Sphaeroma quoianum

Invasion History

First Non-native North American Tidal Record: 1898
First Non-native West Coast Tidal Record: 1898
First Non-native East/Gulf Coast Tidal Record:

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General Invasion History:

Sphaeroma quoianum is native on the eastern coast of Australia (Tasmania and Victoria to Cairns, Queeensland) and New Zealand (Jansen 1971; Harrison and Holdich 1984; Davidson 2006; Davidson et al. 2008; Atlas of Living Australia 2015). A population in the Swan River estuary, Western Australia (Hass and Knott 1998) is of uncertain native status. It appears to be less abundant and conspicuous in Australian and New Zealand estuaries than in its introduced habitats on the West Coast of North America (Davidson et al. 2008). In its native region, it is primarily considered a woodborer, though it is also found in marsh banks, clay, and soft rock (Davidson et al. 2008).

North American Invasion History:

Invasion History on the West Coast:

Sphaeroma quoianum was first found in North America around 1898 at Sausalito, California (CA), on San Francisco Bay (Richardson 1898, cited by Carlton 1979). By the 1930s, it had been collected in South Bay (in 1920, USNM 89805, 1989, United States Museum of Natural History 2007), San Pablo Bay (in 1912, USNM 64473, United States Museum of Natural History 2007); and as far inland as Antioch (Koifoid and Miller 1927, cited by Cohen and Carlton 1995). To the south, it was established in Los Angeles Harbor and San Diego Bay by 1927 (Johnson and Snook 1927, cited by Carlton 1979), but was not collected in Elkhorm Slough until 1998 (Wasson et al. 2001). South of San Francisco Bay, S. quoianum was collected in Morro Bay in 1974 (Iverson 1976, cited by Carlton 1979); Newport Bay in 1962 (Menzies 1962, cited by Carlton 1979); and Bahia San Quintin, Baja California, Mexico in 1960 (Menzies 1962, cited by Carlton 1979; USNM 109311, United States National Museum of Natural History 2007). North of San Francisco Bay, it was collected in Tomales Bay in 1929 (USNM 65813, US National Museum of Natural History 2007) and Humboldt Bay in 1931 (USNM 113887, United States Museum of Natural History 2007). Some smaller estuaries were either subsequently colonized or just sampled at a later date – these include Bolinas Lagoon in 1958 (Riegel 1959, cited by Carlton 1979) and Bodega Harbor in 1972 (Rotramel 1972, cited by Carlton 1979). It was most likely introduced to San Francisco Bay in soft rotten wood on a ship hull, but has become a prominent species boring into marsh sediments and riddling Styrofoam floats in marinas (Cohen and Carlton 1995). This isopod is extending its range northward. It became established in Coos Bay, Oregon (OR) in 1995, and reached Yaquina Bay, OR in 2005 (Davidson 2006).

Invasion History in Hawaii:

In 1915, Sphaeroma quoianum was collected in Pearl Harbor, Hawaii (USNM 113915, United States Museum of Natural History 2007), but has not become established (Davidson 2006).

Invasion History Elsewhere in the World:

In 1961, Sphaeroma quoianum was reported from the coast of Vietnam, in the Gulf of Tonkin, where it is possibly introduced (Kussakin and Malyutuna 1993).

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Description

Sphaeroma quoianum has a compact, convex, elliptical body, which is about twice as long as it is wide. The head is crescent-shaped, with prominent eyes, composed of many ocelli. Antenna 1 has a flagellum of 9 segments, and extends to the posterior edge of Peraeonite 1. Antenna 2's flagellum has 16 segments, and reaches the posterior edge of Peraeonite 2. The peraeonites are roughly equal in width, except for Peraeonite 1, which is somewhat broader than the others. Peraeonites 2-7 each bear a broad transverse ridge. Pereiopods 1-3 bear dense plumose setae on the upper (anterior) surface of segments 3-4, an adaptation for filter-feeding. The pleon has several tubercles. The pleotelson is broad and shield-like, with the terminal edge bluntly curved. The pleotelson has two parallel rows of 4-5 tubercles each, and an elliptical raised transverse ridge near the terminus. The outer edges of the exopods of the uropods each bear 5 prominent teeth. Adults are 8-16 mm long. The color is variable, from sandy brown, gray-green to solid black, and/or with various mottling of brown, black, and red. Description is based on: Richardson 1904, Schultz 1969, Harrison and Holdich 1984, Davidson 2006, and Brusca et al. 2007.

