Morphological structure of arthropods

The morphological and structural characteristics of arthropods are as follows:

1, the body consists of a series of body segments.

2. The whole body is covered with an exoskeleton containing chitin.

3. Most body parts have paired segmented appendages.

4. The body cavity is the blood cavity, and the circulatory organ-dorsal blood vessels are located at the back of the digestive tract, and the aorta is open to the head cavity, so the blood circulation is open.

5. The central nervous system consists of a series of paired ganglia. The brain is located on the back of the digestive tract of the head, and the ventral nerve cord is located on the ventral side of the digestive tract.

Arthropods are symmetrical on both sides. It consists of a row of body segments, which can be divided into three parts: head, chest and abdomen, or head and chest are fused into head and chest, or chest and abdomen are fused into trunk. For example, the body of Insecta (locust) is divided into three parts: chest and abdomen; The body of crustacean (shrimp) is divided into two parts: chest and abdomen.

The body of arachnid (spider) is divided into chest and abdomen; The body of Polypodiaceae (centipede) is divided into head and trunk. There is also a division of physiological functions in the branches of the body: head: sensory and feeding center; Chest: sports and support center; Abdomen: Nutrition and Reproductive Center.

Most arthropods are hermaphroditic, and often hermaphroditic. Terrestrial species are usually fertilized in vivo, while many aquatic species are fertilized in vitro. Generally, they are oviparous, and some are oviparous. The cleavage method is surface cleavage, which has direct development and indirect development.

Scientific value:

The exoskeleton of arthropods can form fossils. Arthropod fossils have been found in Ediacaran fauna about 80 ~/kloc-0 ~ 0 billion years ago, and trilobites have appeared in large numbers since the Early Cambrian. Many arthropod fossils have been used as standard fossils for stratigraphic correlation and indicating sedimentary environment.