Invasion History

First Non-native North American Tidal Record: 1957
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 1957

General Invasion History:

Stenothoe gallensis was described in 1904 from Sri Lanka (Ceylon), and occurs widely in the Indian Ocean. Similar amphipods were found in tropical to warm-temperate waters around the world, sometimes described under different names (e.g. S. cattai Stebbing 1906; S. crenulata Chevreux 1908; S. dentirama Hirayama & Takeuchi 1993), and later treated as synonyms of S. gallensis (Bellan-Santini et al. 1993; LeCroy 2011). Stenothoe gallensis is often assumed to be a widespread invader of Indo-European origin. In the Mediterranean, it was considered a possible 'Lessepsian migrant', through the Suez Canal (Por 1978; Bellan-Santini et al. 1993; Galil et al. 2009). Stenothoe gallensis has been listed as likely introduction in Senegal (Reid 1951), Chesapeake Bay (Fofonoff et al. 2016), Hawaii (Carlton and Eldredge 2009), and New Zealand (Ahyong and Williams 2011). It is an amphipod associated with fouling communities, including algae, hydroids, tubeworms, and tunicates, on pilings, floats, ship bottoms, buoys, mangrove roots, etc., (Shoemaker 1935; Reid 1951; LeCroy 2011).

A recent study of the 'Stenothoe gallensis group' has found that it consists of at least eight species with consistent morphological differences (Krapp-Schickel 2015). The true S. gallensis (Walker 1904) ranges from East Africa to the South China Sea (Kensley 1971; Lowry et al. 2000; Krapp-Schickel 2015). Several of the newly described species have limited known ranges (S. senegalensis- West Africa; S. andamanensis- Andaman Islands; S. clavetta- Bermuda; S. himyara- Red Sea; Krapp-Schickel 2015). Further sampling will probably show that each of these one-location species have larger ranges. At least three species have trans-oceanic or multi-oceanic ranges, and four species occur in the Western Atlantic. We are unsure of the identity of 'S. gallensis' in the Western Atlantic and Hawaii, so we will treat it as a species complex of unknown origin.

Stenothoe crenulata has the largest range of the group. It was described from Mangareva, in French Polynesia and subsequently found in Indonesia (Bali), Hawaii, and the Caribbean (Krapp-Schickel 2015). The first Western Atlantic report of S. crenulata was from St. Thomas, Virgin Islands, in 1905. It was subsequently collected from two locations in Puerto Rico (Shoemaker 1935). In the Caribbean, it is also known from Barbados, Curacao, and Venezuela (Krapp-Schickel 2015). We consider S. crenulata to be, most likely, an Indo-Pacific species introduced to the Western Atlantic. Other species of the S. gallensis complex which have some occurrences in the Western Atlantic are S. cattai (Mediterranean Sea and Bermuda), S. dentirama (Japan and Bonaire), and S. clavetta (so far, known only from the type locality, Bermuda) (Krapp-Schickel 2015).

North American Invasion History:

Invasion History on the East Coast:

Amphipods of the Stenothoe gallensis species complex were first collected in East Coast waters in Beaufort Sound, North Carolina in 1957 (Williams and Bynum 1972). They were reported to be a 'common fouling species, taken occasionally in plankton' (Fox and Bynum 1975). Specimens were collected in lower Chesapeake Bay at Cherrystone and Wachapreague Inlet, Virginia in 1960 (US National Museum of Natural History 2016), and again in 1995 (Ruiz et al. unpublished data). 'Stenothoe gallensis' was found in the Indian River Lagoon, Florida on algal covered rocks (Nelson 1995). The only detailed description of 'S. gallensis' in North American waters (LeCroy 2011) includes a key feature of S. crenulata, the crenulated posterior margin of the merus of gnathopod 2 in males (Krapp-Schickel 2015). However, more examination of East and Gulf Coast specimens is needed to determine their identity.

Invasion History on the Gulf Coast:

In 1978, amphipods of the Stenothoe gallensis species complex were found off the Mississippi Delta in Louisiana (US National Museum of Natural History 2016), and were abundant in the Crystal River estuary, Florida in 1984 (US National Museum of Natural History 2016), and Tampa Bay in 2002 (Grabe et al. 2006). It has also been found near Perdido Key, Alabama (Rakocinski et al. 1996, cited by Le Croy 2011), and on the Texas coast (McKinney, 1977, cited by Le Croy 2011).

