Crayfish Glossary

These aren't the definitions you'll find listed formally in the back of texts but are meant to assist the novice. Terms in the definitions that are underlined are also listed in the glossary.

Term	Definition
abdomen	The "tail" portion of the crayfish, posterior to the cephalothorax.
acumen	The most apical portion of the rostrum, sometimes delineated by marginal spines; varies in shape from rounded and wide to slender and long.
annulus ventralis	The seminal receptacle (where sperm are placed during copulation) of females; quasi-circular structure on ventral surface, midway between the abdomen and cephalothorax, between the 4th and 5th pereiopods.
areola	The space found on the dorsal surface of the carapace between the 2 carapace plates; can be wide (e.g., stream-dwellers) or narrow to linear (e.g., burrowers).
apex/apical	Directional term indicating the tip or end of an object (furthest from its base).
appendage	Any part of the body that is attached but most of the part is free (e.g., antennae, walking legs, swimmerets).
branchiostegal	Directional term indicating a region of the side of the carapace nearest the head (between the head and hepatic region).
brood	The young (offspring) produced as a result of mating; often carried as eggs or small instars on the ventral abdomen of the female.
burrow	The "house" of hypogean species; the subteranean tunnel(s); usually having a circular opening (on the ground in floodplains, in banks, or stream bottoms), and sometimes having a chimney.
carapace	The exoskeleton of a crayfish that covers the cephalothorax portion.
caudal	Directional term indicating "toward the animal's tail", or posterior.
caudal process	The caudal-most terminal element of a gonopod; found in Procambarus species (in NC).
central projection	The central, or "main", terminal element of a gonopod extending directly from the shaft; found in all species; C-shaped in Cambarus and Fallicambarus, long, straight, and slender in Orconectes, and variable but short in Procambarus.
cephalic process	The cephalic-most terminal element of a gonopod; found in Procambarus species (in NC).
cephalic	Directional term used to indicate "toward the animal's head", or anterior.
cephalothorax	Indicating the portion of the body containing the head and thorax, anterior to the abdomen.
cervical	Directional term indicating the region on the side of the carapace approximating the area between the head and thorax; along cervical groove.
cervical groove	Groove (sinuous but approaches linear at an angle) along side of carapace; differentiates head and thorax region.
chela (chelae)	The "claw" or pincer, composed of 2 fingers, the dactyl and propodus (entire first walking leg is called the cheliped).
chimney	Evidence of a subterranean burrow (not all burrows have chimneys) indicated by a cylindrical pile of mudballs elevated above the surface.
corneous	Slightly harded yet pliable proteinaceous material; often found at tips of form-I gonopods (see sclerotized).
costate	Descriptor, usually of tubercles, that indicates that the tubercles are strong, raised, or rib-like.
dactyl	The moveable finger of a chela.
decapod	A 10-legged crustacean (e.g., crayfishes, shrimps, lobsters, crabs).
detritus	Decaying organic material (leaf matter, decomposing aquatic vegetation, dead animal tissue) often found on stream bottoms.
distal	Directional term indicating "toward the free (unattached) end" of an object (i.e. gonopod, leg, spine); away from the body.
dorsal	Directional term indicating the "back" or "top" of an animal or object.
epigean	An animal that lives above-ground (e.g., stream-dwelling crayfishes), as opposed to hypogean.
excavate	Indicating that there is a depression, large shallow pit, or concave area.
exoskeleton	The hard chitinous outer covering (skeleton) of arthropods; this covering is shed during molting.
exuvium	The remaining exoskeleton after an animal has molted.
finger	The 2 long appendages of a chela, the dactyl and the propodus, used for grasping or defending.
first-form male	A male that is reproductively active, having form-I gonopods.
second-form male	A male that is not reproductively active, having form-II gonopods.
form-I gonopod	The reproductive structure of a reproductively active (breeding) male; terminal elements are usually sharp and sclerotized.
form-II gonopod	The reproductive structure of a male that is not in its reproduction phase; terminal elements are usually blunt/rounded and not sclerotized.
