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Gonionemus vertens

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Datasheet

Gonionemus vertens

Summary

  • Last modified
  • 21 May 2019
  • Datasheet Type(s)
  • Invasive Species
  • Preferred Scientific Name
  • Gonionemus vertens
  • Taxonomic Tree
  • Domain: Eukaryota
  •   Kingdom: Metazoa
  •     Phylum: Cnidaria
  •       Class: Hydrozoa
  •         Order: Limnomedusae
  • Summary of Invasiveness
  • G. vertens is a small hydrozoan jellyfish whose type specimen was recorded in Puget Sound, Washington State, USA in 1861 (...

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Pictures

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PictureTitleCaptionCopyright
Gonionemus vertens (clinging jellyfish); approx. 2cm diameter. The four radial canals, with attached frilly gonads and the hanging manubrium, can be seen. Found on eelgrass in Padilla Bay, Washington State, USA. July, 2007.
TitleAdult
CaptionGonionemus vertens (clinging jellyfish); approx. 2cm diameter. The four radial canals, with attached frilly gonads and the hanging manubrium, can be seen. Found on eelgrass in Padilla Bay, Washington State, USA. July, 2007.
Copyright©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); approx. 2cm diameter. The four radial canals, with attached frilly gonads and the hanging manubrium, can be seen. Found on eelgrass in Padilla Bay, Washington State, USA. July, 2007.
AdultGonionemus vertens (clinging jellyfish); approx. 2cm diameter. The four radial canals, with attached frilly gonads and the hanging manubrium, can be seen. Found on eelgrass in Padilla Bay, Washington State, USA. July, 2007.©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); view of a swimming individual. Note the 'knee-like' articulation of several of the tentacles at the adhesive pad. Also note the tan-colour on the manubrium, the gonads and, on the tentacle bulbs.
TitleSwimming individual
CaptionGonionemus vertens (clinging jellyfish); view of a swimming individual. Note the 'knee-like' articulation of several of the tentacles at the adhesive pad. Also note the tan-colour on the manubrium, the gonads and, on the tentacle bulbs.
Copyright©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); view of a swimming individual. Note the 'knee-like' articulation of several of the tentacles at the adhesive pad. Also note the tan-colour on the manubrium, the gonads and, on the tentacle bulbs.
Swimming individualGonionemus vertens (clinging jellyfish); view of a swimming individual. Note the 'knee-like' articulation of several of the tentacles at the adhesive pad. Also note the tan-colour on the manubrium, the gonads and, on the tentacle bulbs.©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); close-up of several tentacles, showing the distinct nematocyst rings and also the adhesive pads.
TitleTentacles
CaptionGonionemus vertens (clinging jellyfish); close-up of several tentacles, showing the distinct nematocyst rings and also the adhesive pads.
Copyright©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); close-up of several tentacles, showing the distinct nematocyst rings and also the adhesive pads.
TentaclesGonionemus vertens (clinging jellyfish); close-up of several tentacles, showing the distinct nematocyst rings and also the adhesive pads.©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); in this close-up, the velum can be clearly seen along the margin of the bell.  The manubrium is at top center, a gonad is seen along a radial canal down through the center of the picture. The bell margin, with velum and single row of tentacles, with tan tentacle bulbs is visible across the lower third of the picture.
TitleVelum
CaptionGonionemus vertens (clinging jellyfish); in this close-up, the velum can be clearly seen along the margin of the bell. The manubrium is at top center, a gonad is seen along a radial canal down through the center of the picture. The bell margin, with velum and single row of tentacles, with tan tentacle bulbs is visible across the lower third of the picture.
Copyright©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); in this close-up, the velum can be clearly seen along the margin of the bell.  The manubrium is at top center, a gonad is seen along a radial canal down through the center of the picture. The bell margin, with velum and single row of tentacles, with tan tentacle bulbs is visible across the lower third of the picture.
VelumGonionemus vertens (clinging jellyfish); in this close-up, the velum can be clearly seen along the margin of the bell. The manubrium is at top center, a gonad is seen along a radial canal down through the center of the picture. The bell margin, with velum and single row of tentacles, with tan tentacle bulbs is visible across the lower third of the picture.©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); in this view of the subumbrella, the frilly lips of the manubrium can be seen.
TitleSubumbrella
CaptionGonionemus vertens (clinging jellyfish); in this view of the subumbrella, the frilly lips of the manubrium can be seen.
Copyright©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts
Gonionemus vertens (clinging jellyfish); in this view of the subumbrella, the frilly lips of the manubrium can be seen.
SubumbrellaGonionemus vertens (clinging jellyfish); in this view of the subumbrella, the frilly lips of the manubrium can be seen.©David Cowles/Walla Walla University, Anacortes, WA. USA - http://rosario.wallawalla.edu/inverts

