Grandidierella japonica -

Grandidierella japonica naturally occurs in the marine region around Japan, China, and Korea ^[2,3].

First observation in Belgium

Grandidierella japonica was first recorded in Belgian territory in the Scheldt estuary on 18 April 2018, near the Paardenschor, close to Doel ^[4].

Distribution in Belgium

Grandidierella japonica was regularly encountered in the Sea Scheldt during several sampling campaigns with a bongo net (towed over a distance of 200 meters at a depth of half a meter) since April 2018. However, its presence was confined to the most downstream (and therefore saltiest) monitoring station near the Paardenschor (Doel). The observed numbers remained low, ranging between 1 and 12 specimens ^[4]. Outside the Paardenschor, the species has only been found in Belgium at the nearby Galgenschoor, this time in regular sediment samples, both intertidal and high subtidal. In November 2021, the species was also identified in a subtidal sample (taken with a Van Veen grab) from the Yser estuary ^[5].
 

Distribution in neighbouring countries

The first record of this Japanese amphipod outside its natural habitat occurred in 1966 when the species was observed in San Francisco Bay (California, USA) ^[3]. Since then, the species has become widespread in intertidal and subtidal sediments of bays and estuaries in the Pacific region, from British Columbia to Mexico, as well as in Hawaii and New South Wales (Australia) ^[6-11].

Closer to home, Grandidierella japonica was first observed in Southeast England near Southampton in 1997, followed by a sighting in the Orwell estuary in 2007 ^[12-14]. These were the first records outside the Pacific region ^[15]. The first suspected observations along the coasts of mainland Europe took place during a sampling campaign in the Bay of Marennes-Oléron (Bay of Biscay, France) in 2010. Due to identification challenges, confirmation of the species' presence in the region took until 2012, when around 70 individuals (including brooding females) were collected ^[15]. The species was also found slightly further south in the Bay of Arcachon, near Bordeaux, in the same year ^[16]. Subsequently, the species was detected in bays and estuaries along the French Basque coast (2015, 2016, 2017) ^[17] and the southern coast of Brittany (2015; Gulf of Morbihan) ^[18].

In 2013, around 200 specimens were captured in the brackish zones of the Viareggio marina (northwestern Italy), marking the first observation in the Mediterranean region ^[19]. Additionally, the amphipod was observed along the southern coast of Sweden (2014) ^[20]. In 2017, the species was also found in the Netherlands, near Amsterdam ^[2], followed by sightings in the Dutch part of the Western Scheldt in 2020 ^[4]. 

The most plausible vector for the introduction of this Japanese amphipod is the import of the Japanese oyster Crassostrea/Magallana gigas into the affected regions ^[3,15,16]. Additionally, a potential introduction via ballast water or hull fouling on ships (as a secondary vector) cannot be ruled out ^{[4,8,12,13,15,21]}. Secondary dispersal through recreational boating is also suggested, a theory supported by the occurrence of Grandidierella japonica in the marina of Viareggio, Italy ^[19].

Despite the species gradually spreading across Western European bays and estuaries, observations in Belgium remain limited. The species primarily inhabits muddy substrates in the intertidal or subtidal zones (up to a depth of 10 meters) of brackish water systems ^[3,22], making the Scheldt estuary and the Yser estuary suitable habitats. The unique osmoregulatory tissue in its gills enables the amphipod to thrive in the highly fluctuating salinity levels of estuaries ^[23]. For instance, in a study on the effectiveness of saline solutions as an additional treatment to eradicate halotolerant species in ballast water, 65% of Grandidierella japonica survived 48 hours at 45 psu ^[24]. This adaptability allows the species to establish populations in bays with salinity levels of 34-35 psu ^[25].

Although the species is often associated with muddy substrates, it has been observed in various habitats, such as rocky environments and tidal pools on solid rock along the North American east coast ^[25], seagrass beds in the Bay of Arcachon (France) ^[16], and in reefs of the non-native Australian tubeworm Ficopomatus enigmaticus in the marina of Viareggio (Italy) ^[19]. In the Yser estuary, one specimen was found in a reef of the native sand mason worm Lanice conchilega ^[5].
 

The life cycle of most amphipods is characterised by direct development without a larval stage ^[26], which means passive long-distance dispersal via ocean currents as a secondary distribution mechanism is unlikely.

The influence of salinity as a limiting factor on the species' further spread remains somewhat unclear. While Grandidierella japonica is frequently reported in brackish environments, and salinity appeared to play a significant role in the species' presence in the Viareggio marina (Italy) ^[19], this parameter seems less important in other regions ^[25].

