Intro
An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and joint appendages. Arthropods are part of the phyla Arthropoda. They include insects, arachnids, crustaceans, etc. Arthropods are recognized for their joint limbs. There are over a million discovered species that make up eighty percent of all living animals. Arthropods have the various system of the body which include , the respiratory, circulatory, and execratory, etc. To see they have a combination of compound eyes and pigment-pit ocelli. Arthropods reproduction methods vary. Almost all arthropods lay eggs but sometimes the fertilization is internal and sometimes it is external.
Nervous System
The nervous system in an arthropod functions differently to others. They use a system of cuticles that would normally block out senses but instead have been bombarded with an array of sensors. There are touch sensors to detect force and touch, chemical sensors that equate to smell and taste, and pressure sensors which act like ear drums.
Crustacean
This large subphylum include animals such as crabs, lobster, crayfish, shrimp, etc. There are sixty seven thousand discovered species in this phyla. Like other arthropods, crustaceans have an exoskeleton which they molt to grow. Most live in the sea but some are terrestrial and some are parasites. Over ten million tons are fished every year for human consumption.
Myriapoda
This subphylum contains millipedes, centipedes, etc. There are thirteen thousand species all of which live on land or are terrestrial. They have a pair of antennae, and for the the most part, simple eyes.
Chelicerata
This subphylum includes horseshoe crabs, spiders, mites, scorpions, etc. There are seventy seven thousand discovered species. They have segmented bodies with joint limbs. They have an open circulatory system and most rely on modified bristles for touch and information on vibrations, air currents, and chemical change. Some of theses animals can be very harmful to humans but they are being studies for uses to heal.