Identity

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Preferred Scientific Name

  • Gonionemus vertens A. Agassiz, 1862

Other Scientific Names

  • Gonionemus depressus Goto, 1903
  • Gonionemus murbachi Mayer, 1901
  • Gonionemus murbachii Mayer, 1901
  • Gonionemus oshoro Uchida, 1929
  • Gonionemus vindobonensis Joseph, 1918
  • Haleremita cumulans Schaudinn, 1894

International Common Names

  • English: angled hydromedusa; clinging jellyfish; orange-striped jellyfish

Local Common Names

  • Netherlands: kruiskwal

Summary of Invasiveness

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G. vertens is a small hydrozoan jellyfish whose type specimen was recorded in Puget Sound, Washington State, USA in 1861 (Agassiz, 1861). The natural range of this nearshore limnomedusa appears to span from southern California through British Columbia, Alsaka and Kamchatka to northern Japan, and also to include the Arctic Ocean. On the Pacific coast of north America it is not common south of Puget Sound (Washington State) but some blooms have appeared farther south such as near Santa Barbara, California (McConnaughey et al., 1986). It is also relatively common on parts of the Atlantic coast of North America (Maine, Massachusetts) although it is not clear if this is a part of its natural range or a result of translocation. Japanese populations appear to be centred along the northwest coast of Honshu from Niigata northwards to Hokkaido, i.e. the eastern shore of the Sea of Japan (Otsuru et al., 1974). This is directly opposite the coastline of eastern Russia and Vladivostok, and the proximity of the Japanese and Russian locations for Gonionemus vertens most probably accounts for the presence of the species in both countries. The spread of this species beyond its natural range (i.e. European waters) is likely to have been influenced by movements of oysters, shipping and marginal spread of established populations (Carlton, 1985). Transport on ships' hulls at the polyp stage from the western Pacific Ocean in the nineteenth century appears to be the most probable mechanism of introduction although hydromedusae can disperse in water currents and ballast water (Carlton, 1985). Specimens were found in Argentinean waters in  2008. Apart from its ability to inflict severe stings on humans in the north-western Pacific ocean (but not most other parts of its range), the species appears to have few adverse effects in either its native or its introduced range.

Taxonomic Tree

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  • Domain: Eukaryota
  •     Kingdom: Metazoa
  •         Phylum: Cnidaria
  •             Class: Hydrozoa
  •                 Order: Limnomedusae
  •                     Family: Olindiasidae
  •                         Genus: Gonionemus
  •                             Species: Gonionemus vertens

Notes on Taxonomy and Nomenclature

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In addition to Gonionemus vertens a number of species and local forms within the genus have been described from different geographical regions, distinguished by the shape and thickness of the bell, and the number of tentacles and statocysts (Edwards, 1976); these are listed by WoRMS (2015), and some examples are described in the 'Description' section of this datasheet. Most are now considered synonymous with G. vertens (WoRMS, 2015).

Early references often list this species as a member of the Trachyline medusae which has now been revised (McConnaughey et al., 1986).

