Invasion History
First Non-native North American Tidal Record: 1993First Non-native West Coast Tidal Record: 1993
First Non-native East/Gulf Coast Tidal Record:
General Invasion History:
Littorina saxatilis has an extensive native distribution in the Atlantic, stretching from the Arctic Ocean (up to 80°N) south to the Mid-Atlantic States (New Jersey-Virginia) and the Iberian Peninsula (Reid 1996). Isolated southern populations in the Azores, Canary Islands, and the Mediterranean Sea (Tunisia) could represent remnants of Pleistocene populations, although fossil evidence is lacking. Natural transport by birds or rafting is also possible. In the Northeast Atlantic, L. saxatilis has colonized the isolated islet of Rockall, between Britain and Iceland (Johannesson 1988). Johannesson (1988) suggests that the ovoviparous life history has adapted this species to colonizing remote sites, since a single fertilized female rafted on driftwood or seaweed, or carried by a ship, can start a population. Alternatively, these southern records could represent early introductions by shipping. On the East coast of North America, the construction of stone jetties and riprap may have favored the extension of L. saxatilis’ range to the Atlantic coast of Virginia, near the mouth of Chesapeake Bay (Counts and Bashore 1991). The type population in Venice Lagoon, Italy, from which the species was first described in 1792, is probably introduced (Panova et al. 2011), as are occurrences in four estuaries on the coasts of South Africa and Namibia (Mead et al. 2011b). The most recent invasion is in San Francisco Bay, where this snail was first collected in 1993 (Carlton and Cohen 1998).
North American Invasion History:
Invasion History on the West Coast:
Littorina saxatilis has been introduced to the West Coast of North America, in San Francisco Bay, California. In 1993, this periwinkle was collected in rocky debris along the shore at Emeryville Marina, on central San Francisco Bay, by James T. Carlton (Carlton and Cohen 1998). In 1996, a second population was found at Taney Marina Beach, Coast Guard Island, on the Oakland estuary (Carlton and Cohen 1998). A research group, led by Whitman Miller of the Smithsonian Environmental Research Center, began a series of surveys in 2002 in order to evaluate the possibility of eradication. They found that L. saxatilis was already sufficiently widespread so that eradication was not feasible. Several populations were found on South San Francisco Bay, including one at the Port of Redwood City (Miller et al. 2004) and in Brisbane Lagoon (Cohen et al. 2005). The probable vector for introduction of this periwinkle was imported baitworms (Neanthes virens) wrapped in seaweed (Ascophyllum nodusum) from Maine and Maritime Canada. The seaweed packing material is usually discarded along the shore, and often contains living marine invertebrates, including L. littorea, L. saxatilis, and L. obtusata (Carlton and Cohen 1998; Miller et al. 2004).
Invasion History Elsewhere in the World:
Littorina saxatilis was first described from Venice Lagoon, Italy in 1792 (Reid 1996). This population has been considered to be one of several cryptogenic remnant populations in Pleistocene refuges (Reid 1996). However, genetic analysis of Venetian specimens shows low genetic diversity and similarity to British and Scandinavian populations, strongly supporting introduced status (Panova et al. 2011). Other isolated populations, in the Gulf of Gabés, Tunisia and in the Azores and Canary Islands, could be Pleistocene remnants, or natural colonists (Johannesson 1988; Reid 1996), but to our knowledge, have not been studied genetically.
Isolated populations of L. saxatilis occur in South Africa and Namibia. It was first reported in 1963 from Langebaan Lagoon, South Africa (Robinson et al. 2004; Robinson et al. 2005; Mead et al. 2011b). Fossils believed to date to about 40,000 years BP, and postglacial fossils, are known from the vicinity of Cape Town (Johannesson 1988; Reid 1996). However, dates have not been determined by radiological methods. As Mead et al. (2011b) have noted, if the fossil populations had survived to the present, this periwinkle would probably be much more widespread on the South African coast.
Description
Littorina saxatilis is a medium-sized marine snail, with a turban-shaped shell, having a moderately elevated, pointed spire. The shell is dextrally coiled and adult shells have 4-5 convex whorls with well-defined sutures. The sculpture of the shell is variable, but consists of many poorly-defined, or as few as five, more definite spiral ribs. The color is highly variable, from drab-gray to yellow-brown or dark brown, and sometimes white, yellow, orange, red, brown, or black. Some individuals, especially young snails, are banded or spotted with yellow and black. Mature snails can range from 1.2 to 25.8 mm, but are more usually 6-13 mm. Development is direct, with young developing in a brood pouch and emerging as tiny snails, about 0.45 to 0.75 mm. Description from: Abbott 1974; Morris 1975; and Reid 1996.
