Potamopyrgus antipodarum - New Zealand mud snail

The New Zealand mud snail is native to freshwater habitats in New Zealand ^{[2, 3]}.

First observation in Belgium

The New Zealand mud snail was first observed in Belgium on 26 March 1927 in the Scheldt, near Antwerp ^[4].

Spreading in Belgium

Although the New Zealand mud snail is common in our fresh waters ^[5], including in the canals and ponds of the ‘Provinciaal Groendomein Prinsenpark’ in Retie (province of Antwerp) ^[6], the species also occurs in the Sea Scheldt ^{[7, 8]} and since 1999 in the Canal of Ghent-Terneuzen ^[9]. This snail was also found at various brackish water locations in the Zwin area ^[10] and the polders ^[5].

Spreading in neighbouring countries

The New Zealand mud snail was first introduced in Australia. From Australia or Tasmania, this snail was brought to Europe, where it was first observed in the Thames estuary in 1859. From there, the species extended its range and had colonised the whole of Britain by 1920, from the Shetland Islands in the north to the Scilly Islands in the south. The distribution in Scotland is limited to the coastal areas ^[11-13].

The New Zealand mud snail was probably transported outside its native range through shipping, in particular as stowaway in drinking water barrels on ships from New Zealand. In this way, this snail reached Australia and England ^[12], between 1850 and 1860 ^{[2, 3]}. The snails probably ended up in the Thames estuary after washing and rinsing the barrels ^[11]. Another possibility is an introduction via ballast water ^[14].

Colonisation from the Thames estuary along the English coast was initially slow, but from the moment the freshwater areas were colonised, the range extension accelerated considerably. The New Zealand mud snail initially spread along large streams and canals, followed by a range extension towards smaller streams ^[11].

The New Zealand mud snail can reproduce very rapidly and throughout the year through asexual (parthenogenetic) reproduction ^[15]. Reproduction occurs between April and August ^[10]. Each brood can contain 20 to 120 embryos, and one female can produce up to 230 offspring per year ^[14].

The species is characterised by a high degree of adaptability to different environments, both in terms of flow rate, acidity and nutrient richness of the water ^[10]. These snails can easily survive short dry periods. On a wet surface, they can even survive droughts up to 50 days ^[16] and tolerate varying temperatures (0 to 28°C, with a maximum of up to 43°C for short periods). Furthermore, it is very likely that New Zealand mud snails adjust their shell morphology to flow rates ^[17]. They also show a broad tolerance towards soil habitat: the snails have already been found on silt, sand, mud, concrete, cobblestones, vegetation and gravel ^[14].  

The behaviour, and consequently the degree of invasiveness of the species, can also be determined by population related and possibly (heritable) genotypic effects ^[18].

In its natural habitat, the species has to deal with different types of parasites. In the North Sea, the number of parasites that infects the New Zealand mud snail is limited to one species (Sanguinicola sp., a trematode). The latter is also found in the snails’ area of origin. The lower infection risk plays in favour of the species and promotes further colonisation ^[19].

The New Zealand mud snail occurs in fresh to slightly brackish water (0-17.5 psu, optimal 5 psu), but can tolerate salinity levels up to 32 psu ^{[10, 12, 15, 20]}. For comparison: the seawater of the North Sea has a salinity of about 35 psu. In salt water, the species is less active ^[15], produces fewer offspring, and the growth of both embryos and adult animals slows down ^[21].

These snails are very small (5 to 6 mm), so they can easily stick to the feathers or on the feet of waterfowl. Humans can contribute to a further spreading by boating or while swimming ^[16]. Due to their rigid shells, the species can even survive the passage through the intestines of some birds and fishes ^{[20, 22]}.

The New Zealand mud snail usually lives on or under stones and waste ^[16]. The species has a diverse diet consisting of algae, cyanobacteria, diatoms, certain microbes, and plant and animal wastes ^{[14, 21]}.

The New Zealand mud snail has almost no natural enemies ^[13]. In Europe, the snails are infected by a single parasitic worm (Sanguinicola sp.), which has an adverse effect on growth, fertility and survival of the snail. The worm larvae infect the snail as an intermediate host ^[20].

Human activities, such as current disruptions in a river (e.g. through a dam or industrial pollution), can stimulate the spread of these snails. After such disturbances, water quality and biodiversity often deteriorate. Such environments are the ideal place for colonisation by the New Zealand mud snail ^[23].

In the early 20^th century, this snail caused obstructions in the freshwater supply of London, but this problem could be solved quickly by placing filters ^[11].