In several regions, Grandidierella japonica has been observed alongside the non-native Australian tubeworm Ficopomatus enigmaticus ^[2,19,27]. These tubeworms often form reefs of interconnected calcareous tubes. Whether a similar association exists between the two species in the North Sea Canal and the Scheldt estuary is a subject for further study. It's possible that these Japanese amphipods prey on the tubeworms and/or use their tunnels for habitation ^[2].

Pollution, specifically elevated metal concentrations, appears to have a negative impact on the presence of Grandidierella japonica ^[12,13]. Additionally, the species has been used in toxicity testing ^[28,29].

The presence of Grandidierella japonica may potentially have negative effects on native fauna through habitat modification (digging), predation, and competition for space and food ^{[10,22,30-32]}. However, since the species has only been found in very localised areas and in low concentrations in Belgian territory ^[4], no adverse effects related to its presence have been observed or are expected at this time.

No measures have been taken to control the species thus far.

Male amphipods can grow up to 22 mm in length, while females reach a maximum length of 13 mm ^[3,9,26]. Living specimens have a dark head with a silver-white to gray or gray-brown body ^[2,3]. Specimens found in the Netherlands showed a dense pattern of gray-brown or more purplish-brown spots on the dorsal side ^[2]. The body is slender and laterally somewhat flattened. The following features characterise males: (i) the first claw has 18 to 20 ridges, which may be used for sound production (stridulation); (ii) besides a larger spine on the claw, there are also two additional smaller spines; (iii) of the three pairs of posterior swimming legs (uropods), the third is unbranched (whereas in other related species it is branched). Female specimens are much harder to identify ^[2]. A detailed species description can be found in the literature ^[26,33].

The species digs U-shaped burrows in the muddy substrates of bays and estuaries, where males and females are often found together. Males are also observed outside the burrows in tidal pools at low tide ^[3]. The amphipod is a detritivore, feeding on epiphytes and suspended particles, but is also known to prey on other amphipods and even conspecifics (cannibalism) ^[22,26].

[1]          World Register of Marine Species (WoRMS) (2024). Grandidierella japonica Stephensen, 1938. https://www.marinespecies.org/aphia.php?p=taxdetails&id=238740 (2024-10-18). 

[2]          van Haaren, Ton.; de Bruyne, R. (2018). Nieuwe exoot: Japanse vlokreeftjes in het Noordzeekanaal. Nature Today. 22 april 2018. https://www.naturetoday.com/intl/nl/nature-reports/message/?msg=24294 

[3]          Chapman, J.W.; Dorman, J.A. (1975). Diagnosis, systematics, and notes on Grandidierella japonica (Amphipoda: Gammaridea) and its introduction to the Pacific Coast of the United States. Bull. South. Calif. Acad. Sci. 74(3): 104-108. [https://www.vliz.be/en/imis?module=ref&refid=381623] 

[4]          Soors, J.; de Beukelaer, J.; Bezdenjesnji, O.; Buerms, D.; Lefranc, C.; Speybroeck, J.; Van de Meutter, F. (2022). Two new alien crustacean invaders Grandidierella japonica (Stephensen, 1938) and Neomysis americana (S.I. Smith, 1873) in Belgium. Bioinvasions Records 11(3): 747-757. [https://www.vliz.be/nl/imis?module=ref&refid=355791] 
[5]          Soors, J. (2024). Persoonlijke mededeling.

[6]          Greenstein, D.J.; Tiefenthaler, L.L. (1997). Reproduction and population dynamics of a population of Grandidierella japonica (Stephensen) (Crustacea: Amphipoda) in Upper Newport Bay, California. Bull. South. Calif. Acad. Sci. 96(1): 34-42. [https://www.vliz.be/en/imis?module=ref&refid=381624] 

[7]          Okolodkov, Y.B.; Bastida-Zavala, R.; Ibanez, A.L.; Chapman, J.W.; Suárez-Morales, E.; Pedroche, F.F.; Gutiérrez-Mendieta, F.J. (2007). Especies acuáticas no indígenas en México. Ciencia y Mar 11: 29-67. [https://www.vliz.be/en/imis?module=ref&refid=381625] 

[8]          Coles, S.L.; DeFelice, R.C.; Eldredge, L.G.; Carlton, J.T. (1999). Historical and recent introductions of non-indigenous marine species into Pearl Harbor, Oahu, Hawaiian Islands. Mar. Biol. (Berl.) 135(1): 147-158. [https://www.vliz.be/en/imis?module=ref&refid=381306] 

