Invasion History

First Non-native North American Tidal Record: 1953
First Non-native West Coast Tidal Record: 1953
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Tenellia adspersa was described from Odessa, Ukraine and is now widely distributed around the world, most likely spread by shipping (Roginskaya 1970; Thompson and Brown 1984). It is native in the Eastern Atlantic, from Europe (Norway to Portugal and Spain) and the Western Mediterranean (Roginskaya 1970). In the Baltic, it occurs eastward to the Gulf of Finland (Roginskaya 1970; Evertsen et al. 2004). In much of its European range, it is confined to brackish lagoons (Thompson and Brown 1984).

On the East Coast of North America, the range and invasion status of T. adspersa is unclear, owing to frequent confusion with a very similar native species, T. fuscata (Gould 1870), which has an overlapping range (Marcus 1972; Chester 1996). It has been introduced to Brazil, the West Coast of North America, Japan, and the Caspian Sea (Roginskaya 1970; Antsulevich and Starobogatov 1990). It feeds on many species of hydroids and tolerates a wide range of salinity and temperature (Roginskaya 1970). Hydroid prey include a number of global invaders: Cordylophora caspia, Garveia franciscana, and Ectopleura crocea (Roginskaya 1970). The mode of larval development is variable according the adult's nutritional status, between lecithotrophic development, with a short planktonic period, and planktotrophic development, with a longer planktonic phase (Chester 1996), more favorable for ballast water transport.

North American Invasion History:

Invasion History on the West Coast:

Tenellia adspersa was first found on the West Coast at Point Richmond, San Francisco Bay in 1953 (Jones 1954, cited by Carlton 1979). It was subsequently found at many locations within the Bay, including Berkeley Yacht Harbor in 1963 (Steinberg 1963); Lake Merritt Oakland in 1970 (Carlton 1979); San Leandro in 1993 (Cohen and Carlton 1995); Sausalito around 1995 (Cohen and Carlton 1995), and the Napa River in 2004 (Cohen et al. 2005). It was found on hydroids in Monterey Bay (Steinberg 1963), but was not seen there after 1958 (Carlton 1979). However, it was found in Elkhorn Slough in 1977 (Carlton 1979), and was established by 1998 (Wasson et al. 2001). It was also found in Alamitos Bay, in Long Beach in 1968 (Carlton 1979). In 1986, T. adspersa was found in upper Coos Bay, Oregon (Goddard 1990).

Invasion History on the East Coast:

Tenellia adspersa was first reported from the East Coast in 1969, based on collections made in Chesapeake Bay, starting in 1969 (Marcus 1972). However, its status in the Northwest Atlantic is complicated by confusion with the very similar T. fuscata, described from the Charles River estuary, Massachusetts, which overlaps in range and habitat (Marcus 1972; Vogel 1977). Consequently, we regard T. adspersa as cryptogenic in the Northwest Atlantic, until the status and distribution of the two species is resolved. At least one population, initially identified as T. fuscata, in Great Bay, New Hampshire (Gaulin et al. 1986) was later found to be T. aspersa (Chester 1996). Currently, T. adspersa is known from Great Bay, New Hampshire to Beaufort, South Carolina (Marcus 1972; Eyster 1979; Chester 1996; Caine 1998), while T. fuscata is reported from Maine to Chesapeake Bay (Gould 1870; Franz 1968), with one report from the Indian River Lagoon, Florida (Clark 1995). Vogel (1977) reported both species from Chesapeake Bay, with T. adspersa tending to occur at lower salinities (average 12.5 PSU) than T. fuscata (14.5-30 PSU). On Smithsonian Environmental Research Center (SERC) fouling plates in Chesapeake Bay, Terrence Gosliner found only T. adspersa, but only a few animals were examined (Ruiz et al., unpublished data).

Invasion History Elsewhere in the World:

Tenellia adspersa was described from Odessa, Ukraine on the Black Sea in 1845, but was not found in the Sea of Azov until 1963 (Roginskaya 1970). It could have been overlooked, or transported by ships. Increased salinity in the Sea, due to hydroelectric dams, could have favored the invasion. Its introduction to the Caspian Sea in 1990 was clearly due to transport in ballast water, by ships traversing the canal from the Black Sea (Antsulevich and Starobogatov 1990).

