Crayfish Home
Horton H. Hobbs Jr.
Section I
Section II
Section III
Section IV
Section V
Section VI
Web Links
Key Contents (Species)

 Glossary of Crayfish Terminology

A more in-depth glossary containing terms relating to crustaceans can be viewed from a link on the The Crustacean Society home page. 


A {Top}

  • Abdomen
    • region of body posterior to the cephalothorax, consisting of six body segments and the telson.
  • Acumen -
    • pointed apical part (tip) of rostrum, frequently delineated basally by marginal spines.
  • Annulus Ventralis -
    • crayfish seminal receptacle, consisting of median sclerite between fourth and fifth pereiopods.
    • the spermatophore receptacle on sternum of female.
  • Antenna -
    • whiplike, generally long sensory organ arising from anterior region of cephalothorax.
  • Antennal Scale -
    • bladelike exopod of antenna situated at base of antenna.
  • Antennal Spine -
    • spine on, or adjacent to, anterior margin of carapace and ventral to orbit.
  • Antennular Peduncle -
    • proximal segments of antennule, from which flagella arise.
  • Antennule -
    • one of pair of appendages of first cephalic somite.
    • "first antenna".
  • Anterior -
    • front end of organism.
    • "head end".
  • Apical -
    • apex; tip.
  • Areola -
    • dorsomedial area (usually hourglass-shaped) of thoracic region of carapace of crayfishes, bounded laterally by paired arched (branchiocardiac) grooves delineating dorsomedial limits of gill chamber.

B {Top}

  • Basis -
    • second segment (from proximal end) of segmented appendage.
  • Benthos -
    • "bottom" of a body of water (e.g., lakes, streams, and ponds), providing habitat for various aquatic organisms on or within.
  • Boss
    • an expanded portion (rounded protuberance) on the mesial surface of coxa of fourth pereiopod of male crayfishes.
  • Branchiostegal Spine -
    • short spine situated on or near anterior margin of carapace, ventral to antennal spine in shrimps.
    • in crayfishes, located immediately ventral to anterior extremity of cervical groove.
  • Burrower -
    • crayfishes (usually all) that spend some or nearly all of their life history in confines of excavated burrow.
    • PRIMARY - crayfishes that spend almost their entire lives in subterranean galleries.
    • SECONDARY - crayfishes that spend much of their lives in burrows but frequently move into open water during rainy seasons.
    • TERTIARY - crayfishes that live in open water and retreat to burrows in response to several factors:  a) to remain below frost line during winter, b) females enter as period of ovulation approaches and remain in burrows to lay and brood eggs, c) to find protective cover and to avoid desiccation as water bodies disappear.

C {Top}

  • Carapace -
    • "shield" (exoskeleton) overlying cephalothoracic somites of body.
  • Carapace Length -
    • in crayfishes, the distance from tip of rostrum to midcaudodorsal margin of carapace.
  • Carina -
    • median middorsal ridge on rostrum, oriented parallel to lateral margins of rostrum.
  • Carpus -
    • fifth segment from proximal end of segmented appendage.
  • Caudal -
    • posterior (rear, tail) end of organism.
  • Central Projection -
    • Terminal projection on crayfish male gonopod formed by fusion of two processes, poorly developed in second form male, located centrally on apex of Procambarus gonopod, distally on that of Cambarus, Fallicambarus and Orconectes.
  • Cephalic -
    • Pertaining to head, of head.
  • Cephalothorax -
    • portion of body bearing eyes and all appendages through fifth pereiopod (fused head and thorax).
  • Cervical Groove -
    • major arclike suture (groove) on carapace of crayfish, dividing it into anterior (cephalic) and posterior (thoracic) regions.
  • Cervical Spine -
    • spine on lateral surface of carapace immediately posterior to cervical groove of crayfishes.
  • Chela -
    • forceps-like structure ("claw" or "pincer"), consisting of two opposed distal podomeres of first, second, and third pereiopods of crayfishes.
    • dactyl (moveable finger) and propodus.
  • Cheliped -
    • Pereiopods bearing chela.
    • in crayfish literature applied almost exclusively to first pereiopod.
  • Collector -
    • functional group category based on feeding mechanisms into which immature and adult aquatic insects are generally placed.
    • crayfishes herein are also assigned to this group to indicate their functional role in aquatic community trophic relations, that is, they consume decomposing fine particulate organic matter and associated microbes.
  • Condyl -
    • knob, rounded process at base of central projection of male first pleopod (gonopod);
    • "condyl length" is the measured distance between the base of the condyl and the distal tip of the central projection.
  • Copulation -
    • joining of male and female for transference of sperm.
    • sexual union.
  • Corneous -
    • structures that are horny (sclerified), particularly as related to reproductive appendages (modified first pleopod) of first form males.
  • Coxa -
    • Proximal (first) segment of segmented appendage.

