Crawfish/Crayfish Dissection Prelab Notes
Taxonomic Classification
Kingdom-Animalia
Phylum-Arthropoda
Class-Crustacea
Order-Malacostraca
Family-Astacidea
Genus-Cambarus
Species-affinis
What do crayfish look like?
External Anatomy (Dorsal View)
Label the uropods, chelipeds, antennae, and antennules
Body is divided into 2 regions:
1. Cephalothorax (the head and carapace)
2. Abdomen (posterior portion of body)
External Anatomy (Ventral View)
Label the mandibles and swimmerets
Appendages:
•Crayfish appendages are biramus – branched – and jointed
Crayfish have 7 pairs of feeding appendages, including the mandibles and chelipeds.
Antennules contain hearing and balancing mechanisms
Antennae contain organs of touch, taste and smell
Swimmerets are abdominal structures for swimming
Walking legs are thoracic structures for walking
Where do they live?
In nearly all bodies of fresh water that contain lime
Why would lime be important to the crayfish?
--used to harden the exoskeleton of chitin
What adaptations do crayfish show for their aquatic habitat? (look at each slide and TAKE NOTES
below)
Respiration
•They have gills as their respiratory organs. Gills take in oxygen from water and pass carbon dioxide
back to the water
•The gills can hold oxygen for a long time once the crayfish is out of the water
What are the gills attached to? –the walking legs
How do crayfish move?
Use telson, uropods, & swimmerets to swim backwards
Use walking legs (4 pairs) to crawl over the bottom
5th pair of walking legs (crayfish are decapods) is modified as the chelipeds (pincers/claws)
What do crayfish eat?
Omnivorous
fish & shrimp larvae
pond vegetation
small water insects
Tracing food through the crayfish
1. Mandibles move from side to side to crush food as
2.it enters the mouth
3.Food then passes through the esophagus to the
4.cardiac stomach, where it is ground up (part of the stomach is lined with “teeth”).
5.Food then passes through the digestive glands and for digestion and temporary storage.
6.Undigested food travels through the intestine and is eliminated through the anus
Excretory System: The Green Gland
The green gland is located internally just behind each antenna and right under the brain. These
structures filter fluid waste from the blood
The green glands are analogous to what human structure? _kidneys_
Based on the crayfish’s habitat, do you think the green gland retains salt in the body of the
crayfish, or excretes salt to osmoregulate? Retain salt
Nitrogenous waste exits the body through nephridiopores into the surrounding water.
Reproduction
Crayfish reproduce sexually, sexes are separate, and fertilization is internal:
Males – testes (white) produce sperm that exit the body through a pore at the base of the 5th pair
of walking legs
Females – ovaries (orange) produce eggs which are released after internal fertilization through a
pore at the base of the 3rd pair of walking legs
Females usually have 10-800 eggs, which hatch in 2-20 weeks, depending on the water
temperature.
Eggs are retained until mature on the swimmerets of the female
An average crayfish life span is 3-4 years
Swimmerets role in Reproduction
located on the ventral side of abdomen (used for swimming and for reproduction)
Difference between males and females:
Females: crescent shaped slit; are all soft to the touch
Males: sperm duct opening (actual pore); hardto the touch
Internal Male & Female structures
The male’s gonads are very difficult to find (they are located underneath the heart)
The ovaries are yellow/orange. They are located just below the carapace.
Circulation of the Crawfish
Heart – located on dorsal side just below digestive glands
_Open circulatory system
Nervous System
Large nerves travel from brain to ventral part of body
A _ventral nerve cord is present
Compound Eyes with more than 2,000 lenses