Palaemon macrodactylus - Oriental shrimp

The original distribution area of Palaemon macrodactylus is in the northwest Pacific Ocean, where the species occurs along the coasts of Japan, China and Korea ^[2]. The species generally occurs in sheltered areas, mainly in estuaries ^[3].

First observation in Belgium

The first report of Palaemon macrodactylus in Belgium was on the 5^th of December 2002, near Doel (in the Sea Scheldt). On the 12^th of June 2004, specimens were found on the coast, between the pontoons in the marina of Zeebrugge ^[4]. However, a re-examination of samples previously collected by the Flanders Environment Agency (VMM) revealed that the species was already present in the Ghent-Terneuzen Canal (near the Dutch border) in 1998. ^[5].

Spreading in Belgium

In November 1998, the oriental shrimp was found in our study area near Walsoorden along the Dutch Western Scheldt ^[3]. Four years later, this exotic species was reported near Doel ^[4], where it was later observed more often (even so near Fort Liefkenshoek) ^{[6, 7]}. In the Ghent-Terneuzen Canal, the species slowly expanded its range upstream and since 2003 it can be found in Ghent ^[5].

In 2004, this non-native species was seen along our coast, around pontoons in the marina of Blankenberge, between pontoons in Zeebrugge Marina ^[5], at the estuary of the Yser, in Nieuwpoort and the Sluice Dock of Ostend ^[3]. Subsequent observations followed in both Zeebrugge Marina and on the beach of Heist ^{[8, 9]}.

Spreading in neighbouring countries

From its area of origin in Southeast Asia (Japan, China and Korea) ^[10], the species spread in the middle of the last century (1957) towards the west coast of North America. Except for the failed introduction to Australia in the 1960s and 1970s, the species was not discovered in a new area for several decades ^[11]. Around the turn of the century, Palaemon macrodactylus was observed in Europe (England, Spain, Germany, France, the Netherlands, Belgium) ^{[3, 10, 12, 13]}, Argentina (2000) and along the East Coast of the United States (2001) ^[14]. In Europe, the species was first found in the Thames Estuary (United Kingdom) in 1992 ^[15]. From there, the species broadened its range and reached the Orwell and Stour estuaries (Western United Kingdom) in 2001. The fact that egg-bearing females were often observed – ranging from 12-100% of females – pointed to permanent settlement in these areas ^{[12, 15]}.

Currently, this species occurs at several locations in the Netherlands, including the North Sea Canal, the ship canal “Nieuwe Waterweg” (English translation: “New Waterway”) and the Eastern Scheldt around the Zeeland bridge and Wemeldinge ^[3]. The species is also common in Lake Veerse, Lake Grevelingen and in the Wadden area (Harlingen, Lauwersoog and Eemshaven) ^{[16, 17]}.

In France, this shrimp was first observed in 1998 in the Gironde Estuary. The species seemed to be very common in some parts of the estuary. Egg-bearing females were also often observed here ^[10]. The species is considered to be established here since 2011 ^[18]. Furthermore, the oriental shrimp can be found in France in the Seine Estuary (since 2006) ^[19].

In May 1999, this species was caught in Spain ^[13], where it established itself in the Guadalquivir in 2011 ^[18]. Palaemon macrodactylus is also observed in the Black Sea near Romania and Bulgaria (since 2002) ^{[20, 21]}, the Weser Estuary and Hooksiel in Germany (since 2004) ^[22]. Recently, it has also been spotted in the Mediterranean Sea, more specifically in the Po delta and Marano lagoon (since 2013) ^[23]. As expected ^[22], Palaemon macrodactylus also settled in the Baltic Sea, where it was observed for the first time in 2014 ^[24].

Today, Palaemon macrodactylus occurs almost everywhere on the western European coast, from the southern part of the North Sea alongside Germany to the southern part of Spain. This distribution was most likely achieved by a combination of multiple introductions with the ballast water of ships as well as natural spreading with the help of the sea currents ^[21].

