Pennsylvania Crayfish Reference Collection

Ted R. Nuttall, Ph.D., Curator

Lock Haven University of PA

Note:  The descriptions and illustrations come from many sources and authors (listed in the References below).  Many of the descriptions are from authors describing crayfishes from other states, as well as my own observations of voucher specimens and new specimens from around PA (special thanks to John Rawlins of the Carnegie Institute and Ned Gilmore of the Academy of Natural Sciences for helping me obtain voucher specimens from their collections).  I am solely responsible for the organization and scientific accuracy of this key...which, by the way, is likely to be updated as I see more species from around the state.  Please do not publish any part of the key.  While I believe it to be scientifically accurate, until published and reviewed by other crayfish biologists, it is for educational purposes only.

Crayfish Information

• A Key to the Crayfishes of PA.
• Glossary of Scientific terms about Crayfishes
• Figures of Crayfishes showing names of their parts.
• A list of Pennsylvania crayfishes, both native and invading.  (coming soon).
• Scientific Information:  Keith Crandall's site at BYU.  Dr. Crandall is a leading scientist specializing in the evolutionary genetics of crayfish.
• International Association of Astacology's website (it's slow...it's in Finland).  The IAA is the worldwide organization for Astacology (the study of crayfishes).
• General Crayfish Information:  the Crayfish Corner

Collection and Preservation of Crayfishes

• Use nets or hands.  Look under rocks, around water plants, under mud banks, in burrows near water (notice chimneys of mud), in swamps, lakes, etc.  Crayfish can dart backwards very fast, and bigger ones can pinch hard.  The biggest crayfish are found under large rocks, usually in deeper water.  Sometimes the young crayfishes are found near the water's edge in just a few inches of water (they are escaping being eaten by the big crayfishes in deeper water).
• To preserve, drop crayfish into alcohol (ethanol) until dead (just a few minutes), then preserve in 80% ethanol. (I don't like doing this, but it is the best way to preserve them.)  Using rubbing alcohol (isopropanol) does not work as well (it won't penetrate the carapace very well), but may work for temporary preservation.  If you send me a sample, I will exchange your alcohol with fresh 80%.
• Information needed to make a specimen valuable:  collection date, county of PA, nearest city, name of stream, good location description (cross streets, bridges, etc.) or map showing collection point, name of collector, time of day, and method of collection.
• To send me a specimen:  Wrap the container in paper towels and place in a ziplock bag.  Then wrap and pad the bagged jar in a sturdy box...remember that you must guard against breakage.  You should have enough padding (newspaper) to soak up all the alcohol in the container.  If you collect crayfishes often, especially if you are part of a high school biology class, contact me and I'll send a box with plastic containers for you to use.  Address it to me at LHU (my address).

Equipment Helpful in Crayfish Identification:

• A digital caliper that measures in mm (always use the metric system...the US is the only country not using the metric system!)
• A stereomicroscope (dissecting microscope) with a good light.  A hand magnifying lens is fine for some features, but for some measurements (the gonopod), you need your hands free.
• A curved pair of pointy forceps to gently move structures around.

Crayfish Ecology

Crayfishes are Keystone Species

    Keystone species are those species that are most important in shaping the total ecology of a system.  Crayfish are often keystone species in that they are an important resource for many other animals and can affect species diversity and abundance directly.  The invading species, the Rusty Crayfish (Orconectes rusticus) can remove all plants from a system and eats fish eggs, too.  This crayfish is very aggressive and removes local crayfish species (extirpates them), grows quickly (too big for fish to eat), and reaches high densities.  Water systems dramatically change when the rusty crayfish moves in and takes over.

FAQs (Frequently Asked Questions)

Who eats a crayfish?

    Birds (herons, barred owls, other water birds), water snakes, large salamanders, frogs, raccoons, muskrats, minks, river otters, many fish (trout, bass, etc.), turtles, other crayfish, and people (Cajun crawfish!).  Crayfishes represent high-quality protein that nearly any animal will want to eat.  The shell (carapace) of a crayfish, however, is not digestible by animals (although the calcium may be removed) and is typically broken down by microbes.

What do crayfishes eat?

    Insects, plants, detritus (decomposing plants and animals), worms, other crayfishes, fish eggs (especially the invading Rusty Crayfish...very bad for the streams ecology), etc.  Crayfishes are basically omnivores...they'll eat anything, but prefer high protein content in their food.

How many species are in PA?

    Good question!  So far there are 12 species (13 if you include subspecies) of crayfishes reported in PA.  Sometimes they are easy to tell apart, others are very hard to distinguish.  I suspect a few more species will be found since they are found in neighboring states.  Two species are introduced to the state, the rusty crayfish and the northern crayfish (Orconectes virilis).  To determine what species a crayfish is, go to the Key to PA Crayfishes.

Do crayfishes live on land?

    Some crayfishes are burrowers and can live far from surface water.  They must have underground water, though, like a shallow aquifer, underground spring, or nearby water.  Burrows can be quite deep with many branching tunnels, some leading to nearby water.  If you live in the right places (southwestern and eastern PA), you might see crayfishes walking around a garden far from water during the humid summer nights.

What colors can crayfishes be?

    Crayfishes can be nearly any natural color:  yellow, green, blue, red, white (cave species), and every possible combination of colors.  They can have intricate patterns of color, solid colors with different colored edges, spotted, and multiple colors at once.  Oddly, burrowing crayfish that are rarely or never seen in open water can be the most colorful.  Species found in open water are generally the color of the rocks, sand, mud, grass, etc. of the background substrate so that predators can't see them.  I have found brick-red crayfish in streams with leaf litter of the same color, and greenish crayfish (same species as the brick-red crayfish) in rocky steams.  Natural selection will determine which color is best for survival.

References

Crocker, D.W. 1957. The Crayfishes of New York State. SUNY at Albany. Albany, NY.

Crocker, D.W. and D.W. Barr. 1968. Crayfishes of Ontario. University of Toronto Press, Canada.

Hobbs, Jr., H.H. 1972. Crayfishes (Astacidae) of North and Middle America. US Government Printing Office, Washington, D.C.

Jezerinac, R.F., G.W. Stocker, and D.C. Tarter. 1995. The Crayfishes (Decapoda: Cambaridae) of West Virginia. Ohio Biological Survey, Ohio State Unversity, Columbus, Ohio.

Ortmann, A.E. 1906. The Crawfishes of the State of Pennsylvania. Memoirs of the Carnegie Museum, Vol. II, No. 10., Pittsburgh, PA.

Page, L.M. 1985. The Crayfishes and Shrimps (Decapoda) of Illinois. Illinois Natural History Survey Bulletin, Vol. 33, Article 4, Sept.

Peckarsky, B.L., P.F. Fraissinet, M.A. Penton, and D.J. Conklin, Jr. 1990. Freshwater Macroinvertebrates of Northeastern North America. Cornell University Press, Ithaca, NY.

Pflieger, W.L. 1996. The Crayfishes of Missouri. Missouri Dept. of Conservation, Jefferson City, MO.

Taylor, C.A. et al. 1996. Conservation Status of Crayfishes of the United States and Canada. Fisheries, Vol. 21, No. 4:25-38.