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| NAS - Nonindigenous Aquatic Species |
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Common Name: a tubificid worm
Synonyms and Other Names: formerly Phallodrilus aquaedulcis (Hrabe 1960)
Taxonomy: available through 
Identification: Externally Gianius can be distinguished by a rounded prostomium, as long as it is broad at the peristomium, bifid setae with upper teeth thinner and shorter than lower, 3-4 setae per bundle toward the anterior, and 2 per bundle toward the posterior posterior. Internally, G. aquaedulcis has short and narrow spermathecal ducts (Brinkhurst 1971).
Size: 4mm
Native Range: Western Europe in Germany's River Weser and inland caves in Spain and France (Farara and Erseus 1991).
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Interactive maps: Continental US, Alaska, Hawaii, Caribbean
Nonindigenous Occurrences: This species is established in the Niagara River in Erie and Niagara Counties, New York (Mills, 1993).
Ecology: The highest densities of Gianius aquaedulcis in the Niagara River were found at depths ranging from 1.8m to 17.3m, the vast majority residing in 3-6m of water, and at stations with flow rates greater than 0.2m/s at the sediment surface (Farara and Erseus 1991).
Means of Introduction: Noted as being dispersed into the Great Lakes region by ballast water from international shipping in 1983 (Spencer and Hudson 2003).
Status: Gianius aquaedulcis is established throughout most of the course of the Niagara River, but no specimens have been found in the Great Lakes proper or elsewhere in North America (Farara and Erseus 1991).
Impact of Introduction: Farara and Erseus (1991) found G. aquaedulcis to be the most dominant taxa at many stations along the Niagara River, but its impact on native ecosystems is unknown.
Remarks: During a baseline study of benthic invertebrates of the Niagara River in 1983, a substantial number of G. aquaedulcis were found and identified under the old taxonomy, Phallodrilus aquaedulcis (Hrabe, 1960), a new record in North America (Farara and Erseus 1991). Later, Erseus (1992) revised the Phallodrilinae, splitting the genus into 20 different genera and Phallodrilus aquaedulcis became Gianius aquaedulcis.
References
Brinkhurst, R. O. and B. G. M. Jamieson. 1971. Genus Phallodrilus, pp. 564-567. In: Aquatic Oligochaeta of the World.
Farara, D. G. and C. Erseaus. 1991. Phallodrilus aquaedulcis Hrabe, 1960, a meiobenthic freshwater oligochaete (Tubificidae) previously known only from Europe, recorded from the
Spencer, D. R. and P. L. Hudson. 2003. The Oligochaetea (Annelida, Clitellata) of the St. Lawrence
Author: Greg Jacobs
Contributing Agencies: 
NOAA - GLERL
Revision Date: 7/26/2005 Citation for this information:
Greg Jacobs. 2009. Gianius aquaedulcis. USGS Nonindigenous Aquatic Species Database, Gainesville, FL.
<http://nas.er.usgs.gov/queries/FactSheet.asp?speciesID=2542> Revision Date: 7/26/2005
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