Melita nitida -
SCIENTIFIC NAME
Melita nitida S.I. Smith in Verrill & Smith, 1874
1991 - 2000
NE Pacific
NW Atlantic
Shipping (ballast water)
Shipping (hull fouling)
The original distribution area of Melita nitida extends along the Atlantic – from St. Lawrence Bay (Canada) to the Yucatan Peninsula (Mexico) – and Pacific coast of North America – from Georgia Strait in Canada to Elkhorn Slough in California [2].
Possibly, the origin of this amphipod is on the east coast of North America and it was introduced to the west coast by the mass importation of the American oyster Crassostrea virginica for aquaculture [2].
First observation in Belgium
The first observation of Melita nitida in the study area was also the first sighting of the species in Europe. On the 13th of October 1998, an amphipod, originally identified as Melita sp., was found in the brackish part of the Dutch Western Scheldt, near Bath [3]. Later it turned out that it was the amphipod Melita nitida [4].
New observations of this species in the Belgian Sea Scheldt were not until 2003 when Melita nitida was observed near Oude Doel (north of Doel) [5].
Spreading in Belgium
In the study area, after the first observations in the Dutch Western Scheldt, individuals of this exotic species were found near Walsoorden (1999) and Baarland (2000) [2]. In 2003, the species appeared for the first time upstream on Belgian territory, near Doel. It was observed here for a second time in 2004, as well as near Fort Liefkenshoek [5]. Relatively large quantities of this exotic species are found in this limited area [2].
In the autumn of 2009, Melita nitida was found in the ‘Verbindingsdok’ (English translation: ‘Connection dock’) of Zeebrugge [6]. This turned out to be just two individuals, out of a total of 43 samples collected in the ports of Ostend, Nieuwpoort, Blankenberge and Zeebrugge. This indicates that the species only occurs to a limited extent and in very low densities in the Belgian coastal ports [6].
Spreading in neighbouring countries
In the Netherlands, besides the Western Scheldt, Melita nitida was also found in the North Sea Canal – which connects Amsterdam to the North Sea – near IJmuiden and in the Nieuwe Waterweg, the artificial mouth of the Rhine connecting Rotterdam to the North Sea [7].
In 2010, in the brackish part of the Kiel Canal (Germany), several individuals of this amphipod were found on artificial solid substrates [7]. In 2014, 13 specimens, of which three males, were found in the port of Gdynia (Poland) [8]. In France, this amphipod was found between 2013 and 2016 in intertidal oyster beds and under rocks in the Arcachon Basin, the Hossegor Lake and the Gironde estuary [9].
Melita nitida probably reached the Western Scheldt from North America, attached to ships’ hulls or via ballast water [2]. After its introduction, the good swimming capacity of adults permits the active dispersal of this non-native species [10].
The distribution of Melita nitida in the Western Scheldt is mainly favoured by the presence of hard substrates, like river bank stabilizations made of stone and quaysides. Oysters that attach themselves to these substrates create the ideal habitat for this non-native amphipod [2].
The high tolerance and adaptability of Melita nitida allow it to settle successfully almost anywhere. It is found in brackish water with salinities of 3 to 20 PSU (and exceptionally up to 30 PSU) and water temperatures of up to 32 °C [2]. By way of comparison, the seawater of the North Sea has a salt concentration of about 35 PSU.
In addition, the species occurs in a wide range of habitats: from intertidal marshes and muddy river bottoms to hard substrates below the low water line
It is noteworthy that in our area Melita nitida was mainly collected in crevices between Japanese oysters Crassostrea gigas and the substrate to which they are attached [2]
Melita nitida (size: max. 12 mm) can be found in our region together with two native species, the common intertidal amphipod Gammarus locusta (size: up to 30 mm) [12] and the closely related Melita palmata (size: up to 16 mm)[13]. For the time being, no competition with the native species has been demonstrated, but this may change as the exotic species’ range expands and numbers increase [2]. Indeed, the permanent establishment of Melita nitida in new areas indicates that this is a robust and highly competitive species. On the other hand, competition may not be possible because Melita nitida settles mainly in niche habitats – the gaps in between oysters and rocks – that are not occupied by indigenous species [2].
