Arthropods: Crayfish vs Grasshopper

Arthropod Investigation Jennifer Dong 4/2/14 GUZMAN-P7

Today's Objectives:

Students will examine two arthropods -- a crayfish and a grasshopper. After investigating the characteristics closely, students will be able to identify the similar phylum traits and the different class traits. Moreover, students will understand why grasshoppers belong to the class Insecta, while crayfish belong to the class Crustacea.

Ecological Niche Synopsis

The crayfish has an important role in the ecosystem since it provides energy for a variety of predators when it is preyed on. Moreover, crayfish keeps the prey populations in check. In the ecosystem grasshoppers play the role of transferring energy from plants to secondary consumers when they are preyed upon.

Ecological Adaptations Overview

Crayfishes have evolved pinchers for defense against predators. Moreover, they have have developed the behavioral adaptation of nocturnal hunting, which increases its chances of capturing an unsuspecting prey in the dark. Furthermore, the musty brown color of the exoskeleton ensures adequate camouflage against predators against the muddy or silty ground. On the other hand, grasshoppers have developed big hind legs for long jumps. This provides efficient locomotion that also allows them to easily escape predators. Moreover, the burnt brown to green color of the grasshopper provides camouflage among the dried grasses and soil. Furthermore, grasshoppers sometimes spit a bitter brown liquid as a defense technique against potential predators.

Evolutionary Relationships of Crayfish and Grasshopper

The Respiratory System

Crayfishes breathe through gills located between the carapace, which is part of the skeletal system and the body wall. The gills are folded, which increases the surface area for oxygen in the water to diffuse into the blood and for carbon dioxide in the blood to diffuse out into the water. The circulatory system then plays the role of distributing this oxygen around the body.

The respiratory system of the grasshopper is called the tracheal system. Oxygen from the air diffuses into air filled tubes called tracheae and co2 diffuses out. Openings, called spiracles, allows the outside air to enter the tracheae, leading to finer tracheal tubes, and eventually extremely thin tubes called tracheoles. The spiracles are located on the thorax, which is part of the exoskeleton.

Scientific Classification



PHYLUM: Arthropods

CLASS: Crustacean

ORDER: Decapods

FAMILY: Cambaridae

GENUS: Cambarus

SPECIES: Robustus


Phylum Arthropoda

Subphylum Hexapoda

Class Insecta

Order Orthoptera

Suborder Caelifera

Family Acrididae

Subfamily Melanoplinae

Tribe Melanoplini

Genus Melanoplus

Species differentialis

Bonus Fun Facts...

Did you know...

-The first land animals were arthropods.

-Arthropods compose over three quarters of all known living things and fossils.

-Grasshoppers can jump 20 times their own body length.

-There are over 18,000 different species of grasshoppers.

-There are red, white, and blue colored crayfish species.

-350 out of the 500 species of crayfish thrive in the United States.

Grasshopper Dissection
Crayfish Anatomy Part 2

Human Impact

Crayfish are eaten as a delicacy and are even kept as pets. Some varieties of crayfish have been so sought after that they are nearly extinct. On the other hand, humans also drive grasshoppers out of their habitats in the fields and pastures by using chemical pesticides.