In the future, it is expected that the oriental shrimp will colonize new areas along the coasts of northwest Africa, southern Norway, etc. It is also likely that existing populations will continue to develop along coasts where the species is already established. In addition, climate change (warming) is expected to encourage colonisation towards new areas (where the species cannot yet thrive) ^[21].

According to some scientists, the distribution of the oriental shrimp is linked to international shipping, as this animal occurs in higher densities in seaports with an international character (e.g. the North Sea Canal, the Port of Zeebrugge or the Western Scheldt). However, in the Eastern Scheldt, more important for mussel and oyster farming than for international shipping, the species is significantly less common. As a result, there is a strong suspicion that this exotic species is spread via ballast water in ships and not via the import of oyster seed ^[3]. As this shrimp tends to live on the seabed and the uptake of ballast water is only a few metres below the surface, it is assumed that it is mainly the young free-swimming larvae that are transported. Due to the high density of larvae per m³ of water, more than 10,000 individuals can easily be caught at a time, which increases the chance of a successful introduction ^[21].

The ability to adapt to a wide range of environmental factors – like fluctuating temperatures, salinities and oxygen concentrations – contributed to the success of Palaemon macrodactylus ^[25]. Therefore, the species might become the most dominant estuarine shrimp in Europe ^[11]. Females carry many eggs (100-2,800 per brood), the number of eggs depending on the size of the female. Two broods are laid per year ^[12].

The eggs of the oriental shrimp are resistant against a certain fungus infection common in other crustaceans. Around the oriental shrimp’s eggs, a layer of bacteria (Alteromonas sp.) produces a specific chemical compound that suppresses the infection-inducing fungi, resulting in the survival of more eggs ^[26].

Spanish research showed that the oriental shrimp showed better resistance to acute thermal stress and consumed less oxygen than native species, indicating greater resistance to changing environmental conditions ^[27].

The global spread of Palaemon macrodactylus is more than likely to be further accelerated by intercontinental shipping ^[3]. The capacity to tolerate fluctuating environmental conditions (such as temperate, salinity, oxygen levels) facilitates the permanent establishment of the species after an accidental introduction ^[25]. This is confirmed by the frequent presence of egg-bearing female individuals. Because this species prefers waters with low salt concentrations – from 27 to 32.5 PSU – it thrives in estuaries ^[12]. To compare: the seawater of the North Sea has a salinity of 35 PSU. Both the adults and the embryos tolerate salinities between 2 and 35 PSU ^[28]. At salinities lower than 5 PSU, Palaemon macrodactylus struggles to survive and develops reproductive problems ^[29].

Concerning global warming, it is expected that many shrimp species will suffer from the higher metabolic cost that is associated with increased temperatures. The invasive Palaemon macrodactylus appears to be an exception due to its adaptability to high temperatures, thanks to its high metabolic control. ^[30]. Because of this, this invasive species may eventually displace native species ^[27]

Off the West Coast of the United States, Palaemon macrodactylus has little or no competition from other Palaemonidae (i.e. shrimps belonging to the same family as Palaemon macrodactylus). This allows them to rapidly colonize suitable areas. In contrast to the U.S., there are native Palaemonidae species present in Europe. These are widespread along European coasts and occupy a wide range of habitats. In Europe, Palaemon macrodactylus will have to share food sources ^[31] and space with the other Palaemonidae species. Most likely, this will result in competition with the native species ^[3].

However, this exotic species is advantaged over native species. Upon arrival, this newcomer may be protected for a while from the negative influence of (species) specific parasites that hindered their growth in their original range ^[32]. Along the coasts of Argentina, it has been observed that many oriental shrimps are infected with the white spot syndrome virus (WSSV). This increases the chance of transporting infected specimens, thus spreading the virus together with the shrimp ^{[21, 33]}.

Palaemon macrodactylus has a striking feature: a lightly coloured stripe on the dorsal side of adult individuals. Young individuals can be overlooked since they lack this characteristic ^[17]. The colour of this shrimp is red- to brownish or green- to blueish ^[3]. However, the distinctive colour pattern quickly fades when the animals are kept in an aquarium ^[4]. Remarkable is the absence of the vertical lines that characterize the rockpool prawn (Palaemon elegans) and common prawn (Palaemon serratus) ^[16]. The oriental shrimp can easily be confused with the estuarine shrimp Palaemon longirostris. Both species can be distinguished based on their rostrum: P. longirostris has 7-9 dorsal spines on its rostrum, while P. macrodactylus has 10-12 spines ^[3].