The taxonomy of this snail is one of the most confused of any mollusk, including 28 synonymous names and 31 varieties, resulting from its high morphological variability (Reid 1996). At least two very similar species, L. arcana and L. compressa, are known from European waters, but have not been reported from North American waters (Reid 1996). The occurrence of numerous ecotypes and divergent populations probably stems from brooding reproduction and the limited dispersal ability of this snail (Reid 1996; Mäkinen et al. 2008; Doellman et al. 2011).
Taxonomy
Taxonomic Tree
Kingdom: | Animalia | |
Phylum: | Mollusca | |
Class: | Gastropoda | |
Order: | Neotaenioglossa | |
Family: | Littorinidae | |
Genus: | Littorina | |
Species: | saxatilis |
Synonyms
Littorina davidus (Roding, 1798)
Littorina groenlandica (Menke, 1830)
Littorina jugosa (Montagu, 1803)
Littorina neglecta (Bean, 1844)
Littorina obligatus (Say, 1822)
Littorina rudis (Lyell, 1835)
Littorina rudis var. groenlandica (Menke, 1830)
Littorina rudis var. saxatilis (Harmer, 1921)
Littorina rudis var. tenebrosa (Jeffreys, 1865)
Littorina saxatilis (Brusina, 1870)
Littorina saxatilis rudis (Dautzenberg and Fischer, 1912)
Littorina saxatilis tenebrosa (Dautzenberg and Fischer, 1912)
Littorina tenebrosa (Gould, 1841)
Littorina vestita (Say, 1822)
Turbo rudis (Maton, 1797)
Turbo saxatilis (Olivi, 1792)
Turbo tenebrosus (Montagu, 1803)
Potentially Misidentified Species
Hannaford Ellis 1978; Known from the British Isles, Brittany, Normandy (France) and Norway. The shell is morphologically identical to L. saxatilis, but reproduction is oviparous and anatomical details differ (Reid 1996).
Littorina compressa
Jeffreys 1865 (=L. nigrolineata); Known from the British Isles, Brittany (France), and Norway. The shell is strongly ribbed, reproduction is oviparous, and the radular and soft anatomical details differ from L. saxatilis (Reid 1996).
Littorina sitkana
Some erroneous reports of L. saxatilis from the Pacific Ocean have been due to confusion with this northeastern Pacific species (Reid 1996).
Ecology
General:
Littorina saxatilis occurs mostly on mid-to-upper shore rocky coasts, but is also found in lagoons and marshes, usually on hard substrates. Sexes are separate and fertilization is internal. This snail can mature at sizes as small as 1-2 mm. In a Quebec population, L. saxatilis matured at about 3.2-3.5 mm (Pardo and Johnson 2005). Larval development is ovoviviparous, with the young developing in a brood pouch and emerging at 0.4-0.75 mm, with a shell of 1.6-2.1 whorls. The number of embryos varies with size of the female, from 10 in a female with a shell length of 2 mm to 750-900 embryos in the largest shells. Breeding occurs year-round, but is reduced in late summer and winter (Reid 1996).
Littorina saxatilis inhabits a wide range of habitats. On the most exposed coasts, they are usually confined to sheltered crevices, but can also occur in the spray zone, above normal tidelines. More usually, they are found from the mid-tide to mean high-water of spring tides, but they also occur in subtidal regions of brackish lagoons and marshes, associated with solid substrate such as stones, shells, and the roots of Spartina. As with L. littorea, occurrence in the subtidal zone is limited by predation by crabs, fishes, and other predators (Reid 1996). In a Quebec population, the smaller snails tend to be concentrated in the upper intertidal, while larger specimens were more frequently found in the lower zone (Pardo and Johnson 2005). As an upper-intertidal snail, the Rough Periwinkle is tolerant to a wide range of air and water temperatures and also exposure to low salinity, especially over short durations (Reid 1996; Sokalova and Portner 2003). However, its range is probably limited by high temperatures in southern Europe, where it is largely confined to lagoonal habitats and the West Atlantic coast south of New York Harbor, where it is restricted to man-made rocky habitats (Reid 1996; Counts and Bashore 1991; Prezant et al. 2002).