Description

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Cowles (2015), referring to the form found in the coastal waters of Washington State (USA) and British Columbia (Canada) from which the type specimen of G. vertens was collected, describes the species thus: 'This bell-shaped hydromedusa (usually just slightly broader than tall) has about 60-80 unbranched tentacles which are evenly spaced around the margin of the bell. The tentacles have large rings of nematocysts all along their length, and halfway back from the tip of each tentacle is a larger adhesive knob or pad used for attachment to objects. The tentacle tends to bend at the disk. The tentacle bulbs at the base of the tentacles are yellowish-tan. The 4 radial canals are unbranched and continue all the way to the margin of the bell. There are no centripetal canals. Ruffled flap-like orange, red, violet (in females), or yellow-brown (in males) gonads hang down along the 4 radial canals and form a clearly visible X shape. The manubrium is coloured tan and hangs down about to the bell margin, with 4 slightly frilly lips. The bell may be clear or light green (it is unusual for a hydrozoan medusa to be coloured). Diameter to 2.5 cm'. According to Wrobel (undated), referring to the genus Gonionemus as found in the Pacific, the number of statocysts is approximately equal to the number of tentacles.

Species now synonymised (WoRMS, 2015) with G. vertens include: G. murbachii from the northeastern seaboard of North America, which is somewhat shallower than a hemisphere and has 60-80 tentacles, half the number of statocysts, and a stomach smaller than that of G. vertenssensu stricto (Mayer, 1909); G. agassizi from the Aleutian Islands, which is stated to have more tentacles than G. vertenssensu stricto (probably up to 100) and be characterised by a much shallower bell (Murbach and Shearer, 1902, 1903); G. depressum from southern Japan, which has 64 tentacles, about twice as many as statocysts, and a bell shallower than a hemisphere (Goto, 1903); and G. oshoro from northern Japan, which has up to 80 tentacles and about the same number of statocysts, is very shallow with a thin bell, and has fewer gonadial folds than G. murbachii (see Edwards, 1976).

Distribution Table

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The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

Continent/Country/RegionDistributionLast ReportedOriginFirst ReportedInvasiveReferenceNotes

Sea Areas

Arctic SeaPresentRomer and Schaudinn, 1906General distribution, specific site not detailed.
Atlantic, NortheastPresentIntroducedLand et al., 2001; Fofonoff et al., 2015
Atlantic, NorthwestPresentAnon, 1980; Fofonoff et al., 2015
Atlantic, SouthwestPresent, few occurrencesIntroduced2008Fofonoff et al., 2015Near Mar del Plata, Argentina
Mediterranean and Black SeaWidespreadIntroducedpossibly early 1900sLand et al., 2001Broad but patchy distribution throughout Mediterranean sea, not fully defined
Pacific, Eastern CentralPresent, few occurrencesMcConnaughey et al., 1986
Pacific, NortheastPresentNativeFenner, 1997; Fofonoff et al., 2015
Pacific, NorthwestPresentNativeYakovlev and Vaskovsky, 1993; Fofonoff et al., 2015

Asia

JapanPresentNativeMaas, 1909; Otsuru et al., 1974Centered around north-west coast of Honshu

North America

CanadaPresentFenner, 1997
-British ColumbiaPresentNativeMcClean Fraser, 1942; Fofonoff et al., 2015
USAPresentNativeUncertain whether east coast populations are native or introduced
-AlaskaPresentNativeMurbach and Shearer, 1902; Fofonoff et al., 2015
-CaliforniaPresent, few occurrencesMcConnaughey et al., 1986
-FloridaLast reported1901Mayer, 1901Dry Tortugas
-MaineLocalisedAnon, 1980; Anon, 1980; WoRMS, 2015Cobscook Bay, Washington County
-MassachusettsPresentFofonoff et al., 2015; WoRMS, 2015First recorded at Woods Hole in 1894; disappeared in 1931; reappeared in recent years
-New YorkLast reported1898Hargitt, 1898
-WashingtonPresentAgassiz, 1861; Cowles, 2015Type specimen recorded in Puget Sound in 1861

South America

ArgentinaPresent, few occurrencesIntroduced2008Fofonoff et al., 2015Near Mar del Plata

