Crayfish Anatomy Overview

Crayfish Anatomy Overview

• Crayfish body consists of two main parts: the cephalothorax (head and thorax, 13 segments) and the abdomen (tail, 6 segments).
• Carapace is the protective exoskeleton covering the cephalothorax.
• Cervical groove is an indentation on the carapace, separating the head from the thorax.

Head Structure

• Rostrum is the pointed extension at the front of the head.
• Compound eyes are positioned beneath the rostrum, located at the ends of stalks.
• Mandibles function as "true jaws" for biting and crushing food.
• Antennae serve as sensory organs for touch, taste, and smell.
• Maxillae assist in handling food, tearing it, and directing it to the mouth.
• Antennules are for balance, touch, and taste, located at the foremost segment.

Appendages and Locomotion

• Maxillipeds are three pairs that hold food during consumption.
• Chelipeds are the largest appendages (claws) used for defense and food manipulation.
• Walking legs are four pairs aiding in movement, one on each thoracic segment.
• Swimmerets (first five abdominal segments) are used for slow movement and reproduction.

Reproductive Structures

• Genital pore (female) is located on the base of the second pair of walking legs as a crescent-shaped slit.
• Sperm duct opening (male) is found at the base segment of the fourth walking legs.

Body Parts in the Abdomen

• Uropods are pointed appendages on the last abdominal segment, contributing to movement.
• Telson is triangular, central to the uropods, bears the anus, and forms the tail fan.

Internal Organs and Digestive System

• Ovary appears as a large, pinkish mass under the heart for reproduction.
• Testis is a long, whitish organ located under the heart.
• Esophagus transports food from the mouth to the stomach.
• Stomach processes food using gastric mill (chitinous teeth) for grinding.
• Digestive gland produces digestive substances and absorbs nutrients.
• Intestine conducts undigested material away from the stomach to the anus, where waste is expelled.

Circulatory and Excretory Systems

• Dorsal tubular heart lies beneath the dorsal carapace, anterior to the abdomen, part of the open circulatory system.
• Sinuses allow blood to flow into tissues, creating spaces for nutrient and waste exchange.
• Arteries transport blood throughout the body.
• Gills, feather-like structures, facilitate oxygen absorption and carbon dioxide removal.

Nervous System

• Dorsal brain consists of two lobes located behind the compound eyes.
• Ventral nerve cord runs from the brain, encircling the esophagus, branching out to ganglia.
• Ganglia are segmental enlargements of the ventral nerve cord, responsible for processing sensory and motor information.