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.
TermDefinition
abdomen                  The "tail" portion of the crayfish, posterior to the cephalothorax.
acumenThe most apical portion of the rostrum, sometimes delineated by marginal spines; varies in shape from rounded and wide to slender and long.
annulus ventralisThe 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.
areolaThe 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/apicalDirectional term indicating the tip or end of an object (furthest from its base).
appendageAny part of the body that is attached but most of the part is free (e.g., antennae, walking legs, swimmerets).
branchiostegalDirectional term indicating a region of the side of the carapace nearest the head (between the head and hepatic region).
broodThe young (offspring) produced as a result of mating; often carried as eggs or small instars on the ventral abdomen of the female.
burrowThe "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.
carapaceThe exoskeleton of a crayfish that covers the cephalothorax portion.
caudalDirectional term indicating "toward the animal's tail", or posterior.
caudal processThe caudal-most terminal element of a gonopod; found in Procambarus species (in NC).
central projectionThe 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 processThe cephalic-most terminal element of a gonopod; found in Procambarus species (in NC).
cephalicDirectional term used to indicate "toward the animal's head", or anterior.
cephalothoraxIndicating the portion of the body containing the head and thorax, anterior to the abdomen.
cervicalDirectional term indicating the region on the side of the carapace approximating the area between the head and thorax; along cervical groove.
cervical grooveGroove (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).
chimneyEvidence of a subterranean burrow (not all burrows have chimneys) indicated by a cylindrical pile of mudballs elevated above the surface.
corneousSlightly harded yet pliable proteinaceous material; often found at tips of form-I gonopods (see sclerotized).
costateDescriptor, usually of tubercles, that indicates that the tubercles are strong, raised, or rib-like.
dactylThe moveable finger of a chela.
decapodA 10-legged crustacean (e.g., crayfishes, shrimps, lobsters, crabs).
detritusDecaying organic material (leaf matter, decomposing aquatic vegetation, dead animal tissue) often found on stream bottoms.
distalDirectional term indicating "toward the free (unattached) end" of an object (i.e. gonopod, leg, spine); away from the body.
dorsalDirectional term indicating the "back" or "top" of an animal or object.
epigeanAn animal that lives above-ground (e.g., stream-dwelling crayfishes), as opposed to hypogean.
excavateIndicating that there is a depression, large shallow pit, or concave area.
exoskeletonThe hard chitinous outer covering (skeleton) of arthropods; this covering is shed during molting.
exuviumThe remaining exoskeleton after an animal has molted.
fingerThe 2 long appendages of a chela, the dactyl and the propodus, used for grasping or defending.
first-form maleA male that is reproductively active, having form-I gonopods.
second-form maleA male that is not reproductively active, having form-II gonopods.
form-I gonopodThe reproductive structure of a reproductively active (breeding) male; terminal elements are usually sharp and sclerotized.
form-II gonopodThe reproductive structure of a male that is not in its reproduction phase; terminal elements are usually blunt/rounded and not sclerotized.
fossaThe plating on the annulus ventralis.
gillsThe feathery structures that an animal uses for respiration; found tucked under the carapace on the sides.
gonopodsThe first pair (most cephalic in position) of abdominalpleopods ("swimmerets") that are used by males in sperm transfer.
hepaticDirectional term indicating the region posterior to the branchiostegal region but anterior to the cervical region.
hooksClasping devices on ischia of certain walking legs used in copulation; much more highly developed in first-form males.
hypogeanAn 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.
inflatedIndicating that a structure is "puffy" or bulbous, rather than flat or spatulate.
instarAny 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).
ischiaThe third segment from the base of segmented legs; ischia of certain walking legs may contain hooks in reproductively active males.
lateralDirectional term indicating "to the side, away from midline of animal".
lenticStanding water environments (e.g., lakes, ponds, backwaters, swamps, temporary pools).
littoral zoneThe area of water shallow enough to allow rooted macrophytes (aquatic plants) to grow; generally indicates waterbody edges.
longitudinalDirectional term indicating along the main axis, as in "longitudinal ridges" on chela fingers.
loticFlowing waters (e.g., brooks, streams, rivers).
marginalDirectional term; in crayfishes, describes spines placed at base of acumen on rostrum.
mesialDirectional term indicating "to the side, toward midline of animal".
mesial processThe 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.
moltingThe process of growing by shedding the exoskeleton and regrowing a new one (begins soft, gets hard through time).
palmThe portion of the chela that is not composed of fingers; the widest part to which fingers are attached.
pereiopodsThe 5 pairs of walking legs attached to the cephalothorax (as opposed to the 5 "swimmerets").
pleopodsThe 5 pairs of abdominal appendages known as "swimmerets" (as opposed to the 5 pairs of walking legs attached to the cephalothorax).
postorbital ridgeThe ridge (raised area) directly behind the eyes on the head portion of the carapace.
propodusThe immoveable, or attached finger of a chela.
proximalDirectional term indicating "toward the attached end" of an object (i.e. gonopod, leg, spine); close to the body.
punctationIndicates pitting, or marked with many small pits in the surface (e.g., of chelae or carapace).
rostrumThe "nose" of the crayfish; the portion of the carapace on the head region that is anterior to the eyes.
sclerotizedComprised of a corneous substance, orange to orangeish-yellow or tan-brown in color.
setaeProjections, or "hairs" from the surface of objects (e.g., of chelae or carapace).
sexually dimorphicIndicating that females and males of a taxon can be distinguished visually.
shaftReferring to the main portion of a gonopod; the long, cylindrical segment along the main axis.
shoulderA rounded portion extending from the shaft of an appendage (usually a gonopod).
spatulateDescriptor of a flat, rather than a rounded or bulbous, structure.
spineSimilar to a tubercle but ending in severe point; used as defence and ornamentation on body parts.
suborbital angleThe angle of the carapace around (behind) the eye; can be obtuse or acute, or variations on these.
spatulateDescribing a structure as flat, rather than bulbous or rounded.
terminal elementsDistal projections of gonopods.
tubercleRaised projetion or bump; similar to a spine, but blunt.
vaultedUsed 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.
ventralDirectional term indicating the "belly" or "bottom/underside" of an animal or object.