NEMESIS Bioregion Distribution:

Native  Introduced  Cryptogenic  Failed

First Non-native North American Marine/Estuarine Record: 1949
First Non-native West Coast Marine/Estuarine Record: 1949

General Invasion History:

Molgula manhattensis is native to the East and Gulf coasts of the United States. It was described from Manhattan Island, NY by De Kay in 1843 (De Kay 1843), but it was collected earlier by Gould (in 1841, near Boston), and earlier still by Couthouy (1838) in Massachusetts (Van Name 1912). In the northwest Atlantic, M. manhattensis occurs from Maine to Texas (Van Name 1921; Van Name 1945; Gosner 1978; McDougall 1943; US Museum of Natural History 2009). It was reported from several locations on the East Coast, from Boston to North Carolina in the 19th century (Gould 1841; DeKay 1843; Perkins 1871; Gould 1870; Verrill and Smith 1873). By the early 20th century, it was known over its present range on the Atlantic coast of North America (Van Name 1921). Some authors considered it synonymous with Ascidia tubifera and Molgula socialis, which gives it a wide European range, from Portugal to the White Sea (Van Name 1945; Carlton 2001 personal communication), while others consider it a distinct introduced species, confined to scattered European ports (Monniot 1969). Currently, M. tubifera is considered synonymous with M. manhattensis, while M. socialis has been found to be genetically distinct and presumably native to the northeast Atlantic (Haydar et al. 2011, Shenkar et al. 2011).

Recent genetic analysis supports M. manhattensis' native status in the northwest Atlantic, and introduced status in Japan, San Francisco Bay, and the Black Sea (Haydar et al. 2011). The genetic diversity of European populations was much lower than that of the northwest Atlantic M. manhattensis, but the presence of some unique genotypes led Haydar et al. (2010) to consider this species cryptogenic in Europe. However, this could be explained by under-sampling of American populations, or by the extinction of American source populations (James T. Carlton; April Blakeslee, personal communications). The data presented by Haydar et al. (2010) appear to us to be consistent with introduced status in Europe. In European waters, treating it separately from M. socialis, M. manhattensis ranges from Bergen, Norway to Galicia (northern Spain), and a few locations in the Mediterranean Sea, such as the Venice Lagoon (Monniot 1969; Dybern 1969; Vazquez and Urgorri 1992). 

Molgula manhattensis has been introduced to the Pacific coast of North America, from Newport Beach, California (Lambert and Lambert 1998) to British Columbia (Cohen and Carlton 1995; Cohen et al. 1998; Lambert 2003). It is also introduced to Japan (Asakura 1992), Australia (Hewitt et al. 1999), and Argentina (Orensanz et al. 2002). It is tolerant of a wide range of temperatures, salinity, and pollution levels (Van Name 1945).

North American Invasion History:

Invasion History on the West Coast:

Molgula manhattensis was first discovered in Tomales Bay, California in 1949 (Hedgepeth 1952, cited by Carlton 1979) and in San Francisco Bay in the 1950s (Hopkins 1968, cited by Cohen and Carlton 1995), where it is now abundant and widespread (Carlton 1979; Cohen and Carlton 1995; Cohen et al. 2005). Possible vectors include ship hull fouling or Eastern Oyster (Crassostrea virginica) aquaculture (Carlton 1979).

South of San Francisco Bay, M. manhattensis was collected in Long Beach Harbor and Newport Bay in 1984 (Lambert and Lambert 1998). Newport Bay marks the current southern limit for this tunicate on the West Coast (Lambert and Lambert 1998; Lambert and Lambert 2003; Ruiz et al. unpublished data). It has been found in most of the bays and harbors between San Francisco Bay and Los Angeles, including Elkhorn Slough (in 1998, Wasson et al. 2001), Morro Bay (in 2005, Needles 2007), Santa Barbara (in 2001, Fairey et al. 2002), Ventura (in 1994, Lambert and Lambert 1998), Channel Islands Harbor (in 2001, Fairey et al. 2002), and Marina del Rey (in 1995, Lambert and Lambert 1998).

North of San Francisco and Tomales Bays, it was found in Coos Bay, Oregon (in 1974, Carlton 1989; Wonham and Carlton 2005), Humboldt Bay, California (in 1996, Boyd et al. 2002), Willapa Bay, Washington (in 2000; Cohen et al. 2001), Puget Sound, Washington (in 1998; Cohen et al. 1998), Vancouver Island, British Columbia (in 1998, Lambert 2003) and Prince Rupert, British Columbia (in 2009, Murray et al. 2011). In 2010, it was discovered heavily fouling a barge in Yaquina Bay, Oregon, its first record in that estuary (Estabrook et al. 2010). Its current northern limit is Prince Rupert, British Columbia (Murray et al. 2011).

Invasion History elsewhere in the World:

One specimen of Molgula manhattensis was collected in 1973 in Panama Bay, on the Pacific side of the Panama Canal (USNM 19556, US Museum of Natural History 2007) but we know of no other records from the Canal area. In the Northwest Pacific, it was first recorded in Japan in Hiroshima Harbor in 1972 and in Tokyo Bay in 1975 (Asakura 1991; Nishikawa 1991). It now ranges from Golden Horn Bay, Sea of Japan, near Vladivostok, Russia (in 1999, Zvyagintsev et al. 2003) to Guangdong (Canton), China (Huang 2001). In the Southwest Pacific, M. manhattensis was first recorded in Australia in Port Phillip Bay, Victoria, in 1967 (Kott 1985, Keough and Ross 1999). By 1976, it had become established in Moreton Bay, in Queensland, Australia (Kott 1985). In the Southwest Atlantic, it is established in Mar del Plata, Argentina (in 1945, Orensanz et al. 2002).

In European waters, M. manhattensis ranges from Bergen, Norway to Galicia, Spain and a few locations in the Mediterranean Sea, such as the Venice Lagoon (Monniot 1969; Dybern 1969; Vazquez and Urgorri 1992). It has also been identified by molecular analysis from Germany (Sylt, Wadden Sea), the Netherlands (Grevelingen and Delfzijl), Belgium (Oostende) and France (Le Havre) (Haydar et al. 2011).