Arthropoda Characteristics

Symmetry
An arthropod's body can be divided vertically into two mirror images. This is called bilateral symmetry.

Reproduction
Sexual reproduction is carried out internally or externally. Their reproductive organs are found on the ventral or belly side of the animal. In aquatic arthropods, they sexually reproduce externally. First, the female lay her eggs and the male releases sperm into the water and, the eggs are fertilized in the water. In terrestrial arthropods, the sperm cells is covered by a mucus called ''spermatophore. ''This is because it prevents loss water moisture of the egg, and guards it against any chemicals before and after fertilization. Other times, insects or crabs mate with each other during the mating season.

Organs
Arthropod have exoskeletons. Exoskeletons are hard outer shells made of chitin. A crab, lobster, or insect has this tough shell that protects it from predators. Next on the list are the arms and legs. They have jointed appendages. Inside, those joints and exoskeletons are muscles that help the organisms move. For its organ systems, it has a discreet circulatory, digestive, and respiratory systems. Arthropods have an open circulatory system. A well-developed heart pumps blood through arteries that branch and enter the tissues. Aquatic arthropods have gills for gas exchange. In terrestrial arthropods, they possess tracheae and book lungs as respiratory organs.