Invasion History
First Non-native North American Tidal Record: 1986First Non-native West Coast Tidal Record: 1986
First Non-native East/Gulf Coast Tidal Record:
General Invasion History:
Microcosmus squamiger is native to the coast of Australia, where it is widespread. Available records include most of the Australian states (Kott 1985; Australian Faunal Directory 2009), but we are unaware of records from the Northern Territories. It also occurs in several locations including the Indo-Pacific region, from Vizhinjam, India, the Arabian Sea (Abdul and Sivakumar 2007), the Red Sea (Michaelsen 1918, cited by Kott 1985), Ibo Island, Mozambique, (Monniot 2002), and New Zealand (1st record in 2003, Inglis et al. 2005). This species appears to have been frequently transported in ship fouling and may be introduced in New Zealand and is definitely introduced in South Africa, where it is known from the harbor of Port Elizabeth, in the Indian Ocean (Rius et al. 2008; Griffiths et al. 2009). Other recent invasions have occurred on the coasts of California and Mexico (Lambert and Lambert 1998; Lambert and Lambert 2003; Rius et al. 2008; Rodriguez and Ibarra-Obando 2008), the western Mediterranean (Mastrototaro and Dappiano 2005; Turon et al. 2007), the Atlantic coast of Spain, Madeira, and the Canary Islands (Turon et al. 2007).
North American Invasion History:
Invasion History on the West Coast:
Microcosmus squamiger was first collected in Alamitos Bay, Long Beach, California in 1986 (Lambert and Lambert 1998). By 1994 its range extended from San Diego Bay to Santa Barbara Harbor (Lambert and Lambert 1998; Lambert and Lambert 2003). In 2000 it was collected in Ensenada, Mexico, (Lambert and Lambert 2003) and in 2002 it was observed fouling cultured oysters in Bahia San Quintin, Baja California (Rodriguez and Ibarra-Obando 2008). In 2015-2016, M. squamiger was found growing on several fouling plates at the Oakland Yacht Club in San Francisco Bay (Tracy et al. 2017). We consider this population to be established.
Invasion History in Hawaii:
Microcosmus squamiger is not established in Hawaii, but has been found in fouling on ships travelling from California to Honolulu, Pearl Harbor, and Barber's Point harbors (Godwin 2003).
Invasion History Elsewhere in the World:
Microcosmus squamiger was first collected in the Mediterranean Sea in 1971 at Savona, Italy in the western basin near the French border, but was initially misidentified by Monniot as M. exasperatus (Monniot 1981, Mastrototaro and Dappiano 2005). In 1963 it was collected in the Tyrrhenian Sea at Bizerte, Tunisia (Mastrototaro and Dappiano 2005), and the central basin, at Taranto, Italy by 1977 (Mastrototaro and Dappiano 2005). This seems to be its present eastward limit - it has not been recorded in the Adriatic or the eastern basin where M. exasperatus has been found (Turon et al. 2007). To the west, M. squamiger occurs along the Mediterranean coast of Spain from Barcelona to Alicante (in 1988) and Algeciras Bay near Gibraltar (in 1996) (Turon et al. 2007). In 1994 it was collected at Cape Trafalgar on the Atlantic Ocean and has subsequently been collected at several sites in the Gulf of Cadiz, at Cascais, Portugal and on the Bay of Biscay at Santander and in the Ria San Vicente (Turon et al. 2007). It has also been collected at Madeira and Tenerife, Canary Islands off the coast of northwest Africa (Turon et al. 2007). In 2007, it was found in 8 locations on the Pacific coast of Japan, and 2014, in Okinawa (Nishikawa and Ueda 2011; Nishikawa `07, boith cited by Bae eta l. 2022(. In 2022, Microcosmus squamiger was found in two harbors on Jeju Island, South Korea (Bae et al. 2022).
Description
Microcosmus squamiger is a solitary tunicate, but usually occurs in dense clumps or aggregates. Each tunicate can grow up to 50 mm in diameter. The surface of the tunic rises into ridges and swellings with adhesive projections. The tunic is purple, leathery, tough, and sometimes hard and brittle. The apertures are usually located on short, wart-like siphons about a third of the body length and are directed away from each other. But sometimes the oral siphon is terminal with a long straight siphon, while the atrial siphon is short and about half-way along the body (Kott 1985).