Beyond Europe, it was introduced to brackish waters in Brazil before 1953 (Vannucci and Hosoe 1953, cited by Roginskaya 1970). One specimen was found in the Seto Inland Sea, Japan in 1959 (Baba and Hamatani 1963). More recently, it was found in a bypass canal in Vladivostok, Russia, on the Sea of Japan in 1995, but did not become established (Zvyagintsev et al. 2011). One record is known from Botany Bay, Sydney, Australia in 1988 (Australian Museum Malacology C.155082, Atlas of Living Australia 2014), but establishment is unknown.


Description

Tenellia adspersa has a slender body and a rounded head with lateral lobes, sometimes prolonged into oral tentacles, resulting in a crescent shape. The rhinophores (dorsal head tentacles) are smooth and cylindrical. There are 2 to 6 rows of cerata (dorsal outgrowths containing nematocysts) across the back, each with 1-3 cerata on each side of the body. The penis has an apical stylet. The animal rarely exceeds 8 mm in length. The overall color is yellowish to pale brown in color with black stippling over the body. Description based on Roginskaya (1970), Marcus (1972), Vogel (1977), Thompson and Brown (1984), and Behrens (1991).


Taxonomy

Taxonomic Tree

Kingdom:   Animalia
Phylum:   Mollusca
Class:   Gastropoda
Subclass:   Opisthobranchia
Order:   Nudibranchia
Family:   Tergipedidae
Genus:   Tenellia
Species:   adspersa

Synonyms

Embeltonia mediterranea (Vannucci and Hosoe, 1953)
Embletonia grayi (Saville-Kent, 1869)
Embletonia pallida (Alder and Hancock, 1854)
Eolis ventilabrum (Dalyell, 1853)
Tenellia mediteranea (Costa, 1866)
Tenellia pallida (Thompson and Brown, 1976)
Tenellia ventilabrum (Dalyell, 1853)
Tergipes adspersa (Nordmann, 1845)
Tergipes lacinulatus (Schultze, 1849)

Potentially Misidentified Species

Calliopaea bellula
Calliopaea bellula (Stiliger bellulus) is an herbivorous sacoglossan native to the Northeast Atlantic, from Norway to the Mediterranean and Black Seas (Rudman 2009). Tenellia adspersa in the Sea of Azov was originally identified as this animal (Roginskaya 1970).

Stiliger fuscata
Stiliger fuscata is native to the Northwest Atlantic from New Hampshire to Florida. It is an herbivorous sacoglossan, found on algae, but superficially resembles Tenellia spp. However, the cerata are concentrated in the posterior part of the body (Abbott 1974).

Stiliger fuscovittata
Stiliger fuscovittatus is native to the Northeast Pacifiic from Alaska to Mexico. It has been introduced to Florida and Texas, but has not become established. It is an herbivorous sacoglossan, found on algae, but superficially resembles Tenellia spp. However, S. fuscovittatus lacks the crescent-shaped pair of lobes on the head, and is marked with two parallel reddish-brown streaks on the body (Behrens 1991).

Tenellia fuscata
Tenellia fuscata is very similar to T. adspersa, but differs by lacking a penial stylet and having a hermaphroditic valve (Chambers 1934, cited by Franz 1968; Marcus 1972). It has been reported from Massachusetts to Florida (Gould 1870; Franz 1968; Clark 1995). Careful morphological examination and genetic analysis may be needed to determine the distribution of the two species of Tenellia spp. and confirm their status as separate species.

Ecology

General:

Tenellia adspersa is a small nudibranch associated with hydroids, often in brackish water. Nudibranchs are simultaneous hermaphrodites and copulate reciprocally or unilaterally. Tenellia adspersa lays its eggs in an oval gelatinous mass containing 3-40 eggs, attached to hydroid stalks (Roginskaya 1970). The mode of development of the eggs varies with the nutritional status of the adults. This species can produce direct-developing larvae, lecithotrophic larvae (<1 day in plankton), and planktotrophic larvae (4-5 days in plankton) (Eyster 1979; Thompson and Brown 1984). Chester (1996) found that development time at 20°C was 5-6 days for eggs of continuously fed animals, but decreased to 3 days for starved animals. Both the type of larva produced and the rate of development appear to be variable between and within populations. This non-genetic variation in larval development is unusual in invertebrates, and is known as 'poeciligony'.