Invasion History in Hawaii:

Stenothoe 'gallensis' was first reported from Kaneohe Bay, Oahu in 1935, and in 1944 in Pearl Harbor (Barnard 1955, cited by Carlton and Eldredge 2009). It was also found on Molokai and in Kawahai Harbor, Hawaii in 2002-2003 (Coles et al. 2004). Krapp-Schickel (2015), working from Barnard's (1955) drawings, identified Hawaiian specimens as S. crenulata.

Invasion History Elsewhere in the World:

The nature of Stenothoe 'gallensis' as a group of cryptic species makes it difficult to evaluate its invasion status worldwide. Stenothoe crenulata appears to be widespread in the Caribbean. It was collected in St. Thomas, U.S. Virgin Islands, in 1905, 'from the branchial sac of Microcosmus exasperatus' (a tunicate), and from a 'Cane wharf’ in Guanica Harbor, Puerto Rico in 1915 (Shoemaker 1935). Krapp-Schickel (2015) supported this identification and found it also in Barbados. Additional specimens were collected off Venezuela in 1936 and Curaçao in 1964 (Krapp-Schickel 2015). Another member of the S. 'gallensis' group, S. dentirama, described from Japan, has also been found in Curaçao (Krapp-Schickel 2015). Further sampling, together with morphological analysis is required to determine the native ranges and the extent of invasions in the S. 'gallensis' complex.


The Stenothoidae family is distinguished by having coxal plates 2-4 greatly enlarged, covering the basal segments of most of the appendages. The abdomen is flexed downward. They are sometimes called 'seed-amphipods', for their laterally-compressed elliptical shape. At least three species have been synonymized with Stenothoe gallensis. Krapp-Schickel (2015) re-split these species and described four others, all roughly resembling the type species, S. gallensis. Some of these species have limited known ranges, while others have been collected in both the Atlantic and Indo-Pacific. At least four of Krapp-Schickel's (2015) species (S. cattai, S. clavetta, S. crenulata, S. dentirama) have been reported from Bermuda or the Caribbean. The specific identity of the 'S. gallensis' in North American waters is unknown, but we will treat the entire complex as introduced. Members of the complex are listed below under 'Potentially Misidentified Species'. We will use a description by LeCroy (2011) of animals from Florida waters. A detailed morphological examination is needed to assign East Coast and Hawaii animals to one of the species in the S. gallensis complex as described by Krapp-Schickel (2015).

In specimens of S. 'gallensis' from Florida, the eye is relatively small. Antenna 1 is less than 1/2 the body length and is equal or slightly longer than Antenna 2. Gnathopod 2 is larger than Gnathopod 1 in both males and females, and is sexually dimorphic. The propodus of gnathopod 1 has a straight to slightly concave posterior margin, roughly equal to the margin of the palm in length. Gnathopod 2 of the male has the posterior margin of the merus scalloped (crenulate) (Lecroy 2011). [This feature matches S. crenulata (Krapp-Schickel 2010)]. The distal palmar tooth is relatively small. On gnathopod 2 in females the propodus has a convex posterior margin, without a distal palmar tooth, and the merus is smoothly curved. Pereiopod 7 has segment 4 (merus) slightly enlarged, with a curved, angular postero-distal tip. Uropod 1 extends beyond Uropod 2. Its peduncle has a distoventral spur. Both Uropods 1 and 2 are biramous. Uropod 3 of the male has the terminal article of the ramus expanded proximally. The telson is oval, with 3-4 pairs of marginal spines. Florida specimens range from 2 to 6 mm, with males generally larger than females (LeCroy 2011). Genetic and molecular studies are needed to determine the identity of East and Gulf Coast specimens of 'S. gallensis', and how they fit into the species described by Krapp-Schickel (2015).


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Amphipoda
Suborder:   Gammaridea
Family:   Stenothoidae
Genus:   Stenothoe
Species:   gallensis complex


Probolium polyprion (Catta, 1876)

Potentially Misidentified Species

Stenothoe andamanensis
(Krapp-Schickel 2015); member of S. gallensis complex, described from Andaman Island, Indian Ocean (Krapp-Schickel 2015).

Stenothoe cattai
(Stebbing, 1906); member of S. gallensis complex, described from Marseille, Mediterranean Sea, Bermuda (Krapp-Schickel 2015).

Stenothoe clavetta
(Krapp-Schickel 2015); member of S. gallensis complex, described from Bermuda (Krapp-Schickel 2015).

Stenothoe crenulata
(Chevreux, 1908); member of S. gallensis complex, described from Gambier Archipelago, Polynesia. Range includes Indonesia, Polynesia, Hawaii, Caribbean Sea (Krapp-Schickel 2015).

