Ciona savignyi

Invasion History

First Non-native North American Tidal Record: 1985
First Non-native West Coast Tidal Record: 1985
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

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).

North American Invasion History:

Invasion History on the West Coast:

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 unpublished data).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).

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Description

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).

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Taxonomy

Ecology

General:

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).

Food:

Phytoplankton

Trophic Status:

Suspension Feeder

SusFed

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Habitats

General Habitat	Marinas & Docks	None
General Habitat	Rocky	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None

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Life History

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Tolerances and Life History Parameters

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	None	Cold temperate-Warm temperate
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

Economic Impacts

Shipping and Industry: Ciona savignyi is now an abundant component of the fouling community in southern California and Puget Sound (Lambert and Lambert 2003). It is likely that fouling by C. savignyi affects shipping and harbor uses, but no impacts have been reported.


Ecological Impacts

Competition: Currently, little is known about species competition with C. savignyi despite the fact that it is an abundant component of the fouling community in southern California and Puget Sound (Lambert and Lambert 2003). In southern California, it has been speculated that species competition is possible with C. intestinalis. However, die-offs of both species, due to environmental changes, make it difficult to determine the extent of competition. Lambert and Lambert (2003) state that 'Perhaps C. savignyi would eventually replace C. intestinalis were it not that the frequently changing habitat apparently tends to stabilize their co-occurrence in nearly equal numbers.'

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References

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Smith, Kirsty F.; Cahill, Patrick L.; Fidler, Andrew E. (2010) First record of the solitary ascidian Ciona savignyi Herdman, 1882 in the Southern Hemisphere, Aquatic Invasions 5(4): 363-368

Smith, Kirsty F.; Thia, Joshua; Gemmill, Chrissen E. C.; Cary, S. Craig; Fidler, Andrew E. (2012) Barcoding of the cytochrome oxidase I (COI) indicates a recent introduction of Ciona savignyi into New Zealand and provides a rapid method for Ciona species discrimination, Aquatic Invasions 7: in press

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