Ciona savignyi appears to be native to Japan and possibly offshore waters of Alaska and British Columbia. Introduced populations were first reported on the West Coast of North America in 1985 at Long Beach Harbor, southern California. Since then it has been reported in a number of southern, central and northern California locations, including San Diego Bay, Santa Barbara Harbor, Monterey, Moss Landing, San Francisco Bay, Tamales Bay, Bodega Harbor, and Humboldt Bay. In 1998 it was found in Puget Sound near Seattle, Washington, and there are reports of extensive populations in several areas of Puget Sound and the northern reaches of the San Juan Islands. It is abundant in harbors and marinas and was likely spread through hull fouling on commericial and recreational boats. Despite its abundance in the fouling community, very little is known about its impacts, but it might compete with C. intestinalis, however, die-offs of both species due to environmental changes make this difficult to assess.
Image Credit: Melissa Frey, Royal BC Museum, Canada
|Bioregion||Region Name||Year||Invasion Status||Population Status|
|NEP-VI||Pt. Conception to Southern Baja California||1985||Def||Estab|
|NEP-V||Northern California to Mid Channel Islands||1993||Def||Estab|
|NEP-III||Alaskan panhandle to N. of Puget Sound||1903||Crypto||Estab|
|NEP-IV||Puget Sound to Northern California||2001||Def||Estab|
|P050||San Pedro Bay||1985||Def||Estab|
|P020||San Diego Bay||1994||Def||Estab|
|P023||_CDA_P023 (San Louis Rey-Escondido)||1998||Def||Estab|
|P060||Santa Monica Bay||1995||Def||Estab|
|P065||_CDA_P065 (Santa Barbara Channel)||1994||Def||Estab|
|P090||San Francisco Bay||1993||Def||Estab|
|P292||_CDA_P292 (San Juan Islands)||2008||Def||Estab|
|P112||_CDA_P112 (Bodega Bay)||2004||Def||Estab|
|P027||_CDA_P027 (Aliso-San Onofre)||2011||Def||Estab|
Ciona savignyi is a solitary tunicate with a smooth, elongated, cylindrical or vase-shaped body which can reach a length of 150 mm long. It is widest near the permanently attached posterior end and tapers toward the anterior end, compressed laterally. The tunic is transparent, translucent, and white or yellowish-green in color. Much of the tunic is soft, flexible and gelatinous. The muscle bands and organs are often visible beneath the tunic surface. Its siphons are on short, forwardly directed (not divergent) and the oral siphon is larger than the atrial siphon. The oral siphon has 8 lobes, each with a yellow margin containing 8 reddish-orange spots. The atrial siphon has 6 lobes, each with a yellow margin containing 6 reddish-orange spots. There are 5-7 conspicuous longitudinal muscle bands on each side of the body that extend nearly the entire length of the body (Van Name 1945; Kott 1985; Lambert and Lambert 1998).
Ciona savignyi is very similar in appearance to C. intestinalis, but there are a few notable morphological differences. Ciona savignyi always has white pigmented flecks, or spots, in its body wall while C. intestinalis lacks these. Additionally, C. savignyi has orange pigmentation around the siphon while C. intestinalis has yellow pigmentation (Smith et al. 2010). The number of tentacles around the oral siphon is variable in both species, but generally C. savignyi have fewer (n<50) tentacles than C. intestinalis (Hoshino and Nishikawa 1985). Ciona savignyi does not have an endostylar appendage while C. intestinalis has endostyles. Additionally, the pharyngeo-epicardiac openings in C. savignyi are located close to the oesophageal opening while in C. intestinalis these openings are usually very small and located near its base (Hoshino and Nishikawa 1985). Lastly, the color of the enlarged end of the vas deferens is always white in C. savignyi and red in the West Coast C. intestinalis (Lambert and Lambert 1998).
