Sea Pork

Aplidium californicum is a compound Ascidian tunicate commonly known as Sea Pork. Belonging to the Phylum Chordata, this organism has the “tadpole larvae” common to tunicates and salps. Ranging from Alaska to Northern Mexico and the Galapagos, this organism is intertidal down to 85m. Aplidium californicum buds asexually to cover hard rocky substrate (Lamb & Hanby, 2005).

Aplidium californicum exhibits the same larval form as many tunicates and salps: the tadpole larva. This larval form has the notochord unique to the Phylum Chordata, but the notochord is lost in the adult form of A. californicum. The larva metamorphoses into a filter-feeding, benthic adult stage, then buds asexually to produce additional zooids (Lamb and Hanby 2005). The zooids created by asexual reproduction, called blastozoids, are nearly identical to the parental zooid, but do not necessarily contain every cell type of the parental zooid (Kürn, Rendulic, Tiozzo, & Lauzon, 2011). Blastozoids and their parental zooid share a common tunic (Lamb and Hanby, 2005).

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.

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.

Geographical Range: Alaska to Baja California Mexico; Galapagos Islands

Depth Range: Intertidal to 85 m

This colonial, encrusting tunicate forms lumpy incrustations usually 1-3 cm thick. Most zooids are arranged in systems in which each zooid has its own opening for its oral 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. The pharynx has 7-15 rows of stigmata. Color is variable: tan, yellowish, gray, opalescent white, orange, transparent, or orange-brown. Up to 3 cm thick and 30 cm across, irregular shape.

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

Aplidium californicum is a species of colonial sea squirt, a tunicate in the family Polyclinidae. It is commonly known as sea pork.