Phylum Arthropoda Digestive System

Instructor: Jeremy Battista
A wide variety of species in the animal kingdom belong to the group called Arthropoda; commonly called arthropods. In this lesson, we will be looking at the anatomy of their unique digestive system and how it functions.

What Are Arthropods?

Think about a lobster, a spider, a butterfly, and a scorpion. Four completely different animals, correct? In fact, these animals have some things in common, which is that they are all arthropods.

Arthropods belong to the phylum Arthropoda in the animal kingdom. A phylum is the third broadest of the classical taxonomic classifications, kingdom and domain being the larger two. Arthropods have segmented bodies and legs as well as exoskeletons, which sets them apart from animals that have internal skeletal structures such as ourselves. We study these creatures to see how evolution has influenced their anatomy in comparison to other animal groups.

Arthropod Anatomy Basics

As stated before, some of the distinguishing features of arthropods are their segmented bodies and appendages; such as legs or antennae. The exoskeleton of these animals is another thing that sets them apart from other living creatures.

An exoskeleton is a skeletal structure on the outside of the body versus on the inside. We'll highlight more characteristics of arthropod anatomy in the following sections, in particular their digestive system.

A crab is an arthropod. Its hard shell is a type of exoskeleton and its claws are an example of segmented appendages.

Digestive System

The digestive system of an arthropod is not too far removed from how a human being eats and digests food. They have appendages near their mouths that they use to move food into their body, whether it's plant matter or another living thing. There are a broad variety of species that are arthropods, so they have varied dietary habits. With each individual species, their mouthparts are adapted for the type of food they eat. Some insects, for example, have mouthparts (think small arms that help push the food into their mouth) that are used to get nectar; some for eating other insects. All arthropods have some type of specialized appendage used to get food.

The digestive tract of a spider is shown in green.
Spider cutaway

Their digestive system is also adapted to what the animal likes to eat. A butterfly's digestive system might look different from a spider or a lobster since its diet is primarily nectar. As a phylum, there remain many common features that all arthropods share in their digestive systems. Their digestive system includes a foregut (pharynx and esophagus to the stomach), midgut (stomach), and hindgut (colon, anus), similar in some ways to the human digestive tract. The foregut and hindgut are lined with a chitin-like material, the same material that makes up the exoskeleton. Chitin is similar to cellulose in plants and bones in humans. It is the chief substance responsible for an arthropod's exoskeleton.

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