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Taxonomy

Ecology

General:

Sphaeroma quoianum has separate sexes and fertilization is internal. The young are brooded by the female and development is direct. Breeding takes place year-round, but brood size varies, with means of 64 in spring and 19 in fall in the San Francisco region. Its young mature in about 6 months and live for about 1.5 to 2 years (Schneider 1976, cited by Davidson 2006). Reported sizes for adults range from 8 to 16 mm (Schultz 1969; Hurley and Jansen 1977, cited by Davidson 2006; Harrison and Holdich 1984).

Sphaeroma quoianum inhabits intertidal estuarine coastlines in cold-temperate to tropical climates, and tolerates a wide range of temperature and salinity. In experiments with rapid heating (1C/min.), the lethal temperature was 42C, but limits for long-term survival are probably considerably lower. This isopod survived for 3 days at 5C. Sphaeroma quoianum is a burrower, in substrates including decaying wood, soft sandstone, salt-marsh peat and Styrofoam. In substrate preference experiments, S. quoianum most frequently colonized decayed wood in the intertidal zone (Davidson et al. 2008b). In experiments, the extent of burrowing (per isopod) varied with temperature, being greatly reduced below 10 C and reaching a maximum between 15 and 20 C (Davidson et al. 2013). Colonization of new sites is primarily by juveniles under 5 mm in length (Davidson et al. 2008b).

Sphaeroma quoianum burrows by chewing the substrate with its mandibles and expelling the particles with the current created by its beating pleopods. This animal is not known to get any nutrition from the substrate. Within its burrow, S. quoinaum sits head inward, creating a current with its pleopods, flowing inward dorsally, and outward ventrally. Phytoplankton and detritus are caught on the dense setae of the legs (Pereiopods 1-3). Periodically, the animal ceases beating of its pleopods and cleans particles off the legs with the maxillipeds (Rotramel 1975). The burrows and the flow of food particles provide food and shelter for at least two specialized symbionts and a variety of more casual visitors. The isopod Iais californica, also introduced from New Zealand or Australia, is a common obligate commensal of S. quoianum, now occurring from San Diego to Coos Bay (Rotramel 1972; Coos 1979; Davidson 2006). In experiments, I. californica had little or no effect on the survival of S. quoianum (Rotramel 1972). Another symbiont is the ciliate, Lagenophrys cochinensis, which occurs on the appendages of S. quoianum and other Sphaeroma spp. in their native and introduced ranges (Clamp 2006). Impacts of this commensal have not been studied. A wide variety of native and introduced free-living benthic invertebrates use the burrows of S. quoianum for shelter (Davidson et al. 2010).

Food:

Detritus; Phytoplankton

Trophic Status:

Suspension Feeder

SusFed

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Habitats

General Habitat	Coarse Woody Debris	None
General Habitat	Vessel Hull	None
General Habitat	Salt-brackish marsh	None
General Habitat	Unstructured Bottom	None
General Habitat	Marinas & Docks	None
Salinity Range	Mesohaline	5-18 PSU
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Tidal Range	Low Intertidal	None
Tidal Range	Mid Intertidal	None
Vertical Habitat	Endobenthic	None
Vertical Habitat	Epibenthic	None

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Tolerances and Life History Parameters

