Anatomy of the Amazing Arthropods

by Kierra Morris

Arthropods: Crawfish

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  • Crawfish go by many names, "Astaciodea" is the scientific name, and then we have the interpretations- crayfish, crawdads, freshwater lobsters, and mudbugs. The crawfish has an appearance similar to a small lobster, where it has the same type of segmented pattern and physical characteristics like colour, small eyes, and eight legs.
  • Crawfish live in all fresh water environments with the exception of some species being able to thrive sea/salt water. Many crawfish can survive in a large span of temperatures, through the do not survive well in extremely cold conditions. Many crawfish are found hidden under rocks, in logs and twigs, and vegetation. The niche of the crawfish is to be an omnivoric scavenger that will eat plants and other animals within their ecosystem.
  • The crawfish prey on small animals like insects, insect larva, frogs, toads, fish eggs, and salamanders. The predators of the crawfish include snapping turtles, fish and frogs large enough to swallow them, alligators, and other large animals. Crawfish adaptations are eyes located at the top of short stalks- which enhances vision, colour differentiation- camouflage to its environment, and chemical signals- to attract mates.

Kingdom: Animalia

Phylum: Arthropod

Class: Malacostraca

Order: Decapod

Trophic Level

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Arthropods, like that of the crawfish and crabs are primary consumers. Depending on their environment and how much variety there is, arthropods can easily move up the food chain to secondary consumers.

Crawfish have been known to larger animals such as angel fish and frogs.


Students will be learning about the external and internal physiology of a crawfish. Their main focus will be directed to integumentary system of this arthropod.



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Walking Legs: As suggested by the name, walking legs are used to achieve mobility. The walking leg is related to a crawfish's respiration because, the gills of the crawfish are attached to the leg. They are connected because when the crayfish walks, they are able to receive oxygen ,this can become a problem because if the leg was detached the gill would break and the respiration process will be severely damaged.

Eye: Arthropods have what we call a "compound eye", which is made of repeating units called ommatidia. The compound eye is excellent at detecting motion, allowing the crawfish to see its predator a lot faster and easier then other animals.

Rostrum: The rostrum is a hard rigid structure, like a beak, that extends from the crawfish's head as a source of protection for the eyes and the brain.

Antennas: The crawfish has two sets of antennas, the smaller ones called the antennules, which are used for gathering information about their environment. The act as vibration and thermal sensors, they somewhat resemble the function of a human hand.

Cheliped: They are large anterior pinches used for protection and hunting.

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Carapace: Carapace is the name of the exoskeleton covering the cephalothorax. This covering sometimes project over the head to act as protection for the eyes, as well as varying degrees of calcification.

Thorax: The thorax is the midsection of the crawfish that has section of four pairs of walking legs.

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Uropod: The Uropod is the posterior appendages found on a wide variety of crawfish. They are used primarily for movement and keeping locomotion.

Abdominal Segments: The crawfish has a total of 7 segments including the Uropod and telson. On the ventral side of these appendages, you can see that this is were swimmerets lie.

Telson: The Telson is the very last appendage, number 7, on the crayfish. The telson has fan-like fins that spread over each side, the telson is used for movement, especially in rapid backward escape swimming.

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Swimmeret: The smaller appendages attached to the abdomen. the first pair can be used to find the sex of the crawfish, in males, they have larger and harder swimmerets, and in females, theirs are softer and smaller.

1st Maxilliped, 2nd Maxilliped, and 3rd Maxilliped, All are small appendages located around the mouth. Their function is to hold the food and use the senses of touch and taste, at the ventral and forward part of the thorax region.


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Green Gland: The green glands are the excretory structures located at the base of the antenna, their function is similar to the kidney, in which blood carries waste to these glands, and then they excrete out the secrete out the waster by using the pores located near the antennas.

Esophagus: The esophagus is a body part the connects the mouth to the digestive tract in the stomach. Food and fluid travels down the esophagus, where enzymes help break it down, and then it is deposited into the stomach.

Stomach: In the stomach of the crawfish is where most of the digestion takes place, the stomach grinds the food and uses stomach acids to further lessen the size of the food. The stomach connects the digestive tract by lying in-between the esophagus, where it receives its food, and the intestine, where it deposits its waste.

Heart: The heart is two chambered and part of the open circulatory system. Blood is pumped into the body cavity and surrounding tissues, and then it diffuses back.

Gonad: Gonads are the male and female reproduction organs, they are located just under the heart. Special swimmerets are responsible fro the release of each sex cell during sex.

Extensor Muscles: The muscle the extends and elongates the crawfish's "tail", abdominal appendages, aids motion movements.

Flexor Muscles: The muscles that bends, helps the crawfish propel through water.

Fun Fact

Crayfish are crustaceans that swim backward but walk forward!

