Astounding Arthropods

Arthopod Lab: PAP Bio - Vu 7 - April 6, 2014 - J Chen

Objectives

Students will be able to observe and compare the external anatomy of arthropods.

Acknowledging Your Arthropods

The arthropods we are looking at are the crayfish and the grasshopper. The grasshopper's scientific name is Caelifera and the crayfish's scientific name is Astacoidea. The crayfish lives in most any source of freshwater that is not over-polluted such as lakes, ponds, and streams. Crayfish feed on worms, insects, insect larvae, and eggs of fish. They are prey upon by raccoons, opossums, snakes, and muskrats. Crayfish clean up dead plant and animal matter that has gathered on bottoms of water bodies and have adapted to their environment by having short "stems" which their eyes rest upon, allowing for full rotation of the eyes for better vision. They often have shells that blend into their environment to offer protection from predators. Their pincers also aid in the crayfish's burrowing and eating, as well as some protection. The grasshopper lives in most any area that isn't under harsh condition like the freezing cold or dry heat. They usually live in grassy areas, forests, trees, most any area with vegetation. The grasshopper is preyed upon by larger insects, spiders, birds, lizards, and turtles. Food for them consists mainly of grasses, leaves, and cereal tops, though they can be omnivorous. The grasshopper can return nutrients to plants and is an available food source for other animals. The grasshopper has adapted to its environment by developing strong jaws to grab, crush, and chew its food. Feelers in front of the mouth allow for a taste in what the grasshopper is about to feed on. The grasshopper also has strong hind legs, which allow them to jump far distances and escape from danger.

Integumentary System

An arthropod's integumentary system is made of protective layers of proteins and a tough polysaccharide called chitin. In addition to chitin, proteinases, resilin, and some waxes (for insects). The chitin layer can vary from a hard, thick armor, to a papery thin shield. The crayfish has a stiffer, more rigid exoskeleton, whereas the grasshopper has a thinner one. The integumentary system of these arthropods also provide senses. The crayfish has exterior antennules which aids in its perception to smell and touch. The crayfish also has three maxillipeds which aid in sensory and touch perception as well. It is spilt into two major sections, abdomen and thorax. The exoskeleton covering the abdomen has segments, allowing the crawfish to tuck in the lower part of its body if needed. The shell over the crayfish's claws act as protectors and can shield away danger. Compared to the crayfish, the grasshopper is quite similar. The grasshopper also has antennae used to touch and sense things around it. Both arthropods molt, or shed their exoskeleton, revealing newer layers of protection underneath. Proteinases aid in the digestion of the endocuticle when molting. The exoskeleton of both functions to prevent water loss and provide protection against pathogens, parasites, and predators. Resilin is found at the joints of wings and legs. it is a rubbery protein that stores energy due to tension. Lastly, a waxy layer that some insects have, like the grasshopper, functions to prevent water loss and aid in protection.

Facts of the Arthropoda...

-Arthropods have been on Earth since about 428 million years ago.

-Arthropods compose approximately 90% of the animal kingdom.

-All arthropods have an exoskeleton.

-Ancestral arthropods were the first land animals

-The oldest land living arthropod is the Pneumodesmus newmani.