Minimum Temperature (ºC)	5	Experimental, lowest tested. No mortality in 3 days (Jansen 1971).
Maximum Temperature (ºC)	42	In short-term experiments, heating at 1 C/min, 90% of animals died at 42 C (Jansen 1971). Long-term survival limits are probably much lower.
Minimum Salinity (‰)	5	Field, Not found at salinities below 5 PSU (Davidson 2006). Experimental, 50% survival after 11 days (Riegel 1959, cited by Davidson 2008). Absent at salinities below 5 PSU in Coos Bay, Oregon, and Port Philip Bay and Tamar estuary, Australia (Davidson 2006; Davidson 2008).
Maximum Salinity (‰)	40	Field Data, Swan Estuary, Western Australia (Hass and Knott 1998).
Maximum Length (mm)	16	(Hurley and Jansen 1977, cited by Davidson 2006)
Broad Temperature Range	None	Cold temperate- Warm temperate
Broad Salinity Range	None	Mesohaline-Euhaline

General Impacts

Sphaeroma quoianum is an estuarine isopod which burrows into wood, marsh peat, sandstone, and Styrofoam. It creates complex habitats by boring, and can alter shorelines by increasing erosion. Consequently, its invasion on the West Coast has had significant ecological and economic impacts (Cohen and Carlton 1995; Talley et al. 2001; Davidson 2006; Davidson and de Rivera 2010; Davidson 2010; Davidson et al. 2010; Davidson and de Rivera 2012).

Economic Impacts

Shipping and Boating- Sphaeroma quoianum burrows into the walls of marsh channels and levees, contributing to erosion, increasing flood threats, and damaging Styrofoam floats in marinas. However, the extent of this damage in San Francisco Bay, California (CA) has not been quantified (Carlton 1979; Cohen and Carlton 1995). In Coos Bay, Oregon (OR), burrowing by S. quoianum destroyed one floating dock with Styrofoam floats and is damaging wooden pilings (Davidson 2006; Davidson 2008). 'Dikes infested with S. quoianum failed in Coalbank Slough, Coos Bay during winter storms of 2005-06 causing tens of thousands of dollars of damage to several residences (S. Rumrill, pers. comm.)' (Davidson 2008). In Coos Bay, marshes colonized by S. quoianum eroded at a much faster rate than uninfested marshes (Davidson and de Rivera 2010), with implications for waterfront property. Sphaeroma quoianum's habit of burrowing into Styrofoam floats has ecological impacts, by releasing millions of plastic particles, with serious implications for marine food webs (Davidson 2012).

Fisheries- Aquaculture facilities involving cages and ropes, suspended from floats, are vulnerable to S. quoianum. An oyster-rearing facility in Yaquina Bay had its floating docks extensively damaged (Davidson 2012).

Ecological Impacts

Habitat Change- Sphaeroma quoianum burrows into the walls of marsh channels, contributing to erosion, and modifying the marsh habitat. Higgins (1956, cited by Davidson 2008) observed that this isopod increased the erosion of sandstone terraces in San Francisco Bay. Carlton (1979) suggested that the isopod was responsible for the loss of 'tens or scores of meters of shoreline since the 19th century'. In San Diego Bay, S. quoianum creates dense networks of tunnels in walls of marsh channels. Enclosure experiments showed that S. quoianum increases the rate of marsh erosion, roughly doubling it in steeply sloping areas. Estimated marsh loss due to S. quoianum in San Diego Bay can be as great as 1 m per year in some locations (Talley et al. 2001). Burrowing by S. quoianum is accelerating erosion of marsh banks and sandstone terraces in Coos Bay, Oregon. Burrows were present at 75% of the sites examined within the Bay (Davidson 2006; Davidson 2008). In experiments, the extent of burrowing (per amphipod) varies with temperature, greatly reduced below 10C, reaching a maximum between 15 and 20C, and declining at higher temperatures. Projected global warming is likely to increase erosive impacts of S. quoianum in Coos Bay by 15-38%. This isopod's impact on erosion in other West Coast bays is likely to vary, increasing greatly in the northern portions of the invasion range, but increasing less (San Francisco Bay, Elkhorn Slough) or decreasing in the southern portion of the range (e.g. San Diego Bay and the Tijuana estuary) (Davidson et al. 2013).