Europe

BelgiumPresentIntroducedpossibly early 1900sLeloup, 1948Atlantic seaboard
DenmarkPresentIntroducedWoRMS, 2015Kattegat
FranceLocalisedIntroducedpossibly early 1900sLeloup, 1948; Leewis, 2002; Müller, 2004; WoRMS, 2015English Channel and Mediterranean
GermanyPresentIntroducedpossibly early 1900sGollasch and Nehring, 2006German Bight
ItalyPresentIntroducedearly 1900sNappi, 1918Bay of Naples
NetherlandsLocalisedIntroducedLeloup, 1948; Leentvaar, 1961; Bakker, 1980; Leewis, 2002
NorwayPresentIntroducedpossibly early 1900sEdwards, 1976Patchy distribution
Russian FederationPresentPresent based on regional distribution.
-Eastern SiberiaPresentNativeFofonoff et al., 2015
-Russian Far EastPresentYakovlev and Vaskovsky, 1993
ScandinaviaWidespreadIntroducedpossibly early 1900sLeloup, 1948Skaggerak, broad but patchy distribution
SwedenPresentIntroducedWoRMS, 2015
UKWidespreadIntroducedpossibly early 1900sEno et al., 1997Patchy distribution around British coasts, low density

History of Introduction and Spread

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This species shows a variable, generally moderate rate of spread beyond its natural range in the North Pacific (and possibly the Atlantic coast of North America -- see Summary of Invasiveness). It is thought to have been initially introduced to Europe in Portugal where the population was localised due to currents, temperatures and salinities. It was exported from 1867 onwards from Portugal to France, this time attached at the polyp stage to oysters. This mechanism has probably allowed spread to other European countries including the UK and Ireland, since France was a major oyster exporter (Edwards, 1976). By 1960 the species had been recorded from several coastal locations in Europe. Records in Europe are dated from England (1913), Norway (1922), Sweden (1930), France (1930, 1932, 1950), Belgium (1948), northwest Germany (1950), the Mediterranean (1952, 1953), Ireland (1953), and the Netherlands (1960) (Russell, 1953; Leentvaar, 1961).

Edwards (1976) also postulated that G. vertens may have arrived much earlier from Japan with importations of Japanese oysters, Crassostrea gigas, 500 or more years ago; this study also discusses other shipping- and seaplane-associated methods of transport. Nonetheless, the notion of transportation on commercial oysters is supported by the occurrence of medusae in aquaria at Vienna (Austria), Prague (Czech Republic), Cullercoats (UK), Port Erin (Isle of Man), Aberdour (UK) and Dunstaffnage (UK) following the introductions of oysters to the respective facilities (see Edwards, 1976). The exact nature of how the species was presumably translocated from the North Pacific to the Atlantic coast of North America is not known, although commercial shipping or attachment to commercial items again seem probable candidates.

The first report of the species from the south-western Atlantic was in 2008, when specimens were found in an aquarium filled with benthic organisms that had been collected near Mar del Plata, Argentina; shipping is considered to be the likely vector (Fofonoff et al., 2015).

Risk of Introduction

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G. vertens might be introduced / translocated into new areas via biotic and abiotic pathways. For example, in its medusa form the species can be moved over local scales (within suitable climatic envelopes) by current transport, as for any zooplanktonic species. Areas that introduce non-native oysters (particularly from the North Pacific) for commercial purposes may be at an increased risk as the polyps of G. vertens have been shown to attach to their shells, budding off to produce new medusae if the new site is characterised by suitable environmental parameters. Deliberate introductions of G. vertens itself are highly unlikely as the species has no commercial value and is typically considered a nuisance owing to its potent sting.

Habitat

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This species seems to thrive in temperate to warm-temperate regions. It can be found attached to kelp, eelgrass, and other substrates (e.g. the shells of epibenthic bivalve molluscs) in summer, in at least partly protected waters (Cowles, 2005). Yerkes (1906) suggested that the preferred habitat of G. vertens is sheltered harbours which are affected by the tides, but where these tides are not to strong so as to dislodge the species from the algal fronds it is typically attached to. Any disturbance in the water causes the animals to detach themselves from the object to which they are attached – either by the viscid bodies of the tentacles or the lips of the manubrium – and swim to the surface.

Habitat List

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CategorySub-CategoryHabitatPresenceStatus
Marine
Bays Present, no further details
 

Biology and Ecology

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Reproductive Biology

The conspicuous stage in the dimorphic (i.e. metagenic) life cycle is the small medusa. The polyploid stage is present as a tiny solitary polyp attached to a substrate at the seabed (including mollusc shells) which feeds on protozoa and other small plants and animals. The polyp stage closely resembles Hydra and is seldom seen (McConnaughey et al., 1986).

