Facts About Arthropods & Crustaceans

Many arthropods and crustaceans appear otherworldly.

Arthropods make up a large percentage of the animal kingdom, including millions of species in an assortment of shapes and sizes. One of the most interesting types of arthropods is the subphyla of the crustaceans, which make up many familiar species, such as lobsters and shrimp. There are many interesting facts about arthropods and crustaceans that help people to appreciate the nature of their diversity.

Arthropod Overview

Arthropods make up over 90 percent of all animals. They have an exoskeleton---meaning a skeleton that is on the outside of the body. They also have bilateral symmetry, where one side of the body matches the other side. Other common features of arthropods include jointed legs, as well as appendages.

Classes of Arthropods

Arthropods divide up into several classes, including insects, arachnids, crustaceans, chilopods and diplopods. The largest class of arthropods includes insects, which have over 1,000,000 different recorded species. Arachnids---which are made up of over 65,000 species---include species, such as spiders, ticks and scorpions. Chilopods are a much smaller group---only consisting of around 2,800 known species. Chilopods are also known as centipedes; they have a well-defined head, a pair of legs on each segment and are venomous. Diplopods---also known as millipedes---are the last group of arthropods. They are made up of over 10,000 species and have far more legs than chilopods, which makes them easily distinguishable.

Crustacean Overview

Crustaceans are made up of an estimated 44,000 species and include animals such as crabs, lobsters and shrimp. Their makeup generally consists of two different body regions, two pair of antennae, and normally above five pairs of legs. The majority of crustaceans are aquatic as opposed to terrestrial.

Sight and Respiration of Crustaceans

Crustaceans have compound eyes, an antenna, as well as three mouth parts. Crustaceans breathe in different ways---some use their body surface and respire by diffusion, while the larger crustaceans respire with gills.

Crustacean Fossil Record

Crustaceans are relatively common fossils---mostly from the Cretaceous and Caenozoic periods. Most smaller crustaceans have exoskeletons that are soft and delicate and therefore don't have a good fossil record; however, larger crustaceans contain larger and thicker exoskeletons, which allows them to have a more complete fossil record.

References

• Arizona State University: Arthropod Information
• Jungle Walk: Crustacean Information