Gonionemus vertens - Clinging jellyfish

The clinging jellyfish is native to the northwest of the Pacific Ocean, along the coasts of China and Japan. Although, some authors suggest the Atlantic coast of North America as an alternative area of origin ^[2-4]. Furthermore, the species is present in the northeastern Pacific Ocean, from Washington to the Aleutian Islands ^[3-5]. The species is not found in Arctic waters and is restricted to temperate and warm-temperate climates ^[5]. It is a strictly coastal species, as it depends on the availability of seagrass or algae beds ^[3].

First observation in Belgium

The first report of the clinging jellyfish in Belgium dates back to 1946. The jellyfish was found during the late spring and summer in the Sluice Dock of Ostend during a study by the Royal Belgian Institute of Natural Sciences (RBINS), which investigated the potential changes in the fauna and flora of the sluice dock after the construction of a dam ^[6].

Spreading in Belgium

The clinging jellyfish is not observed along the Belgian coast, except in the Sluice Dock of Ostend. Since its first observation in 1946, it was not observed again until the spring of 2014 ^[7]. Afterwards, the species was occasionally observed here ^[8].

Spreading in neighbouring countries

In July 1960, the species was observed for the first time in the Netherlands in a creek near Vlissingen ^[9]. Later, in July 1976, it was seen in Lake Grevelingen. The species is established here, and its distribution further increased due to the expansion of the local seagrass beds. Furthermore, it was observed in the port of Goes, which is connected to the Eastern Scheldt. The species is probably not present in the Eastern Scheldt itself because of its stronger tides and less developed beds of seagrass ^[4].

Further observations took place in the coastal areas of England, Norway, Sweden, France, Germany and Ireland ^{[6, 9, 10]}. In Atlantic Europe, the jellyfish was observed in Portugal in the 19^th century. In 1913, it was observed in northeast England. Later, in 1921, scientists observed the jellyfish in the Oslofjord (Norway) ^[10]. In the Mediterranean Sea, the species occurs along the coast of France but probably also lives in the Adriatic Sea. In the 1910s, it was present in aquariums in Vienna, Prague and Berlin, which were filled with seawater from Croatia ^[3].

The clinging jellyfish is ​​a strictly coastal species. This trait makes it impossible for this jellyfish to have naturally dispersed from its original habitat in the Pacific Ocean to its current distribution range. The International Council for Exploration of the Sea (ICES) proposes three possible ways in which the jellyfish could have spread, namely via ballast water, by attaching to ship hulls or by introduction along with organisms intended for aquaculture ^{[11, 12]}. In particular, the transport of alien oyster species is mentioned in this context. The clinging jellyfish would have spread from Portugal to western Europe via the transport of Portuguese oysters (Crassostrea/Magallana angulata). Before that, the species may have been transported to Europe with the import of Japanese oysters (Crassostrea gigas) from East Asia ^[5]. The attachment (to hulls or molluscs) happens during the polyp stage. In this stage, cnidarians are not free-living, but after metamorphosis, they become adult jellyfish that float freely.

Long-distance transport may also be the result of the attachment of the polyps to ship hulls ^[13]. This is even more likely across shorter distances and is probably how this jellyfish spread to Lake Grevelingen in the Netherlands. Small recreational boats can sail over seagrass beds in shallow waters and spread the jellyfish across relatively short distances ^[4]. Adult jellyfish may also spread via ballast water ^[14].

The clinging jellyfish originates from temperate to warm-temperate regions. Therefore, it can survive in the prevailing climate conditions in our area ^[5]. The jellyfish depends on the presence of seagrass or algae beds. This dependence explains why it thrives among the algae of the genus Ulva in the Sluice Dock of Ostend ^[6].

The transport of Japanese and European oysters from their original habitats to western Europe has most likely facilitated the spread of this jellyfish ^[5]. Increased shipping traffic would also be an important means of spreading. If local conditions allow it, established populations can spread naturally by slow expansion of their distribution area ^[15]. This natural spread can be hindered by a sudden change in salinity, even if this is just 1 to 2 PSU ^[16]. This means it is not easy for the clinging jellyfish to reach the Sluice Dock of Ostend naturally, as the salinity here can be very different from that of the neighbouring port (30-35 PSU in the sluice dock compared to 0-35 PSU in the port) ^[17].

Almost nothing is known about the potential ecological effects of the introduced clinging jellyfish. However, the species can be a nuisance to swimmers and water sports enthusiasts since this jellyfish can sting them. In our regions, there are some cases of relatively violent reactions to its sting. However, these victims were sensitive to jellyfish stings ^[4].

To avoid potential problems, it is recommended not to swim in water where the species is present or, as in the Sluice Dock, to wear wetsuits and avoid drifting to areas where Ulva is present. Removing dense vegetation of seaweed and/or seagrass in recreational zones would also be an effective measure ^[14].

The medusa (the free-living, jellyfish-like phase) of the clinging jellyfish is small (3-4 cm) and a bell-shaped body. The species is recognized by the yellow-brown to orange-red cross (the reproductive organs) underneath the bell. The jellyfish has many bent – due to the presence of adhesive patches – tentacles ^{[4, 18]}.

Although not life-threatening, a sting of the clinging jellyfish can be painful. Cramps occur after the sting, which can last for a day. Itching and tingling may occur, and the skin may turn red at the location of the sting. In the Russian Far East, there have been cases of temporary blindness and deafness, hallucinations, prolonged pain and even death. So far, this has not yet occurred in Europe. In addition, most serious health problems occur in people who are very sensitive to jellyfish poison ^{[4, 7, 14, 15]}. When stung,  it is advised not to rinse the wound with fresh water but to use 96% ethanol followed by diluted ammonia ^[4].