fossa	The plating on the annulus ventralis.
gills	The feathery structures that an animal uses for respiration; found tucked under the carapace on the sides.
gonopods	The first pair (most cephalic in position) of abdominalpleopods ("swimmerets") that are used by males in sperm transfer.
hepatic	Directional term indicating the region posterior to the branchiostegal region but anterior to the cervical region.
hooks	Clasping devices on ischia of certain walking legs used in copulation; much more highly developed in first-form males.
hypogean	An animal that lives below-ground (e.g., burrowing crayfishes), as opposed to epigean.
hyporheic	Referring to the region of water exchange between groundwater and surface water; often inhabited by numerous invertebrates.
inflated	Indicating that a structure is "puffy" or bulbous, rather than flat or spatulate.
instar	Any development stage between molts, generally referring to first several-very young animals.
"in berry"	Term used to describe a female crayfish carrying eggs or a brood of young attached to her abdomen (ventral).
ischia	The third segment from the base of segmented legs; ischia of certain walking legs may contain hooks in reproductively active males.
lateral	Directional term indicating "to the side, away from midline of animal".
lentic	Standing water environments (e.g., lakes, ponds, backwaters, swamps, temporary pools).
littoral zone	The area of water shallow enough to allow rooted macrophytes (aquatic plants) to grow; generally indicates waterbody edges.
longitudinal	Directional term indicating along the main axis, as in "longitudinal ridges" on chela fingers.
lotic	Flowing waters (e.g., brooks, streams, rivers).
marginal	Directional term; in crayfishes, describes spines placed at base of acumen on rostrum.
mesial	Directional term indicating "to the side, toward midline of animal".
mesial process	The second "main" terminal element of a gonopod; found in all species; bulbous in Cambarus, spatulate in Fallicambarus, similar to the central projection in Orconectes, and variable but short in Procambarus.
molting	The process of growing by shedding the exoskeleton and regrowing a new one (begins soft, gets hard through time).
palm	The portion of the chela that is not composed of fingers; the widest part to which fingers are attached.
pereiopods	The 5 pairs of walking legs attached to the cephalothorax (as opposed to the 5 "swimmerets").
pleopods	The 5 pairs of abdominal appendages known as "swimmerets" (as opposed to the 5 pairs of walking legs attached to the cephalothorax).
postorbital ridge	The ridge (raised area) directly behind the eyes on the head portion of the carapace.
propodus	The immoveable, or attached finger of a chela.
proximal	Directional term indicating "toward the attached end" of an object (i.e. gonopod, leg, spine); close to the body.
punctation	Indicates pitting, or marked with many small pits in the surface (e.g., of chelae or carapace).
rostrum	The "nose" of the crayfish; the portion of the carapace on the head region that is anterior to the eyes.
sclerotized	Comprised of a corneous substance, orange to orangeish-yellow or tan-brown in color.
setae	Projections, or "hairs" from the surface of objects (e.g., of chelae or carapace).
sexually dimorphic	Indicating that females and males of a taxon can be distinguished visually.
shaft	Referring to the main portion of a gonopod; the long, cylindrical segment along the main axis.
shoulder	A rounded portion extending from the shaft of an appendage (usually a gonopod).
spatulate	Descriptor of a flat, rather than a rounded or bulbous, structure.
spine	Similar to a tubercle but ending in severe point; used as defence and ornamentation on body parts.
suborbital angle	The angle of the carapace around (behind) the eye; can be obtuse or acute, or variations on these.
spatulate	Describing a structure as flat, rather than bulbous or rounded.
terminal elements	Distal projections of gonopods.
tubercle	Raised projetion or bump; similar to a spine, but blunt.
vaulted	Used to describe the carapace of burrowing crayfishes; raised rather than dorso-ventrally compressed, presumably to allow more room for gill respiration; vaulted carapaces often have very narrow or linear areolas.
ventral	Directional term indicating the "belly" or "bottom/underside" of an animal or object.