Crayfish Dissection

Students dissect a preserved crayfish to investigate arthropod characteristics, including exoskeleton, jointed appendages, body segmentation, gills, and major organ systems. The activity emphasizes external identification, safe opening of the carapace and abdomen, and tracing digestive, circulatory, and reproductive structures.

• Follow instructions provided in the links below.

Crayfish Dissection || Aw Snap! [EDU] - Silvergrass Institute:

📄 Crayfish Dissection - PBS Learning Media: https://www.pbslearningmedia.org/resource/047ec6ad-11a0-447b-8802-240dcc1a2758/dissection-101-crayfish-dissection-lesson-plan/

📄 Anatomy of a Crayfish - Biology Corner: https://biologycorner.com/worksheets/anatomy_crayfish_virtual.html

• Compare freshwater crayfish with a crab or shrimp and record similarities and differences in gills, appendages, and carapace.
• Inject a small amount of colored water near the mouthparts to visualize gill ventilation across the branchial chamber.
• Focus study: dissect only the stomach to examine the gastric mill in detail and relate form to function.
• Use an interactive quiz or pinned practical the next class to reinforce identification.

• Wear gloves, eye protection, and protective clothing; keep an eyewash and spill cleanup materials available.
• Use scissors for most cuts; if a scalpel is needed, make shallow, controlled strokes on the tray and cut away from fingers.
• Handle preserved specimens and fluids as potential irritants; work in a well-ventilated area and avoid skin and eye contact.
• Keep food and drink out of the lab; wash hands after cleanup.
• Dispose of biological waste and blades in approved containers; disinfect instruments and benches after use.

• Which features identify crayfish as arthropods? (Exoskeleton, jointed appendages, segmented body, and paired appendages)
• How do swimmerets differ between males and females, and what are their functions? (Males have enlarged hardened first swimmerets for sperm transfer; females use swimmerets to carry eggs and aid ventilation)
• Where are the gills located and how are they ventilated? (Inside branchial chambers under the carapace; water is drawn across feathery gills by mouthpart movements)
• What is the function of the gastric mill in the cardiac stomach? (It mechanically grinds food before it passes to the pyloric stomach and midgut)
• How does the open circulatory system differ from a closed system? (Hemolymph leaves vessels to bathe tissues in sinuses; a dorsal heart pumps it back into arteries)
• What structures power the rapid tail-flip escape response? (Large abdominal extensor and flexor muscles attached to the tail fan)
• Where are the excretory organs and what are they called? (Green or antennal glands at the base of the antennae; they remove wastes and regulate ion balance)