Crayfish

CRAYFISH

Phylum: Arthropoda

DIGESTIVE SYSTEM

The crayfish's digestive system consists of a mouth, cardiac and pyloric stomach (located near the head), an digestive gland, intestine, and an anus.

 http://www.cnsweb.org/extra/digestvertebrates/GITFigures/EvolutionDigestiveSystemCrustaceanCrayfish%20F12_07.gif

This simple digestive system includes many enzymes to aid in chemical digestion. There is a cardiac stomach, located above the mouth, storing and grinding the food down. The food is then led into the pyloric stomach, transporting the food into the digestion glands to be digested. The digestive gland contains many enzymes, aiding to absorb nutrients, and break food down extensively. The Crayfish is the only organism to have more than one stomach, compared to the other organisms. The system is based on enzymes, and it is a simple digestive system, therefore this organism can consume a lot, and the digestive system is fairly quicker compared to an complex digestive system.

CIRCULATORY SYSTEM

The Crayfish has no veins, making it an open circulatory system. Similar to other crustaceans, there are two arteries from the dorsal sided heart, tracing down both Posterior and Anterior sides of the body, into tissue spaces called Sinuses. Blood pumps from the heart, through arteries, into open sinuses.

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The Crayfish contains a three chambered heart. The vessels leading from the heart are led into a ventral sinus, collecting the blood. The blood is filtered through the heart, then is lead back towards the heart. 

SKELETAL/MUSCULAR SYSTEM

The Crayfish is the only organism to have an exoskeleton. Having an exoskeleton could be an advantage, due to the fact on how it is "armor-like". A disadvantage may be in case of anything, if the exoskeleton were to crack or break, the crayfish's internals are immediately being exposed. Compared to the Earthworm, the earthworm does not even contain a skeletal system. Although, the earthworm is almost made entirely of muscle. Compared to the Rat, Human, and Frog, these organisms contain endoskeletons, which are complete opposites when it comes to endo/exoskeletons. Again, making the Crayfish the only organism to have an exoskeleton. 

The Crayfish's muscular system includes powerful abdominal muscles to rely on movement. It also allows the organism to swim backwards rapidly and powerfully. Multiple legs also to aid in movement. Unlike other organisms, the tissues do not support the skeletal system, for the muscles line the exoskeleton, compared to muscles supporting an endoskeleton. The muscular system for the crayfish are made mostly of ligaments.

RESPIRATORY SYSTEM

The Crayfish's respiratory system uses gills. These Gills are connected to it's legs. Whenever the Crayfish walks, it uses it's legs to filter the water for respiration. The Crayfish has a water "pocket" allowing it to walk on land as well. 

The Gills have high surface area, because of the flat stacks of gills. Each plate has a spiked-like shape to extend further surface area. If you take a closer look at the Gills, each "flap" contains blood capillaries to aid in gas exchange. This respiratory design is highly efficient, for it adapts on both land on water. If the respiratory layout of this organism were to be inefficient, this organism would result in extinction; since it clearly would not be able to survive.