Arthropoda
An Arthropod is an animal that comes from the Phylum Arthropoda, which in Greek means “jointed leg”. The
animals in this Phylum are invertebrates that have an exoskeleton, a segmented body, and jointed
appendages. This phylum contains creatures such as insects, arachnids, crustaceans (crabs, lobsters,
shrimp), and others.
The Digestive System of the Arthropod
Arthropods exhibit every type of feeding mode: carnivores, herbivores, detritus feeders, filter feeders, and parasites. The
paired appendages around the mouth of Arthropods are usually specialized in accordance with the particular diet of the
animal. For example, many butterflies have mouthparts adapted for sucking out the nectar in flowers. There are so many
different ways of feeding in this phylum, that there are also various digestive systems. Each arthropod has a different
digestive system according to their method of feeding and body structure. This is why we will be focusing on three digestive
systems of three animals from this Phylum: the butterfly, the spider, and the scorpion.
paired appendages around the mouth of Arthropods are usually specialized in accordance with the particular diet of the
animal. For example, many butterflies have mouthparts adapted for sucking out the nectar in flowers. There are so many
different ways of feeding in this phylum, that there are also various digestive systems. Each arthropod has a different
digestive system according to their method of feeding and body structure. This is why we will be focusing on three digestive
systems of three animals from this Phylum: the butterfly, the spider, and the scorpion.
The Digestive System of the Butterfly
The Butterflies Digestive system is located in the abdomen and is generally well concealed. The butterfly only eats and feeds on liquids: nectar, dissolved pollen, liquefied dung, sweat, mineral water, bodily fluids from decomposing animal corpses, and in some very rare cases even alligator tears. The butterfly then digests and extracts proteins and other minerals from these foods. One this is completed the butterfly excretes waste in liquid form or as tiny fecal pellets from the anus.
The Digestive System of the Spider
After capturing and poisoning their prey with their venom, spiders use two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipals, while flooding it with enzymes; in these species the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing. The spiders stomach acts as a pump that send food deeper into the spiders digestive system. The spiders mid gut bears most of its cec, where the nutrients is extracted from their food. At the end, most spiders convert nitrogenous bases into uric acid, which can be excreted as dry material. Finally. spiders use "little tubes" called Malphigian tubules to extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Although some other types of spiders use large amounts of water to excrete nitrogenous waste products such as ammonia.
The Digestive System of the Scorpion
For the scorpion, digestion begins outside the mouth. The food is semi-digested by digestive juices that are supplied to the preoral cavity by the gut, before it enters the scorpion's mouth. Setae, which is in the preoral cavity, filter indigestible material such as prey exoskeleton. These indigestible particles are matted togehter and expelled. Food passes from the mouth to the pharynx to the esophagus to the mid gut to the hind gut and is finally expelled through the anus. Drawing food into the body, the muscular pharynx acts as a pumping organ. Excretion wastes are expelled through the anus with feces.