The gonads are four yellowish structures embedded in the surface of the epidermis beneath the radial canals. The ovaries are more granular in appearance than the testes (sexes are separate). The gametes are shed into the sea, and the zygotes develop into ciliated planula larvae which grow into minute polyps. These polyps can bud off other polyps or medusae, the latter occurring typically during the spring/summer to enable individuals to capitalise upon the seasonal abundance of their zooplankton prey. At Woods Hole, Massachusetts the medusae occur from June to October (Yerkes, 1906).

Physiology and Phenology
 
The species is present year round at temperate latitudes in the benthic polyp stage. Unpublished work on G. vertens around British Columbia (Claudia Mills, personal communication in Fenner, 1997) suggests that medusae are released from the polyps from late April through to early June, are mostly mature by July, and last until early-mid August. At Woods Hole, Massachusetts the medusae occur from June to October (Yerkes, 1906). No specific studies on the physiology of G. vertens have been conducted since the early 1900s, when they were largely descriptive in nature.
 
Nutrition
 
G. vertens feeds on small crustaceans, especially copepods (McConnaughey et al., 1986). Upon reaching the surface the bell relaxes, the tentacles become fully extended and any small fish or crustaceans encountered as the medusa slowly drifts toward the bottom are ensnared. Alternatively, the medusae can use their adhesive pads to attach to seaweeds or other objects near the bottom, extending their tentacles and waiting for prey to bump into them.
 
The manubrium hangs down from the centre of the subrellum. It bears the cross-shaped mouth and the four short oral lobes which grip the food. Digestion begins in the centre of the manubrium which communicates with the four radial canals and the ring canal. The velum is well developed and used in swimming. Having a velum is characteristic of the hydrozoan medusae.

A very early, yet detailed, account of feeding in G. vertens is provided by Yerkes (1906). Prey items in Massachusetts consisted of small fishes, crustaceans, larvae of various kinds, and such dead organic material as came within reach. G. vertens were found attached by a few tentacles to a weed, with the exumbrellar surface of the bell against the weed and the manubrium swinging free in the water. It was additionally proposed that the the restricted range of G. vertens (on a localised scale) may relate to the distribution of its food supply, as sheltered coastal regions where the species is abundant are frequently found to contain masses of organic matter (Yerkes, 1906).

Associations

G. vertens use adhesive discs near the middle of each tentacle to attach to eelgrass, sea lettuce (Ulva spp.) or various types of algae instead of swimming. They are small (bell diameter to 25 mm) and hard to see when hanging on to swaying seaweed. Nevertheless they are capable of swimming when necessary. In Europe the species has been found in close association with the commercial oyster Crassostrea angulata (Edwards, 1976) which has been proposed as its principal artificial vector for introduction.
 
Environmental Requirements

This species appears to be adaptable to the seasonal temperature fluctuations found at temperate latitudes and into the Arctic Ocean. Like many gelatinous zooplankton with a metagenic life cycle, it appears to be present year round in its polyp form with the planktonic medusa budding off in late spring/early summer to take advantage of seasonal abundances of its zooplankton prey.

Notes on Natural Enemies

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No specific studies have been undertaken on the predators of G. vertens. However, the general perception of gelatinous zooplankton within marine food webs as trophic dead ends (or conduits at best) has been radically challenged in recent years with many species now considered to be intrinsic dietary components for an increasing range of vertebrate and invertebrate species (see Arai (2005) for a full review).

Means of Movement and Dispersal

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Although typically attached to algae or shellfish near the seabed the medusae are also active swimmers that can propel themselves upward in the water column by rhythmic pulsations of the bell. G. vertens typically swims in bouts of 5 to 10 bell contractions, each bout lasting 1 to 3 s followed by periods of quiescence lasting around 10 to 90 s (Daniel, 1985). Natural mechanisms of dispersal include direct current transport and potential transportation on detached, rafting macroalgae. The introduction of non-native oysters into European waters more than a century ago has been proposed as the principal mechanism by which G. vertens, as attached polyps, became established in the region. This notion is backed up by the presence of species in aquaria in landlocked European countries where oysters were on display. Abiotic dispersal mechanisms include transport of polyps on ships' hulls and medusae in ballast water.

