Invasion History

First Non-native North American Tidal Record: 1993
First Non-native West Coast Tidal Record: 1993
First Non-native East/Gulf Coast Tidal Record:

General Invasion History:

Melita rylovae was described from the Russian Sea of Japan and has been reported from the Yellow and East China Seas of China, Korea, and Japan, and the Sea of Japan north to Hokkaido (Yamato 1987; Kim et al. 1992; Huang 2001; Shin et al. 2005). It was first collected in North American waters in San Francisco Bay, California in 1993 and is established there (Cohen and Carlton 1995; Cohen et al. 2002; Chapman 2007; California Department of Fish and Wildlife 2011). This amphipod was collected in ballast water aboard a ship from Japan, which was sampled in Australia (Williams et al. 1988). To our knowledge, it has not been collected in Australian waters.

North American Invasion History:

Invasion History on the West Coast:

Melita rylovae was first collected on the West Coast in 1993 in San Francisco Bay, California (Cohen and Carlton 1995). In San Francisco Bay, it has been collected from the central bay, the South Bay, and San Pablo Bay. It is often collected in fouling communities on docks and marinas (Cohen et al. 2005; Chapman 2007; California Academy of Sciences 2015). In 2000, it was collected in yacht harbors in Los Angeles and Huntington Harbor (Cohen et al. 2002). This amphipod was collected again in Huntington Harbor in 2011 (California Department of Fish and Wildlife 2014).


Melita rylovae has a slender and laterally compressed body with small, oval eyes. Coxal plates 1-4 are large and rounded below. Pleosomites 2 and 3 have paired sub-dorsal medial teeth on the rear margin. In larger specimens teeth are also present on Pleosomite 1. The ventrodistal corners of Epimeral Plates 1-3 end in a sharp tooth, most pronounced in Plate 3. Plates 2 and 3 have spines along their lower margins. Antenna 1 is long and robust, ~2/3 body length, with a large flagellum of 40+ segments lined with short setae, and a small accessory flagellum of 5 segments. On Antenna 2, peduncle segments 4 and 5 have groups of small spines and setae on their inner surfaces. Most specimens have few or no spines on the outer (ventral) surface.

Segment 2 of Gnathopod 1 in males has long setae on its anterior side, while segments 3-5 have dense setae on their posterior side. The distal lobe of segment 6 (propodus) has a roughly rectangular anterior-distal lobe with two tubercles on the anterior-distal margin. The short dactyl, arises on the anterior margin, with the tip curled inward, closing on the inner face of the propodus (segment 6). The palm of the propodus is lined with stout spines. In the female, Gnathopod 1 is missing the rectangular anterior-distal lobe. Gnathopod 2 is larger than Gnathopod 1 in both sexes, but the male has segment 6 greatly enlarged, distally, with a palm lined with spines and setae, and with the dactyl tip closing on the inner side of the palmar angle. The female Gnathopod 2 is similar, but smaller, and has 2-3 stout subterminal spines at the distal end of the palm.

The basal segments of pereiopods 5-7 are greatly expanded, especially on the posterior-distal corner. The female's Coxa 6 is ventrally extended into a curved hook. Uropod 2 is biramous, but the outer ramus is tiny and scale-like, with 3 apical spines. The telson is deeply bilobed, with each lobe having apical and subapical spines, with one apical spine much longer than the others. Males range from 7.5 to 11.7 mm in size, while females range from 6.7 to 9.8 mm. Description based on: Yamato 1987, Kim et al. 1992, Shin et al. 2005, and Chapman 2007.


Taxonomic Tree

Kingdom:   Animalia
Phylum:   Arthropoda
Subphylum:   Crustacea
Class:   Malacostraca
Subclass:   Eumalacostraca
Superorder:   Peracarida
Order:   Amphipoda
Suborder:   Gammaridea
Family:   Melitidae
Genus:   Melita
Species:   rylovae


Melita rylovae (Bulycheva, 1955)
Melita rylovi (Cohen et al., 2005)
Abludomelita rylovae (Karaman, 1981)

Potentially Misidentified Species

Melita koreana
Melita koreana Stephensen 1944 was once considered synonymous with M. rylovae, but has been found to be distinct (Yamtao 1987; Kim et al. 1992).

Melita nitida
Melita nitida Smith 1873 is native to the Northwest Atlantic (Chapman 2007).

Melita oregonensis
Melita oregonensis Barnard 1954 is a West Coast native of rocky shores (Chapman 2007).

Melita setiflagellata
Melita setiflagellata Yamato 1987 is a very similar species described from Japan. Some authors have treated this amphipod as conspecific with M. nitida and an introduction in Japan, but most regard it as native in Japan (Doi et al. 2011). Given the similarity, some populations of 'M. nitida' on the West Coast could be really be M. setiflagellata (Chapman 2007; Graening et al. 2012). Molecular studies of this amphipod are desirable.

Melita sulca
Melita sulca Barnard 1954 is a West Coast native of harbors, cobble bottoms, and kelp beds (Chapman 2007).