Littorina saxatilis grazes unselectively on diatoms, cyanobacteria, and filamentous and leafy macroalgae (Reid 1996). Littorina saxatilis and L. littorea are potential competitors, and overlap in the intertidal zone, but L. saxatilis ranges higher up on the shore (Dexter 1945; Clay 1961). Predators include crabs, including Carcinus maenas (Green Crab), fishes, and shorebirds (Reid 1996). This snail also hosts a variety of parasites. Fourteen trematode species were found in L. saxatilis sampled at 29 East Coast sites from Newfoundland to Connecticut, but only 4 of those trematodes are known from its introduced range in San Francisco Bay (Blakeslee et al. 2012).
Food:
Macroalgae; microalgae
Consumers:
Fish; Shorebirds; land mammals
Competitors:
Littorina littorea
Trophic Status:
Herbivore
HerbHabitats
General Habitat | Marinas & Docks | None |
General Habitat | Rocky | None |
General Habitat | Salt-brackish marsh | None |
General Habitat | Canals | None |
Salinity Range | Mesohaline | 5-18 PSU |
Salinity Range | Polyhaline | 18-30 PSU |
Salinity Range | Euhaline | 30-40 PSU |
Tidal Range | Mid Intertidal | None |
Tidal Range | High Intertidal | None |
Vertical Habitat | Epibenthic | None |
Tolerances and Life History Parameters
Minimum Temperature (ºC) | -20 | In air at low tide (Sokalova and Portner 2006) |
Maximum Temperature (ºC) | 35 | In air at low tide, tolerates short term exposures up to 47 C (Sokalova and Portner 2006) |
Minimum Salinity (‰) | 5 | Field observations for estuarine populations (Reid 1996) A marine White Sea population had more than 30% mortality at 14 ppt (Sokalova 2000). Snails from two Swedish Skaggerak (high-salinity) populations ceased activity at 16 ppt. Snails from an exposed coastal region, found in upper tidepools, survived longer in fresh water (17 days) than those from a sheltered region, occurring lower on the shore (Sundell 1985). Todd (1964) found that survival at low salinities varied with temperature, with lower limits of 8 PSU at 5 C, but 16 at 15 C. |
Minimum Length (mm) | 1.2 | Minimum size of mature snail (Reid 1996) |
Maximum Length (mm) | 25.8 | More usually 6-13 mm (Abbott 1974; Morris 1975; Reid 1996) |
Broad Temperature Range | None | Polar-Warm Temperate |
Broad Salinity Range | None | Mesohaline-Euhaline |
General Impacts
Impacts of Littorina saxatilis have not been studied in San Francisco Bay or in other invaded areas. However, since L. saxatilis is larger than native Northeast Pacific periwinkles and survives under a very wide range of environmental conditions, it is potentially capable of competing with and displacing native snails from California to Alaska. The native periwinkles L. scutulata, L. plena and L. keanae were absent in the immediate vicinity of introduced L. saxatilis populations in San Francisco Bay (Carlton and Cohen 1998), suggesting possible competition or behavioral exclusion. If L. saxatilis extends its range north of San Francisco Bay competition with the morphologically similar species, L. subrotundata and L. sitkana is possible (Carlton and Cohen 1998). Modeling based on the present range of L. saxatilis, and ocean conditions, indicates that it could potentially colonize the entire West Coast from California to the Arctic Ocean (de Rivera et al. 2011). If this snail develops large populations, then impacts from increased grazing on intertidal algal communities are possible (Carlton and Cohen 1998).Partly because of potential impacts, but also based on this snail's limited introduced range and dispersal, an attempt was made to eradicate introduced populations in San Francisco Bay (Smithsonian Environmental Research Center 2004). However, in the 9+ years since its introduction, L. saxatilis had spread over enough area of the coastline to render eradication impractical (Ruiz et al., unpublished data).
