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The Nonindigenous Occurrences section of the NAS species profiles has a new structure. The section is now dynamically updated from the NAS database to ensure that it contains the most current and accurate information. Occurrences are summarized in Table 1, alphabetically by state, with years of earliest and most recent observations, and the tally and names of drainages where the species was observed. The table contains hyperlinks to collections tables of specimens based on the states, years, and drainages selected. References to specimens that were not obtained through sighting reports and personal communications are found through the hyperlink in the Table 1 caption or through the individual specimens linked in the collections tables.



Synidotea laevidorsalis
Synidotea laevidorsalis
(an isopod)
Crustaceans-Isopods
Exotic
Collection Info
Point Map
Species Profile
Animated Map

Copyright Info
Synidotea laevidorsalis
Common name: an isopod
Taxonomy: available through www.itis.govITIS logo

Size: can reach 30 mm
Native Range: Western Pacific Ocean region.
Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences:

Table 1. States with nonindigenous occurrences, the earliest and latest observations in each state, 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 Synidotea laevidorsalis are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
CA189719953San Francisco Bay; San Pablo Bay; Suisun Bay
NJ199920232Cohansey-Maurice; Sandy Hook-Staten Island
SC199819981South Carolina Coastal

Table last updated 12/11/2025

† Populations may not be currently present.
Means of Introduction: Probable ship hull fouling introduction.
Impact of Introduction: Fouls pilings and buoys.
Remarks: Found in temperate to subtropical estuaries in shallow water; brackish water to full seawater.  Feeds on hydroids; larvae not pelagic.
References: (click for full references)

Mees, J. and N. Fockedey 1993. First record of Synidotea laevidorsalis (Miers, 1881) (Crustacea: Isopoda) in Europe (Gironde estuary, France). Hydrobiologia 264: 61-63.

Author: Benson, A.J.
Revision Date: 4/27/2004

 Citation Information:
Benson, A.J., 2025, Synidotea laevidorsalis: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?speciesID=1072, Revision Date: 4/27/2004, Access Date: 12/12/2025

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.

Disclaimer:

The data represented on this site vary in accuracy, scale, completeness, extent of coverage and origin. It is the user's responsibility to use these data consistent with their intended purpose and within stated limitations. We highly recommend reviewing metadata files prior to interpreting these data.

Citation information: U.S. Geological Survey. [2025]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [12/12/2025].

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