As with Crangon species (e.g. the common European shrimp Crangon crangon), the females of P. longirostris grow larger than the males. In a study in Great Britain, the length of males varied between 2.5 and 3.5 centimetres and that of females between 2.5 and 7 centimetres. Larger females tended to carry more eggs ^[12].

With amphipods as its main food source, the oriental shrimp is a carnivore. During summer, these shrimps consume large numbers of Chironomidae larvae in the Thames Estuary ^[31]. Palaemon macrodactylus shows vertical diurnal migration. These animals live lower in the water column during the day and migrate towards the water surface at night ^[12]. Its hidden lifestyle (during the day) makes it difficult to study the geographical distribution of the species.

[1]          World Register of Marine Species (WoRMS) (2020). Palaemon macrodactylus Rathbun, 1902. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=181372] (2020-11-17).

[2]          Holthuis, L.B. (1980). FAO species catalogue. Vol. 1. Shrimps and prawns of the world. An annoted catalogue of species of interest for fisheries. Digital edition. FAO Fisheries Synopsis, 125(1). FAO: Rome. ISBN 92-5-100896-5. xvii, 271 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=142556]

[3]          d'Udekem d'Acoz, C.; Faasse, M.; Dumoulin, E.; De Blauwe, H. (2005). Occurrence of the Asian shrimp Palaemon macrodactylus in the Southern Bight of the North Sea, with a key to the Palaemonidae of north-western Europe (Crustacea: Decapoda: Caridae). Ned. Faunist. Meded. 22: 95-111. [http://www.vliz.be/vmdcdata/imis2/imis.php?module=ref&refid=76221]

[4]          De Blauwe, H. (2006). De RugstreepSteurgarnaal Palaemon macrodactylus in België. De Strandvlo 26(1): 22-23. [http://www.vliz.be/vmdcdata/imis2/imis.php?module=ref&refid=98569]

[5]          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]

[6]          Janssen, C.R. (2006). Vlaams Instituut voor de Zee (VLIZ). ENDIS-RISKS fysico-chemical measurements and hyperbenthos in the Scheldt river, 2002-2006. [http://www.vliz.be/imis/imis.php?module=dataset&dasid=1422]

[7]          De Blauwe, H.; Dumoulin, E. (2009). De zeefauna en -flora uit de jachthaven van Zeebrugge, in het bijzonder de fouling-organismen van drijvende pontons. De Strandvlo 29(2): 41-63. [http://www.vliz.be/imis/imis.php?module=ref&refid=139489]

[8]          Soors, J.; Faasse, M.; Stevens, M.; Verbessem, I.; De Regge, N.; Van den Bergh, E. (2010). New crustacean invaders in the Schelde estuary (Belgium). Belg. J. Zool. 140(1): 3-10. [http://www.vliz.be/en/imis?module=ref&refid=145536]

[9]          Waarnemingen afkomstig van Waarnemingen.be: een initiatief van Natuurpunt Studie vzw en de Stichting Natuurinformatie (2018). RugstreepSteurgarnaal - Palaemon macrodactylus (Rathbun, 1902). [https://waarnemingen.be/soort/view/80690?waardplant=0&poly=1&from=2004-08-10&to=2018-11-14&akt%5B%5D=0&method=0&rar=0&only_approved=0&maand=0&prov=0&rows=20&os=0&hide_hidden=0&hide_hidden=1&show_zero=0] (2018-11-14).