Stenothoe dentirama
(Hirayama & Takeuchi, 1993); member of S. gallensis complex, described from Japan. Range includes Japan and Caribbean Sea (Krapp-Schickel 2015).

Stenothoe gallensis
(Walker 1904); member of S. gallensis complex, described from Sri Lanka, ranges from South Africa to South China Sea (Krapp-Schickel 2015).

Stenothoe georgiana
(Bynum and Fox, 1977); described from Georgia, ranges from Virginia to Florida (LeCroy 2011).

Stenothoe himyara
(Krapp-Schickel 2015); member of S. gallensis complex, described from Port Sudan, Red Sea (Krapp-Schickel 2015).

Stenothoe minuta
(Holmes, 1903); described from Massachusetts ranges from Cape Cod to Texas (LeCroy 2011).

Stenothoe senegalensis
(Krapp-Schickel 2015); member of S. gallensis complex, described from Senegal, Atlantic Ocean (Krapp-Schickel 2015).

Stenothoe valida
(Dana 1852); described from Rio de Janeiro, currently 'considered cosmopolitan in warm water' which is questionable (Krapp-Schickel 2015).



Amphipods of the Stenothoe gallensis species complex have separate sexes, the young are brooded and development is direct (Bousfield 1973).

Amphipods of the Stenothoe gallensis species complex are known from warm-temperate to tropical climates, and polyhaline to euhaline salinities (Shoemaker 1935; Lecroy 2011; Krapp-Schickel 2015). Among invertebrates, hosts include hydroids (Pennaria sp), bryozoans, polychaete reefs, and the tunicates Didemnum sp., Styela sp., and Microcosmus exasperatus. Stenothoe 'gallensis' is also known from algae, seagrasses, and mangrove roots (Shoemaker 1935; Marsh 1973; Lecroy 2011; Krapp-Schickel 2015). It occasionally occurs in coastal plankton (Fox and Bynum 1975) and has been collected in the mid-Pacific (Krapp-Schickel 2015). Stenothoe 'gallensis' is common in dock, buoy, and ship fouling (Shoemker 1935; Reid 1951; Krapp-Schickel 2015). Its mode of feeding may resemble that of S. valida, which is a suspension feeder - animals sit in place, with uropods pressed against a surface and the body pointed upward at a 30-degree angle, with the antennae and gnathopods in motion, and periodically wiped across the mouthparts (Lewis 1992).


Phtyoplankton, detritus

Trophic Status:




General HabitatGrass BedNone
General HabitatMarinas & DocksNone
General HabitatRockyNone
Tidal RangeSubtidalNone
Vertical HabitatEpibenthicNone
Vertical HabitatLittoralNone

Tolerances and Life History Parameters

Minimum Salinity (‰)16Grabe et al. 2006, Tampa Bay
Maximum Salinity (‰)37Approximate Gulf of Mexico salinity
Minimum Length (mm)2LeCroy 2011; Krapp-Schickel 2015. Females are generally smaller than males.
Maximum Length (mm)6LeCroy 2011; Krapp-Schickel 2015.
Broad Temperature RangeNoneWarm temperate-Tropical
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No impacts have been reported for amphipods of the Stenothoe gallensis complex in their native or introduced ranges.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
CIO-II None 1904 Crypto Estab
RS-2 None 0 Crypto Estab
RS-1 None 0 Crypto Estab
RS-3 None 2003 Crypto Estab
MED-II None 1907 Crypto Estab
SP-XVI None 1907 Crypto Estab
CAR-IV None 1915 Def Estab
NWP-2 None 1994 Crypto Estab
CIO-I None 0 Crypto Estab
MED-IV None 0 Crypto Estab
CAR-I Northern Yucatan, Gulf of Mexico, Florida Straits, to Middle Eastern Florida 1978 Def Estab
CAR-VII Cape Hatteras to Mid-East Florida 1957 Def Estab
NA-ET3 Cape Cod to Cape Hatteras 1960 Def Estab
SP-XXI None 1935 Def Estab
NEA-IV None 1925 Crypto Unk
WA-V None 1955 Crypto Estab
EA-IV None 1955 Crypto Estab
M130 Chesapeake Bay 1960 Def Estab
S030 Bogue Sound 1957 Def Estab
S020 Pamlico Sound 1962 Def Estab
M128 _CDA_M128 (Eastern Lower Delmarva) 1960 Def Estab
CAR-II None 1984 Def Estab
MED-I None 1976 Crypto Estab
MED-VI None 1978 Crypto Estab
MED-V None 1978 Crypto Estab
S190 Indian River 1995 Def Estab
G200 Barataria Bay 1978 Def Estab
WA-IV None 1969 Crypto Estab
WA-I None 1951 Crypto Estab
G070 Tampa Bay 2002 Def Estab
NZ-IV None 2004 Def Estab
G050 Charlotte Harbor 2011 Def Estab
G140 Perdido Bay 1996 Def Estab
G074 _CDA_G074 (Crystal-Pithlachascotee) 1984 Def Estab
CAR-III None 1936 Def Estab
NA-ET4 Bermuda 1910 Crypto Estab
MED-III None 2013 Crypto Estab
MED-VII None 1992 Crypto Estab
EAS-VIII None 0 Crypto Estab
NWP-3a None 0 Crypto Estab
NWP-3b None 0 Crypto Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Ahyong, Shane T.; Wilkens, Serena L. (2011) In the wrong place- Alien marine crustaceans: Distribution, biology, impacts, Springer, Dordrecht, Netherlands. Pp. 451-485

