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.

Geothelphusa dehaani
Geothelphusa dehaani
(a freshwater crab)

Copyright Info
Geothelphusa dehaani

Common name: a freshwater crab

Identification: Geothelpusa dahaani is actually a species complex comprised of 2-3 species.

Native Range: Japan.

Hydrologic Unit Codes (HUCs) Explained
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences: Several small crabs (about 1 inch across the carapace) were found at a Hyatt Hotel along the shore of Lake Las Vegas, a freshwater, artificial lake in the Las Vegas area, on two separate occasions in 2000. The first sighting, around March, included about a dozen crabs. All those collected at that time were females. The second sighting, around June, was of 2 males and 2 females. No females with eggs were found.

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 Geothelphusa dehaani are found here.

StateFirst ObservedLast ObservedTotal HUCs with observations†HUCs with observations†
NV200020001Las Vegas Wash

Table last updated 7/22/2024

† Populations may not be currently present.

Means of Introduction: Although it was intially speculated that their introduction was likely the result of an aquarium release, their release has been traced to a sushi bar (A. Cook, pers. comm.).

Status: No more crabs have been collected since the initial find.

Impact of Introduction: The impacts of this species are currently unknown, as no studies have been done to determine how it has affected ecosystems in the invaded range. The absence of data does not equate to lack of effects. It does, however, mean that research is required to evaluate effects before conclusions can be made.

Remarks: Photos

Although these were identified by Dr. Neil Cumberlidge, Northern Michigan University, Peter ng kee lin, a crab expert in Singapore, reports that G. dahaani is actually a species complex comprised of 2-3 species.

Author: Fuller, P.

Revision Date: 6/29/2023

Citation Information:
Fuller, P., 2024, Geothelphusa dehaani: U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=193, Revision Date: 6/29/2023, Access Date: 7/23/2024

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.


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. [2024]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [7/23/2024].

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