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Regional Impacts

P090	San Francisco Bay		Economic Impact	Shipping/Boating
Sphaeroma quoianum burrows into the walls of marsh channels and levees, contributing to erosion, increasing flood threats, and damaging Styrofoam floats in marinas. However, the extent of this damage has not been quantified (Carlton 1979; Cohen and Carlton 1995). Damage to plastic floats was extensive in San Francisco Bay and Elkhorn Slough, CA (Davidson 2012).
NEP-V	Northern California to Mid Channel Islands		Economic Impact	Shipping/Boating
Sphaeroma quoianum burrows into the walls of marsh channels and levees, contributing to erosion, increasing flood threats, and also damaging Styrofoam floats in marinas. However, the extent of this damage has not been quantified (Carlton 1979; Cohen and Carlton 1995). Damage to plastic floats was extensive in San Francisco Bay and Elkhorn Slough, CA (Davidson 2012).
NEP-V	Northern California to Mid Channel Islands		Ecological Impact	Habitat Change
Sphaeroma quoianum burrows into the walls of marsh channels, contributing to erosion, and modifying the marsh habitat. Higgins (cited by Davidson 2008) observed that this isopod increased the erosion of sandstone terraces in San Francisco Bay. Carlton (1979) suggested that the isopod was responsible for the loss of 'tens or scores of meters of shoreline since the 19th century'. Boring by S. quoianum in plastic foam floats contributes to pollution from plastic particles, with adverse consequences for marine food webs (Davidson 2012).
NEP-VI	Pt. Conception to Southern Baja California		Ecological Impact	Habitat Change
Sphaeroma quoianum creates dense networks of tunnels in walls of marsh channels in San Diego Bay. Enclosure experiments showed that S. quoianum increases the rate of marsh erosion, roughly doubling it in steeply sloping areas. Estimated marsh loss due to S. quoianum in San Diego Bay can be as great as 1 m per year in some locations (Talley et al. 2001). In the Bolsa Chica Reserve, Huntington Brach CA, S. quoianum decreased carbon content in sediement, and increased erosion rates (Brown et al. 2022).
P020	San Diego Bay		Ecological Impact	Habitat Change
Sphaeroma quoianum creates dense networks of tunnels in walls of marsh channels in San Diego Bay. Enclosure experiments showed that S. quoianum increases the rate of marsh erosion, roughly doubling it in steeply sloping areas. Estimated marsh loss due to S. quoianum in San Diego Bay can be as great as 1 m per year in some locations (Talley et al. 2001).
P090	San Francisco Bay		Ecological Impact	Habitat Change
Sphaeroma quoianum burrows into the walls of marsh channels, contributing to erosion, and modifying marsh habitat. Higgins (cited by Davidson 2008) observed that this isopod increased the erosion of sandstone terraces in San Francisco Bay. Carlton (1979) suggested that the isopod was responsible for the loss of 'tens of scores of meters of shoreline since the 19th century'.
NEP-IV	Puget Sound to Northern California		Economic Impact	Shipping/Boating
In Coos Bay, burrowing by S. quoianum destroyed one floating dock with Styrofoam floats, and is damaging wooden pilings(Davidson 2006; Davidson 2008; Davidson 2012). Damage to plastic floats was extensive in Yaquina and Coos Bays, OR (Davidson 2012).
NEP-IV	Puget Sound to Northern California		Ecological Impact	Habitat Change