Ates, A. Suat; Katagan, Tuncer; Sezgin, Murat; Özcan, Tahir (2013) Exotic crustaceans of the Turkish coast, Arthropods 2(1): 20-25

Bellan-Santini, Denise; Karaman, Gordon; Krapp-Schickel, Gertraud; Ledoyer, Michel; Myers, Alan A.; Ruffo, Sandro; Schiecke, Ulrich (1993) The Amphipoda of the Mediterranean: Part 3. Gammaridea: Melphippidae to Talitridae; Ingolfiellidea; Caprellidea, Memoires de l'Institut Oceanographique (Monaco) 13: 577-813

Bynum, Kenneth H.; Fox, Richard S. (1977) New and noteworthy crustaceans from North Carolina, U. S. A., Chesapeake Science 18(1): 1-33

Carlton, J.T., Eldredge, L. (2001) <missing title>, Bernice P. Bishop Museum Press, Honolulu, Hawaii,. Pp. <missing location>

Carlton, James T.; Eldredge, Lucius (2009) Marine bioinvasions of Hawaii: The introduced and cryptogenic marine and estuarine animals and plants of the Hawaiian archipelago., Bishop Museum Bulletin in Cultural and Environmental Studies 4: 1-202

Chevreux, Edward & Fage, Louis (1925) Amphipodes, In: Rue DR Touron(Eds.) Faune de France. , Paris, France. Pp. <missing location>

Çinar, M. E.; Noglu, M. Bilece; Özturk, B.; Katagan, T. ; Aysel, V. (2005) Alien species on the coasts of Turkey, Mediterranean Marine Science 6/2: 119-146

Coles, S. L.; Reath, P. R.; Longenecker, K.; Bolick, Holly; Eldredge, L. G. (2004) <missing title>, Hawai‘i Community Foundation and the U. S. Fish and Wildlife Service, Honolulu. Pp. 1-187

Conradi, Mercedes; López-González, Pablo J. (1999) The benthic Gammaridea (Crustacea, Amphipoda) fauna of Algeciras Bay (Strait of Gibraltar): distributional ecology and some biogeographical considerations., Helgoland Journal of Marine Research 53: 2-8

Emara, Ahmed; Belal, Aisha (2004) Marine fouling in Suez Canal, Egypt, Egyptian Journal of Aquatic Research 30A: 189-206

Feeley, James B.; Wass, Marvin L. (1971) The distribution and ecology of the Gammaridea (Crustacea: Amphipoda) of the lower Chesapeake estuaries., Special Papers in Marine Science 2: 1-58

Fox, Richard S.; Bynum, Kenneth H. (1975) The amphipod crustaceans of North Carolina estuarine waters, Chesapeake Science 16(4): 223-237

Grabe, Stephen A.; Karlen, David J.; Holden, Christina M.; Goetting, Barbara K.; Markham, Sara E; Dix, Thomas L. (2006) <missing title>, Tampa Bay Estuary Program, St. Petersbrug FL. Pp. 1-88

Kensley, Brian (1971) Amphipods from southern Angola, Annals of the South African Museum 57(8): 149-156

Krapp-Schickel, G. (1993) Do algal-dwelling amphipods react to the 'critical zones' of a coastal slope?, Journal of Natural History 27(4): 883-900

Krapp-Schickel, T. (2013) New or amended data on Mediterranean Amphipoda: genera Dexamine, Ericthonius and Stenothoe, Zootaxa 3613(2): 125-145