D {Top}

  • Dactyl -
    • distal-most segment of usually 7-segmented appendage.
    • smaller, mesially situated, and moveable part of chela (moveable finger).
  • Detritus -
    • non-living particulate organic matter inhabited by decomposer organisms. 
    • including dissolved carbon-containing substances excreted by plants and animals as well as soluble organic materials released from decaying plant and animal tissues.
  • Distal -
    • Away from body mid-line.
    • Toward apex (tips) of appendages.
  • Dorsal -
    • Top or back of the crayfish.

E {Top}

  • Endite -
    • mesial lobe-like extension of podomere or of axial part of unsegmented appendage.
  • Endopod -
    • mesial ramus of biramus appendage, originating on basal segment (basis).
  • Epigean -
    • referring to above ground habitats as opposed to hypogean.
  • Epistome -
    • transverse plate (usually somewhat triangular in shape) situated ventrally and anterior to gnathal appendages of crayfishes.
  • Euryphagous -
    • employing wide range of living and decaying plant and animal material as food.
    • "scavenger" strategy.
  • Exopod -
    • lateral ramus of biramus appendage, originating on second segment (basis) from base.
  • Exoskeleton -
    • outer covering of arthropods.
    • "shell".
  • Extensor Surface -
    • Unopposed surface (face) of flexible podomere of an appendage (in opposition to opposed, flexor surface).

F {Top}

  • Finger -
    • one of two rami of the chela.
    • moveable finger (dactyl) and immovable finger of opposable part of propodus.
  • First Form Male -
    • sexually functional male crayfish (Cambaridae).
    • at least one terminal element of first pleopod usually corneous.
  • Flagellum -
    • antennal endopodite.
    • thin, tapering, multiarticulate, elongate extension of antenna and antennule (distal to peduncle).
  • Flexor Surface -
    • opposable surface (face) of flexible podomere of appendage (in opposition to non-opposed extensor surface).

G {Top}

  • Gonopod -
    • pleopod in male modified for reproductive purposes.
  • Gynandromorph -
    • abnormal individual exhibiting secondary characters of both sexes.
    • particularly well known in insects; occurs also in Crustacea, birds, and mammals.

H {Top}

  • Hepatic Area -
    • paired cephalolateral region to either side of carapace between orbit and cervical groove.
  • Hepatic Spine -
    • spine situated near anterior margin of hepatic area of carapace of certain shrimps, or on hepatic area of cambarids.
  • Hypogean -
    • subterranean.
    • referring to beneath surface of earth.
    • burrow or cave environment.
  • Hyporheic Zone -
    • interstices formed in substrate of streams (between coarse sand, gravel, and cobble).

I {Top}

  • Incisor Process -
    • cutting surface (lobe) of mandible (as opposed to molar or grinding lobe).
  • Ischiopodite -
    • third segment from base of segmented appendage.
  • Ischium -
    • see ischiopodite.

