Faxonius

Faxonius species are distinguished from the related genus Orconectes by non-cave-dwelling ecology; Orconectes retained only cave-dwelling species when Faxonius was elevated to genus status in 2017. Species-level identification relies on morphological characters including gonopod structure, rostrum shape, and coloration patterns such as the distinctive rusty spots on F. rusticus.

Freshwater streams and rivers; specific habitat requirements vary by species. F. limosus is constrained to lowland rivers due to flash-flood limitation in streams. F. validus and F. erichsonianus occur in impounded and unimpounded streams in the southern Appalachian Mountains, with stream width positively correlated with genetic diversity in F. validus. F. shoupi is restricted to the Mill Creek watershed in Tennessee.

Native to North America, with highest diversity in the eastern and central United States. F. shoupi is endemic to the Mill Creek watershed in Tennessee, USA, with a disjunct population in the Lower Tennessee River at Pickwick Tailwater. F. quadruncus and F. hylas occur in the St. Francis River drainage of Missouri, USA. F. validus and F. erichsonianus are found in Alabama, USA. Multiple species have established invasive populations in Europe: F. limosus in Eastern Europe and Belarus (spreading at 7–20 km/year), F. immunis in the Upper Rhine River area of Germany since 1993, and F. virilis.

F. immunis has been observed dispersing over land throughout the year except February and July in the Upper Rhine River area. F. quadruncus and F. hylas ovigerous females were sampled in April in Missouri.

F. obscurus occupies the highest trophic position among sympatric crayfish species in Kings Creek, West Virginia, indicating diet partitioning and consumption of distinct food sources compared to Cambarus carinirostris and C. robustus.

• Aphanomyces astaci - pathogenCrayfish plague pathogen; detected via eDNA screening in study context but no direct host-pathogen presence found in connective sectors between invasive and native populations

F. virilis undergoes cyclic dimorphism with seasonal morphological changes associated with reproductive status. F. quadruncus and F. hylas fecundity estimates fall within ranges reported for other Faxonius species; field egg counts on live females underestimate laboratory counts by approximately 22%.

F. immunis disperses over land with high potential to colonize small ponds, recorded throughout the year except February and July. F. limosus expansion in streams is limited by flash-flood potential. F. rusticus females have significantly redder rusty spots than males, suggesting potential mate discrimination function.

Ecosystem engineers and essential components of freshwater food webs. Invasive populations of F. immunis cause collapse of macroinvertebrate communities and eradicate macrophytes in Central European ponds. F. limosus competes with native Austropotamobius bihariensis and A. torrentium in Eastern Europe. Community-level diversity patterns do not reliably proxy population-level genetic diversity in these crayfishes.

Several species are significant invasives threatening native biodiversity. F. rusticus, F. virilis, F. immunis, and F. limosus are managed as invasive species. F. shoupi is federally endangered in the USA with recovery efforts including dam removal and riparian restoration. F. quadruncus is imperiled and declining in presence of invasive F. hylas. Graveling ground beds has been tested as a management method for invasive burrowing species with limited success.

• OrconectesFormerly contained Faxonius as a subgenus; now restricted to cave-dwelling species while Faxonius contains non-cave-dwelling species
• FaxonellaSeparate genus of crayfish in the same family Cambaridae, not closely related within the genus complex
• Procambarus clarkiiInvasive crayfish species also occurring in the Upper Rhine River area, distinguished by overland dispersal behavior recorded in same region
• Pacifastacus leniusculusInvasive crayfish species also recorded with overland dispersal in the Upper Rhine River area
• Austropotamobius bihariensisNative European crayfish species competed with and potentially displaced by invasive F. limosus
• Austropotamobius torrentiumNative European crayfish species competed with and potentially displaced by invasive F. limosus

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• NCBI Taxonomy
• Catalogue of Life
• Headwater refuges: Flow protects Austropotamobius crayfish from Faxonius limosus invasion
• Supplemental Information 6: Diversity metrics, stream habitat characteristics, and fragmentation status of Faxonius erichsonianus collection sites.
• Supplemental Information 5: Diversity metrics, stream habitat characteristics, and fragmentation status of Faxonius validus collection sites.
• Comparative fecundity of the imperiled crayfishFaxonius quadruncusCreaser and invasive crayfishFaxonius hylas(Faxon) in the St. Francis River drainage of Missouri, USA
• A Genomic Perspective on the Conservation Status of the Endangered Nashville Crayfish (Faxonius shoupi)
• Distribution of striped cancer <i>Faxonius limosus</i> in water bodies of Belarus
• Sexual Dichromatism of “Rusty” Spots in a Population ofFaxonius rusticus(Girard)
• Life History of an Invasive Population of Allegheny Crayfish (Faxonius obscurus) in an Eastern Pennsylvania Stream
• Distribution of Striped Crayfish Faxonius Limosus in Water Bodies of Belarus
• Phenology of overland dispersal in the invasive crayfish Faxonius immunis (Hagen) at the Upper Rhine River area
• Analysis of Stable Isotopes for Cambarus carinirostris, Cambarus robustus, and Faxonius obscurus in Kings Creek.
• The invasive crayfish Faxonius immunis causes the collapse of macroinvertebrate communities in Central European ponds
• Differences in growth within and across the reproductive forms of northern crayfish (Faxonius virilis)
• Preliminary Tests on the Effects of Atrazine Exposure on the Food-Seeking Behaviors and Locomotion of Juvenile Virile Crayfish (Faxonius virilis).