Rusty Crayfish, Faxonius rusticus

OTHER COMMON NAMES

None

ETYMOLOGY

Faxonius, named for Walter Faxon (1848-1920), American ornithologist and carcinologist. Former genus, Orconectes, is from Orcus, god of the underworld in Roman mythology + nectes: swimming (Greek); rusticus: of the countryside (Latin)

Ecology, Habitat, & Behavior

One reason that rusty crayfish are so prone to becoming invasive is that they are extreme generalists. They can live in a wide variety of aquatic environments from slow flowing silty bottomed rivers to faster flowing streams lined with rocks and woody debris to densely vegetated shorelines. And everything is on the menu, with juveniles and adults eating debris, plant material, and animals. Compared to other crayfish, rusty crayfish have a high metabolism and burn through food much faster, so they have a disproportionately large impact on food webs. While other species, like virile crayfish, also feed on macrophytes, rusty crayfish will destroy entire vegetative beds, eliminating habitat for fish and macroinvertebrates, ultimately negatively impacting species richness (source). Because of their threat as an invasive, this is one of the more well-studied species of crayfish in our waters.

QUICK FACTS

Avg carapace length: <2 inchesLife expectancy: 3-4 yearsAge at maturity: 1st or 2nd yearHabitat: Generalists (lakes, ponds, streams with silty to gravelly substrates)# of eggs: 80-575 (source)Diet: Opportunistic generalists (detritus, plant matter, macroinvertebrates, fish eggs, and even fish)Native or non-native: Non-nativeActivity pattern:

Diurnal and Nocturnal

Uses: Food, bait, aquarium pet, laboratory resource

Life History Event Date/Season
Mating Late summer through fall, occasionally early spring
Fertilization Delayed, spring
Laying Eggs Spring
Hatch in 3 to 6 weeks
Young detach from female 3-4 molts
Males in F1 Molt into F1 in summer
Males in F2 Molt into F2 in spring

Key features for ID + similar species

  1. Rust colored spots on sides of carapace
  2. S-shaped dactyl, fingers with black bands
  3. Oval gap when fingers are closed
ROSTRUM

Rostrum dished, margins distinctly concave with paired accessory spines.

COLOR/MARKINGS

Rust colored spot on the sides of the carapace. Body has a greenish cast, but can also been reddish brown.

CHELAE

Large, robust chelae, generally smooth. Fingers with orange tips, bordered beneath by a dark black band. Dactyl distinctly S-shaped. Opening when fingers are closed is oval.

AREOLA

Open, wide, with 3 punctations at narrowest point.

Range map for Rusty Crayfish

Range map based on observations from iNaturalist.org

General Research on Crayfish

  • NOBANIS: Invasive Alien Species Fact Sheet : source
  • Crayfish of the White River Watershed: source
  • Crayfish curriculum for educators: source
  • The Crayfishes of New England: source
  • Species of Ontario Crayfish: source
  • Lecture on Crayfish: video
  • Some aspects of the life histories of three closely related crayfish species, Orconectes obscurus, O. sanborni, and O. propinquus: source
  • Dictionary of crayfish names: source
  • Biological synopsis of the rusty crayfish: source
  • Observations on the life cycle of Procambarus acutus acutus in South Carolina culture ponds: source
  • Natural History of the two Crayfish of Northwestern Iowa, Orconectes virilis and Orconectes immunis: source

Crayfish of Vermont species profiles