[9]          Myers, A.A. (1981). Taxonomic studies on the genus Grandidierella Coutière (Crustacea, Amphipoda). III. Fijian, Australian and Saudi Arabian species. Bull. Mus. Natl. Hist. Nat., Sect. A Zool. Biol. Ecol. Anim. 4e série, tôme 3(1): 213-226. [https://www.vliz.be/en/imis?module=ref&refid=381626] 

[10]        Pilgrim, E.M.; Blum, M.J.; Reusser, D.A.; Lee, H.; Darling, J.A. (2013). Geographic range and structure of cryptic genetic diversity among Pacific North American populations of the non-native amphipod Grandidierella japonica. Biological Invasions 15(11): 2415-2428. [https://www.vliz.be/en/imis?module=ref&refid=381307] 

[11]        Muir, D.G. (1997). New records of peracarid Crustacea in Hawaii (Crustacea: Peracarida). Bishop Museum Occasional Papers 49: 50-54. [https://www.vliz.be/en/imis?module=ref&refid=381627] 

[12]        Smith, P.; Perrett, J.; Garwood, P.; Moore, G. (1999). Two additions to the UK marine fauna: Desdemona ornata Banse, 1957 (Polychaeta, Sabellidae) and Grandidierella japonica Stephensen, 1938 (Amphipoda, Gammaridea). Porcupine Newsletter 2: 8-11. [https://www.vliz.be/en/imis?module=ref&refid=381628] 

[13]        Ashelby, C. (2006). Records of the introduced amphipod Grandidierella japonica Stephensen 1938 (Crustacea: Amphipoda: Gammaridea: Aoridae) from the Orwell Estuary, Suffolk. Suffolk Natural History 42: 48-54 [https://www.vliz.be/nl/catalogus?module=ref&refid=353937]

[14]        Noël, P.Y. (2011). Checklist of cryptogenic and alien Crustacea of the European Atlantic coast, in: Galil, B.S. et al. (Ed.) In the wrong place - alien marine crustaceans: Distribution, biology and impacts. Invading Nature - Springer Series in Invasion Ecology, 6: pp. 345-375 [https://www.vliz.be/nl/imis?module=ref&refid=205529] 

[15]        Jourde, J.; Sauriau, P.-G.; Guenneteau, S.; Caillot, E. (2013). First record of Grandidierella japonica Stephensen, 1938 (Amphipoda: Aoridae) from mainland Europe. Bioinvasions Records 2(1): 51-55. [https://www.vliz.be/nl/catalogus?module=ref&refid=353930]

[16]        Lavesque, N.; Gouillieux, B.; de Montaudouin, X.; Bachelet, G.; Bonifacio, P.; Simonet, E. (2014). Premier signalement de l’espèce introduite Grandidierella japonica Stephensen, 1938 (Crustacea: Amphipoda: Aoridae) dans le bassin d’Arcachon. An Aod III(1): 11-19. [https://www.vliz.be/en/imis?module=ref&refid=381629] 

[17]        Foulquier, C.; Bogun, F.; Gouillieux, B.; Lavesque, N.; Blanchet, H. (2018). First record of the non-native species Grandidierella japonica Stephensen, 1938 (Crustacea: Amphipoda: Aoridae) along the French Basque coast. An Aod VI(1): 17-25. [https://www.vliz.be/en/imis?module=ref&refid=381630] 

[18]        Droual, G., Le Garrec, V., Cabelguen, J., Gélinaud, G. & Grall, J. (2017). The spread goes on: the non-indigenous species Grandidierella japonica Stephensen 1938 (Amphipoda: Aoridae) has reached Brittany (Gulf of Morbihan). An aod - les cahiers naturalistes de l’Observatoire marin, V (1), pp. 21–29. [https://www.vliz.be/nl/catalogus?module=ref&refid=353932] 

[19]        Marchini, A.; Ferrario, J.; Nasi, E. (2016). Arrival of the invasive amphipod Grandidierella japonica to the Mediterranean Sea. Marine Biodiversity Records 9(1): 38. https://dx.doi.org/10.1186/s41200-016-0049-y [https://www.vliz.be/nl/catalogus?module=ref&refid=353927]

[20]        Berggren, M.S. (2015). Nya kräftdjur påträffade i Sverige – Grandidierella japonica och Rhithropanopeus harrisii. Fauna Flora 110(1): 20-23. [https://www.vliz.be/en/imis?module=ref&refid=391065] 