The New Zealand mud snail currently acts as an invasive species in some regions (not in Belgium) ^{[2, 16, 22, 24]}. In some areas, this snail has developed large populations and can make up to 97% of the invertebrate biomass. Density can be as high as 3 to 4 million individuals per m². In such numbers, these snails consume a large proportion of the primary production (up to 75%) and compete with other species ^[21]. They can influence the dynamics of the ecosystem and the carbon and nitrogen cycle ^[24].  This also has a negative effect on higher trophic levels ^{[16, 22]}. They can for instance adversely affect fish populations by outcompeting other prey species. The snails in turn are a poor or even indigestible food source for fish, which is why fish with these snails in their stomachs are often in poor condition ^[14].  

The impact of these snails on local ecosystems is determined by its population size and the degree of diet overlap with native species ^[24]. In smaller numbers, the New Zealand mud snail can increase secondary production ^[24]. Competition will also decrease with larger food abundances, as a result of which native species will grow faster ^[25].

Ways to prevent the introduction of the New Zealand mud snail have already been explored. Water recreants should remove the snail form their material by drying, heating, freezing, washing or subjecting it to a chemical treatment (copper sulphate, Formula 409® Disinfectant, Benzethonium Chloride compounds) ^[14]. These are preventive measures, because once the species is established, it is difficult to control ^[16].

A population of New Zealand mud snails can consist entirely of females that reproduce asexually or a mix of individuals that reproduce sexually and asexually. Individuals possessing both male and female reproductive organs (hermaphrodite) have also been observed ^[26]. In female individuals that reproduce asexually (parthenogenesis, by developing unfertilised eggs into adult females), the reproductive organs are reduced. The embryos develop in the brood pouch and also leave the egg there, so the animals are ovoviviparous ^{[10, 15]}.

The size, shape and decoration of the shell is very diverse. This variability can partly be explained by the fact that the species can reproduce via parthenogenesis. Asexual reproduction can lead to the establishment of clonal lineages with no (or only a slight) exchange of genetic material over several generations. Due to a lack of genetic exchange, different lines can evolve more quickly from each other and start to look different. In adult animals the shell measures 3-11 mm (typically 5-6 mm) and has 4 to 8 clockwise turns. The surface of the shell can be smooth, keeled or covered with spines. The snail can close its shell with a lid (the operculum) that is semi-transparent, with a variable colour from yellow, grey to brown. The body of the snail is grey speckled, the head is dark coloured ^{[15, 21]}.

[1]          World Register of Marine Species (WoRMS) (2020). Potamopyrgus antipodarum (Gray, 1843). [http://www.marinespecies.org/aphia.php?p=taxdetails&id=147123] (2020-11-17).

[2]          Städler, T.; Frye, M.; Neiman, M.; Lively, C.M. (2005). Mitochondrial haplotypes and the New Zealand origin of clonal European Potamopyrgus, an invasive aquatic snail. Mol. Ecol. 14(8): 2465-2473. [http://www.vliz.be/imis/imis.php?module=ref&refid=206627]

[3]          Ponder, W.F. (1988). Potamopyrgus antipodarum - a molluscan coloniser of Europe and Australia. J. Moll. Studd. 54(3): 271-285. [http://www.vliz.be/imis/imis.php?module=ref&refid=206519]

[4]          Dupuis, M.P. (1927). Faune malacologique de la Belgique: notes concernant la découverte par le Dr. Giltay de deux espèces de mollusques nouveaux pour la faune belge. Ann. Soc. R. Zool. Bel. 58: 31-38. [http://www.vliz.be/imis/imis.php?module=ref&refid=21083]

[5]          Adam, W. (1960). Mollusques: I. Mollusques terrestres et dulcicoles. Fauna van België = Faune de Belgique, 2. Institut Royal des Sciences Naturellles de Belgique: Bruxelles. 402, plates A-D pp. [http://www.vliz.be/en/imis?module=ref&refid=16569]

[6]          Vercauteren, T.H.; Sablon, R.; Wouters, K. (2006). Exotische ongewervelden in vijvers en grachten van het Provinciaal Groendomein Prinsenpark in Retie: een eerste bilan, in: Nieuwborg, H. et al. Natuurstudie in de provincie Antwerpen: Antwerpse Koepel voor Natuurstudie (ANKONA) Jaarboek 2004-2005. Antwerpse Koepel voor Natuurstudie (ANOKA): Antwerpen, Belgium: pp. 27-39. [http://www.vliz.be/en/imis?module=ref&refid=206260]

[7]          Kerckhof, F.; Haelters, J.; Gollasch, S. (2007). Alien species in the marine and brackish ecosystem: the situation in Belgian waters. Aquat. Invasions 2(3): 243-257. [http://www.vliz.be/en/imis?module=ref&refid=114365]

[8]          Van Haaren, T.; Soors, J. (2009). Sinelobus stanfordi (Richardson, 1901): A new crustacean invader in Europe. Aquat. Invasions 4(4): 703-711. [http://www.vliz.be/imis/imis.php?module=ref&refid=203907]

[9]          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]

[10]        Dumoulin, E. (1990). De brakwatermollusken van België: autecologie en verspreiding. De Strandvlo 10(2): 26-69. [http://www.vliz.be/en/imis?module=ref&refid=18570]

[11]        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]

[12]        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]

[13]        Alonso, A.; Castro-Díez, P. (2008). What explains the invading success of the aquatic mud snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca)? Hydrobiologia 614(1): 107-116. [http://www.vliz.be/imis/imis.php?module=ref&refid=206637]

[14]        Global Invasive Species Database (2018). Potamopyrgus antipodarum. [http://www.iucngisd.org/gisd/species.php?sc=449] (2018-08-17).