Ciona savignyi appears to be native to Japan and possibly northern Asia. In Japan, it can be found from Mutsu Bay (north end of Honshu) to the Seto Inland Sea (south end of Honshu), both on the Pacific and Sea of Japan coasts (Hoshino and Nishikawa 1980; Nishikawa 1991). In 2004, it was first collected as an introduced species in the most northern reaches of the Sea of Japan, in Peter the Great Bay, Russia (Zvyagintsev et al. 2007). In the northeast Pacific, there are two puzzling records from southeastern Alaska (Inside Passage: Loring, in Behm Canal) and northern British Columbia (Stuart Island, in Queen Charlotte Strait) (AK in 1903, USNM 5633, U.S. National Museum of Natural History 2003; BC in 1937, Lambert 2003). These could represent a cryptic species, a very early introduction, or a relict population. There are also disjunct records from Argentina (Hoshino and Nishikawa 1985) and Spain (Perez et al. 1957) which for the purposes of this database, we consider unverified. However, C. savignyi has recently invaded shallow coastal waters of central and southern California and Puget Sound (Cohen and Carlton 1995; Lambert and Lambert 1998; Lambert 2003; Cohen et al. 2005; Blum et al. 2007).
The first record of Ciona savignyi in continental US waters was in 1985 in Long Beach Harbor, southern CA (Lambert and Lambert 1998). In 1993, it was collected in central California, San Francisco Bay (Cohen and Carlton 1995). By 1994 the southern California population ranged from San Diego Bay to Santa Barbara Harbor, CA (Lambert and Lambert 1998; Lambert and Lambert 2003). The central California population soon included specimens collected in 1998 Elkhorn Slough surveys (Wasson et al. 2001) and in 2003 Monterey and Moss Landing Harbors samples (deRivera et al. 2005). As of 2005, C. savignyi has been collected in the central and southern sections of San Francisco Bay, but not the more northern San Pablo Bay (Cohen et al. 2005; Ruiz et al. unpublished data). North of San Francisco Bay, C. savignyi has been found in samples collected from Tomales Bay (in 2001, Fairey et al. 2002), Bodega Harbor (deRivera et al. 2005), and Humboldt Bay, CA (in 2001, Fairey et al. 2002; Ruiz et al. unpublished data).
In Washington, C. savignyi has spread throughout Puget Sound. It was first discovered in 1998 in the Des Moines Marina near Seattle and by 1999 it had spread north to the Brownsville and Edmonds Marinas. In 2001, it was found near the Tacoma Yacht Club in Tacoma, WA (Lambert 2003). Subsequently, scuba divers discovered extensive populations in several other parts of Puget Sound, including Hood Canal in the western portion of Puget sound (in 2005, USGS Nonindigenous Aquatic Species Program 2003-2012) and in more northern reaches of the San Juan Islands (USGS Nonindigenous Aquatic Species Program 2003-2012).
Life History- A solitary tunicate is ovoid, elongate or vase-like in shape, with two openings or siphons. Most solitary tunicates attach to substrates by their side or base, but some attach with a conspicuous stalk. They are sessile filter feeders with two siphons, an oral and an atrial siphon. Water is pumped in through the oral siphon, where phytoplankton and detritus is filtered by the gills, and passed on mucus strings to the stomach and intestines. Waste is then expelled in the outgoing atrial water.
Solitary ascidians are hermaphroditic, meaning that both eggs and sperm are released to the atrial chamber. Eggs may be self-fertilized or fertilized by sperm from nearby animals, but many species have a partial block to self-fertilization. Depending on species, eggs may be externally or internally fertilized. In external fertilizers, eggs and sperm are released through the atrial siphon into the surrounding water column were fertilization takes place. In internal fertilizers, eggs are brooded and fertilized within the atrial chamber and then released into the water column upon hatching. Fertilized eggs hatch into a tadpole larva with a muscular tail, notochord, eyespots, and a set of adhesive papillae. The lecithotrophic (non-feeding, yolk-dependent) larva swims briefly before settlement. Swimming periods are usually less than a day and some larvae settle immediately after release, but the larval period can be longer at lower temperatures. Once settled, the tail is absorbed, the gill basket expands, and the tunicate begins to feed by filtering (Barnes 1983).
|General Habitat||Marinas & Docks|
|Salinity Range||Polyhaline||18-30 PSU|
|Salinity Range||Euhaline||30-40 PSU|
|Maximum Temperature (ºC)||26.7||Field, US East & West Coast marinas (Lord et al. 2015)|
|Maximum Length (mm)||94||Hoshino and Nishikawa 1985|
|Broad Temperature Range||Cold temperate-Warm temperate|
|Broad Salinity Range||Polyhaline-Euhaline|