Missouri Crayfish

These flashcards are to help learn field identification of Missouri's Crayfish. Made in May 2026 by Missouri Department of Conservation Crayfish Field Technician

St. Francis River Crayfish

Scientific Name: Faxonius quadruncus

Conservation Status: SOCC, State Endangered, Federally threatened, MO endemic

Burrowing Type: Tertiary

Ecoregion: Ozarks

Key characteristics:

• On gonopods, primary process length= length of secondary process

• gonopods don’t reach the base of pincers when abdomen is flexed

• Hooks present on 2nd and 3rd pair of walking legs

Big Creek Crayfish

Scientific Name: Faxonius peruncus

Conservation Status: SOCC, State Endangered, Federally Threatened, MO endemic

Burrowing Type: Tertiary

Ecoregion: Ozarks

Drainages: Upper St. Francis

Key characteristics:

• On gonopods, primary process length > length of secondary process

• Secondary process thicker than primary process and is broad and flared

• Processes separated by a definite space

• Hooks present on 2nd and 3rd pair of walking legs in Form 1 males

• Has areola

• in females, annulus ventralis is more elongated vertically

Woodland Crayfish

Scientific Name: Faxonius hylas

Conservation Status: Secure, Missouri Endemic, Invasive

Burrowing Type: Tertiary

Ecoregion: Ozarks

Native Drainages: Big Meramec, Upper Black

Introduced Drainages: Upper St. Francis

Key characteristics:

• On gonopods, primary process thickness = thickness of secondary process

• Hooks only on bases of 2nd pair of walking legs

• Long slender processes which touch and reach past base of walking legs

• Has areola

Where are the two hotspots for crayfish diversity in North America?

1. The Cumberland Plateau: Kentucky, Tennessee, Alabama, and Georgia

2. The Ozark and Ouachita Plateaus: Missouri, Arkansas, and Oklahoma

What are the 4 principal aquatic faunal regions in Missouri?

1. Ozarks

2. Praire

3. Lowland

4. Big River

What phylum are crayfish in?

Arthropoda-characterized by jointed legs, segmented bodies, and external skeletons made of chitin

Includes insects, spiders, and crustaceans

1. How many species of crayfish are there globally?

2. How many in North America?

3. How many in U.S.?

1. more than 750 spp.

2. more than 470

3. about 400 in U.S

What region are the state’s 3 cave crayfish in?

The Ozark region

Why should people care about crayfish?

1. Keystone/ecological dominant species: they restructure plant and invertebrate assemblages and influence the availability of resources for other species through their diet.

2. Main diet for many fish; including popular game fish like small and large mouth bass

3. They create a healthy flow of energy in streams by acting as decomposers of leaf litter, razing on macrophytes, and disturbing sediments.

What Class are crayfish in?

Class Crustacea: primarily aquatic arthropods, two pair of antennae and branched appendages.

Class includes crabs, lobsters, isopods, and amphipods (scuds).

What order are crayfish in?

Order Decapoda: means “ten-footed”;first pair ending in terminal claws, gills enclosed in the carapace.

Includes crabs, lobsters, and shrimp

Globally, crayfish are divided into 2 major lineages. What are they?

1. Superfamily Astacoidea (northern Hemisphere; North America, Europe, and Asia)

2. Superfamily Parastacoidea (southern hemisphere; South America, Madagascar, Australia, and New Zealand).

What is the dominate crayfish family in North America?

Family Cambaridae

About how many crayfish species are in Missouri?

~40 species

How many genera (genus) of crayfish are there in MO? What are they?

8 genera.

1. Cambarellus (2)

2. Cambarus (4)

3. Creaserinus (1)

4. Faxonella (1)

5. Faxonius(22)

6. Lacunicambarus (5)

7. Orconectes (1)

8. Procambarus (5)

What are characteristics of Cambarellus genus?

1. small; usually less than 1 inch long

2. occur in swamps, sloughs, and roadside ditches of the southern US and Mexico.

Two species in MO: Swamp Dwarf Crayfish (C. puer) and Shufeldt’s Dwarf Crayfish (C. shufeldtii)

Big Creek Crayfish vs St. Francis River Crayfish (F. quadruncus)

1. Range- Both in St. Francis River Watershed but they’re distribution within it does not overlap in many places

2. Gonopods look very different. F. peruncus (Big creek) primary process is longer than secondary and there is a space between them. In St. Francis River crayfish the two processes are about equal in length and are not separated by a space

Big Creek Crayfish vs. Woodland Crayfish

1. In gonopods, Big Creek Crayfish have a broader secondary process compared to their primary process whereas Woodland Crayfish processes are more similar in thickness

2. Secondary process of Big Creek Crayfish is just thicker compared to secondary process of Woodland.

3. Woodland Crayfish Form 1 males only have hooks on 2nd pair of walking legs whereas Big Creek crayfish have them on 2nd AND 3rd

4. In females, fossa of female sperm receptacles is deeper.

St. Francis River Crayfish vs Woodland Crayfish

1. Gonopods of St. River Crayfish have nearly equal length processes whereas woodland crayfish have a longer primary process

2. Does not reach base of pincers when abdomen is flexed.

3. In females, fossa of female sperm receptacles is deeper in woodland crayfish.

How many crayfish are Species of Conservation Concern in MO? How many are state endangered? How many are federally listed?

26/40 SOCC; Over half!

5 species are state endangered

2 Species are federally threatedned ( Big Creek and St. Francis)