Melita rylovae has separate sexes, with brooded young, and direct development (Bousfield 1973). Based on its native range, from southern Pacific Russia, to the central coast of China, this amphipod tolerates a wide range of temperatures. In California, it has been collected at salinities of 20-34 PSU (Cohen et al. 2002; Cohen et al. 2005). Its inhabits rocky intertidal zones, muddy shores, oyster and mussel beds, cultured abalones, and docks, floats, and marinas (Yamato 1987; Shin et al. 2005; Cohen et al. 2002; Cohen et al. 2005; Chapman 2007). Its food habits have not been described, but it is likely omnivorous, feeding on algae, detritus, and occasional invertebrates or carrion (Barnes 1983).

Trophic Status:




General HabitatMarinas & DocksNone
General HabitatRockyNone
General HabitatOyster ReefNone
Salinity RangePolyhaline18-30 PSU
Salinity RangeEuhaline30-40 PSU
Tidal RangeSubtidalNone
Tidal RangeLow IntertidalNone
Tidal RangeMid IntertidalNone
Vertical HabitatEpibenthicNone

Tolerances and Life History Parameters

Minimum Salinity (‰)20Port Sonoma, San Pablo Bay (Cohen et al. 2005)
Maximum Salinity (‰)34Field (Huntington Harbor, Cohen et al. 2002)
Minimum Length (mm)6.7Female, Japan, 6.7 mm, 7.3 mm, male (Yamato 1987a)
Maximum Length (mm)11.7Male, 11.7 mm, Japan, female 9.8 mm (Yamato 1987a)
Broad Temperature RangeNoneCold temperate-Warm temperate
Broad Salinity RangeNonePolyhaline-Euhaline

General Impacts

No impacts have been reported for Melita rylovae in West Coast waters.

Regional Distribution Map

Bioregion Region Name Year Invasion Status Population Status
NWP-4a None 0 Native Estab
NEP-V Northern California to Mid Channel Islands 1993 Def Estab
P090 San Francisco Bay 1993 Def Estab
NWP-3a None 0 Native Estab
P050 San Pedro Bay 2000 Def Estab
NEP-VI Pt. Conception to Southern Baja California 2000 Def Estab
P030 Mission Bay 2011 Def Estab
NWP-4b None 0 Native Estab
NWP-3b None 0 Native Estab

Occurrence Map

OCC_ID Author Year Date Locality Status Latitude Longitude


Barnes, Robert D. (1983) Invertebrate Zoology, Saunders, Philadelphia. Pp. 883

Bousfield, E.L. (1973) <missing title>, Comstock Publishing Associates, Ithaca, NY. Pp. <missing location>

California Academy of Sciences 2005-2015 Invertebrate Zoology Collection Database. <missing URL>

California Department of Fish and Wildlife (2014) Introduced Aquatic Species in California Bays and Harbors, 2011 Survey, California Department of Fish and Wildlife, Sacramento CA. Pp. 1-36

Chapman, John W. (2007) The Light and Smith Manual: Intertidal invertebrates from Central California to Oregon (4th edition), University of California Press, Berkeley CA. Pp. 545-611

Cohen, Andrew N. and 10 authors (2005) <missing title>, San Francisco Estuary Institute, Oakland CA. Pp. <missing location>

Cohen, Andrew N. and 12 authors (2002) Project report for the Southern California exotics expedition 2000: a rapid assessment survey of exotic species in sheltered coastal waters., In: (Eds.) . , Sacramento CA. Pp. 1-23

Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>

Huang, Zongguo (Ed.), Junda Lin (Translator) (2001) Marine Species and Their Distributions in China's Seas, Krieger, Malabar, FL. Pp. <missing location>

Integrated Taxonomic Information System 2004-13 Integrated Taxonomic Information System. <missing URL>

Kim, Chan, Bae; Kim, Won; Kim, Hoon Soo (1992) Three species of the genus Melita from Korea (Crustacea, Amphipoda, Melitidae), Korean Journal of Systematic Zoology Molluscan Research Special Issue 3: 113-120

Shin, Myung-Hwa; Kim, Il-Hoi; Lee, Kyung Sook (2005) Three species of gammaridean amphipods (Crustacea) associated with cultured abalones (Gastropoda) in Korea, Korean Journal of Systematic Zoology Molluscan Research 21(2): 157-169

Williams, R. J.; Griffiths, F. B.; van der Wal, E. J.; Kelly, J. (1988) Cargo vessel ballast water as a vector for the transport of non-indigenous marine species, Estuarine, Coastal and Shelf Science 26: 409-420

Yamato, Shigeyuki (1987a) Four intertidal species of the genus Melita (Crustacea: Amphipoda) from Japanese waters, lncluding descriptions of two new species, Publications of the Seto Marine Biological Laboratory 32(4/6): 275-302

Yamato, Shigeyuki (1987b) Two species of the genus Melita (Crustacea: Amphipoda) from brackish waters in Japan, Publication of the Seto Marine Biological Laboratory 33(1/3): 79-95