The Crazy Crayfish and Grasshopper

Rachel Shen. Vu-PAPBio-P2. Anthropod Lab.

Crayfish and Grasshopper

Both the Crayfish and the Grasshopper come from the phylum Arthropoda. The scientific name for the crayfish is Astacoidea while the scientific name for the grasshopper is Caelifera. The crayfish is a Malacostraca in class while a grasshopper is classified under the class Insecta.

Crayfish are also commonly known as crawfish, a type of food that is eaten by humans at many parties during late March and early April as it is “crawfish season”. Crayfish are more closely related to lobsters than to grasshoppers for they come from the same class. Crayfish use feather-like gills to breathe and cannot stand polluted water. They live in areas of fresh water (running) and do not live in water bodies that freeze to the bottom. The body contains 2 main parts—the cephalothorax and abdomen. They also may have one pair of appendages. It uses its claws (chelipeds) to catch prey and to defend itself. Its prey include insects, worms, insect larvae, and the eggs of many smaller creatures. They eat both dead and live things, as long as the dead things have not died too long ago. Its predators include snakes, raccoons, opossums, and muskrats.

Grasshoppers are found in fields, gardens, and crops worldwide in different climates. They are herbivores and they mainly consume plants such as grass. Grasshoppers are divided into 3 main areas—the head, the thorax, and the abdomen. They can walk, hop, and fly as a way of maneuvering around and they grow up to 5 inches long in length. They have large back legs and smaller frontal legs. They go through 3 stages as they grow—the egg, the nymph, and then adult. The nymph stage looks like the adult stage except the grasshopper is missing its wings. It will develop wings as it sheds and becomes an adult. The life expectancy for a grasshopper is 1 year. Its main predators include birds, rodents, lizards, and spiders.

Examining the Crayfish and Grasshopper

We were not able to dissect the crayfish or the grasshopper, but we were able to see it close up and saw its organs through diagrams. The two animals were amazingly different and similar as they come from the same phylum but different families and habitats.

Objectives of the Anthropods

Circulatory System of the Crayfish

A crayfish has an open circulatory system (which many arthropods have as well). Open circulatory system work when there is blood pumped into a hemocoel and have blood to diffuse again into the system between cells. The tissues surrounding the heart cavity is surrounded by blood and blood is pumped into body cavities by the heart. There are two arteries which are connected to the heart which transports blood into opposite directions. The abdominal aorta flows towards the posterior end while the anterior dorsal aorta flows towards the anterior end. In open systems, there are no veins involved as well. However, sinuses (tissue spaces) act like veins when blood flows into the capillaries from dorsal arteries.

The circulatory system is related to the respiration system in order to allow oxygen rich blood cells to travel around the body of the animal as the digestive system is related when there are nutrients taken from the small intestine for body circulation.

Fun Facts!

Did you know that crayfish are nocturnal? They do most of their hunting at night.

Did you know that grasshopper can make music by rubbing their wings/legs together?

Did you know that you can tell the gender of a grasshopper apart by its abdomen? (males have one part, females have two separate parts)

Did you know that both animals have a dorsal blood vessel?

Did you know that both animals have a nerve cord on the inside of their body?

Did you know that the green glands of a crayfish act like the kidneys?