[10]        Beguer, M.; Girardin, M.; Boët, P. (2007). First record of the invasive oriental shrimp Palaemon macrodactylus Rathbun, 1902 in France (Gironde Estuary). Aquat. Invasions 2(2): 132-136. [http://www.vliz.be/imis/imis.php?module=ref&refid=120855]

[11]        Lejeusne, C.; Saunier, A.; Petit, N.; Béguer, M.; Otani, M.; Carlton, J.; Rico, C.; Green, A. (2014). High genetic diversity and absence of founder effects in a worldwide aquatic invader. NPG Scientific Reports 4(5808): 1-9. [http://www.vliz.be/nl/catalogus?module=ref&refid=240110]

[12]        Ashelby, C.W.; Worsfold, T.M.; Fransen, C.H.J.M. (2004). First records of the oriental prawn Palaemon macrodactylus (Decapoda: Caridea), an alien species in European waters, with a revised key to British Palaemonidae. J. Mar. Biol. Ass. U.K. 84(5): 1041-1050. [http://www.vliz.be/vmdcdata/imis2/imis.php?module=ref&refid=67873]

[13]        Cuesta, J.A.; Gonzalez-Ortegon, E.; Drake, P.; Rodríguez, A. (2004). First record of Palaemon macrodactylus Rathbun, 1902 (Decapoda, Caridae, Palaemonidae) from European Waters. Crustaceana 77: 377-380. [http://www.vliz.be/imis/imis.php?module=ref&refid=142555]

[14]        Warkentine, B. (2010). The first record of Palaemon macrodactylus (Oriental Shrimp) from the eastern coast of North America. Northeastern naturalist 17(1): 91-102. [http://www.vliz.be/nl/catalogus?module=ref&refid=312331]

[15]        Worsfold, D. (2006). Eating out: Consumer perceptions of food safety. Int. J. Environ. Heal. R. 16(3): 219-229. [http://www.vliz.be/nl/catalogus?module=ref&refid=303085]

[16]        Faasse, M. (2005). Een Aziatische Steurgarnaal in Nederland: Palaemon macrodactylus Rathbun, 1902 (Crustacea: Decapoda: Caridea). Het Zeepaard 65(6): 193-195. [http://www.vliz.be/vmdcdata/imis2/imis.php?module=ref&refid=78070]

[17]        Tulp, A. (2006). De RugstreepSteurgarnaal Palaemon macrodactylus in meerdere Waddenhavens. Het Zeepaard 66(1): 27-28. [http://www.vliz.be/imis/imis.php?module=ref&refid=79912]

[18]        Beguer, M.; Bergé, J.; Martin, J.; Martinet, J.; Pauliac, G.; Girardin, M.; Boët, P. (2011). Presence of Palaemon macrodactylus in a European estuary: evidence for a successful invasion of the Gironde (SW France). Aquat. Invasions 6(3): 401-418. [http://www.vliz.be/imis/imis.php?module=ref&refid=207689]

[19]        Lavesque, N.; Bachelet, G.; Beguer, M.; Girardin, M.; Lepage, M.; Blanchet, B.; Sorbe, J.-C.; Modéran, J.; Sauriau, P.-G.; Auby, I. (2010). Recent expansion of the oriental shrimp Palaemon macrodactylus (Crustacea: Decapoda) on the western coasts of France. Aquat. Invasions 5(1): 103-108. [http://www.vliz.be/imis/imis.php?module=ref&refid=208394]

[20]        Micu, D.; Nita, V. (2009). First record of the Asian prawn Palaemon macrodactylus Rathbun, 1902 (Caridea: Palaemonoidea: Palaemonidae) from the Black Sea. Aquat. Invasions 4(4): 497-604. [http://www.vliz.be/imis/imis.php?module=ref&refid=208395]

[21]        Ashelby, C.W.; De Grave, S.; Johnson, M.L. (2013). The global invader Palaemon macrodactylus (Decapoda, Palaemonidae): an interrogation of records and a synthesis of data. Crustaceana 86(5): 594-624. [http://www.vliz.be/nl/catalogus?module=ref&refid=297597]

[22]        González-Ortegón, E.; Cuesta, J.A.; Schubart, C.D. (2007). First report of the oriental shrimp Palaemon macrodactylus Rathbun, 1902 (Decapoda, Caridea, Palaemonidae) from German waters. Helgol. Mar. Res. 61(1): 67-69. [http://www.vliz.be/imis/imis.php?module=ref&refid=117493]