Burrowing by S. quoianum is accelerating erosion of marsh banks and sandstone terraces in Coos Bay, Oregon. Burrows were present at 75% of the sites surveyed within the Bay (Davidson 2006; Davidson 2008). Burrowed areas had rates of erosion that were 300% higher than those of adjacent unburrowed areas (Davidson and de Rivera 2010). Burrows in marsh peat were, on average, to 15X individual body volume, but only 2.5X body volume in wood. Individual impacts are smaller than those of some borers and burrowers, but high abundances can result in large population impacts (Davidson and de Rivera 2012). Boring by S. quoianum in plastic foam floats contributes to pollution by plastic particles, with adverse consequences to marine food webs (Davidson 2012). In experiments, the extent of burrowing (per amphipod) varies with temperature, greatly reduced below 10C, reaching a maximum between 15 and 20C, and declining at higher temperatures. Projected global warming is likely to increase erosive impacts of S. quoianum in Coos Bay by 15-38% (Davidson et al. 2013).
P170	Coos Bay		Economic Impact	Shipping/Boating
In Coos Bay, burrowing by S. quoianum destroyed one floating dock with Styrofoam floats, and is damaging wooden pilings (Davidson 2006; Davidson 2008). Damage to plastic floats was extensive in Yaquina and Coos Bays, OR (Davidson 2012).
P170	Coos Bay		Ecological Impact	Habitat Change
Burrowing by S. quoianum is accelerating erosion of marsh banks and sandstone terraces in Coos Bay, Oregon. Burrows were present at 75% of the sites sampled within the Bay (Davidson 2006; Davidson 2008). Burrowed areas had rates of erosion that were 300% higher than those of adjacent unburrowed areas (Davidson and de Rivera 2010). Burrows in marsh peat were, on average, 15X individual body volume, but only 2.5X body volume in wood. Individual impacts are smaller than those of some other borers and burrowers, but high abundances can result in large population impacts (Davidson and de Rivera 2012). Boring by S. quoianum in plastic foam floats contributes to pollution from plastic particles, with adverse consequences for marine food webs (Davidson 2012). In experiments, the extent of burrowing (per amphipod) varies with temperature, greatly reduced below 10C, reaching a maximum between 15 and 20C, declining at higher temperatures. Projected global warming is likely to increase erosive impacts of S. quoianum in Coos Bay by 15-38% (Davidson et al. 2013).
P210	Yaquina Bay		Economic Impact	Shipping/Boating
Damage to plastic floats was extensive in Yaquina and Coos Bays, OR (Davidson 2012).
P210	Yaquina Bay		Ecological Impact	Habitat Change
Boring by S. quoianum in plastic foam floats contributes to pollution by plastic particles, with adverse consequences for marine food webs (Davidson 2012).
P080	Monterey Bay		Economic Impact	Shipping/Boating
Damage to plastic floats was extensive in San Francisco Bay and Elkhorn Slough, CA (Davidson 2012).
P080	Monterey Bay		Ecological Impact	Habitat Change
Boring by S. quoianum in plastic foam floats contributes to pollution by plastic particles, with adverse consequences to marine food webs (Davidson 2012).
NEP-IV	Puget Sound to Northern California		Economic Impact	Fisheries
In Yaquina Bay OR, burrowing by S. quoianum riddled ~60 Styrofoam floats in a n oyste-rearing facility, requiring replacement and extensive repairs (Davidson 2012).
P210	Yaquina Bay		Economic Impact	Fisheries
In Yaquina Bay OR, burrowing by S. quoianum riddled ~60 Styrofoam floats in a n oyste-rearing facility, requiring replacement and extensive repairs (Davidson 2012).
P050	San Pedro Bay		Ecological Impact	Habitat Change
). In the Bolsa Chica Reserve, Huntington Beach CA, S. quoianum decreased carbon content in sediement, and increased erosion rates (Brown et al. 2022).
CA	California		Ecological Impact	Habitat Change
