Anatomy and Morphology

Anatomy Definitions

Antennae: In these fresh water crabs there are two pairs of antennae unlike other groups of arthropods, the outer antennae pair are longer and much other arthropods, but there is an inner paid of antennae called antennules which in these groups of crabs tends to be smaller. The outer pair of anntenae are not segmented.

Abdomen: See Pleon

Antennules: These are the inner smaller pair of antennae which are segmented.

Carapace: The dorsal surface of the cephalothorax is often called the carapace, which forms the hard calcified shell of the crab

Cephalothorax: The fused head and thorax segment of the crab body which is encased in a calcified carapace

Chelae: The pincer-like claws that are formed on the ends of the first pair of legs. The classic feature of decapod crabs, their claws.

Chelaped: This is the name for the first pair of legs that terminate distally in pincers used for the capture of prey and feeding. The word comes from Chela, meaning claw, and ped, meaning foot.

Chitin: the exoskeleton is made from this substance that is variable in function and thickness depending on location of the body and body part use. It forms the exoskeleton, the setae, the eyes, and appendages.

Exoskeleton: The hard outer suface of the crab body that is made up of chitin

Gills: the aparatus used by crabs for breathing

Mandibles: The mouthparts responsible for fragmenting food items

Maxillae: The mouthparts responsible for ingesting food items. Comprised of the first maxilla which sports a chewing ridge directed inward, and a second maxilla which is larger and made of a medially extended endopodite and exoposite used for the continous water flow for breathing (Hohle & Singheiser, 2016).

Maxillipeds: While not technically legs they originate from the thorax but are modified into mouthparts with the purpose of feeding and for keeping the gills saturated

Ommatidia: the compound eye receptors or facets that detect light

Pereon: The thorax that in fresh water crabs is fused with the

Pleon: this is the body section in freshwater crabs that is folded underneath the crab which covers the reproductive organs and the pleopods. Females have a much broader pleon while males have a much narrower pleon that is largely traingular shaped.

Pleopod: these are segments used in reproduction, females use them to hold onto the eggs under the pleon and males use them largely to hold onto females druring copulation.

Pereopods: the four pairs of walking legs and the chelipeds steming from the thorax make up what is known as the pereods, the name stemming from pereo~meaning thorax, and pod~ from podus meaning foot, thorax legs. Made up of 7 segments: coxa, base, ischium, merus, carpus, propodus, dactylus.

Setae: hair-like sensory organs.

Terminal Telson: the final portion of the pleon which serves as the anal segment