[23]        Cuesta, J.A.; Bettoso, N.; Comisso, G.; Froglia, C.; Mazza, G.; Rinaldi, A.; Scovacricchi, T. (2014). Record of an established population of Palaemon macrodactylus Rathbun, 1902 (Decapoda, Palaemonidae) in the Mediterranean Sea: confirming a prediction. Mediterr. Mar. Sci. 15(3): 569-573. [http://www.vliz.be/nl/catalogus?module=ref&refid=297599]

[24]        Janas, U.; Tutak, B. (2014). First record of the oriental shrimp Palaemon macrodactylus M. J. Rathbun, 1902 in the Baltic Sea. Oceanol. Hydrobiol. St. 43(4): 431-435. [http://www.vliz.be/nl/catalogus?module=ref&refid=302994]

[25]        Newman, W.A. (1963). On the introduction of an edible oriental shrimp (Caridea, Palaemonidae) to San Francisco Bay. Crustaceana 5(2): 119-132. [http://www.vliz.be/imis/imis.php?module=ref&refid=121261]

[26]        Gil-Turnes, M.S.; Hay, M.E.; Fenical, W. (1989). Symbiotic marine bacteria chemically defend crustacean embryos from a pathogenic fungus. Science (Wash.) 246(4926): 116-118. [http://www.vliz.be/imis/imis.php?module=ref&refid=120874]

[27]        Lejeusne, C.; Latchere, O.; Petit, N.; Rico, C.; Green, A.J. (2014). Do invaders always perform better? Comparing the response of native and invasive shrimps to temperature and salinity gradients in southwest Spain. Estuar. Coast. Shelf Sci. 136: 102-111. [http://www.vliz.be/nl/catalogus?module=ref&refid=303077]

[28]        Vazquez, M.G.; Bas, C.C.; Spivak, E.D. (2016). Ontogeny of Salinity Tolerance in the Invasive Shrimp Palaemon Macrodactylus (Caridea: Palaemonidae). J. Crustacean Biol. 36(2): 214-219. [http://www.vliz.be/nl/catalogus?module=ref&refid=303080]

[29]        Vazquez, M.G.; Ituarte, R.B.; Bas, C.C.; Spivak, E.D. (2013). Effects of Temperature and Salinity on the Ovarian Cycle and the Embryonic Development of the Invasive Shrimp Palaemon Macrodactylus. J. Crustacean Biol. 33(2): 218-223. [http://www.vliz.be/nl/catalogus?module=ref&refid=303083]

[30]        Magozzi, S.; Calosi, P. (2015). Integrating metabolic performance, thermal tolerance, and plasticity enables for more accurate predictions on species vulnerability to acute and chronic effects of global warming. Global Change Biol. 21(1): 181-194. [http://www.vliz.be/nl/catalogus?module=ref&refid=303079]

[31]        Ashelby, C.; De Grave, S.; Johnson, M. (2016). Diet analysis indicates seasonal fluctuation in trophic overlap and separation between a native and an introduced shrimp species (Decapoda, Palaemonidae) in the tidal river Thames (U.K.). Crustaceana 89(6-7): 701-719. [http://www.vliz.be/nl/catalogus?module=ref&refid=312330]

[32]        Torchin, M.E.; Lafferty, K.D.; Dobson, A.P.; McKenzie, V.J.; Kuris, A.M. (2003). Introduced species and their missing parasites. Nature (Lond.) 421(6923): 628-630. [http://www.vliz.be/imis/imis.php?module=ref&refid=32191]

[33]        Martorelli, S.R.; Alda, P.; Marcotegui, P.; Montes, M.M.; La Sala, L.F. (2012). New locations and parasitological findings for the invasive shrimp Palaemon macrodactylus in temperate southwestern Atlantic coastal waters. Aquat. Biol. 15(2): 153-157. [http://www.vliz.be/nl/catalogus?module=ref&refid=297605]

VLIZ Alien Species Consortium (2020). Palaemon macrodactylus – Oriental shrimp. Non-native species of the Belgian part of the North Sea and bordering estuaries anno 2020. Flemish Institute for the Sea (VLIZ). 8 pp.