The movement mode is peristalsis and contraction, and several body segments are in a ball. In one group, the internal longitudinal muscles contract, the annular muscles relax and the body segments shorten. At the same time, the pressure in the body cavity increases and the bristles protrude and attach. In the adjacent body segment group, the annular muscle contracted, the longitudinal muscle relaxed, the body segment lengthened, the pressure in the body cavity decreased and the bristles retracted.
Each sarcomere group alternately contracts the longitudinal and annular muscles with the adjacent sarcomere groups, so that the body moves forward in waves. Earthworms can advance 2-3cm each time they contract, and the direction of contraction can be reversed, so they can retreat. ?
Extended data:
Earthworms feed on decaying plants or other organic matter. Swallow soil and sand to obtain organic matter. The digestive tract of earthworm is a straight tube, and its mouth is located on the joint around stoma. Behind the mouth is a very small mouth, and behind the mouth is the pharynx, which can't be opened.
There are developed muscles in the pharyngeal wall, which form a ball and have the suction effect of a pump. There are a large number of muscle fibers connected with the body wall on the pharyngeal wall of earthworm, thus forming a muscle disc, which is wrapped around the pharynx to enhance its attraction.
The vascular system is complex in structure, such as dorsal blood vessels on the back of earthworm digestive tract. Because the muscles on the blood vessel wall are well developed, there is still a valve in the tube, and the blood is forced to flow from back to front by its wave-like contraction.