Cambarus affinis and Caelifera


Students will learn the anatomy and general aspects of an arthropod with the examples of crayfish and grasshopper. By the end of this lab, students should be able to label external features and understand the characteristics, using compare and contrast with the crayfish and grasshopper.


The crayfish belong to Kingdom Animalia, phylum Arthopoda, class Malacostraca, order Decapod, and family Cambaridae. They mostly inhabit freshwater rivers or streams but can be found in any clean freshwater. They reside under rocks and stones for protection and are nocturnal, which means they hunt at night. This makes them harder to see and can reduce chance of being caught by predators. Crayfish are mainly scavengers but also eat plants and animals like small fish. Their main diet are insects, insect larvae, worms, and eggs of frogs, fish, and other aquatic species. They have a wide range of predators including birds, fish, alligators, snakes, raccoons. Crayfish are an important source of food for many animals.


The grasshopper belongs to the Kingdom Animalia, phylum Arthopoda, class Insecta, order Orthoptera, and family or suborder Caelifera. Grasshoppers tend to live in grassy areas with many plants such as fields, forests.Some can even survive in deserts and others in rain forests. Grasshoppers eat a variety of plants such as grasses, weeds, shrubs, and even bark! Common predators include birds, small mammals, reptiles, other insects, spiders, lizards,and rodents.
Can Eating Insects Save the World - BBC

Niche, Impact, and Population Dynamic

Crayfish are an important source of food for many animals and provides as food for humans too. They are located on the primary consumer level, secondary consumer level, and since they are detritivores they can be considered on the last trophic level too.Humans sometimes use crawfish as bait and also catch them and sell them. But crawfish can also be labeled as an invasive species and can throw the ecosystem they invaded out of balance. They bring in more competition for food and space in a given area.

Crayfish population appears to be self - regulated and stabilized.They have dominance in biomass and play a fundamental role as they interact with a range of species.

Grasshoppers are primary consumers and eat producers. Many animals eat grasshoppers and the grasshoppers also provide nutrients for plants with their droppings.Grasshoppers can have a negative impact when they come in large numbers. They can destroy crops and eat anything plant material in their path, resulting in loss of food(and money for humans) for animals and humans. There comes huge economic losses with the destruction of crops and livestock feed. By consuming all plant life, they can cause major disturbances in ecosystems and nutrient cycles. When an outbreak of grasshoppers occur, harmful chemical pesticides are used to get rid of them, which in turn are unhealthy for the overall environment. There seems to be no definite population dynamics and so humans are unable to defend and prepare against the unpredictable outbreaks of grasshoppers in the region.


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Ecological Adaptations of Crayfish

Crayfish have a two pairs of antennae that can detect disturbances and vibrations in the water. Their eyes are located on stems that can rotate completely in either direction. They have large pincers in the front of their body that they use to catch unsuspecting prey and tear it into smaller pieces. Crayfish also use these pincers as warnings to predators. Their hard exoskeleton also serves as a defense mechanism, and if a limb is lost, crayfish can just grow it back during its molting period. Another way of avoiding a predator's eye is camouflage. Most crayfish have adapted to match their habitat's colors.

Adapatations of a Grasshopper

Grasshoppers have powerful mandibles to chew up the plants they ingest. Some grasshoppers have bold colors that tell predators not to eat them, while the less flashy grasshoppers use camouflauge to blend in with their surroundings. Most grasshoppers don not have functional wings and use their specially adapted hind legs to leap incredible distances. By using these long thin legs they can belt out mating songs or territorial sounds. The grasshoppers that do have functional wings use them to fly long distances and are efficient fliers, especially with their skinny elongated bodies.Antennae are extremely important to grasshoppers;they can detect moisture in the environment and possible food sources.