A Dictionary of Non-Scientific Names of Freshwater Crayfishes ...

NUMBER 38
example, all too often used to refer to lobsters and
other crustaceans.
Fabricated names usually refer to specific species,
and their proper use, if, indeed, there is one, calls for
some scientific sophistication.
To call a word "common" that has been invented by
an individual or committee and published in an obscure
journal might charitably be called exaggeration. If
taken seriously, it begs for a redefinition of the word
"common," which is usually accepted to mean universal,
widespread, or ubiquitous.
Such wonderous words as crawldaddy, crow pappy,
koura, mudbug, yabbie, shawgashee, tsiskagili, and
koongooloo are examples of vernacular names, but one
would be hard-pressed to find such poetic creations in
latter day fabrications, where "common names" have
been contrived according to rules almost as complex as
those used in the composition of scientific names.
WHAT ARE CRAYFISHES?—Freshwater crayfishes,
sensu stricto, belong to the crustacean superfamilies
Astacoidea and Parastacoidea. They superficially
resemble marine lobsters, and some of the vernacular
names even incorporate the word "lobster," as in freshwater
lobster. In Australia the term lobster is commonly
used for the larger crayfishes such as Euastacus
and Astacopsis.
Crayfishes range in size from the tiny Cambarellus
diminutus found in the southeastern United States (~20
mg), to the large Astacopsis gouldi of Tasmania (up to
4.5 kg).
Persons not trained in zoology or in the distributions
of animals sometimes call freshwater atyid and palaemonid
shrimps "crayfish," a mistake that is more
common in places where shrimp and crayfish distributions
overlap or where crayfishes do not exist. The
same problem occurs with freshwater crabs, although to
a lesser extent. Crayfishes may be distinguished from
salt water lobsters, freshwater shrimps, and crabs by
bearing in mind the following guidelines:
Crayfishes (found in fresh to slightly brackish
water) Figures 1,2, and 6 (pages 2, 3, and 84).
1. The body is elongate and not dorsoventrally flattened.
2. The segmented abdomen is usually freely
extended and is not carried flexed against the sternum
(i.e., the belly of the leg-bearing part of the body).
3. The first three pairs of walking legs are chelate
(i.e., bear opposable claws).
4. A rostrum is present and flattened dorsoventraliy.
CEPHALOTHORAX
Figure 2.—Crayfish with parts labeled that are used in identifications.
Note body shape, abdomen, areola, and rostrum.
5. An hour-glass shaped "areola" (on the dorsal
midline between two paired branchiocardiac grooves) is
found in the posterior portion of the carapace.
6. Swimming is restricted to backward movement
resulting from rapid flexion of the entire abdomen (the
abdominal pleopods have little locomotor function).
This backward movement is widely recognized as a
salient crayfish behavioral trait (see crayfish as a verb).
Lobsters (found in salt water)
Lobsters look much like crayfishes, and the two
names are frequently used interchangably. True
lobsters and spiny lobsters are most readily differentiated
from crayfishes by living in salt rather than fresh
water. In addition, they do not have an areola (see
Figure 2).
Shrimps (found in fresh and salt water) Figure 5 (page
83).
1. Body elongate and not dorsoventrally flattened.
2. The first pair of walking legs are chelate; the second
may be chelate; the third pair are not chelate.
3. A rostrum is present and laterally flattened
(except in the Atyidae, which are easily distinguished