The Amazing Arthropods

Arthropod Dissection Lab by Katherine Lee; Vu P1

Objectives

Students will observe the similarities and differences in the external anatomy of crayfish and grasshoppers. They will distinguish whether certain traits are those of Phylum Arthropoda of belong to Class Insecta of Crustacea. Students will also take a closer look at the respiratory system of an arthropod.

Background Information of Crayfish

Taxonomy:


  • Kingdom- Animalia
  • Phylum- Arthropoda
  • Subphylum- Crustacea
  • Class- Malacostraca
  • Order- Decapoda
  • Family- Cambaridae
  • Genus- Cambarus


Predator-Prey Relationships:

Crayfish are omnivorous eating fish, shrimp, water plants, plankton, snails, and more. They are also scavengers and will eat dead organisms, as long as they're relatively fresh. Crayfish are known to be consumed by animals such as opossums, muskrats, and snakes.


Habitat & Niche:

Crayfish can be found mostly in aquatic or semi-aquatic environments throughout Canada and the United States. They can be found in any body of water that isn't too polluted. However rivers and brooks are the main living habitat for crayfish because of the water clarity and thin ice conditions.


Adaptations:


  • Crayfish adapted eyes on short stems that move around allowing them to see in all directions.
  • They have 2 pairs of antennae that detect movement in the water.
  • Female crayfish have adapted a way of storing sperm until they're ready to lay eggs instead of fertilizing immediately.
  • The color of a crayfish tends to reflect their habitat so they can camouflage.
  • The crayfish's front pincers help bring food to the mouth and tear it into smaller pieces.


Did you know?

  • The oldest fossil records of crayfish, found in Australia, are believed to be 115 million years old.
  • Crayfish tail meat is used as baits for channel catfish, pike, largemouth bass, and muskellunge.
  • The most consumption of crayfish is in regions like Scandinavia, Spain, China, France, and the United States.
  • Crayfish have a significant calorific value and high sodium and protein content with almost no fats and carbohydrates.

Respiratory System of a Crayfish

Crayfish have the ability to breathe underwater because of their gills. A crayfish's gills are located outside the body between the body wall and the carapace. The gills are attached to the walking legs - each leg has a gill attached - so that when a crayfish walks the gills spread allowing more oxygen to enter. There is a thin, transparent layer of exoskeleton separating the gills from the body cavity so that water covers the gills without getting in to the body cavity.
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Background Information of a Grasshopper

Taxonomy:
  • Kingdom- Animalia
  • Phylum- Arthropoda
  • Subphylum- Hexapoda
  • Class- Insecta
  • Order- Orthoptera
  • Suborder- Caelifera


Predator-Prey Relationships:

Grasshoppers are fond of cotton, oats, wheat, and alfalfa. However they will also consume grasses, weeds. shrubbery, and leaves. Newborn grasshoppers, nymphs, are too fragile to digest tough plants so they eat easily digested plants such as shoots, grasses, and clover.


Habitat & Niche:

Grasshoppers can be found in gardens, fields, on crops, and in forests in almost all climates in the world. The northern grass hopper lives in a variety of habitats in including mountain meadows, bogs, and swamps.


Adaptations:


  • Some grasshoppers eat toxic plants and store the toxins in their body to discourage predators.
  • Grasshoppers have specialized hind legs that allow them to jump almost a meter.
  • Since it has five eyes and no ears, grasshoppers hear through an organ in its abdomen called a tympanal organ.
  • Females dig a hole with their abdomen to lay eggs.


Fun Facts:

  • Some grasshoppers spit out a brown liquid as a defensive behavior in response to being handled.
  • Before molting, grasshopper do no eat and are less active.
  • During the molt, they swallow air to build up pressure to split from the old cuticle.
  • Females are larger than males and have sharp points on the ends of their abdomens.
  • They can make sound by rubbing their wings or legs together.

Respiratory System of a Grasshopper

Gases are exchanged in a grasshopper through the tracheal system but it begins at the spiracles where air is first taken into the body. The tracheal system is composed of 10 pairs of spiracles, located laterally at the body surface near the abdominal area.


  • Spiracles- Small holes where tracheae open to the outside and where air is taken into the body. They are guarded by valves controlled by muscles that enables the grasshopper to open and close them. Hairs also filter out dust as air enters the spiracles, They open to small spaces called atria that continue to tracheae.
  • Tracheae- This is a system of air-filled tubes in which oxygen and carbon dioxide gases are exchanged between tissues. These fine tubes have a wall of single layered epithelial cells.

  • Air sacs- Where oxygen flows to once it has entered the spiracles. They serve as temporary storage spaces for air as oxygen is circulated throughout the grasshopper's body.