Natural Dispersal (Non-Biotic)
 
Like all gelatinous zooplankton, G. vertens can be transported in localised and broad-scale current regimes. Establishment in new areas is dependent on suitable abiotic and biotic conditions.
 
Vector Transmission (Biotic)
 
Detached macroalgae can form rafts which have been inferred as a dispersal vector for a range of marine invertebrate species (Thiel and Gutow, 2005). Although no empirical evidence exists of rafting in G. vertens, this dispersal mechanism should not be discounted as it is receiving increasing attention in studies of broad-scale population connectivity.
 
Accidental Introduction
 
G. vertens can persist in an area in the polyp stage. If the species is introduced into aquaria, the polyp can persist for long periods and may produce medusae from time to time under the artificial conditions of temperature and food availability. This reproductive potential may explain the occurrence of medusae in aquaria at Vienna (Austria), Prague (Czech Republic), Cullercoats (UK), Port Erin (Isle of Man), Aberdour (UK) and Dunstaffnage (UK) (see Edwards, 1976).
 
The occurrences, distribution and apparent spread of G. vertens in Europe during the past 100+ years are all consistent with the supposition that it has been transported on oysters, especially Crassostrea angulata, for which there is much circumstantial evidence (Edwards, 1976).

Transport on ships' hulls in the polyp stage (Carlton, 1985) from the western Pacific Ocean in the nineteenth century may be another mechanism of introduction. Edwards (1976) suggested that it may have arrived much earlier from Japan with importations of Japanese oysters, Crassostrea gigas, 500 or more years ago.

Economic Impact

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No specific economic impacts have been identified to date beyond the localised effects of G. vertens causing severe stings to female swimmers employed to harvest seaweed around Honshu, Japan (Fenner, 1997; see Social Impact section).

Environmental Impact

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G. vertens feeds largely on zooplanktonic taxa (i.e. copepod crustaceans) which are super-abundant at temperate latitudes, so it would not be expected to have a dramatic impact as an invasive species at an environmental level.

Impact on Habitats
 
Effects at a habitat level would not be predicted to be problematic as the species does not occur in super-abundance.
 
Impact on Biodiversity

There are no predicted impacts on biodiversity as G. vertens is a mero-planktonic species operating within the extremely diverse planktonic communities found at temperate latitudes. In areas to which it has been accidentally introduced (i.e. Europe’s Atlantic fringe) the species poses no immediate threat in terms of outcompetition of native species.

Social Impact

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Stings from G. vertens are unusually venomous in parts of its range, and dense shoals of such jellyfish in warm seas pose a danger to swimmers. A sting from G. vertens causes a burning sensation in the skin, which is accompanied by rapid blistering and local oedema, followed in turn by general weakness after 10 to 30 minutes (see Fenner, 1997). However, there appears to be some regional variation regarding the severity of the stings (see Cornelius (1995) and references therein). For example, in the Pacific Northwest of North America G. vertens lacks a sting that is felt by people, but the same species in the Russian Far East is known to be venomous. 

Russia: In an area around Vladivstok, G. vertens causes a severe envenomation syndrome at certain times of year. In humans this envenomation syndrome induces symptoms similar to the Irukandji syndrome*. However, some victims have even more bizarre symptoms with neurological and psychiatric symptoms also occurring (Yakovlev and Vaskovsky, 1993).
 
Northeast Pacific: Although this small orange hydromedusan species produces very serious stings around Vladivostok, it does not appear to sting in the northeast Pacific around British Columbia (Fenner, 1997).
 
Japan:G. vertens causes numerous stings in swimmers in Honshu. It occurs in the eastern side of the Sea of Japan amongst seaweed that is harvested by female swimmers. It causes an Irukandji-like syndrome* with apparent temporary psychiatric symptoms (Pigulevsky and Michaleff, 1969; Otsuru et al., 1974). Interestingly, the same symptoms can occur from eating the seaweed that the swimmers harvest, probably as a result of G. vertens being present as a contaminant (Uchida, 1929, from Fenner, 1997).
 
Massachusetts, USA: There have been cases of researchers being stung, causing serious health symptoms in at least one case; the species is not likely to be abundant in areas heavily used by swimmers (Fofonoff et al., 2015).
 