Sphaeroma quoianum burrows into the walls of marsh channels, contributing to erosion, and modifying the marsh habitat. Higgins (cited by Davidson 2008) observed that this isopod increased the erosion of sandstone terraces in San Francisco Bay. Carlton (1979) suggested that the isopod was responsible for the loss of 'tens or scores of meters of shoreline since the 19th century'. Boring by S. quoianum in plastic foam floats contributes to pollution from plastic particles, with adverse consequences for marine food webs (Davidson 2012)., Sphaeroma quoianum creates dense networks of tunnels in walls of marsh channels in San Diego Bay. Enclosure experiments showed that S. quoianum increases the rate of marsh erosion, roughly doubling it in steeply sloping areas. Estimated marsh loss due to S. quoianum in San Diego Bay can be as great as 1 m per year in some locations (Talley et al. 2001)., ). In the Bolsa Chica Reserve, Huntington Beach CA, S. quoianum decreased carbon content in sediement, and increased erosion rates (Brown et al. 2022). , Sphaeroma quoianum burrows into the walls of marsh channels, contributing to erosion, and modifying marsh habitat. Higgins (cited by Davidson 2008) observed that this isopod increased the erosion of sandstone terraces in San Francisco Bay. Carlton (1979) suggested that the isopod was responsible for the loss of 'tens of scores of meters of shoreline since the 19th century'., Boring by S. quoianum in plastic foam floats contributes to pollution by plastic particles, with adverse consequences to marine food webs (Davidson 2012).
CA	California		Economic Impact	Shipping/Boating
Sphaeroma quoianum burrows into the walls of marsh channels and levees, contributing to erosion, increasing flood threats, and also damaging Styrofoam floats in marinas. However, the extent of this damage has not been quantified (Carlton 1979; Cohen and Carlton 1995). Damage to plastic floats was extensive in San Francisco Bay and Elkhorn Slough, CA (Davidson 2012)., Sphaeroma quoianum burrows into the walls of marsh channels and levees, contributing to erosion, increasing flood threats, and damaging Styrofoam floats in marinas. However, the extent of this damage has not been quantified (Carlton 1979; Cohen and Carlton 1995). Damage to plastic floats was extensive in San Francisco Bay and Elkhorn Slough, CA (Davidson 2012)., Damage to plastic floats was extensive in San Francisco Bay and Elkhorn Slough, CA (Davidson 2012).
OR	Oregon		Ecological Impact	Habitat Change
Burrowing by S. quoianum is accelerating erosion of marsh banks and sandstone terraces in Coos Bay, Oregon. Burrows were present at 75% of the sites sampled within the Bay (Davidson 2006; Davidson 2008). Burrowed areas had rates of erosion that were 300% higher than those of adjacent unburrowed areas (Davidson and de Rivera 2010). Burrows in marsh peat were, on average, 15X individual body volume, but only 2.5X body volume in wood. Individual impacts are smaller than those of some other borers and burrowers, but high abundances can result in large population impacts (Davidson and de Rivera 2012). Boring by S. quoianum in plastic foam floats contributes to pollution from plastic particles, with adverse consequences for marine food webs (Davidson 2012). In experiments, the extent of burrowing (per amphipod) varies with temperature, greatly reduced below 10C, reaching a maximum between 15 and 20C, declining at higher temperatures. Projected global warming is likely to increase erosive impacts of S. quoianum in Coos Bay by 15-38% (Davidson et al. 2013)., Boring by S. quoianum in plastic foam floats contributes to pollution by plastic particles, with adverse consequences for marine food webs (Davidson 2012).
OR	Oregon		Economic Impact	Shipping/Boating
In Coos Bay, burrowing by S. quoianum destroyed one floating dock with Styrofoam floats, and is damaging wooden pilings (Davidson 2006; Davidson 2008). Damage to plastic floats was extensive in Yaquina and Coos Bays, OR (Davidson 2012)., Damage to plastic floats was extensive in Yaquina and Coos Bays, OR (Davidson 2012).
OR	Oregon		Economic Impact	Fisheries
In Yaquina Bay OR, burrowing by S. quoianum riddled ~60 Styrofoam floats in a n oyste-rearing facility, requiring replacement and extensive repairs (Davidson 2012).

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