Cryptorchestia garbinii -

The native range of the semi-terrestrial amphipod extends across the Caspian Sea, the Black Sea and the Eastern Mediterranean ^[3].

First observation in Belgium

When examining the collections of the Royal Belgian Institute of Natural Sciences (RBINS), the oldest preserved specimen appeared to have been collected in 1927, on the 26^th of March, in Antwerp, near the left bank of the Scheldt ^[4]. However, it is suspected that the species was already present in the Belgian Scheldt around 1900 ^[5].

Spreading in Belgium

Especially in the estuaries of the Yser, the Scheldt, the Meuse, and their upper courses, the semi-terrestrial amphipod is common. This exotic species was also found in the Leopold Canal near the port of Zeebrugge ^[6]. The species can occur far inland and feels perfectly at home in freshwater. However, it also thrives in the brackish estuaries of both the Yser and the Scheldt ^{[3, 4, 7]}.

In our study area, this species was found in very high densities (more than 200 individuals per m² ) along the Ghent-Terneuzen Canal in March 2009 ^[8].

In Belgian waters, Orchestia gammarellus is the semi-terrestrial amphipod’s native counterpart. This species can be observed in Nieuwpoort in the nature reserve "De Ijzermonding" and in Ostend, along the “Halve Maandijk”. Its way of life is similar to that of the semi-terrestrial amphipod ^[9].

Spreading in neighbouring countries

The first Western European sighting dates back to 1878 when the species was found in the Netherlands under flowerpots in a garden in Zaltbommel (province of Guelders). Probably, this amphipod ended up there by watering the flowers with water from a nearby stream, located close to the Waal river ^[10]. After its initial introduction in the Dutch Waal, the species spread throughout the Rhine-Meuse-Scheldt delta. From the Scheldt - along which it reached the northern French town of Cambrai in 1906 - it advanced further upstream to the Seine river ^[4].

This exotic species was then able to migrate to Germany via the Marne - along the Rhine-Moselle canal. The colonisation of the German Upper Rhine and Moselle only took place after 1950 ^[4]. In 2011, the species had appeared in eastern Germany in the Warnow estuary and Szczecin lagoon on the border between Germany and Poland ^[11]. Since 2009, the species has been observed in the Polish Vistula river, where it is believed to have arrived by natural migration from the Baltic Sea ^[12]. Furthermore, the semi-terrestrial amphipod can be found in the Black Sea and on the Atlantic coast of North Africa. In 2000, it was found for the first time along the Turkish coast ^{[13, 14]}.

How exactly the species ended up in the Dutch Waal is unknown. What is certain is that the many (freshwater) canals have facilitated its further spread ^[4]. Transport via ballast water in cargo ships may also have played a role ^[15].

The semi-terrestrial amphipod can reproduce very rapid. In addition, our colder winters do not seem to be a problem and do not lead to mortality within the populations ^[15]. The ability of this species to survive above the water level - in damp places - also contributes to its success. This way it avoids negative impacts from water pollution ^[9].

The semi-terrestrial amphipod is found in both fresh and brackish waters. It cannot thrive in the open sea, due to the high salt level ^{[15, 16]}.

Temperature and moisture in the sediment are the main environmental factors influencing the occurrence of the species. Due to its dependence on this microhabitat, the semi-terrestrial amphipod cannot disperse very far on its own ^[13]. It depends on migrating birds for its dispersal, but can also be transported via ships' ballast water and thus reach new areas. Moreover, this exotic species has been observed on floating remains of plants, allowing them to be transported naturally with the water currents ^{[16, 17]}.

No effects of the semi-terrestrial amphipod on our local species and their habitat have been reported so far. However, very high densities of this species - up to 1,975 individuals per m² - have been measured. It goes without saying that when a species is present in such high densities, this can impact the other organisms present ^{[15, 16]}.

Males can reach a length of 22 mm, and females can grow up to 16 mm in size. The semi-terrestrial amphipod is dark brown and has round black eyes ^[18].

Cryptorchestia garbinii belongs to the family of Talitridae. The beach dwellers within this family are often referred to as sand fleas or sandhoppers. Although this is a large family, there are only five genera, including the genus Cryptorchestia, to which the semi-terrestrial amphipod belongs. The species within this genus have a 'semi-terrestrial' way of life. They live both underwater and in damp places above the water level, e.g. underneath stones, between moist vegetation and in the upper layer of the sediment ^[18].

The family Talitridae also includes our native sandhopper Talitrus saltator. Species of the genus Talitrus are characterised by a terrestrial way of life, in contrast to the semi-terrestrial way of life of species belonging to the genus Cryptorchestia. The native sandhopper lives on the beach, within the zone where algae and other organic material are deposited by the tide ^[18].

[1]         World Register of Marine Species (WoRMS) (2020). Cryptorchestia garbinii Ruffo, Tarocco & Latella, 2014. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=817504] (2020-11-17).

