Eochelidium sp. A

Invasion History

First Non-native North American Tidal Record: 1988
First Non-native West Coast Tidal Record: 1988
First Non-native East/Gulf Coast Tidal Record:

---

General Invasion History:

Although Eochelidium sp. A has not been identified to species, it belongs to a genus known only from the Western Pacific. It most closely resembles E. miraculum Imbach 1967, described from the South China Sea and E. carinorostrum Jo 1990, described from Korea (Paquette and Cadien 1996; Chapman 2007). It was first reported from Long Beach Harbor, California (CA) in the 1980s, and later found in San Francisco Bay, CA (1st record 1993) and Puget Sound, Washington (1st record 1997) (Cohen and Carlton 1995; Paquette and Cadien 1996; Cohen et al. 1998).

North American Invasion History:

Invasion History on the West Coast:

Eochelidium sp. A was first collected in the channel of Long Beach Harbor in the late 1980s (Paquette and Cadien 1996). It was subsequently found in 1998 in Alamitos Bay and Newport Bay (Ranasinghe et al. 2005). In a 2011 survey it was collected in Huntington Harbor and Dana Point Harbor (1 specimen) (California Department of Fish and Wildlife 2014). A few specimens were collected in San Francisco Bay in the 1990s (Cohen and Carlton 1995), and by 2005, it was found to be established in the Central and South Bays (Foss 2009). Eochelidium sp. A was first collected in Puget Sound in 1997 (Cohen et al. 1998) and is apparently established, although we have found no information on its distribution in the Sound. Because this amphipod is known primarily from infaunal communities, ballast water is considered the likeliest means of introduction (Paquette and Cadien 1996), but it has also been collected in epifaunal communities (California Fish and Wildlife 2014).

---

Description

Eochelidium sp. A does not match any known species, but is similar to E. miraculum Imbach 1967, described from the Gulf of Thailand, and E. carinorostrum Jo 1990, described from Korea (Paquette and Cadien 1996). Among distinctive features of the family Oedicerotidae are: having the two eyes merged into a single mass on the rostrum; the lack of an accessory flagellum on Antenna 1; having perieopods weakly adapted for digging; having an exceptionally long pereiopod 7, and having a smoothly-rounded, shield-like telson (Chapman 2007). Paquette and Cadien (1996) list features separating E. sp. A from seven described species of Eochelidium.

The head has a change in slope just behind the eye and the junction of the head and body is distinct. The rostrum does not extend beyond the first segment of the peduncle of Antenna 1 and points downward with a strong ventral keel. Antenna 1 is roughly equal to the peduncle of Antenna 2. Segments 1 and 2 of antenna 1 are roughly equal. Gnathopod 1 is much shorter than Gnathopod 2, but the propodus (segment 6) of Gnathopod 1 is greatly inflated, and has a prominent dactyl, equal in length to the posterior margin of the propodus. Gnathopod 2 is longer, but less robust, with a small propodus and dactyl, forming a fully closing claw. The dactyl is about 1/4 of the propodus' length. The posterior-ventral edge of Coxa 3 is beveled, and Coxa 5 is as long as it is wide. The dactyls are roughly equal to segments 5 for pereiopods 3 and 4. For pereiopods 5 and 6, segments 6 are about 2X as long as segment 5. The posterior edges of pereiopods 3-5 are densely covered with setae. Uropods 1 and 2 have outer rami slightly shorter than the inner ones. The inner margin of the inner rami have spines (two spines on U1, one on U2). Eochelidium sp. A is about 5 mm long, and its body is pale, mottled with dark pigment. Description based on: Paquette and Cadien 1996 and Chapman 2007.

---

Taxonomy

Ecology

General:

Eochelidium sp. A is a free-living marine gammarid amphipod, occurring over sand and silty bottoms, and around marinas and docks. Sexes are separate, the young are brooded, and development is direct (Bousfield 1973). Little is known of the life history or biology of this untdentified amphipod. It occurs over sandy and silty bottoms, and also burrows into them (Paquette and Cadien 1996; Ranasinghe et al. 2005: Chapman 2007).

Trophic Status:

Omnivore

Omni

---

Habitats

General Habitat	Unstructured Bottom	None
General Habitat	Marinas & Docks	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Vertical Habitat	Epibenthic	None

---

---

Tolerances and Life History Parameters

Maximum Length (mm)	5	Imbach 1967; Chapman 2007
Broad Temperature Range	None	Cold temperate-Warm temperate
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

No impacts have been reported for introduced populations of Eochelidium sp. A.

---

References

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

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.; 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>

Cohen, Andrew; and 16 authors. (1998) <missing title>, Washington State Department of Natural Resources, Olympia, Washington. Pp. 1-37

Foss, Stephen (2009) <missing title>, California Department of Fish and Game, Sacramento CA. Pp. <missing location>

Hirayama, Akira (1986) Two species of Synchelidium (Crustacea: Amphipoda: Oedicerotidae) from the seacoast of northern Japan, Zoological Science 3: 357-366

Hirayama, Akira (1992) Oedicerotidae (Crustacea: Amphipoda) from Hong Kong, Asian Marine Biology 9: 139-166

Imbach, Marilyn Clark (1967) Gammaridean Amphipoda from the South China Sea, Naga Reports: Scientific Results of Marine Investigations of the South China Sea 4(1): 39-167

Jo, Young Won (1990) Oedicerotid Amphipoda (Crustacea) from shallow waters of Korea, Beaufortia 39(5): 155-200

Paquette, Carol; Cadien, Don 1996 <em>Eochelidium</em> sp. A; Southern California Association of Marine Invertebrate Taxonomists. <missing URL>



Ranasinghe, J. Ananda and 6 authors. (2005) The prevalence of non-indigenous species in southern California embayments and their effects on benthic macroinvertebrate communities, Biological Invasions 7: 679-686

---