Two Arthros in a Pod

by Edward Cen Period 4 Mrs. Guzman

Objectives

Students will be learning about the external anatomy and structure of arthropods, the grasshopper and crayfish through a demonstration lab. Students will focus on the organs, structures, and functions of the respiratory system through diagrams. Students will also understand the ecological role of the crayfish and grasshopper.

Background Information

Arthropods are a large phylum of animals that are invertebrates and have the special evolution of jointed appendages, such as a head, thorax, and abdomen. They include insects, crayfish, spiders, centipedes, and others.


The two in our lab today is the grasshopper which contains many species but is the suborder Caelifera. The grasshopper is an insect which eats plants and small insects. The predators of the grasshopper include rodents, spiders, birds and frogs. Grasshoppers prefer to live in the fields and meadows because they feast mainly on crops. They have a special adaptation of hair on their abdomen and feet with which they use to hear.


The other arthropod we study today is the crayfish, which is an aquatic animal that is a bottom feeder and dweller. Like grasshoppers, there are hundreds of species that live in all kinds of habitats, from freshwater to seawater but all are a superfamily called astacoidea. Crayfish eat worms, insects, plants, larvaes and eggs. They also have predators such as raccoons, oppossums, muskrats and snakes. Crayfish have adapted to being nocturnal and hunting at night to avoid predators. Also, crayfish have adapted swimerettes under their abdomen for their eggs.

Grasshopper Food Web

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Crayfish Food Web

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Crayfish External

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Grasshopper Respiratory

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Crayfish Respiratory

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Respiratory System

Grasshopper

The resiratory system begins with the abdomen where 10 sets of spiracles take in and take of oxygen and other gases. The oxygen then goes into the tracheae and the smaller tracheoles where the gas is spread around the body and is diffused into the body. The air sacs of the grasshopper serve as a storing and exchange place for oxygen and carbon dioxide. The respiratory system is used in combination with the circulatory to provide oxygen and nutrients to the body.

Crayfish

The respiratory system begins with the gills where oxygen is taken in from water. There, the oxygen and blood is exchanged across the gill surface by circulating around the branchial chamber by the beating of the gill bailer. The circulatory then circulates the oxygen around the body.

Human Impact

Grasshoppers are a great source of food for humans, they contain tons of protein and are an abundant supply. Unfortunately, they are also a pest and known as "locusts" and often cause billions of dollars in damage when they rampage fields for food. They can eat half of their body weight in one day!


Crayfish are also an abundant source of food for humans. Commonly caught in traps, they are especially good game in this month, April! You can find crayfish easily because they tend to hide under rocks; the bigger the rock, the larger the crayfish.

Do you think you know your arthropods? Test Yourself!