K {Top}

  • Karst -
    • terrain (or topography) characterized by numerous sinkholes, swallow holes, springs, and caves formed by extensive dissolution of carbonate rocks.

L {Top}

  • Lateral -
    • referring to or toward the side.
  • Lentic -
    • denotes standing water environments (e.g., lakes, ponds, bogs).
  • Limnetic -
    • Upper circulating, open-water zone of lakes beyond direct influence of shore or bottom.
  • Littoral Zone -
    • shore region of lake.
    • peripheral shallows of lake.
  • Lotic -
    • refers to running water environments (e.g., springs, rivers).

M {Top}

  • Mandible -
    • most anterodorsally situated of gnathal appendages.
    • one, of a pair, of heavily calcified jaws.
    • the "teeth".
  • Maxilla -
    • one of a pair of two sets of gnathal appendages situated immediately posteroventral to mandibles.
  • Maxilliped -
    • one of pair of three sets of gnathal appendages lying immediately posterior to second pair of maxillae.
  • Merus -
    • fourth segment from proximal end of segmented appendage.
  • Mesial -
    • referring to or toward the middle.
  • Mesial Process -
    • terminal process located mesially on modified first pleopod (gonopod) of male cambarid crayfishes.
  • Morphology -
    • the study of form and structure.
  • Moveable Finger -
    • (=dactyl).
    • distal-most podomere of segmented appendage.

O {Top}

  • Orbit -
    • one of pair of excavations on anterior margin of carapace bordering the eye (or remnant).

P {Top}

  • Palm -
    • expanded portion of propodus of chela situated proximal to "fingers".
  • Palp -
    • relatively slender 2- or 3-segmented appendage of mandible.
  • Pereiopod (Pereopod)-
    • one of five pairs of appendages (legs) supporting cephalothorax.
    • walking and chelate legs.
  • Pleopod -
    • one of five pairs of appendages on the first five abdominal segments ("swimmerets," or modified into male gonopod).
  • Pleuron -
    • lateral overhanging plate of abdominal segments.
  • Podomere -
    • single segment of any appendage.
  • Postannular Plate -
    • medially situated sclerite (plate) immediately posterior to annulus ventralis.
  • Posterior -
    • toward caudal or "hind" end.
  • Postorbital Carapace Length -
    • distance from orbit to mid-caudodorsal (posterior) margin of carapace.
  • Propodus -
    • penultimate segment (sixth from base) of segmented appendage.
  • Proximal -
    • toward the body.
    • that portion of the appendage nearest the body.
  • Pterygostomian Region -
    • paired anteroventral area of carapace ventral to antennal region.
  • Punctation -
    • small depression (pit).

R {Top}

  • Rostrum -
    • dorsomedian anterior projection of cephalothorax.
    • in crayfishes, partly covering eyestalks, and bases of antennae and antennules.

S {Top}

  • Scraper -
    • functional group category, herbivores that graze on algae attached to stony or organic surfaces (periphyton feeders).
  • Second Form Male -
    • one of two morphological form of male cambarids.
    • sexually nonfunctional male lacking corneous terminal element on first pleopod (gonopod).
  • Shredder -
    • functional group category, herbivores and detritivores that masticate coarse organic particulates.
  • Spelean -
    • referring to subterranean habitats (caves).
  • Stadia -
    • a stage in the life history of an organism.
    • interval between successive molts.
  • Sternum -
    • mid-ventral plate-like surface of body, situated between coxae of appendages.

T {Top}

  • Telson -
    • terminal (posterior) portion of abdomen.
    • caudomedian element of "tail fan".
  • Troglobite -
    • obligate inhabitant of subterranean habitats (caves).
  • Tubercle -
    • low protuberance on exoskeleton.

U {Top}

  • Uropod -
    • paired biramous appendage on sixth abdominal segment.
    • lateral parts of "tail fan".

V {Top}

  • Ventral -
    • on or toward the underside.





Last Updated:  10 Sep 2004