[1]          World Register of Marine Species (WoRMS) (2020). Gonionemus vertens A. Agassiz, 1862. [http://www.marinespecies.org/aphia.php?p=taxdetails&id=117768] (2020-11-17).

[2]          Rodríguez, C.S.; Pujol, M.G.; Mianzan, H.W.; Genzano, G.N. (2014). First record of the invasive stinging medusa Gonionemus vertens in the southern hemisphere (Mar del Plata, Argentina). Lat. Am. J. Aquat. Res. 42(3): 653-657. [http://www.vliz.be/nl/catalogus?module=ref&refid=297326]

[3]          Bakker, C. (1980). On the distribution of Gonionemus vertens A. Agassiz (Hydrozoa, Limnomedusae), a new species in the eelgrass beds of Lake Grevelingen (S.W. Netherlands). Hydrobiol. Bull. 14(3): 186-195. [http://www.vliz.be/nl/imis?module=ref&refid=135719]

[4]          Bakker, C. (1982). De kruiskwal - Gonionemuis vertens A. Agassiz in de Zeegrasvelden van het Grevelingenmeer, in: [s.d.]. Vita Marina Zeebiol. Doc. Holtedieren. Vita Marina Zeebiologische Dokumentatie: zeebiologie, zeeaquariologie, malacologie., 16. Holtedieren. Stichting Biologia Maritima: Den Haag: pp. 27-46. [http://www.vliz.be/en/imis?module=ref&refid=239211]

[5]          Edwards, C.J. (1976). A study in erratic distribution: the occurrence of the medusa Gonionemus in relation to the distribution of oysters. Adv. Mar. Biol. 14: 251-284. [http://www.vliz.be/nl/catalogus?module=ref&refid=117002]

[6]          Leloup, E. (1948). Contributions à l'étude de la faune belge: XVI. Présence de la Trachyméduse, Gonionemus murbachi Mayer, 1901, à la côte belge. Bull. Mus. royal d'Hist. Nat. Belg./Med. Kon. Natuurhist. Mus. Belg. 24(27): 1-4. [http://www.vliz.be/nl/catalogus?module=ref&refid=19842]

[7]          Riebbels, G.; Vansteenbrugge, L. (2014). ILVO persbericht 140625: ILVO identificeert Japanse kruiskwal in de Spuikom te Oostende. [http://www.vliz.be/docs/vlizine/15-06/ILVOpersbericht-140625_Japanse-Kruiskwal-Spuikom-Oostende.pdf] (2014-06-25).

[8]          Vansteenbrugge, L. (2019). Persoonlijke mededeling

[9]          Leentvaar, P. (1961). Two interesting invertebrates, Limnadia lenticularis (L.)(Crustacea Phyllopoda) and Gonionemus vertens A. Agassiz (Limnomedusae), found in the Netherlands. Zool. Meded. 37: 225-231. [http://www.vliz.be/nl/catalogus?module=ref&refid=297327]

[10]        Naylor, M. (2007). Alien species in Swedish seas: Clinging jellyfish (Gonionemus vertens). Alien species in Swedish seas and coastal areas. Informationscentralerna för Bottniska viken, Egentliga Östersjön och Västerhavet: Sweden. 4 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=302995]

[11]        Wolff, W.J. (2005). Non-indigenous marine and estuarine species in the Netherlands. Zool. Meded. 79(1): 3-116. [http://www.vliz.be/en/imis?module=ref&refid=101200]

[12]        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]

[13]        Tambs-Lyche, H. (1964). Gonionemus vertens L. Agassiz (Limnomedusae) - a zoogeographical puzzle. Sarsia 15: 1-8. [http://www.vliz.be/nl/catalogus?module=ref&refid=206547]

[14]        Yakovlev, Y.M.; Vaskovsky, V.E. (1993). The toxic Krestovik medusa (Gonionemus vertens). Biol. Morya/Mar. Biol. 5-6: 3-16. [http://www.vliz.be/nl/catalogus?module=ref&refid=239814]

[15]        Eno, N.C.; Clark, R.A.; Sanderson, W.G. (Ed.) (1997). Non-native marine species in British waters: a review and directory. Joint Nature Conservation Committee: Peterborough. ISBN 1-86107-442-5. 152 pp. [http://www.vliz.be/nl/imis?module=ref&refid=24400]

[16]        Mills, C.E. (1984). Density is altered in Hydromedusae and Ctenophores in response to changes in salinity. Biol. Bull. 166(1): 206-215. [http://www.vliz.be/nl/catalogus?module=ref&refid=297336]

[17]        Mees, J.; Seys, J.; Haspeslagh, J. (Ed.) (2002). De Oostendse Spuikom: historiek, onderzoek en perspectieven. Relaas Spuikom Studiedag 8 december 2000 Duin en Zee (Oostende). VLIZ Special Publication, 8. Vlaams Instituut voor de Zee (VLIZ): Oostende. 44 pp. [http://www.vliz.be/nl/catalogus?module=ref&refid=24880]

[18]        Yerkes, R.M. (1902). A contribution to the physiology of the nervous system of medusa Gonionemus murbachii: Part 1. The sensory reaction of Gonionemus. Am. J. Physiol 6: 434-449. [http://www.vliz.be/nl/catalogus?module=ref&refid=239813]

VLIZ Alien Species Consortium (2020). Gonionemus vertens – Clinging jellyfish. Non-indigenous species in the Belgian part of the North Sea and adjacent estuaries anno 2020. Flanders Marine Institute (VLIZ). 5 pp.