[2]         Ruffo, S.; Tarocco, M.; Latella, L. (2014). Cryptorchestia garbinii n. sp. (Amphipoda: Talitridae) from Lake Garda (Northern Italy), previously referred to as Orchestia cavimana Heller, 1865, and notes on the distribution of the two species. Ital. J. Zoolog. 81(1): 92-99. [http://www.vliz.be/en/imis?module=ref&refid=330560]

[3]         Kinzelbach, R. (1972). Zur Verbreitung und Ökologie des Süßwasser-strandflohs Orchestia cavimana Heller, 1865 (Crustacea: Amphipoda: Talitridae). Bonn. Zool. Beitr. 23: 267-282. [http://www.vliz.be/en/imis?module=ref&refid=120964]

[4]         Wouters, K. (2002). On the distribution of alien non-marine and estuarine macro-crustaceans in Belgium. Bull. Kon. Belg. Inst. Natuurwet. Biologie 72: 119-129. [http://www.vliz.be/en/imis?module=ref&refid=35968]

[5]         van der Velde, G.; Rajagopal, S.; Kelleher, B.; Muskó, I.; Bij de Vaate, A. (2000). Ecological impact of crustacean invaders: general considerations and examples from the Rhine River, in: von Vaupel Klein, J.C. et al. The Biodiversity Crisis and Crustacea: Proceedings of the Fourth International Crustacean Congress, Amsterdam, Netherlands, 20-24 July 1998, volume 2. Crustacean Issues, 12. A.A. Balkema: Rotterdam, Brookfield: pp. 3-33. [http://www.vliz.be/en/imis?module=ref&refid=207016]

[6]         D'Udekem d'Acoz, C. (2020). Persoonlijke mededeling

[7]         den Hartog, J.C. (1963). The amphipods of the deltaic region of the rivers Rhine, Meuse and Scheldt in relation to the hydrography of the area. II. The Talitridae. Neth. J. Sea Res. 2(1): 40-67. [http://www.vliz.be/en/imis?module=ref&refid=120958]

[8]         Boets, P.; Lock, K.; Goethals, P.L.M. (2011). Using long-term monitoring to investigate the changes in species composition in the harbour of Ghent (Belgium). Hydrobiologia 663(1): 155-166. [http://www.vliz.be/en/imis?module=ref&refid=201947]

[9]         Boets, P. (2019). Persoonlijke mededeling

[10]       Hoek, P.P.C. (1879). Carcinologisches, grössentheils gearbeitet in der zoologischen Station der niederländischen zoologischen Gesellschaft: III. Eine Orchestide des Festlandes. Tijdschr. Ned. Dierkd. Ver. 4: 130-134. [http://www.vliz.be/en/imis?module=ref&refid=207007]

[11]       Wittfoth, A.K.J.; Zettler, M.L. (2013). The application of a Biopollution Index in German Baltic estuarine and lagoon waters. Manag. Biol. Inv 4(1): 43-50. [http://www.vliz.be/en/imis?module=ref&refid=287758]

[12]       Konopacka, A.; Grabowski, M.; Bącela-Spychalska, K.; Rewicz, T. (2009). Orchestia cavimana Heller, 1865 (Amphipoda: Talitridae) enters freshwater inland habitats in the Vistula River, Poland. Aquat. Invasions 4(4): 689-691. [http://www.vliz.be/en/imis?module=ref&refid=207600]

[13]       Pavesi, L.; De Matthaeis, E. (2010). Life history and temporal distribution of Orchestia sp. cf. cavimana (Amphipoda, Talitridae) on a lake shore in central Italy. Limnologica 40(4): 300-306. [http://www.vliz.be/en/imis?module=ref&refid=296665]

[14]       Akbulut, M.; Sezgin, M. (2000). Orchestia cavimana Heller, 1865 (Amphipoda, Talitridae) in the Turkish Black Sea Fauna. Turk. J. Mar. Sci. 6: 241 -244. [http://www.vliz.be/en/imis?module=ref&refid=296666]

[15]       ICES Advisory Committee on the Marine Environment (2006). Report of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO) 16-17 March 2006 Oostende, Belgium. CM Documents - ICES. CM 2006(ACME:05). ICES: Copenhagen. 330 pp. [http://www.vliz.be/en/imis?module=ref&refid=111237]

[16]       Herkül, K.; Kotta, J.; Kotta, I. (2006). Distribution and population characteristics of the alien talitrid amphipod Orchestia cavimana in relation to environmental conditions in the Northeastern Baltic Sea. Helgol. Mar. Res. 60(2): 121-126. [http://www.vliz.be/en/imis?module=ref&refid=100429]

[17]       Herkül, K. (2006). Invasion history of the amphipods Orchestia cavimana and Gammarus tigrinus in the Estonian coastal sea. MSc Thesis. University of Tartu: Tartu, Estonia. 60 pp. [http://www.vliz.be/en/imis?module=ref&refid=120960]

[18]       Lincoln, R.J. (1979). British marine Amphipoda: Gammaridea. British Museum (Natural History): London, UK. ISBN 0-565-00818-8. VI, 658 pp. [http://www.vliz.be/en/imis?module=ref&refid=17631]

VLIZ Alien Species Consortium (2020). Cryptorchestia garbinii – Semi-terrestrial amphipod. Non-native species of the Belgian part of the North Sea and adjacent estuaries anno 2020. Flemish Institute for the Sea (VLIZ). 5 pp.