Arthropods: Grasshopper

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The grasshopper is an insect belonging to the phylum arthropodia. A common mistake is the people assume brush crickets or katydids are grasshoppers, but the way to distinguish them apart is the grasshoppers have shorter antennas. The habitat of a grasshopper is quite broad to say the least, grasshoppers can be found in multiple environments because they tend to live where their food is. As there name infers, grass would be the best place to find them, as well as meadows, forests, and grasslands. Their niche is said to be to cultivate crops and range land grasses. These animals are herbivores, and are known for jumping extremely long distances. The grasshopper's prey is usually grass, weeds, and shrubs, The predators of the grass hopper are birds, rodents, reptiles, and other larger insects. Some of their ecological adaptation are long hind legs- used for jumping, the ability to detect moisture in their environment, and shape of antenna.

Kingdom: Animalia

Phylum: Arthropod

Class: Insecta

Order: Orthoptera


Examine the grasshopper's internal and external anatomy. Students look specifically towards the Integumentary system of arthropods.
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Arachnids, insects and crustaceans are similar in that they are all invertebrates. Grasshoppers are separated from the Arachnids and Crustaceans because they have six legs, among other features, while Arachnids can have eight legs and Crustaceans, who have limbs with two parts. Insects have three pairs of legs. They use the legs for walking, but sometimes an insect may have a pair of legs that are specially designed for jumping. Insects also have two pairs of wings.

Dissection Time !


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Ovipositor: (In certain female insects like the grasshopper) it is an organ at the end of the abdomen, by which eggs are deposited. The Ovipositor is often very long and may be modified for piercing, sawing, or stinging, need be for protection.

Fore Wing: The crickets forewing are tough opaque tegima, which are narrow and cover the abdomen and hind wings at rest. When grasshoppers want to be heard, they rub their femurs against their forewings to make a rattling sound.

Femur: The femur is the third segment of the leg, between the tibia and the trochanter. The femur in grasshoppers is enlarged hind femurs with more muscle tissue in them, this allows them to jump the great distances that they do.

Tibia: The fourth segment of the grasshopper leg, the Tibia supports most of the wait of the grasshopper and is covered in razor like hairs called Spurs. The spurs on their legs allow them to grip onto surfaces, make melodic noises by rubbing them together, and grooming.

Tarsus: Tarsus are like the little feet of grasshoppers except that they have a hook on the bottom of them which allows them to grip onto things,

Coxa: The Coxa is the segment that connects the leg to the body, it acts as the functional base for the leg and for its movement.

Trochanter: Commonly seen as the basal segment of a telopodite, trochanters are like hinges that are stuck the femur of the grasshopper, and has restricted mobility.

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Labrum:"The Labrum is a simple, fused sclerite, often called the upper lip, and moves longitudinally, which is hinged to the clypeus."

Prothorax: The Prothorax is the first anterior segment that closest to the head, their main features are the first pair of legs, and the pronotum.

Mesothorax: This is the middle three segments of the grasshopper, it bears the forewings and legs in adult insects.

Palp: Structures used to sense the characteristics of certain food sin their environment.

Antenna: Antennas help the grasshopper by acting as a sensory function, where they are able to detect motion, sound, humidity, and orientation. Grass hoppers have short antennas, the last segments of a grasshopper antennas are called the flagellum, where the size and shape of them differ in each grasshopper species.


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The difference between male and female grasshoppers is that female grasshoppers have a somewhat tapered abdomen that ends in narrow egg laying tube called the ovipositor. Males have more rounded abdomens that turn upwards at the ends, and have four distinguishable plates: cerci, furcula, subgenital and supraanal.

Fun Fact

Grasshoppers can jump 20 times their body length!

Grasshopper are consumed as food all over the world, in China, Mexico, and Uganda.

Effects On Us

The Integumentary System of Arthropods

The Integumentary System is the outer covering of an organisms body, usually the skin, scales, hair, or in this case, the exoskeleton. The Integumentary system is used for protection, which makes grasshoppers and crawfishes lucky. The exoskeleton is made up of a tough polymer called Chitin, this acts as two ways of protection, from predators, as well as from keeping their bodies form drying up when they are in extreme conditions. " The exoskeleton has four layers, namely epicuticle, procuticle, epidermis and basement membrane. The topmost layer, or the epicuticle, serves to lock in water, while the procuticle is the layer that gives strength to the exoskeleton. The third layer, or the epidermis, is responsible in secreting the procuticle. " The disadvantage of exoskeletons being the animals integumentary system, is that when the animal loses its shell, it has no protection at all, as well as that it has to molt every once in a while to adjust to the animals body. The tiny hairs on its legs are also part of the Integumentary system, for crawfish they play their part by detecting motion in the water, and in grasshoppers, they can use it to sense and grip onto objects.

In Arthropods, the muscles are connected to the integumentary system and the exoskeleton because the animals lack an internal skeleton. The Integumentary system acts as a shield for the muscular system and as well as plays a vital part in how it moves. Because the muscles are attached to the inside, the animal has to have the right size of skeleton to move.

Interesting Facts About Arthropods

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

Aquatic arthropods vary in their reproductive methods, with some species using internal fertilization and others external fertilization. Most arthropods lay eggs

The Subphylum Trilobitomorpha is a group of arthropods that were a dominant marine animal between 345 and 600 million years ago.