Scolex pleuronectis
Müller, 1788
Common Name:
A cestode
Synonyms and Other Names:
S. polymorphus
Identification:
S. pleuronectis refers to a complex of species of cestodes in the order Tetraphyllidea. They exhibit proglottids containing male and female genitalia that can be shed to develop into new individuals. Plerocercoids and adults have a scolex for attachment to the host with various bothridia (hooked holdfasts) and an accessory apical sucker. The number of loculi per bothridium has been recorded to range from 1-74 in species from around the world. Larvae can encyst as metacestodes in some hosts and are difficult to identify at this stage (Anantaraman 1963; Avdeeva and Avdeev 1980; Post 1983; Radhakrishnan et al. 1984; Wojciechowska 1990; Pronin et al. 1997; Chambers et al. 2000; Fernandez et al. 2004).
Size information is lacking for S. pleuronectis collected from the Great Lakes basin. However, other species in this group can measure 0.1-8.8 mm in length by ‹0.1-0.4 mm in width. Measurements vary according to whether or not the worm is relaxed and its life history stage, and whether width is measured at the apical sucker or in the middle of the worm (Anantaraman 1963; Reimer 1977; Radhakrishnan et al. 1984; Wojciechowska 1990; Chambers et al. 2000).
Size:
0.1-8.8 mm in length by ‹0.1-0.4 mm in width
Native Range:
As a species complex, S. pleuronectis is cosmopolitan in distribution. Little is known about individual species’ ranges within this group. However, it is known that at least one species in this group occurs in the Black Sea watershed using the Round Goby (Neogobius melanostomus) as its host (Pronin et al. 1997).
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This map only depicts Great Lakes introductions.
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Great Lakes Nonindigenous Occurrences:
Scolex pleuronectis was first isolated in 1994 from round goby in the St. Clair River at the Clinton River mouth and Marine City, Michigan (Pronin et al. 1997).
Table 1. Great Lakes region nonindigenous occurrences, the earliest and latest observations in each state/province, and the tally and names of HUCs with observations†. Names and dates are hyperlinked to their relevant specimen records. The list of references for all nonindigenous occurrences of Scolex pleuronectis are found here.
Table last updated 5/2/2024
† Populations may not be currently present.
Ecology:
Plerocercoids in the species complex S. pleuronectis were found in the intestinal walls of two individual N. melanostomus collected from the Lake St. Clair watershed. For some tetraphyllidean species it is known that copepods are common intermediate hosts. This group is very common in diadromous, marine and brackish water fish species, including those in the families Cottidae, Salmonidae, and Clupeidae. Each proglottid of a cestode is a single unit containing all reproductive organs for development in a host (Anantaraman 1963; Post 1983; Groenewold et al. 1996; Pronin et al. 1997). Species within this group have been recorded in the Atlantic Ocean, the Pacific Ocean, the Mediterranean, the Black Sea, the Gulf of St. Lawrence and St. Lawrence estuary, and rivers on the east coast of North America. They occur in at least 60 species of teleost fishes from the Atlantic Ocean alone. They also occur in marine mammals and various invertebrates (Anantaraman 1963; Rosenthal 1967; Brooks and Brothers 1974; Radhakrishan et al. 1984; Scott 1988; Landry et al. 1992; Hogans et al. 1993; Reimer 1993; Arthur et al. 1995; Groenewold et al. 1996; Moran et al. 1996; Chambers et al. 2000; Gonzalez and Kroeck 2000; Oliva 2001; Moravec 2003; Fernandez et al. 2003, 2004; O’Connell and Fives 2004; Tavares et al. 2004).
Means of Introduction:
The species was likely introduced with N. melanostomus to the Lake St. Clair watershed in ships’ ballast water (Pronin et al. 1997).
Status:
Established where recorded.
Great Lakes Impacts:
Summary of species impacts derived from literature review. Click on an icon to find out more...
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There is little or no evidence to support that Scolex pleuronectis has significant environmental impacts in the Great Lakes.
Realized:
According to Muzzall and Whelan (2011), Great Lakes detection of S. pleuronectis have been limited to infections of the introduced Round Goby (Neogobius melanostomus) at 13.5% prevalence with light infections (1-2 parasites/host) (Pronin et al. 1997). As such, it is unlikely to exert negative impacts on native fish species.
There is little or no evidence to support that Scolex pleuronectis has significant socio-economic impacts in the Great Lakes.
Potential:
In 1989, S. pleuronectis was detected in Brown Trout (Salmo trutta) and Rainbow Trout (Oncorhynchus mykiss) in Chile (Torres et al. 1990). However, no such infections have been realized in the Great Lakes.
There is little or no evidence to support that Scolex pleuronectis has significant beneficial effects in the Great Lakes.
Realized:
Scolex pleuronectis is believed to be unlikely to help regulate populations of the introduced Round Goby (Pronin et al. 1997).
Management:
Regulations (pertaining to the Great Lakes)
There are no known regulations for this species.
Note: Check federal, state/provincial, and local regulations for the most up-to-date information.
Control
Biological
There are no known biological control methods for this species.
Physical
There are no known physical control methods for this species.
Chemical
There are no known chemical control methods for this species.
Note: Check state/provincial and local regulations for the most up-to-date information regarding permits for control methods. Follow all label instructions.
Remarks:
In 1788, Mueller proposed to name a group of metacestodes from intestines of teleost fish as S. pleuronectis. In 1819, Rudolphi, who doubted whether this species was valid, chose S. polymorphus to synonymize these species. Scientists have gradually realized that these two names actually include a large number of tetraphyllidean metacestodes (Chambers et al. 2000).
References
(click for full reference list)
Author:
Kipp, R.M., A.K.Bogdanoff, A. Fusaro and R. Sturtevant.
Contributing Agencies:
Revision Date:
9/13/2019
Citation for this information:
Kipp, R.M., A.K.Bogdanoff, A. Fusaro and R. Sturtevant., 2024, Scolex pleuronectis Müller, 1788: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, and NOAA Great Lakes Aquatic Nonindigenous Species Information System, Ann Arbor, MI, https://nas.er.usgs.gov/queries/greatLakes/FactSheet.aspx?Species_ID=2722&Potential=N&Type=0&HUCNumber=DGreatLakes, Revision Date: 9/13/2019, Access Date: 5/2/2024
This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.