This species is frequently confused with the very similar species Microcosmus exasperatus (Mastrototaro and Dappiano 2005; Turon et al. 2007). One of the few characteristics used to distinguish between the two species is the shape of the internal siphonal spines. The spines of M. squamiger are very short, about 15-25 µm long, and shaped like fingernails with serrated rims, while M. exasperatus has longer pointed spines, about 40-50 µm long, which are posteriorly hooked (Kott, 1985; Mastrototaro and Dappiano 2005).
Taxonomy
Taxonomic Tree
| Kingdom: | Animalia | |
| Phylum: | Chordata | |
| Subphylum: | Tunicata | |
| Class: | Ascidiacea | |
| Order: | Stolidobranchia | |
| Family: | Pyuridae | |
| Genus: | Microcosmus | |
| Species: | squamiger |
Synonyms
Microcosmus exasperatus australis (Michaelsen, 1908)
Potentially Misidentified Species
Many confused records in the Mediterranean- most reports of M. exasperatus are actually M. squamiger (Turon et al. 2007).
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 the 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; Detritus
Trophic Status:
Suspension Feeder
SusFedHabitats
| 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 |
Life History
Tolerances and Life History Parameters
| Maximum Duration | 1 | Swimming time of larva (Turon et al. 2010) |
| Maximum Length (mm) | 50 | Kott 1985 |
| Broad Temperature Range | None | Warm temperate-Tropical |
| Broad Salinity Range | None | Polyhaline-Euhaline |
General Impacts
Economic Impacts
Oyster culture racks, ropes, and shells (of Crassostrea gigas, Pacific Oyster) in Bahia San Quintin, Baja California, Mexico were badly fouled by tunicates beginning in 2002. Microcosmus squamiger was a major organism in this fouling (Rodriquez and Ibarra-Obando 2008).
Ecological Impacts
Competition: Microcosmus squamiger now greatly outnumbers Styela canopus in San Diego Bay. It forms single-species patches at some locations suggestive of competition (Lambert and Lambert 2003), for example it forms dense monospecific crusts, and can outcompete native species in shallow water communities. Microcosmus squamiger is considered a potential threat to Mediterranean littoral communities, but further monitoring is needed to assess its impacts (Turon et al. 2007).
Regional Impacts
| NEP-VI | Pt. Conception to Southern Baja California | Economic Impact | Fisheries | ||
| Oyster culture racks, ropes, and shells (of Crassostrea gigas, Pacific Oyster) in Bahia San Quintin, Baja California, Mexico were badly fouled by tunicates, beginning in 2002. Microcosmus squamiger was a major organism in this fouling (Rodriquez and Ibarra-Obando 2008). | |||||
| NEP-VI | Pt. Conception to Southern Baja California | Ecological Impact | Competition | ||
| Microcosmus squamiger now greatly outnumbers Styela canopus, an earlier invader, in San Diego Bay. It forms single-species patches at some locations, suggestive of competition (Lambert and Lambert 2003). | |||||
| P020 | San Diego Bay | Ecological Impact | Competition | ||
| Microcosmus squamiger now greatly outnumbers an earlier invader, Styela canopus in San Diego Bay. It forms single-species patches at some locations, suggestive of competition (Lambert and Lambert 2003). | |||||
| MED-II | None | Ecological Impact | Competition | ||
| 'The ability of M. squamiger to form dense, monospecific crusts that outcompete native species in shallow water communities (authors' personal observation) indicates that it is a potential threat to Mediterranean littoral communities and deserves further monitoring' (Turon et al. 2007). | |||||
| CA | California | Ecological Impact | Competition | ||
| Microcosmus squamiger now greatly outnumbers an earlier invader, Styela canopus in San Diego Bay. It forms single-species patches at some locations, suggestive of competition (Lambert and Lambert 2003). | |||||
Regional Distribution Map
| Bioregion | Region Name | Year | Invasion Status | Population Status |
