Massive Mini Monsters: Jointed Legs

Crawfish and Grasshopper Dissection Aaron Wong Per.6 Guzman

The Joints

Arthropods are the most diverse phylum of all animals, making up over 80% of all animal species with over 1 million described species. The name arthropod comes from Greek and is the combination of the words for joint, arthron, and leg or foot, podos, as arthropods were the first organisms to have jointed appendages. Arthropods can range in size from the lightest insects at 25 micrograms to the crustaceans that can be 4 meters long. This disparity is because crustacea didn't evolve for life on land, where the body needs to support more weight as there isn't water to support the body mass. This is a similar problem that the first land plants faced when evolving. Arthropods are some of the oldest animals on earth.

Objectives

Students will learn about the internal and external anatomy of the crawfish and grasshopper. Students will take note of the organs, structures, and functions of the skeletal system of arthropods. Students will learn about the ecological roles of arthropods like the crawfish and grasshopper.
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Taxonomy tree of arthropods; crawfish are in the subphylum crustacea and grasshoppers are in the subphylum hexapoda.

The World-Travelling Crawfish

The crawfish belongs to the families Parastacidae, Astacidae, and Cambaridae . The common name, crawfish, comes from French, and the variants on crawfish are based on geography; the crawfish is called crayfish in eastern US, crawdad in central and southwestern US, and crawfish further south. The study of crawfish is called astacology. The three families are also split by geography; Parastacidae are found in the Southern Hemisphere, Astacidae in western Eurasia and western North America, and Cambaridae in eastern Asia and eastern North America. Crawfish live in freshwater bodies of water that do not freeze to the bottom, such as streams. Crawfish dig holes in small rocks for homes.
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Crawfish are both omnivores and scavengers, eating worms, insects, fish eggs, and salamanders, as well as the remains of dead animals. Animals such as turtles, perch, and raccoons as well as birds such as the kingfisher and heron prey on crawfish. Crawfish have adapted to life under water by absorbing oxygen through feathery gills, which have feathers to increase surface area and thus the oxygen intake. Crawfish also have swimmeretes to swim backwards very quickly to evade predators. Crawfish are mostly raised for consumption as food but can also be pets.
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Taxonomy tree of the subphylum Crustacea.

The Straight Flyers

Grasshoppers are insects in the order Orthoptera and suborder Caelifera. The name Orthoptera came from Greek for straight and winged, Grasshoppers are herbivores, eating grasses, weeds, and fruit. Some grasshoppers migrate south in the winter, but others do not. Grasshoppers are preyed upon by many animals, such as bass, toad, turtle, and other arthropods such as ants and spiders, Grasshoppers have been seen as pests to farmers and are controlled by pesticides. Locusts, certain species of grasshopper, have caused havoc by swarming and damaging crop fields. Grasshoppers change throughout their life cycle, performing partial metamorphoses as development. Grasshoppers are capable of making noise by rubbing the femurs of legs or snapping wings, which can help grasshoppers to attract mates.
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Taxonomy tree of the group Neoptera. Grasshoppers are in the order Orthoptera.

Inside Insecta and Cut Crustacea

Skeletal System

The skeletal system of arthropods is comprised of an exoskeleton, a covering on the arthropod made of chitin. The exoskeleton provides protection of the body within, support the animal, and a place where muscles can attach for the arthropod. There are spiracles on the exoskeletons of land arthropods, holes that allow oxygen to enter the respiratory system. Spiracles can be opened and closed by the contraction of muscles. in order to grow bigger, the arthropod moults and sheds the old exoskeleton to grow another, bigger one.
Crayfish Moult
A video of a Crawfish moulting.
Crayfish Dissection
This video goes over the dissection of a crawfish.
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Internal views of a crawfish.
This page goes describes a crawfish dissection.
Grasshopper Dissection
This video goes over the dissection of a grasshopper.
This page goes over a grasshopper dissection.
Grasshopper dissection lab.
An online quiz over arthropods.