Regional Impacts
NEP-V | Northern California to Mid Channel Islands | Ecological Impact | Competition | ||
The native periwinkles L. scutulata, L. plena and L. keenae were absent in the vicinity of introduced L. saxatilis populations in San Francisco Bay (Carlton and Cohen 1993). However, the mechanisms for this apparent exclusion have not been studied, to our knowledge. | |||||
P090 | San Francisco Bay | Ecological Impact | Competition | ||
The native periwinkles L. scutulata, L. plena and L. keenae were absent in the vicinity of introduced L. saxatilis populations in San Francisco Bay (Carlton and Cohen 1993). However, the mechanisms for this apparent exclusion have not been studied, to our knowledge. | |||||
CA | California | Ecological Impact | Competition | ||
The native periwinkles L. scutulata, L. plena and L. keenae were absent in the vicinity of introduced L. saxatilis populations in San Francisco Bay (Carlton and Cohen 1993). However, the mechanisms for this apparent exclusion have not been studied, to our knowledge., The native periwinkles L. scutulata, L. plena and L. keenae were absent in the vicinity of introduced L. saxatilis populations in San Francisco Bay (Carlton and Cohen 1993). However, the mechanisms for this apparent exclusion have not been studied, to our knowledge. |
Occurrence Map
OCC_ID | Author | Year | Date | Locality | Status | Latitude | Longitude |
---|---|---|---|---|---|---|---|
698601 | Cohen et al. 2005 (SF Bay Area RAS) | 2004 | 2004-05-27 | Coyote Point Marina, San Francisco Bay | Non-native | 37.5907 | -122.3180 |
699391 | Introduced Species Study | 2010 | 2010-06-13 | Coyote Point | Non-native | 37.5920 | -122.3210 |
699411 | Introduced Species Study | 2005 | 2005-07-06 | Coyote Point | Non-native | 37.5920 | -122.3210 |
701928 | Cohen et al. 2005 (SF Bay Area RAS) | 2004 | 2004-05-24 | Coast Guard Island Marina, San Francisco Bay | Non-native | 37.7812 | -122.2458 |
704288 | Cohen et al. 2005 (SF Bay Area RAS) | 2004 | 2004-05-23 | Brisbane Lagoon, San Francisco Bay | Non-native | 37.6862 | -122.3906 |
713157 | Miller et al. 2004 | 2002 | Port of Redwood City | Non-native | 37.5133 | -122.2086 |
References
Abbott, R. Tucker (1974) American Seashells, Van Nostrand Reinhold, New York. Pp. <missing location>Backeljau, T.; De Meyer, M.; Janssens, L.; Proesmans, R. (1984) Prosobranch and shelled opisthobranch molluscs from Store Ekkeroya, Varangerfjorden (northern Norway), Fauna Norvegica Series A A5: 1-5
Balch, Francis Noyes (1899) List of marine mollusca of Coldspring Harbor, Long Island, with descriptions of one new genus and two new species of nudibranchs, Proceedings of the Boston Society of Natural History 29(7): 133-163
Bequaert, Joseph C. (1943) The genus Littorina in the Western Atlantic, Johnsonia 1(7): 1-27
Blakeslee, April M. H. and 5 authors (2012) Parasites and invasions: a biogeographic examination of parasites and hosts in native and introduced ranges, Journal of Biogeography 39: 609-622
Blakeslee, April M. H.; Miller, A. Whitman; Ruiz, Gregory M.; Kerstin Johannesson · Carl André ·Johannsson, Kerstin;· André, Carl; Panova, Marina (2021) Population structure and phylogeography of two North Atlantic Littorina species with contrasting larval development, Marine Biology 168: <missing location>
Bosso, Luciano; Smeraldo, Sonia; ·Russo, Danilo; Chiusano, Maria Luisa; Bertorelle, Giorgio; · Kerstin Johannesson · Butlin, Roger K. · Danovaro, R (2022) he rise and fall of an alien: why the successful colonizer Littorina saxatilis failed to invade the Mediterranean Sea Luciano Bosso · Sonia Smeraldo · Danilo R, Biological Invasions Published online: Published online
https://doi.org/10.1007/s10530-022-02838-y
Carlton, James T., Cohen, Andrew N. (1998) Periwinkle's progress: the Atlantic snail Littorina saxatilis (Mollusca: Gastropoda) establishes a colony on a Pacific shore, The Veliger 41(4): 333-338
