Arthropod Analysis

By Clarise Trinh, Guzman PAP BIo P4

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Objectives

The objectives of this arthropod laboratory investigation are to examine two preserved arthropods - a grasshopper and a crayfish, look for similarities and differences in these two animals (phylum and class traits), identify the different parts and organs of the two arthropods, and further investigate the bodily systems of the animals.

Crayfish

Scientific Name: Cambarus

Family: Astacoidea

Phylum: Arthropoda

Class: Crustacea

Crayfish live in ponds, lakes, streams, and rivers and live all around the world. They are very durable animals and can tolerate a wide range of temperatures and salinities. However, crayfish are very intolerant of any pollution of their environment. Crayfish eat aquatic plants, mollusks, insect larvae and adults, tadpoles, and small eggs. Crayfish tend to hunt for food at night. Crayfish moult - shedding and regrowing their exoskeleton. Raccoons, foxes, muskrats, snakes, turtles, and birds eat crayfish. Crayfish are very important to stream ecosystems and maintain a high level of water quality by feeding, foraging, and burrowing.

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Grasshoppers

Scientific Name: Caelifera

Phylum: Arthropoda

Class: Insecta

Order: Orthoptera

Grasshoppers feed on a variety of plants. Bird, lizards, spiders, and rodents eat grasshoppers. Grasshoppers are ectothermic and have bilateral symmetry. Grasshoppers are found on all continents except for Antartica. They go through incomplete metamorphosis and shed their skin. Grasshoppers can be crop pests because they can eat so much plant material. Grasshoppers have two pairs of wings and large eyes. Males have special structures on their wings that produce sound when rubbed together. Females are larger, but males are more colorful

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Grasshopper Dissection
grasshopper life cycle

Background Information

Grasshoppers and crayfish both belong to the phylum Arthropoda. However, grasshoppers belong to the class Insecta, and crayfish belong to the class Crustacea. Both grasshoppers and crayfish have an exoskeleton and a segmented abdomen. Grasshoppers have wings while crayfish do not, but crayfish have telson while grasshoppers do not. Both creatures have antennae, mouthparts, eyes, jointed legs, and separate sexes. However, grasshoppers have spiracles for breathing, while crayfish have gills for breathing. Their excretory organs are also different - grasshoppers have a Malpighian tube and crayfish have a green gland.

External Anatomy

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Internal Anatomy

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Interesting Facts

Ancestral arthropods were the first land animals.

Arthropods are a highly successful group of animals—they account for over three quarters of all currently known living and fossil organisms.

Arthropods have an open circulatory system.

When arthropods grow, they must molt their exoskeleton.

Arthropods go through metamorphosis.

The word arthropod means 'jointed feet'.

Arthropods do not possess blood vessels.

Arthropods are divided into four basic groups: Myriapods, Chelicerates, Hexapods, and Crustaceans.

The oldest arthropod known to have lived on land is the Pneumodesmus newmani.

Skeletal System

Arthropods have exoskeletons, external skeletal systems that are made up of chitin and calcium carbonate. The exoskeleton protects the body and its internal organs against predators, supports the body, and allows for movement through the contraction of attached muscles. Exoskeletons are tough and durable, and they are segmented to allow for movement. To move, muscles must cross a joint inside the exoskeleton, and the shortening of the muscle changes the relationship of the two segments of exoskeleton. The exoskeleton is acellular and does not grow as the organism grows, so arthropods must periodically shed their exoskeletons, regrow them, and strengthen them (this process is called molting).

Empty Exoskeleton

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Blue Lobster Molting (full process)