Perophora japonica is a colonial tunicate composed of translucent, yellow-green, round zooids which are connected by stolons. A unique feature of this species is the occurrence of terminal buds, bright yellow star-shaped plaques at the tip of the stolons which can break off, float away and grow into new colonies. It is native to Japan, Korea, and Peter the Great Bay, Russia. It has been introduced to Europe and the West Coast of the United States. In the US, colonies have been found in Humboldt Bay and San Diego Bay, California. This species was likely introduced by fouling on ships hulls or through aquaculture transfers. No impacts have been reported in its introduced range, but it fouls cultured oysters in Japan.
Image Credit: John Bishop, Marine Biological Association, Plymouth, UK. Image shows (A) a colony overgrowing the bryozoan Membranipora membranacea on kelp and (B) the characteristic bright yellow terminal buds of P. japonica.
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|NEP-IV||Puget Sound to Northern California||2003||Def||Estab|
|NEP-VI||Pt. Conception to Southern Baja California||2011||Def||Estab|
|P020||San Diego Bay||2011||Def||Estab|
|P112||_CDA_P112 (Bodega Bay)||2012||Def||Estab|
|NEP-V||Northern California to Mid Channel Islands||2012||Def||Estab|
|P090||San Francisco Bay||2014||Def||Unk|
|28173||California Department of Fish and Wildlife 2014||2011||Marine Terminal (Paco), San Diego Bay||Def||32.6584||-117.1191|
Perophora japonica is a colonial tunicate. Colonies consist of small (4-6 mm), translucent, yellow-green ellipsoidal zooids growing from stolons at the base of the tunic. The longitudinal vessels of the branchial sac are incomplete. The mantle musculature is delicate and connected to the anterior region around and between the siphons. The mantle surface is reticulated with pale greenish corpuscles with about 20 mantle muscles on each side; 25-40 stigmata, in rows on both sides of the mantle surface, and 7-8 branchial papillae, in rows. There are about 20 tentacles around the oral aperature. A unique feature of this species is the occurrence of terminal buds, bright yellow star-shaped plaques at the tip of the stolon which break off, float away, and grow into new colonies (Nishikawa 1991; Nishikawa et al. 2000; Lambert 2005).
Perophora japonica is native to Japan, Korea, and Peter the Great Bay, near Vladivostok, Russia (Nishikawa 1991, Sanamyan 1998). It is introduced to Humboldt Bay and San Diego Bay, California and parts of Europe. Ship hull fouling is the probable vector for this tunicate.
Perophora japonica was found on oyster rafts in the North Slough of Humboldt Bay, California (CA) in August 2003. This appeared to be an established population (Lambert 2005). In 2011, P. japonica was identified from San Diego Bay, CA (Gretchen Lambert 2012, personal communication). In 2012, specimens were found on fouling plates in Bodega Harbor, CA, apparently established (Ruiz et al. unpublished data). Fouling on recreational boats and commercial ships or with aquaculture species are possible vectors for this tunicate.
Perophora japonica was found in Lezardrieux on the north coast of Brittany, France, in 1982 (Monniot and Monniot 1985, cited by Nishikawa et al. 2000). Subsequently, it appeared at other European coastal sites including Guernsey, in the Channel Islands (in 2003, MarLin 2007), Plymouth, England (in 1999, Nishikawa et al. 2000; MarLin 2000), St. Vaast, Normandy, France (Goulletquer et al. 2002), and the Oosterschelde in the Netherlands (in 2000, Gittenberger 2007). From 2008 to 2009, two colonies were found in Baiona, Spain and are the first records on the Iberian peninsula (El Nagar et al. 2010).
Life History- A colonial (or compound) tunicate consists of many zooids, bearing most or all of the organs of a solitary tunicate, but modified to varying degrees for colonial life. Colonial tunicates of the family Perophoridae have zooids resembling solitary tunicates, rounded or oval in shape, but connected by stolons. Zooids can be crowded together, but do not coalesce. Each zooid has an oral and atrial siphon. Water is pumped into the oral siphon, through finely meshed ciliated gills on the pharynx, where phytoplankton and detritus is filtered, and passed on mucus strings to the stomach and intestines. Excess waste is expelled in the outgoing atrial water (Van Name 1945; Barnes 1983).
Colonial tunicates reproduce both asexually, by budding, and sexually, from fertilized eggs developing into larvae. Buds form from the stolons. Colonies vary in size, and can range from small clusters of zooids to huge spreading masses. The zooids are hermaphroditic, with eggs and sperm being released to the atrial chamber. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but some species have a partial block to self-fertilization. Embryos are incubated within the atrial chamber, and hatch into tadpole larvae, with a muscular tail and a notochord, eyespots, and a set of adhesive papillae. The lecithotrophic (non-feeding, yolk-dependent) larvae are expelled on hatching, and swim briefly before settlement. Swimming periods are usually less than a day, and some larvae can settle immediately after release, but the larval period can be longer at lower temperatures. On settlement, the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Van Name 1945; Barnes 1983).
|General Habitat||Marinas & Docks|
|General Habitat||Coarse Woody Debris|
|Salinity Range||Polyhaline||18-30 PSU|
|Salinity Range||Euhaline||30-40 PSU|
|Maximum Length (mm)||4 mm (zooids)|
|Broad Temperature Range||Cold temperate-Warm temperate|
|Broad Salinity Range||Polyhaline-Euhaline|
|Fouling of cultured mussels by a variety of non-native tunicates was reported beginning in 2013, and was a serious problem by 2016 (Palanisamy et al. 2018).|