Clay, E. (1961) Literature survey of the common fauna of estuaries. 9. Littorina littorea (Linnaeus), Littorina littoralis (Linnaeus), Littorina saxatilis (Olive), Littorina neritoides (Linnaeus), In: (Eds.) . , Brixham Laboratory. Pp. <missing location>
Cohen, Andrew N. and 10 authors (2005) <missing title>, San Francisco Estuary Institute, Oakland CA. Pp. <missing location>
Cohen, Andrew N.; Carlton, James T. (1995) Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta, U.S. Fish and Wildlife Service and National Sea Grant College Program (Connecticut Sea Grant), Washington DC, Silver Spring MD.. Pp. <missing location>
Counts, Clement L. III; Bashore, Terry L. (1991) Mollusca of Assateague Island, Maryland and Virginia: A reexamination after seventy-five years., Veliger 34(2): 214-221
Crocetta, Fabio (2011) Marine alien Mollusca in the Gulf of Trieste and neighbouring areas: a critical review and state of knowledge (updated in 2011), Acta Adriatica 52(2): 247 - 260,
Crocetta, Fabio; Macali, Armando; Furfaro, Giulia; Cooke, Samantha; Villani, Guido; Valdés, Ángel (2013) Alien molluscan species established along the Italian shores: an update, with discussions on some Mediterranean 'alien species' categories, ZooKeys 277: 91:108
de Rivera, Catherine E.; Grosholz, Edwin D.; Ruiz, Gregory M. (2011) Multiple and long-term effects of an introduced predatory crab, Marine Ecology Progress Series 429: 145-155
Dexter, Ralph W. (1945) Zonation of the intertidal marine mollusks at Cape Ann, Massachusetts, The Nautilus 58(4): 135-142
Doellman, Meredith M.; Trussell, Geoffrey C.; Grahame, John W.; Vollmer, Steve V. (2011) Phylogeographic analysis reveals a deep lineage split within North Atlantic Littorina saxatilis, Proceedings of the Royal Society of London B 278: 3175-3183
Eastwood, Meg M.; Donahue, Megan J.; Fowler, Amy E. (2007) Reconstructing past biological invasions: niche shifts in response to invasive predators and competitors., Biological Invasions 9: 397-407
Foss, Stephen (2009) <missing title>, California Department of Fish and Game, Sacramento CA. Pp. <missing location>
Geertz-Hansen, Ole; Sand-Jensen, Kaj; Hansen, Dorte F.; Christiansen, Anette (1993) Growth and grazing control of abundance of the marine macroalga, Ulva lactuca L. in a eutrophic Danish estuary, Aquatic Botany 46(2): 101-109
Gruet, Y. (1977) Repartition de quelques mollusques Lacunidae (generes Littorina et Melarapha) et du Trochidae Monodonta lineata (da Costa) sur l'estran des cotes de Love-Atlantique et du nord de la Vendee., Bulletin de la Societe des Sciences Naturelles de l Ouest de la France 75(1): 30-34
Johannesson, K. (1988) The paradox of Rockall: why is a brooding gastropod (Littorina saxatilis) more widespread than one having a planktonic larval dispersal stage (L. littorea)?, Marine Biology 99: 507-513
Johansson, Karl E. (1925) Bemerkungen uber die Kinberg'schen arten der familien Hermellidae und Sabellidae, Arkiv for Zoologi <missing volume>(7): 1-28
Kim, Daemin; Taylor, Andrew T.; Near, Thomas J. (2022) Phylogenomics and species delimitation of the economically important Black Basses (Micropterus), Scientific Reports 12(9113): Published online
https://doi.org/10.1038/s41598-022-11743-2
Kraueter, J. N. (1974) Offshore currents, larval transport, and establishment of southern populations of Littorina littorea along the U. S. Atlantic Coast., Thalassia Jugoslavica 10(1/2): 159-170
Mäkinen, Tuuli and 5 authors (2008) Genetic differentiation on multiple spatial scales in an ecotype-forming marine snail with limited dispersal: Littorina saxatilis, Biological Journal of the Linnean Society 94: 31-40
Mead, A.; Carlton, J. T.; Griffiths, C. L. Rius, M. (2011b) Introduced and cryptogenic marine and estuarine species of South Africa, Journal of Natural History 39-40: 2463-2524
Miller, A. Whitman ; Chang, Andrew L.; Cosentino-Manning, N.; Ruiz, Gregory M. (2004) A new record and eradication of the northern Atlantic alga Ascophyllum nodosum (Phaeophyceae) from San Francisco Bay, California., Journal of Phycology 40: 1028-1031