Tenellia adspersa has been reported from lagoons, estuaries, and harbors of warm-temperate to tropical regions. Substrates include rocks, pilings, floating docks, and boat hulls (Steinberg 1963; Roginskaya 1970; Chester 1996). This nudibranch tolerates an unusually wide range of salinity, from 3 to 50 PSU (Roginskaya 1970; Harris 1980), although some populations show reduced reproduction below 10-12 PSU (Harris et al. 1980; Blezard 1999). Tenellia adspersa feeds on a very wide range of hydroids, including Cordylophora caspia, Garveia franciscana, Ectopleura crocea, Gonothyraea loveni, Obelia spp., Protohydra leukarti, Eudendrium sp., and Bougainvillea sp. (Roginskaya 1970; Vogel 1977; Eyster 1979; Harris et al. 1980; Thompson and Brown 1984; Goddard 1990; Caine 1998). The feeding rate can be quite high. One T. adspersa can consume 100 Garveia hydranths in a day (Turpaeva 1963, cited by Roginskaya 1970). Chester et al. (2000) reported lower rates, up to seven C. caspia polyps eaten per day. Experiments indicate that T. adspersa can survive long periods of time without feeding, so that they can prevent the regrowth of hydroids after extensive predation (Chester et al. 2000). In many nudibranchs, the cnidocysts (stinging cells) of hydroids are ingested and then incorporated into the cerata, as a defensive mechanism (Barnes 1983). This is probably the case in T. adspersa.

Food:

Hydroids

Trophic Status:

Carnivore

Carn

Habitats

General HabitatOyster ReefNone
General HabitatMarinas & DocksNone
General HabitatGrass BedNone
General HabitatCoarse Woody DebrisNone
Salinity RangeMesohaline5-18 PSU
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone


Tolerances and Life History Parameters

Minimum Temperature (ºC)4Lowest tested (Harris et al. 1980)
Maximum Temperature (ºC)25Field (Eyster 1979)
Minimum Salinity (‰)3Lab experiments, cited by Roginskaya (1970)
Maximum Salinity (‰)50Lab experiments, cited by Roginskaya (1970)
Minimum Reproductive Salinity10Experiments cited by Roginskaya (1970)
Maximum Reproductive Salinity50Lab experiments, (Harris et al. 1980)
Minimum Duration0Development appears to vary with adult feeding and condition; well-fed adults lay eggs which develop directly, hatching out juveniles. Lower levels of feeding yield lecithotrophic or planktotrophic larvae (Chester 1996). All three modes of development can be seen simultaneously in a population (Eyster 1979; )
Maximum Duration4.9Planktotrophic larvae hatched from adults fed at lower levels (Chester 1996).
Minimum Length (mm)5Roginskaya 1970
Maximum Length (mm)8Roginskaya 1970
Broad Temperature RangeNoneCold-Temperate-Warm-Temperate
Broad Salinity RangeNoneOligohaline-Polyhaline

General Impacts

Tenellia adspersa is of ecological and economic interest because of its predation on a wide range of fouling hydroids, and because its ease of culture permits study of predator-prey relations (Roginskaya 1970; Harris et al. 1980; Gaulin et al. 1986; Chester et al. 2000).

Economic Impacts

High abundances of Tenellia sp. have been reported on fouling plates near power plants in Chesapeake Bay (Cory 1967; Abbe 1987) and in the Sea of Azov (Roginskaya 1970). Tenellia adspersa might have some beneficial impact on fouling in cooling systems if its predation reduced biomasses of hydroids such as Garveia franciscana and Cordylophora caspia (Chester et al. 2000).

Ecological Impacts

Predation: Tenellia adspersa is potentially an important predator on a wide range of hydroids, including widely introduced Garveia franciscana (Rope Grass Hydroid) and Cordylophora caspia (Freshwater Hydroid) (Roginskaya 1970; Harris et al. 1980). In experimental cultures, T. adspersa's chemical cues and predation caused an alteration of C. caspia's growth form, resulting in a greater density of hydranths. This could limit later settlement of T. adspersa's larva, due to predation. Tenellia adspersa predation on C. caspia thus seems to have complex effects; small numbers of T. adspersa might actually increase C. caspia biomass (Gaulin et al. 1986). However, modelling predicts that under a wide range of conditions, T. adspersa will eliminate C. caspia colonies, resulting in succession of hydroids by other fouling organisms (Chester et al. 2000).

