Digestion
Digestion is one of the many necessary functions that all animals use in order to survive. Because food is too large to pass through cells, the digestive system breaks the particles into small pieces that will fit through the cell membrane and be used for nutrients. In humans, food goes through various parts of the body to be broken down until it reaches the small intestine, which is covered with finger-like projections called villi, which absorb the nutrients from the food as it passes by. The nutrients pass through the villi and enter the blood stream, where they are transported throughout the body to be used for energy. Nutrients that are not being immediately used are stored in various places. For example, glucose, a monosaccharide, is stored in the liver. When glucose is ingested and we breathe in oxygen, a process called cellular respiration occurs, creating water, carbon dioxide - which we breathe out as waste - and ATP, which we use for energy.
Digestion in Mantis Shrimp
For food, Mantis Shrimp usually eat a variety of animals. Mantis Shrimp who spear their food usually eat types of fish, while those who smash their prey usually eat clams, crabs, and snails [1].
Although Mantis Shrimp usually live inside of holes in rocks and coral, they venture out - even if only for a short period of time - to capture prey. Mantis Shrimp usually will wait for prey to pass by, when they will quickly exit their burrows to capture their food. Then, depending on their classification, they will either stab their prey with a spear-like claw - which is what Spearers do - or, if they are Smashers, they will use a club-like appendage (called a raptorial appendage) to smash open the shells of and kill their prey. Smashers also have a spear that can cut their prey as it moves. In their digestive system, crustaceans have one long tube that aids in digestion, where food is ground up and nutrients from the food is absorbed through digestive glands. Mantis shrimp insert food through their mouth, then it goes through the digestive tube, and the waste is expelled through the anus. Some crustaceans have a cardiac stomach and a pyloric stomach that aid in digestion. The cardiac stomach is located above the mouth and grinds and mashes the food. The pyloric stomach is where the mashed up food is sent to be absorbed by digestive glands containing many enzymes that break down food and absorb nutrients.