[15]        Winterbourn, M. (1970). The New Zealand species of Potamopyrgus (Gastropoda: Hydrobiidae). Malacologia 10(2): 283-321. [http://www.vliz.be/imis/imis.php?module=ref&refid=206628]

[16]        Davidson, T.M.; Brenneis, V.E.F.; de Rivera, C.; Draheim, R.; Gillespie, G.E. (2008). Northern range expansion and coastal occurrences of the New Zealand mud snail Potamopyrgus antipodarum (Gray, 1843) in the northeast Pacific. Aquat. Invasions 3(3): 349-353. [http://www.vliz.be/imis/imis.php?module=ref&refid=206632]

[17]        Kistner, E.J.; Dybdahl, M.F. (2014). Parallel variation among populations in the shell morphology between sympatric native and invasive aquatic snails. Biol. Invasions 16(12): 2615-2626. [http://www.vliz.be/nl/catalogus?module=ref&refid=297608]

[18]        Levri, E.P.; Clark, T.J. (2015). Behavior in invasive New Zealand mud snails (Potamopyrgus antipodarum) is related to source population. Biol. Invasions 17(1): 497-506. [http://www.vliz.be/nl/catalogus?module=ref&refid=297609]

[19]        Gérard, C.; Miura, O.; Lorda, J.; Cribb, T.H.; Nolan, M.J.; Hechinger, R.F. (2016). A native-range source for a persistent trematode parasite of the exotic New Zealand mudsnail (Potamopyrgus antipodarum) in France. Hydrobiologia 785(1): 115-126. [http://www.vliz.be/nl/catalogus?module=ref&refid=300325]

[20]        Gérard, C.; Blanc, A.; Costil, K. (2003). Potamopyrgus antipodarum (Mollusca:Hydrobiidae) in continental aquatic gastropod communities: impact of salinity and trematode parasitism. Hydrobiologia 493(1-3): 167-172. [http://www.vliz.be/imis/imis.php?module=ref&refid=206892]

[21]        Crosier, D.; Molloy, D.P. (2006). New Zealand mudsnail - Potamopyrgus antipodarum. New York State Museum: New York. 8 pp. [http://www.vliz.be/imis/imis.php?module=ref&refid=208965]

[22]        Richards, D.C.; Cazier, L.D.; Lester, G.T. (2001). Spatial distribution of three snail species, including the invader Potamopyrgus antipodarum, in a freshwater spring. West. N. Am. nat. 61(3): 375-380. [http://www.vliz.be/imis/imis.php?module=ref&refid=206634]

[23]        Spyra, A.; Kubicka, J.; Strzelec, M. (2015). The influence of the disturbed continuity of the river and the invasive species — Potamopyrgus antipodarum (Gray, 1843), Gammarus tigrinus (Sexton, 1939) on benthos fauna: a case study on urban area in the River Ruda (Poland). Environ. Manag. 56(1): 233-244. [http://www.vliz.be/nl/catalogus?module=ref&refid=297611]

[24]        Alonso, A.; Castro-Díez, P. (2012). The exotic aquatic mud snail Potamopyrgus antipodarum (Hydrobiidae, Mollusca): state of the art of a worldwide invasion. Aquat. Sci. 74(3): 375-383. [http://www.vliz.be/nl/catalogus?module=ref&refid=297607]

[25]        Riley, L.A.; Dybdahl, M.F. (2015). The roles of resource availability and competition in mediating growth rates of invasive and native freshwater snails. Freshwat. Biol. 60(7): 1308-1315. [http://www.vliz.be/nl/catalogus?module=ref&refid=297610]

[26]        Wallace, C. (1985). On the distribution of the sexes of Potamopyrgus jenkinsi (Smith). J. Moll. Stud. 51: 290-296. [http://www.vliz.be/imis/imis.php?module=ref&refid=206413]

[27]        Schmitt, C.; Balaam, J.; Leonards; Brix, R.; Streck, G.; Tuikka, A.; Bervoets, L.; Brack, W.; van Hattum, B.; Meire, P.; de Deckere, E. (2010). Characterizing field sediments from three European river basins with special emphasis on endocrine effects – a recommendation for Potamopyrgus antipodarum as test organism. Chemosphere 80(1): 13-19. [http://www.vliz.be/imis/imis.php?module=ref&refid=195421]