Arthropods: The Creepy-Crawlies


A Lovely Grasshopper

The common grasshopper belongs in the suborder Caelifer in the order Orthoptera. Grasshoppers are characterized by short antennae and short ovipositors. Grasshoppers are part of the insect family, and have many characteristics of insects. Grasshoppers have three pairs of segmented and jointed legs, at least one pair of antennae, multi-faceted eyes, an exoskeleton, and three distinct body segments-the Head, the Abdomen, and the Thorax. Grasshoppers are known for their ability to leap very high up into the air, and are also known for the cricket sounds they make by rubbing their legs against their thoraxes. The scientific name for Grasshoppers are Chorthippus brunneus.

Today's Objectives:

Students will:

  • Be learning about the external and internal anatomy of a grasshopper.
  • Focus on the organs, structures, and functions of the respiratory system.
  • Also understand the ecological role of the grasshopper

More about Grasshoppers

Grasshoppers are among the most common of insects, and can be found virtually anywhere. The ideal habitat for a grasshopper is a low-lying area rich in grasses and leaves. Although a grasshopper's diet usually only consists of grasses and leaves, grasshoppers are not known for being finicky, usually just eating about everything. Grasshoppers are herbivores, and eat plant matter. Grasshoppers are not predatory, but rather are prey for other predators. Larger carnivorous insects eat the grasshopper, such as the praying mantis, arachnids such as scorpions and spiders, rodents, snakes, and some frogs. Grasshoppers make their characteristic chirping and cricketing sound by rubbing their hind legs against their thorax, and use it as a mating call. Upon fertilization, the egg will develop and be laid by the female, hatching typically a month after being laid. Larvae, or nymphs, hatch out of the egg and enter the world. Given it survives that long, the average nymph or larvae will mature into an adult grasshopper in about 3 months. All in all, grasshoppers aren't very long lived as organisms go, having an average lifespan of only one year.

Evolutionary Traits

The grasshopper has developed numerous evolutionary traits that enable it to survive despite the high number of its predators. The grasshopper, like many insects, possess wings and the ability to fly, enabling the grasshopper to get out of threatening positions easily. In addition to wings, the grasshopper has powerful hind legs that it can use to lunge or jump out of harm's way. The grasshopper is always feeling jumpy. Being an insect, the grasshopper has a hard exoskeleton that can protect it to some degree against certain predators.
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The External Anatomy of our friend the Grasshopper

The Grasshopper has many of the basic physical features of Insects, having a thorax, head, and abdomen, three pairs of thin, segmented legs, wings, and a hard exoskeleton. For breathing apparatuses, the grasshopper has openings known as spiracles between the body and legs. The Grasshopper also possesses separate genitalia as male and female are separate, tibia, and a tarsus.
Grasshopper Anatomy Part 1
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How the Grasshopper Breathes (The Respiratory System)

The grasshopper breathes using openings on the sides of its body known as spiracles. All in all, the grasshopper possesses ten pairs of spiracles (eight on the abdomen and two on the thorax). To protect the spiracles and ensure a level of homeostasis, valves that line the spiracles open and close in response to environmental changes, and hairs located around the spiracles prevent foreign objects from falling in. The respiratory system of the grasshopper comprises of a series of air sacs, a spiracular trachea, a visceral trachea, and spiracles. The atria are small spaces connected to the spiracles, feeding into larger spaces known as the trachea. Oxygen is taken in by the first 4 spiracles, and the last 6 excrete carbon dioxide.

Quality Crustaceans: The Crawfish (Or Crayfish)

Crayfish are of the order decapoda, and are water-loving crustaceans. The adult crawfish strikingly resembles a miniature lobster, and has a jointed body, usually a mottled brown, light brown, or gray. Crayfish, however turn bright red when cooked, much like shrimp. The eyes of crayfish are on separate stalks, and the cray fish and the lobster are actually, in a way, related. Both organisms are sea crustaceans that belong to the superfamilies Astacoidea and Parastacoidea.