|---|---|---|---|---|
| NEP-VI | Pt. Conception to Southern Baja California | 1986 | Non-native | Established |
| AUS-II | None | 0 | Native | Established |
| AUS-IV | None | 0 | Native | Established |
| AUS-V | None | 0 | Native | Established |
| AUS-VII | None | 0 | Native | Established |
| AUS-IX | None | 0 | Native | Established |
| AUS-X | None | 0 | Native | Established |
| AUS-XII | None | 1928 | Native | Established |
| AUS-III | None | 0 | Native | Established |
| AUS-VIII | None | 0 | Native | Established |
| RS-1 | None | 0 | Crypogenic | Established |
| RS-2 | None | 0 | Crypogenic | Established |
| RS-3 | None | 0 | Crypogenic | Established |
| MED-I | None | 1996 | Non-native | Established |
| AUS-XIII | None | 0 | Native | Established |
| MED-II | None | 1971 | Non-native | Established |
| WA-V | None | 1950 | Non-native | Established |
| MED-III | None | 1963 | Non-native | Established |
| P020 | San Diego Bay | 1994 | Non-native | Established |
| P050 | San Pedro Bay | 1986 | Non-native | Established |
| P030 | Mission Bay | 1994 | Non-native | Established |
| P023 | _CDA_P023 (San Louis Rey-Escondido) | 1994 | Non-native | Established |
| P027 | _CDA_P027 (Aliso-San Onofre) | 1994 | Non-native | Established |
| P040 | Newport Bay | 1994 | Non-native | Established |
| P060 | Santa Monica Bay | 1994 | Non-native | Established |
| P062 | _CDA_P062 (Calleguas) | 1994 | Non-native | Established |
| P064 | _CDA_P064 (Ventura) | 1996 | Non-native | Established |
| P058 | _CDA_P058 (San Pedro Channel Islands) | 1992 | Non-native | Established |
| MED-IV | None | 1977 | Non-native | Established |
| EA-III | None | 1995 | Crypogenic | Established |
| NZ-IV | None | 2004 | Crypogenic | Established |
| SP-XXI | None | 2003 | Non-native | Unknown |
| P065 | _CDA_P065 (Santa Barbara Channel) | 2001 | Non-native | Established |
| NEA-V | None | 1994 | Non-native | Established |
| WA-I | None | 1992 | Non-native | Established |
| CIO-I | None | 0 | Crypogenic | Established |
| CIO-II | None | 2004 | Crypogenic | Established |
| NEA-VI | None | 2009 | Non-native | Established |
| NEP-V | Northern California to Mid Channel Islands | 2015 | Non-native | Established |
| P090 | San Francisco Bay | 2016 | Non-native | Established |
| MED-VI | None | 2015 | Non-native | Established |
| NWP-3a | None | 2022 | Non-native | Established |
| NWP-2 | None | 2014 | Non-native | Established |
| NWP-3b | None | 2007 | Non-native | Established |
Occurrence Map
| OCC_ID | Author | Year | Date | Locality | Status | Latitude | Longitude |
|---|---|---|---|---|---|---|---|
| 767427 | Ruiz et al., 2015 | 2013 | 2013-07-19 | SeaWorld Marina, Mission Bay, CA, California, USA | Non-native | 32.7676 | -117.2314 |
| 767463 | Ruiz et al., 2015 | 2013 | 2013-07-29 | Mission Bay Yacht Club, Mission Bay, CA, California, USA | Non-native | 32.7778 | -117.2485 |
| 767482 | Ruiz et al., 2015 | 2013 | 2013-08-04 | Bahia Resort Marina, Mission Bay, CA, California, USA | Non-native | 32.7731 | -117.2478 |
| 767496 | Ruiz et al., 2015 | 2013 | 2013-07-31 | Campland on the Bay, Mission Bay, CA, California, USA | Non-native | 32.7936 | -117.2234 |
| 767697 | Ruiz et al., 2015 | 2013 | 2013-07-24 | NAB ACU-1 Docks, San Diego Bay, CA, California, USA | Non-native | 32.6786 | -117.1615 |
| 767749 | Ruiz et al., 2015 | 2013 | 2013-07-18 | NAB Fiddlers Cove, San Diego Bay, CA, California, USA | Non-native | 32.6524 | -117.1486 |
| 767766 | Ruiz et al., 2015 | 2013 | 2013-07-26 | Pier 32 Marina, San Diego Bay, CA, California, USA | Non-native | 32.6516 | -117.1077 |
| 767775 | Ruiz et al., 2015 | 2013 | 2013-07-20 | Chula Vista Marina, San Diego Bay, CA, California, USA | Non-native | 32.6252 | -117.1036 |
| 767789 | Ruiz et al., 2015 | 2013 | 2013-07-28 | Marriott Marquis and Marina, San Diego Bay, CA, California, USA | Non-native | 32.7059 | -117.1655 |
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