* Notes on Irukandji syndrome: Most stings occur during the summer wet season in December–January in North Queensland, Australia, with different seasonal patterns elsewhere (Nickson et al., 2009). Because the jellyfish responsible in that region is very small, and the venom is only injected through the tips of the nematocysts (the cnidocysts) rather than the entire lengths, the sting may barely be noticed at first. It has been described as feeling like little more than a mosquito bite. The symptoms, however, gradually become apparent and then more and more intense in the following 5 to 120 minutes (30 minutes on average). Irukandji syndrome includes an array of systemic symptoms including severe headache, backache, muscle pains, chest and abdominal pain, nausea and vomiting, sweating, anxiety, hypertension, tachycardia and pulmonary oedema (Barnes, 1964; Little et al., 2003; Nickson et al., 2009). Symptoms generally abate in 4 to 30 hours, but may take up to two weeks to resolve completely (Grady and Burnett, 2003).

Risk and Impact Factors

Top of page Invasiveness
  • Proved invasive outside its native range
  • Has a broad native range
  • Is a habitat generalist
  • Capable of securing and ingesting a wide range of food
  • Highly mobile locally
  • Long lived
  • Fast growing
  • Has high reproductive potential
  • Has propagules that can remain viable for more than one year
  • Reproduces asexually
Impact outcomes
  • Modification of natural benthic communities
  • Negatively impacts human health
  • Negatively impacts aquaculture/fisheries
Impact mechanisms
  • Causes allergic responses
  • Fouling
  • Induces hypersensitivity
Likelihood of entry/control
  • Highly likely to be transported internationally accidentally
  • Difficult to identify/detect as a commodity contaminant
  • Difficult to identify/detect in the field
  • Difficult/costly to control

Diagnosis

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Given the small size of G. vertens medusae (~2.5 cm bell diameter) and the elusive nature of their benthic polyps, the species is normally detected first through medical diagnosis of stings (although it is unlikely that in introduced areas the expertise to attribute stings to a particular species would be available).

Edwards (1976) suggested that G. vertens was introduced into European waters as polyps attached to non-native commercial oysters from the Pacific. Close inspection of oyster shells introduced under such circumstances is worthy of consideration to detect the present of minute benthic polyps.

Detection and Inspection

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A convenient mode of capturing G. vertens proposed by Yerkes (1906) is to disturb the water and then dip-net the medusae as they appear at the surface. Upon reaching the surface they turn over, the mouth of the bell facing upwards, and begin to sink by force of gravity. Under ordinary circumstance the medusae are not at the surface of the water and are attached to seagrass fronds (or similar algae or substrates) at the seabed. It would appear, therefore, that they do not migrate upwards in any definite way for the purpose of feeding or in response to light. Surface towing at night has suggested that there are few, if any, more at the surface than in the daytime. In the light of these suggestions, provisional surveys to assess presence or absence should target sheltered bays and harbours where seagrass beds are present. Given that translocation of G. vertens on the hulls of commercial vessels and/or in ballast water may also be a problem (Edwards, 1976), harbour areas are again a logical place to undertake pilot surveys.

Similarities to Other Species/Conditions

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Eperetmus typus (Phylum Cnidaria; Class Hydrozoa; Order Limnomedusae; Family Olindiidae) is also deeply bell-shaped and has nematocyst rings on the tentacles, but it has no adhesive pads on the tentacles and the radial canals usually have many centripetal canals.

Melicertum octocostatum (Phylum Cnidaria; Class Hydrozoa; Order Leptomedusae; Family Melicertidae) is found on both coasts of the USA, being relatively common in coastal areas of the North Atlantic, and also found widely in the North Pacific (Bering Sea south to Oregon, USA). M. octocostatumis a near-shore jelly that can also be found in estuaries. It is a fairly distinct hydromedusa, with eight bright yellow or brownish-yellow linear gonads along the radial canals, easily visible through the transparent bell. The bell reaches a maximum length of 14 mm. The stomach is short and broad. Numerous tentacles line the bell margin, with up to 88 large tentacles alternating with smaller ones.

Prevention and Control

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Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Although G. vertens appears to have little adverse effect in most of its range, there are possible prevention and control measures that could be used if necessary.