Panova, Marina and 6 authors (2011) Glacial history of the North Atlantic marine snail, Littorina saxatilis, inferred from distribution of itochondrial DNA lineages, PLOS ONE 6(3): e17511
Pardo, L. Miguel; Johnson, Ladd E. (2005) Explaining variation in life-history traits: growth rate, size, and fecundity in a marine snail across an environmental gradient lacking predators, Marine Ecology Progress Series 296: 229-239
Perkins, George H. (1869) Molluscan fauna of New Haven. A critical review of all the marine, fresh water and land Mollusca of the region, with descriptions of many of the living animals and of two new species. Part I. Cephalopoda and Gasteropda, Proceedings of the Boston Society of Natural History 13: 109-136
Prezant, Robert; Counts, Clement L.; Chapman, Eric J. (2002) Mollusca of Assateague Island, Maryland and Virginia: additions to the fauna, range extensions, and gigantism., Veliger 45: 337-355
Reid, David G. (1996) <missing title>, Ray Society, London. Pp. <missing location>
Robinson, T. B.; Griffiths, C. L.; Kruger, N. (2004) Distribution and status of marine invasive species in and bordering the West Coast National Park., Koedoe 47: 79-87
Robinson, T. B.; Griffiths, C. L.; McQuaid, C. D.; Rius, M. (2005) Marine alien species of South Africa-- status and impacts, African Journal of Marine Science 27(1): 297-306
Rosenberg, Gary 1995-2023 Malacolog 4.1. http://www.malacolog.org/
Saura, M.; Martinez-Fernandez, M.; Rivas, M. J.; Caballero, A.; Rolan-Alvarez, E. (2011) Lack of early laboratory postzygotic reproductive isolation between two ecotypes of Littorina saxatilis (Mollusca, Gastropoda) showing strong premating sexual isolation, Hydrobiologia 675: 13-18
Smithsonian Environmental Research Center 2004 Rough periwinkle, <i>Littorina saxatilis</i>- Eradication of an exotic snail <i>Littorina saxatilis</i> in San Francisco Bay: A model system. <missing URL>
Sokolova, I. M. (2000) Effects of salinity on the growth rate and survival of juvenile Littorina saxatilis gastropods from habitats with different salinity regimes., Russian Journal of Marine Biology 26(6): 427-431.
Sokolova, Inna M.; Pörtner, Hans-Otto (2003) Metabolic plasticity and critical temperatures for aerobic scope in a eurythermal marine invertebrate (Littorina saxatilis, Gastropoda: Littorinidae) from different latitudes., Journal of Experimental Biology 206: 195-207
Sorte, Cascade J. B.; Jones, Sierra J.; Miller, Luke P. (2013) Geographic variation in temperature tolerance as an indicator of potential population responses to climate change, Journal of Experimental Marine Biology and Ecology 400: 209-217
Sundell, Kristina (1985) Adaptability of two phenotypes of Littorina saxatilis to different salinities., Journal of Experimental Marine Biology and Ecology 92: 115-121
Todd, Mary E. (1964) Osmotic balance in Littorina littorea, L. littoralis, and L. saxatilis (Littorinidae), Physiological Zoology 37: 33-44
Torchin, M. E.; Lafferty, K. D.; Kuris, A. M. (2002) Parasites and marine invasions., Parasitology 124: S137-S151
U.S. National Museum of Natural History 2002-2021 Invertebrate Zoology Collections Database. http://collections.nmnh.si.edu/search/iz/
Wilhelmsen, U. (1999) Rapid colonization of new habitats in the Wadden Sea by the ovoviparous Littorina saxatilis (Olivi), Helgoländer Meeresuntersuchungen 52: 325-335
Yamada, S.B.; Mansour, R.A. (1987) Growth inhibition of native Littorina saxatilis (Olivi) by introduced L. littorea (L.), Journal of Experimental Marine Biology and Ecology 105: 187-196
Zander, C. Dieter; Reimer, Lothar W.; Barz, Kristina; Dietel, Gerolf; Strohbach, Uwe (2000) Parasite communities of the Salzhaff (Northwest Mecklenburg, Baltic Sea) II. Guild communities, with special regard to snails, benthic crustaceans, and small sized fish, Parasitology Research 86(5): 359-372