A quick guide to crayfish anatomy
In using keys to identify crayfish (or in describing the differences between male and female crayfish), it can quickly become a confusing word soup of technical terms. This section will help you wade through the jargon-y maze of words used to describe the anatomy of crayfish.
- (A) coloration
- (B) areola width
- (C) rostrum shape
- (D) chelae (claw) length
- (E) carapace length
- (F) dactyl (thumb) shape.
Glossary of Anatomical Features on Crayfish
| ABDOMEN | the tail of a crayfish, posterior to the cephalothorax |
| ACUMEN | the apical projection on the rostrum; sometimes with marginal spines |
| ANNULUS VENTRALIS (gonopore) | the circular seminal receptacle on females, found between the abdomen and cephalothorax (between 4th and 5th pereiopods). |
| AREOLA | the space between the 2 carapace plates |
| BROOD | the offspring produced at a single hatching, carried in the first 2-3 molts as on the female’s abdomen |
| CARAPACE | the part of a crayfish’s exoskeleton that covers the cephalothorax |
| CEPHALOTHORAX | the fused portion of a crayfish’s body that contains the head and the thorax |
| CERVICAL GROOVE | transverse line that separates the head (cardiac) and thorax (gastric) regions |
| CHELAE | the claw of a crayfish, made up of the two fingers (dactyl and propodus) and the palm |
| DACTYL | the movable finger on a chela |
| EXOSKELETON | The hard chitinous outer covering (skeleton) of arthropods; this covering is shed during molting. |
| EXUVIUM | the exoskeleton shed during a molt |
| FINGER | the 2 long digits (dactyl and propodus) at the end of a chela |
| F1 (FIRST-FORM MALE) | at maturity, the form of a reproductively active male; the exoskeleton has hooks and stiffened gonopods |
| F2 (SECOND-FORM MALE) | the form of a male that is not reproductively active; lacks hooks and stiffened gonopods |
| GILLS | feathery structures on the ventral surface of the carapace used for respiration |
| GONOPODS | on males, the first pair of pleopods, or swimmerets used in reproduction to transfer sperm |
| HOOKS | projections on the ischia of a pair of walking legs on males, used to grasp onto females during mating |
| INSTAR | the phase between molts |
| “IN BERRY” | describes a female who is carrying eggs or young on her abdomen |
| PALM | the wide base of a chela to which the fingers are attached |
| PEREIOPODS | the 5 pairs of walking legs attached to the cephalothorax |
| PLEOPODS | the 5 pairs of swimmerets attached to the abdomen |
| PROPODUS | the immovable finger that extends up from the palm of a chela. |
| ROSTRUM | the nose of a crayfish |
| SETAE | hairlike projections on the surface of the exoskeleton, often between the fingers of chelae |
| SPINE | the sharpened bumps or projections on the carapace |
| TERMINAL ELEMENTS | the projections at the tips of the male reproductive structures (gonopods) |
| TUBERCLE | the raised blunt bumps or projections on the exoskeleton, typically contrasting color to carapace |
