(2) The circulatory system of prawn is an open system, which consists of blood, heart, arteries and sinuses. The heart is located at the back end of the head and chest, and it is polygonal, and its beating can be observed in vitro. The heart has four pairs of heart holes, one pair of anterior arteries sends forward, and there are branched arteries leading to the tissues and organs of the head and chest, and the dorsal artery sends backward into the abdomen and branches to the tissues and organs. On the dorsal artery, there is a descending thoracoabdominal artery leading to the ventral surface from the heart, and branches out the inferior thoracic artery and the inferior abdominal artery. Arteries from the heart gradually branch to form small blood vessels which are distributed in organs and tissues. The blood sinus is a large tissue gap, which collects the blood flowing back from the tissue, mainly including the pericardial sinus outside the heart and the thoracic blood sinus in the chest. The blood of shrimp is colorless and transparent, and hemocyanin carrying oxygen exists in plasma. Blood cells are divided into three types: transparent cells, translucent cells and granular cells, which have the functions of phagocytosis of foreign bodies in blood and coagulation. The circulation process of prawn is as follows: the beating of the heart makes the blood flow out of the heart, and flows to various organs and tissues along the arteries and branched blood vessels. The blood from organs and tissues is concentrated in the thoracic sinus through tissue gaps and small blood sinuses, and then enters the gills for gas exchange, and then flows out of the gills and returns to the heart through the pericardial sinus to participate in the next circulation.
(3) Reproductive system The male reproductive system of prawns includes leafy testis, vas deferens and seminal vesicles. The testis is located at the back of the head and chest, with a pair of anterior lobes, six pairs of lateral lobes and a pair of posterior lobes. A pair of vas deferens are sent out from the posterior lobe, bent backward and then descending to the seminal vesicle. The seminal vesicle is located at the base of the fifth pair of walking feet, and there is a reproductive hole opening outside the body. The external reproductive organs of male shrimp mainly include the adapter changed from the inner limb of the first abdominal limb, and in addition, the inner limb of the second abdominal limb forms the male appendage. The female reproductive system mainly includes ovaries and fallopian tubes. The ovary is located at the back of the body and the back of the head and chest. It sends out a pair of anterior lobes forward, six pairs of lateral lobes to the abdomen, covering the back of the hepatopancreas, and sends out a pair of long posterior lobes backward into the abdomen, extending backward along the back of the intestine to the vicinity of the anus. A pair of fallopian tubes, which emanate from the ends of the fifth pair of lateral lobes, descend and open to the genital foramen at the base of the third pair of walking feet. The external reproductive organ of female shrimp is spermatic sac, which is used to store sperm pods during mating. The seminal vesicle is formed by crustacean pleats and is located on the ventral crustacean between the bases of the fourth and fifth pairs of walking feet. Seminal vesicles are divided into two types: one is a closed seminiferous vesicle, which is a capsule formed by a carapace and is disc-shaped or bag-shaped with a slit in the middle; The other is the open spermatic sac, in which the carapace does not form a saccular structure, but only has protrusions and pleats, and the sperm pods adhere to it after mating.
(4) Respiratory system: The prawns breathe through gills to complete gas exchange. According to the different positions of gills, they are divided into lateral gills, joint gills and foot gills. The gill of prawn is a dendritic gill, which consists of a central gill axis and gill flaps on both sides. Branchial axis has branchial inlet blood vessels and branchial outlet blood vessels; The branchial flap emanates from the branchial axis and has branched gill filaments. The gill of prawn is located in the gill cavity formed by the side armour of the head breastplate and the chest body wall. The swing of the outer limb of the second mandible makes the water flow through the gill cavity, exchange gas on the gill filament, absorb oxygen, discharge carbon dioxide and complete the breathing function.
(5) Excretion system The excretory system of shrimp consists of antenna glands located at the base of the second antenna. The antenna gland is a saccular gland, which is connected with a complex thin-walled vesicular system, and the excretory hole is opened at the base of the second antenna. Because excrement is mostly green, antenna gland is also called green gland.
(6) Nervous system The nervous system of prawns consists of brain and abdominal nerve cords. The brain of prawn is composed of forebrain, midbrain and hindbrain, which is located behind the base of both eyes. A nerve from the back of the brain surrounds the esophagus, which is connected with the hypopharyngeal ganglion at the back of the esophagus and sends out the abdominal nerve cord from the hypopharyngeal ganglion. The ventral nerve cord extends backward from the chest and forms a ganglion at each segment. Many branched nerves from brain and ganglia enter appendages, eyes, stomach, hepatopancreas and other tissues and organs. The sensory organs of shrimp mainly include eyes, chemoreceptors and tactile devices. Two large compound eyes with handles are composed of many small eyes, which have light-sensitive function. There are all kinds of sensory bristles and villi on the body surface, and the balance sac at the base of the first antenna can feel the balance of the body. Antennal whip, mouthparts and claw feet have the function of feeling chemical stimulation.
(7) Muscle system Penaeus vannamei is muscular, mostly striated, distributed in the head, chest and abdomen, with abdominal muscles being the most developed. The muscles of the head and chest are mostly related to the activities of organs, such as moving eyes and swinging tentacles; Abdominal muscles are mainly related to the movement of shrimp, and shrimp can bounce quickly through the contraction of abdominal muscles.
(8) Endocrine system The endocrine system of prawns consists of neuroendocrine system and non-neuroendocrine system. The former consists of neuroendocrine cells, which secrete various hormones and release them into the blood, acting on various target organs. One of the important neuroendocrine organs is the X-organ. X-organ is located in the eyestalk of shrimp, and its main function is to regulate the physiological activities such as molting and gonadal maturation of shrimp. Non-neuroendocrine organs are gland tissues, which secrete hormones and other substances to participate in specific physiological processes. For example, Y-organ can secrete ecdysone to promote the ecdysis of prawns, and its activity is regulated by X-organ secretion.
The content of this article comes from: The History of the Development of Agriculture and Animal Husbandry Science and Technology in Tibet by China Agricultural Publishing House.