ARTHROPODA: SPIDERS, CRUSTACEANS, AND INSECTS
monarch butterfly: Danaus plexippus
Spiders, crustaceans, and insects, oh my! These animals, diverse as they are, all belong the to phylum...
...Arthropoda. Like most of the other phyla we’ve seen, Arthropods are bilaterally symmetrical. Their bodies are divided into segments, some with many but some, like insects, with different body regions. These sections can be equipped with legs, antennae, claws, or pinchers for moving, feeding, hunting, mating, and sensing their environment. All have an exoskeleton, a hard outer covering. This protects the animal’s internal body and can be used to reduce water loss. However, the exoskeleton cannot grow with the animal, so must be shed and replaced at intervals as the animal grows. They have a one-way digestive system, meaning they have one opening for food and one for waste. Interestingly, this phylum has an open circulatory system. This means that, like mollusks, blood flows freely through an arthropod’s body and surrounds the organs instead of flowing through blood vessels. Spiracles, little holes in the exoskeleton, are used for breathing. Most of the time, reproduction is sexual and individuals are split into male and female sexes. Metamorphosis occurs in some of the species in the Arthropoda phylum. Complete metamorphosis is when a species goes from egg to larva to pupa to adult. However, incomplete metamorphosis also takes place, where a species goes from egg to nymph to adult. Arthropods are one of the most highly representative groups on the planet. This may be because of their ability to adapt. For example, insects reproduce rapidly and have short life spans, so the process of natural selection can occur faster. Check out the crazy owl eyed butterfly by clicking the button to the left!