Krapp-Schickel, Traudl (2015) Minute but constant morphological differences within members of Stenothoidae: the Stenothoe gallensis group with four new members, keys to Stenothoe worldwide, a new species of Parametopa and Sudanea n. gen. (Crustace, Journal of Natural History 37-38: 2309-2377

Lecroy, Sara E. (2011) <missing title>, Florida Department of Environmental Protection, Tallahassee FL. Pp. 615-1816

Lewis, John B. (1992) Abundance, distribution and behavior of a commensal amphipod Stenothoe valida Dana on the hydrocoral Millepora complanata Lamarck, Bulletin of Marine Science 51(2): 245-249

Lowry, J. K. (2000) Taxonomic status of amphipod crustaceans in the South China Sea, with a checklist of known species, Raffles Bulletin of Zoology Suppl. 8: 309-342

Manoudis, Georgios; Antoniadou, Chryssanthi; Dounas, Konstantinos; Chintiroglou, Chariton Ch. (2005) Successional stages of experimental artificial reefs deployed in Vistonikos gulf (N. Aegean Sea, Greece) : Preliminary results, Belgian Journal of Zoology 135(2): 209-215

Marsh, G. Alex (1973) The Zostera epifaunal community in the York River, Virginia, Chesapeake Science 14(2): 87-97

Martín, A.; Díaz, Y. J. (2003) [The amphipod fauna (Crustacea: Amphipoda) of the coastal waters of eastern Venezuela], Boletin Insititute Espanol de Oceanografia 19(1-4): 327-344

Nelson, Walter G. (1995) Amphipod crustaceans of the Indian River Lagoon: current status and threats to biodiversity, Bulletin of Marine Science 57(1): 143-152

Paz-Rios, Carlos E. ; Simoes, Nuno; Ardisson, Pedro-Luis (2013) Records and observations of amphipods (Amphipoda: Gammaridea and Corophiidea) from fouling assemblages in the Alacranes Reef, southern Gulf of Mexico, Marine Biodiversity Records 6: e90

Por, F. D. (1978) <missing title>, Springer-Verlag, Heidelberg. Pp. <missing location>

Reid, D. M. (1951) Report on the Amphipoda (Gammaridea and Caprellidea) of the coast of tropical West Africa, Atlantide - Report 2: 189-291

Sezgin, Murat; Bakir, Kerem; Katagan, Tuncer (2007) New record of a lessepsian amphipod from the Levantine coast of Turkey: Elasmopus pectenicrus (Bate, 1862), Crustaceana 80(2): 247-251

Shoemaker, Clarence R. (1935) The amphipods of Porto Rico and the Virgin Islands, Scientific Survey of Porto Rico and the Virgin Islands; New York Academy of Sciences 15: 229-253

U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database.

Venugopalan, V. P.; Wagh, A. (1990) Biofouling of an offshore oil platform: Faunal composition and biomass, Indian Journal of Marine Science 19: 53-56

Watling, Les (1979) Zoogeographic affinities of northeastern North American gammaridean amphipoda, Bulletin of the Biological Society of Washington <missing volume>(3): 256-282

Williams, Austin B.; Bynum, Kenneth H. (1972) A ten-year study of meroplankton in North Carolina estuaries: Amphipods, Chesapeake Science 13(3): 175-192

Winfield, Ignacio; Mucino-Reyes, María del Refugio; Ortiza, Manuel; Cházaro-Olveraay, Sergio; Lozano-Aburto, Miguel Ángel (2015) [Biodiversity of benthic amphipods (Peracarida: Amphipoda) associated with algal beds from Puerto Progreso, Yucatán, Mexico], Revista Mexicana de Biodiversidad 86: 613-619

Xiangiu, Ren (1994) Studies on Gammaridea (Crustacea, Amphipoda) from Hong Kong, Daya Bay and adjacent waters., Studia Marina Sinica 35: 249-271

Zakhama-Sraieb, Rym ; Charfi-Cheikhrouha, Faouzia (2010) First record of two lessepsian amphipods in Tunisia: Elasmopus pectenicrus and Stenothoe gallensis, Journal of the Marine Biological Association of the United Kingdom 90: 1291-1295

Zakhama-Sraieb, Rym; Sghaier, Yassine-Ramzi; Charfi-cheikhrouha, Faouzia (2009) Amphipod biodiversity of the Tunisian coasts: update and distributional ecology, Marine Biodiversity Records 2: 1-7