Prevention

Edwards (1976) suggested that G. vertens was introduced into European waters as polyps attached to non-native commercial oysters from the Pacific. Close inspection of oyster shells introduced under such circumstances is worthy of consideration to detect the present of the minute benthic polyps.
 
Translocation of benthic polyps on the hulls of commercial vessels or of medusae in ballast water is another potential vector for translocation of G. vertens. Again, given the small size (~2.5 cm) and translucent appearance of the medusae, it is not immediately evident how prevention of such translocation could be avoided.
 
Rapid response
 
It is not immediately obvious how medusae could be completely removed from an area to which the species has been introduced as they appear in low or relatively low densities and are typically found attached to seagrass (or suitable benthic substrates). Physical disturbance of a seagrass bed can cause the medusae to rise to the surface and nets could theoretically be used to remove indivividuals from the water column. However, it is extremely unlikely that it would be possible to remove the medusae from an area completely using this method. Regarding the benthic polyps which are 1-2 mm long, detection alone is extremely difficult, rendering rapid response/removal highly problematic at present.
 
Public awareness
 
There are several jellyfish-related public outreach initiatives in place around the world. These operate mainly via the internet and public meetings held periodically. A UK/Irish initiative regarding the introduction and identification of G. vertens in coastal waters is: EcoJel (an initiative between the University of Wales Swansea, UK and University College Cork, Ireland) http://www.jellyfish.ie/index.asp.
 
Eradication
 
Please also see Rapid Response section. Given that G. vertens is a tiny <2 cm) medusae and the benthic polyp stage is ~1-2 mm in length the challenge lies first with detection and then removal. It is possible that net tows (after disturbance of seagrass beds) might lower the densities on a localised scale. There is no immediate solution for the removal of benthic polyps as they are almost impossible to detect by eye underwater and could be dispersed at low densities.
 
Containment/zoning
 
Containment or zoning of G. vertens appears highly problematic for a number of reasons. Firstly, the medusae have the potential for localised transport (and potential broad-scale translocation within a nation state) via natural current regimes in the same manner as any marine zooplankton. Translocation of G. vertens in its benthic polyp stage on the oyster Crassostrea edulis should however receive due attention given that this was the mechanism proposed for the original introduction of the species into European waters (Edwards, 1976).
 
Control
 
Cultural control and sanitary measures
 
The only sanitary measure that is relevant is to check imported non-native oysters for the presence of G. vertens.
 
Monitoring and Surveillance
 
The most logical manner in which to test for the presence of G. vertens would be by routine surveys of seagrass beds in sheltered in-shore locations, followed by dip net sampling. Areas where non-native oysters have been introduced should also be considered as good indicator sites to conduct surveys. The small size of the medusae <2.5 cm) and non-bloom-forming behaviour negats the use of more indirect methods such as remote sensing.
 
Ecosystem Restoration

Ecosystem impacts to a level requiring restorative measures have not been documented to date.

Gaps in Knowledge/Research Needs

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The most immediate gap in our knowledge of G. vertens relates to population connectivity. Studies focussed on the molecular ecology of the species should therefore be considered a priority.

References

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Links to Websites

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WebsiteURLComment
Biodiversity Heritage Libraryhttp://www.biodiversitylibrary.org/
EcoJelhttp://www.jellyfish.ie/index.aspA UK/Irish initiative to assess the opportunities and detrimental impacts of jellyfish in the Irish Sea.
GISD/IASPMR: Invasive Alien Species Pathway Management Resource and DAISIE European Invasive Alien Species Gatewayhttps://doi.org/10.5061/dryad.m93f6Data source for updated system data added to species habitat list.
Global register of Introduced and Invasive species (GRIIS)http://griis.org/Data source for updated system data added to species habitat list.
Jellies Zonehttp://jellieszone.com
Joint Nature Conservation Committeehttp://www.jncc.gov.uk/
Wallawalla Universityhttp://www.wallawalla.edu

Contributors

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14/06/10 Original text by:

Jonathan Houghton, Institute of Environmental Sustainability, School of the Environment & Society, Swansea University, Singleton Park, Swansea SA2 8PP, UK

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