Individuals of this species usually have grey-brown, sometimes green, bands on the body, legs and antennae. With the naked eye, Melita nitida is hardly distinguishable from other amphipods, such as Melita palmata [4]. With a microscope, small spines can be seen along the sides of its carapace, which are unique to Melita nitida [2].
[1] World Register of Marine Species (WoRMS) (2020). Melita nitida Smith, 1873. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=146922] (2020-11-17).
[2] Faasse, M.; Van Moorsel, G. (2003). The North-American amphipods, Melita nitida Smith, 1873 and Incisocalliope aestuarius (Watling and Maurer, 1973) (Crustacea: Amphipoda: Gammaridea), introduced to the western Scheldt estuary (The Netherlands). Aquat. Ecol. 37(1): 13-22. [http://www.vliz.be/en/imis?module=ref&refid=34073]
[3] van Moorsel, G.W.N.M.; Waardenburg, H.W. (1999). De sublitorale begroeiing van de geulwandverdediging bij Bath in de Westerschelde in 1998. Bureau Waardenburg Rapport, 99.02. Bureau Waardenburg: Culemborg. 39 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=135544]
[4] Faasse, M.; Van Moorsel, G. (2000). Nieuwe en minder bekende vlokreeftjes van sublitorale harde bodems in het Deltagebied (Crustacea: Amphipoda: Gammaridea). Ned. Faunist. Meded. 11: 19-44. [http://www.vliz.be/en/imis?module=ref&refid=37555]
[5] Faasse, M. (2019). Persoonlijke mededeling
[6] 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]
[7] Reichert, K.; Beermann, J. (2011). First record of the Atlantic gammaridean amphipod Melita nitida Smith, 1873 (Crustacea) from German waters (Kiel Canal). Aquat. Invasions 6(1): 103-108. [http://www.vliz.be/en/imis?module=ref&refid=207816]
[8] Normant-Saremba, M.; Marszewska, L.; Kerckhof, F. (2017). First record of the North American amphipod Melita nitida Smith, 1873 in Polish coastal waters. Oceanological and Hydrobiological Studies 46(1): 108-115. [http://www.vliz.be/en/imis?module=ref&refid=284454]
[9] Gouillieux, B.; Lavesque, N.; Blanchet, H.; Bachelet, G. (2016). First record of the non-indigenous Melita nitida Smith, 1873 (Crustacea: Amphipoda: Melitidae) in the Bay of Biscay (NE Atlantic). Bioinvasions Records 5(2): 85-92. [http://www.vliz.be/imis?module=ref&refid=296791]
[10] Cadien, D.B. (2005). Hadzioidea of the NEP (Equator to Aleutians, intertidal to abyss): a review. [S.n.]: [s.l.]: 26. [http://www.vliz.be/en/imis?module=ref&refid=207817]
[11] Borowsky, B.; Aitken-Ander, P.; Tanacredi, J.T. (1997). Changes in reproductive morphology and physiology observed in the amphipod crustacean, Melita nitida Smith, maintained in the laboratory on polluted estuarine sediments. J. Exp. Mar. Biol. Ecol. 214(1-2): 85-95. [http://www.vliz.be/nl/catalogus?module=ref&refid=312323]
[12] Telnes, K. (2018). The Marine Flora & Fauna of Norway. [http://www.seawater.no/fauna/arthropoda/locusta.html] (2018-08-06).
[13] Marine Species Identification Portal (2018). Macrobenthos of the North Sea - Crustacea. Melita palmata. [http://species-identification.org/species.php?species_group=crustacea&id=417] (2018-08-06).
VLIZ Alien Species Consortium (2020). Melita nitida. Non-native species of the Belgian part of the North Sea and adjacent estuaries anno 2020. Flemish Institute for the Sea (VLIZ). 5 pp.