Crayfish Invertebrate Research Paper

Crayfish Invertebrate Research Paper

Crayfish are interesting animals to study. Through invertebrate research, experimentation, and observation, there has been much to learn about with these animals. There is much to know about these creatures, including their classification in the "animal kingdom." Anatomy as well as how the crayfish reproduce is an important aspect of these organisms. Perhaps the most important part of the crayfish is there ecology. Studying ecology alone can give substantial information on the life of the animal (or in this case crayfish). Experience with the crayfish had become an increasingly important factor in getting to know more about the crayfish. Observations of their behavior have brought us many first hand interpretations of how these critters eat, wander, defend, escape, live, etc. Experimentation on behavior has given us quantitative data on certain aspects of the crayfish after we hypothesized about the outcomes. We drew conclusions from the data and have related certain specific behavior patterns with past readings on animal behavior.

Crayfish, also called crawfish or crawdad, are closely related to the lobsters, crabs, and even shrimp in the class malacostraca. Crayfish are related to lobsters, crabs, pill bugs, krill, and many more in the phylum crustacea. More than half of the more than 500 species of crayfish occur in North America, especially in Kentucky and Louisiana in the Mississippi basin. Crayfish also live in Europe, New Zealand, East Asia and throughout the world. Mostly all crayfish live in freshwater, although a few survive in salt water. A joined head and thorax, or midsection, and a segmented body characterize crayfish. The body can appear dark red, yellow, green, or dark brown in color. There are also many crayfish that have the potential to turn a bright blue color during their lives. Our crayfish had this potential, as some did turn blue, so they belong to the species Alleni. Our crayfish are classified as follows: Kingdom: Animalia; Phylum: Crustacea; Class: Malacostraca; Order: Decapoda; Family: Cambaridae; Genus: Procambarus; Species: Alleni.

All animals in the crustacea phylum have two pairs of antennae, a pair of mandibles, a pair of compound eyes (usually on stalks), and two pairs of maxillae on their heads, followed by a pair of appendages on each body segment. The appendages are biramous, meaning primitively branched, and although this condition is modified in many species, adults always have at least some biramous appendages. Crustaceans respire with gills. Animals in the Malacostraca class have the hard, calcified exoskeleton typical of crustaceans. The body is divided into three tagmata: cephalon, thorax, and abdomen. The head and thorax are combined into a cephalothorax and may be difficult to distinguish. Most malacostracans have five segments in the head, eight in the thorax, and six in the abdomen. Usually, each segment has a pair of appendages, but in some organisms appendages are lacking on several abdominal appendages.

Crayfish are usually about 7.5 cm, or 3 inches long, and like other arthropods, have a hard but flexible exoskeleton. The underlying epidermis secretes it. An animal with a hard exoskeleton has little need for any additional body wall, thus the body wall consists mainly of the exoskeleton and epidermis. The original body walls in wormlike ancestral arthropods consisted of continuous layers in the body wall. Now crayfish have specialized individual muscles. Potentially continuous layers of circular and longitudinal muscles would be useless under a solid and immovable object like the exoskeleton. The exoskeleton gives a crayfish strength, structural support, and protection from predators. The exoskeleton can limit growth due to its hardness and immovability. Because of this, crayfish regularly get too large for their skeletons. They will shed the skeleton, and grow a new and larger one. This process is called Diagram of a Molting Crayfish

molting. For a few days following each molt, crayfish have soft exoskeletons and are more vulnerable to predators. Molting occurs six to ten times during the first year of rapid growth, and happens less often during the second year towards the end of a crayfish's life. A complicated musculature, known from the circular and long muscles of the ancestors, inserts on the inner surfaces of the exoskeleton and moves its many parts. The exoskeleton between adjacent regions is thin and flexible to allow motion. There is also a complicated endoskeleton made up of internal processes, called apogees, from the inner surface of the exoskeleton. The gills and the anterior and posterior regions of the gut are covered by a thin exoskeleton. Many parts of the exoskeleton have small, movable bristles called setae. These can be seen at many places on the body. The spines tend to be the thicker, jointed processes from the exoskeleton, and the teeth are processes that appear to be outgrowths that aren't really jointed.

The body of a crayfish is made of a series of segments. In malacostracans, there are 19 segments, but not all visible to the naked eye. Each segment has a visible pair of jointed appendages. In ancestral crustaceans, all segments were alike, as well as the appendages. The specialized appendages on present crayfish don't look alike. Groups of aligned segments and their appendages tend to function the same way and together accomplish certain specialized tasks. Tagmata result from this general division and separation of the body. Originally in crustaceans there were three tagmata; the head, thorax, and abdomen. The crustacean head is always composed of five segments, but the numbers vary in the thorax and abdomen between different crustaceans. There are always eight segments in the thorax and usually six in the abdomen for malacostracans. Each of the eight segments in the thorax is called a thoracomere. They have muscles and are very calcified.

The body is still divided into three tagmata but now they are called the cephalothorax, pereon, and abdomen because the pattern of "tagmatization" has been changed by modern science in just about all crustaceans. The cephalothorax, in many crustaceans, is the combined form of the head and part of the thorax. The cephalothorax has five head segments and the first three thoracic segments, which are segments of the thorax. The appendages of the anterior three thoracic segments are maxillipeds, are part of the cephalothorax, and function as mouthparts. Of the mouthpoarts, the mandibles are the most anterior of them. The posterior thorax, composed of five segments, is the pereon. Its segments are pereonites. The appendages of the pereonites are pereopods, and they function as walking legs or pincers. Besides walking, the

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