Taxonomy of the Crawfish/Crayfish

  • Kingdom: Animalia - eukaryotic, multicellular
  • Phylum: Arthropoda - Segmented body, thick or stiff exoskeleton
  • Class: Crustacea- Aquatic, possesses swimmerettes
  • Order: Decapoda - Scavenger, 10 legs
  • Family: Astacoidea
  • Genus: Procambarus

Today's Objectives

Students will:

  • Be learning about the external and internal anatomy of a crayfish.
  • Focus on the organs, structures, and functions of the respiratory system.
  • Also understand the ecological role of the crayfish.

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About the Crayfish

Crayfish are prized as a seafood, and is highly sought after. Unlike most other seafoods, only a small fraction of the crayfish is actually edible to a human. While commercially fished, most crayfish are not endangered in any sort of way. Crayfish are ecologically important to their habitats, as they are scavengers. Being scavengers, crayfish help to keep the floor of their habitat clean, picking through the dead remains of other animals, and other waste, Without organisms like the crayfish, seabeds, riverbottoms, and the bottoms of lakes and ponds would be polluted, dirty, and not suitable for life. Because of its scavenging nature, the crayfish resides in rocky outcrops or around rocks. Crayfish generally are a tell-tale sign of pollution in an area as they have very little tolerance for pollution, being able to die out from only traces of contaminants. Crayfish also do not fare well in cold temperatures, and prefer moderate and warm climates, of around 70-90 degrees Fahrenheit. Being small and common, the crayfish has many predators. Raccoons, opossums, humans, bass, and eagles all prey upon crayfish. Crayfish carry their eggs with them. Mothers have been shown to carry around their fertilized eggs in their swimmerettes for protection. When hatched and ready, the young simply detach themselves from their mother and try to survive until adulthood. For crayfish, it usually takes 3-4 years to reach adulthood. The average life expectancy of a crayfish is 3-8 years.

The Evolution of Crayfish

Having evolved from more primitive crustaceans, crayfish have a wide array of defenses against predators. Firstly, most of the crayfish is covered in a thick and hard exoskeleton, making it hard to chew or attack. Secondly, crayfish possess a small set of pincers that can be used in defense. These pincers are not as effective as the massive pincers on lobsters, mind you, but for a crayfish, small pincers do the job. Lastly, Crayfish instinctively choose to hide in rocky outcrops or rocks, camouflaging against the brown or grayish rocks. And, should a predator find a crayfish, it could be hard to get the crayfish out.
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Anatomy of a Crayfish

Crayfish, like grasshoppers, possess many traits of the arthropod group. Like grasshoppers, crayfish have exoskeletons, and antennae. However, crayfish possess gills instead of spiracles, have a pair of pincers or claws, lack wings, are aquatic, and has a fan-shaped tail with swimmerettes. Crayfish possess swimmerettes, gills, Antennae, antennule, cheliped, a few pairs of walking legs, and a distinct abdomen. Crayfish differ from grasshoppers too if compared internally. Crayfish have a digestive system organ known as the green gland that grasshoppers lack. All in all, crayfish have an encephalon, stomach, heart, gonad, extensor muscles, anus, flexor muscle, digestive gland, ganglion of ventral nerve chord, ventral nerve cord, maxillipid, an esophagus, mandibles, a mouth, and a set of eyes.

Respiratory System of Crayfish

Perhaps the biggest difference between crayfish and grasshoppers is that crayfish have and use gills to breathe, whereas grasshoppers use spiracles to breathe. Crayfish are unique because their gills are outside of their body, between the carapace, exoskeleton of the cephalothorax, and the lateral body wall, branchial chamber. They are attached to the walking legs so that the crayfish can walk and breathe. In addition to all of the above, crayfish have a water pouch, akin to how fish store air in for buoyancy, however the crayfish can utilise the water pouch to 'breathe on land' of sorts, able to travel for short periods of time on land out of the water.
Crayfish dissection-- Internal Anatomy
Crayfish dissection-- External Anatomy