[21]        Carlton, J.T.; Eldredge, L.G. (2009). Marine bioinvasions of Hawai‘i. Bishop Museum Press: Honolulu. ISBN 978-1-58178-096-3. 202 pp. [https://www.vliz.be/en/imis?module=ref&refid=391067] 

[22]        Chapman, J.W. (2007). Gammaridea, in: Carlton, J.T. (Ed.) The Light and Smith Manual. Intertidal Invertebrates from Central California to Oregon, Completely Revised and Expanded. pp. 545-618. [https://www.vliz.be/en/imis?module=ref&refid=391072] 

[23]        Kikuchi, S.; Matsumasa, M. (1993). The osmoregulatory tissue around the afferent blood vessels of the coxal gills in the estuarine amphipods, Grandidierella japonica and Melita setiflagella. Tissue Cell 25(4): 627-638. [https://www.vliz.be/en/imis?module=ref&refid=381417] 

[24]        Santagata, S.; Bacela, K.; Reid, D.F.; Mclean, K.A.; Cohen, J.S.; Cordell, J.R.; Brown, C.W.; Johengen, T.H.; Ruiz, G.M. (2009). Concentrated sodium chloride brine solutions as an additional treatment for preventing the introduction of nonindigenous species in the ballast tanks of ships declaring no ballast on board. Environ. Toxicol. Chem. 28(2): 346-353. [https://www.vliz.be/en/imis?module=ref&refid=381418] 

[25]        Trott, T.; Lazo-Wasem, E.; Enterline, C. (2020). Grandidierella japonica Stephensen, 1938 (Amphipoda: Aoridae) in the Northwest Atlantic Ocean. Aquat. Invasions 15(2): 282-296. [https://www.vliz.be/en/imis?module=ref&refid=381252]

[26]        (2016). Grandidierella japonica: A brackish water amphipod, in: Hiebert, T.C. et al. Oregon estuarine invertebrates: Rudys’ illustrated guide to common species. pp. 278-281. [https://www.vliz.be/nl/catalogus?module=ref&refid=353935]   

[27]        Wasson, K.M.; Zabin, C.J.; Bedinger, L.; Diaz, M.C.; Pearse, J.S. (2001). Biological invasions of estuaries without international shipping: the importance of intraregional transport. Biol. Conserv. 102: 143-153 [https://www.vliz.be/nl/imis?module=ref&refid=140750] 

[28]        Nipper, M.G.; Greenstein, D.J.; Bay, S.M. (1989). Short- and long-term sediment toxicity test methods with the amphipod Grandidierella japonica. Environ. Toxicol. Chem. 8(12): 1191-1200. [https://www.vliz.be/en/imis?module=ref&refid=381308] 

[29]        Black, A.; Bott, G. (2005). CSBP ecotoxicity project: direct toxicity assessment using resident species. Parsons Brinckerhoff: Australia. 49 pp. [https://www.vliz.be/en/imis?module=ref&refid=391066] 

[30]        Myers, A.A. (1970). Taxonomic studies on the genus Grandidierella Coutière (Crustacea: Amphipoda), with a description of G. dentimera, sp.nov. Bull. Mar. Sci. 20(1): 135-147. [https://www.vliz.be/en/imis?module=ref&refid=381309] 

[31]        Barnard, J.L.; Sandved, K.; Thomas, J.D. (1991). Tube-building behavior in Grandidierella, and two species of Cerapus. Hydrobiologia 223(1): 239-254. [https://www.vliz.be/en/imis?module=ref&refid=381310] 

[32]        Greenstein, D.J.; Tiefenthaler, L.L. (1997). Reproduction and population dynamics of a population of Grandidierella japonica (Stephensen) (Crustacea: Amphipoda) in Upper Newport Bay, California. Bull. South. Calif. Acad. Sci. 96(1): 34-42. [https://www.vliz.be/en/imis?module=ref&refid=381624] 

[33]        Zettler, M.L., Zettler, A. (2017). Marine and freshwater Amphipoda from the Baltic Sea and adjacent territories. Die Tierwelt Deutschlands und der angrenzenden Meeresteile nach ihren Merkmalen und nach ihrer Lebensweise, 83. ConchBooks: Harxheim. ISBN 978-3939767749. 845 pp. [https://www.vliz.be/en/imis?module=ref&refid=393470]

VLIZ Alien Species Consortium (2024). Grandidierella japonica. Introduced alien species of the Belgian part of the North Sea and adjacent estuaries anno 2024. Flanders Marine Institute (VLIZ). 7 pp.