the colony.  These canals lead to joint atrial openings in the surface of the colony scattered among the zooids.  The species has no densely packed bladder cells or disk-shaped calcareous concretions.  The texture is gelatinous or fleshy, usually without any embedded sand (but sand may sometimes encrust the surface).  The pharynx has 7-15 (usually 8-12) rows of stigmata.  Color is variable:  tan, yellowish, gray, opalescent white, orange, transparent, or orange-brown.  Up to 3 cm thick (more often 1 cm) and 30 cm across, irregular shape.

How to Distinguish from Similar Species:Aplidium solidum has 12-16 rows of stigmata, forms slabs up to 5 cm thick, and is usually red or orange-brown.

Geographical Range:  Alaska to Baja California Mexico; Galapagos Islands

Depth Range:  Intertidal to 85 m

Habitat:  A variety of solid or semi-solid substrates, such as docks, tubeworm tubes, crab carapaces, shells, surge channels.  Usually in areas protected from direct surf.  One of the commonest compound tunicates in semi-protected sites.

Biology/Natural History:   Predators of this compound ascidian include the seastars Dermasterias imbricata,Asterina miniataMediaster aequalis, and Pteraster tesselatus.
If this tunicate is cut open the individual zooids are clearly visible inside.  The front portion (thorax) of each contains the pharyngeal basket and atrial aperture.  The middle (abdomen) contains the coiled gut and esophagus.  The posterior (postabdomen) looks like a long tail and has the ovaries (yellow), testes (white), and heart.

This species broods its eggs a few at a time, in the atrial cavity dorsal to the pharynx.  The tadpole larvae swim out the atrial aperture to disperse.  During asexual reproduction, the postabdomen detaches from the body and constricts into a linear series of buds, each of which grows up into a complete new zooid.  The colonies may degenerate during the winter months.

The symbiotic amphipod Polycheria osborni may be found living in grooves on these colonies.  The parasitic copepod Pholeterides furtiva may be found as well.



Dichotomous Keys:
  Carlton, 2007
  Kozloff, 1987, 1996

General References:
  Harbo, 1999
  Johnson and Snook, 1955 (as Amaroucium californicum)
  Lamb and Hanby, 2005
  Morris et al., 1980
  Niesen, 1994
  Niesen, 1997
  O'Clair and O'Clair, 1998
  Ricketts et al., 1985

Scientific Articles:

Web sites:

General Notes and Observations:  Locations, abundances, unusual behaviors:
This compound tunicate is especially common on the shaded docks of Fidalgo Marina.


Another colony from Fidalgo Marina docks, 2012

Click HERE for a movie showing a closeup of many buccal siphons and a joint cloacal siphon of a colony, with particles showing the current blowing out of the cloacal siphon.

Authors and Editors of Page:
Dave Cowles (2009):  Created original page
CSS coding for page developed by Jonathan Cowles (2007)