Regional Impacts

N130Great BayEcological ImpactPredation
Predation by Tenellia adspersa on the hydroid Cordylophora caspia stimulated increased growth and budding in the hydroid, resulting in a denser colony, perhaps favoring the persistence of the colonies (Gaulin et al. 1986). However, population modeling, including reproduction and settlement, indicates that T. adspersa is likely to remove colonies of C. caspia, favoring succession in the fouling community (Chester et al. 2000).
S110Broad RiverEcological ImpactPredation
Tenellia adspersa was observed feeding on the hydroid Bougainvillia rugosa. However, the rate of predation was reduced by interference from the caprellid Paracaprella tenuis, which flicked the nudibranch away (Caine 1998).
CAR-VIICape Hatteras to Mid-East FloridaEcological ImpactPredation
Tenellia adspersa was observed feeding on the hydroid Bougainvillia rugosa. However, the rate of predation was reduced by interference from the caprellid Paracaprella tenuis, which flicked the nudibranch away (Caine 1998).
NA-ET2Bay of Fundy to Cape CodEcological ImpactPredation
Predation by Tenellia adspersa on the hydroid Cordylophora caspia stimulated increased growth and budding in the hydroid, resulting in a denser colony, perhaps favoring the persistence of the colonies (Gaulin et al. 1986). However, population modeling, including reproduction and settlement, indicates that T. adspersa is likely to remove colonies of C. caspia, favoring succession in the fouling community (Chester et al. 2000).

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NEA-II None 0 Native Estab
NEA-III None 0 Native Estab
AR-V None 0 Native Estab
B-I None 0 Native Estab
B-II None 0 Native Estab
B-IV None 0 Native Estab
B-III None 0 Native Estab
B-V None 0 Native Estab
B-VII None 0 Native Estab
B-VI None 0 Native Estab
NEA-IV None 0 Native Estab
NEA-V None 0 Native Estab
MED-II None 0 Native Estab
MED-III None 0 Native Estab
MED-IX None 0 Native Estab
MED-X None 1963 Crypto Estab
NA-ET3 Cape Cod to Cape Hatteras 1972 Crypto Estab
CAR-VII Cape Hatteras to Mid-East Florida 1977 Crypto Estab
NEP-V Northern California to Mid Channel Islands 1953 Def Estab
NEP-VI Pt. Conception to Southern Baja California 1968 Def Estab
NEP-IV Puget Sound to Northern California 1986 Def Estab
CASP Caspian Sea 1989 Def Estab
SA-II None 1953 Def Estab
NWP-3b None 1959 Def Unk
M020 Narragansett Bay 2000 Crypto Estab
M130 Chesapeake Bay 1969 Crypto Estab
M010 Buzzards Bay 2000 Crypto Estab
P050 San Pedro Bay 1968 Def Estab
P170 Coos Bay 1990 Def Estab
B-X None 0 Native Estab
P080 Monterey Bay 1977 Def Estab
P090 San Francisco Bay 1953 Def Estab
N130 Great Bay 1980 Crypto Estab
M060 Hudson River/Raritan Bay 2003 Crypto Estab
P093 _CDA_P093 (San Pablo Bay) 1953 Def Estab
AUS-X None 1988 Def Unk
NA-ET2 Bay of Fundy to Cape Cod 1980 Crypto Estab
NWP-4a None 1995 Def Unk
S060 Winyah Bay 0 Crypto Estab
S110 Broad River 1994 Crypto Estab
NA-ET1 Gulf of St. Lawrence to Bay of Fundy 1962 Crypto Estab
P053 _CDA_P053 (Santa Monica Bay) 2015 Def Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude
26657 Wasson et al. 2001 (Elkhorn Slough Survey) 1998 1998-03-01 Elkhorn Slough Station 9 Def 36.8398 -121.7435
27474 Steinberg 1963, cited by Carlton 1979 1963 1963-01-01 Berkeley Marina, San Francisco Bay Def 37.8664 -122.3150
29340 Jones 1954, cited by Carlton 1979 1953 1953-01-01 Point Richmond, San Francisco Bay Def 37.9230 -122.3940
30078 Carlton 1979; Cohen and Carlton, 1995 1968 1968-01-01 Los Angeles/Long Beach Harbor Complex Def 33.7632 -118.2526
33078 Carlton 1979; Cohen and Carlton 1995 1970 1970-01-01 San Francisco Bay- Lake Merritt, Oakland Def 37.8025 -122.2578
33793 Cohen, et al. 2005 (SF Bay Area RAS) 2004 2004-05-28 Napa Valley Marina, San Pablo Bay Def 38.2200 -122.3128

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