Morphology And Ultrastructure Of The Digestive System Of The Vector Leafhopper Psamotettix Striatus (L.)

The vector leafhopper Psammotettix striatus (L.) (Hemiptera: Cicadellidae) is an important economical pest in Northwest China, which is a serious threat to wheat, leading great loss to agricultural products by transmitting wheat blue dwarf (WBD) in a persistent circulative manner. Although some aspects of the biology and behavior of this pest were investigated detailed, and virus was found in the cells of the salivary organs, the filter chamber and gut which had been proved in preview reports, there is no data available on the ultrastructure organization of digestive system of this pest. A microscopic analysis of morphology and ultrastructure of the digestive system were conducted using light, scanning and transmission electron microscopy to aid in injection of pathogenic inoculums for various vector-pathogen relation studies.The gross morphology of the alimentary canal consists of esophagus (foregut), midgut, hindgut, and special filter chamber. The esophagus, a narrow and slender tube, which is special from foregut originated from the food canal in the stylets locating behind the pharynx. It runs through the whole thorax extending into the filter chamber and connecting with anterior midgut. Midgut is longest in digestive organs, with special structure. It consists of three major regions, the anterior midgut, middle midgut and posterior midgut. The anterior midgut is composed of exceptionally thick epithelial cells surrounding a large lumen. Numerous well-developed microvilli place at the basal region of the epithelial. There are a large amount of electron-lucent and lipid-like vesicles observed under the microvilli. The posterior midgut is smaller than the anterior midgut in diameter comparing with the anterior midgut. Numerous different concentric circular are characteristic of the posterior midgut. The hindgut arises from the posterior midgut at the boundary of the filter chamber. It extends downward toward the anus where the hindgut tubules swell to form the rectum. The rectum is formed by various cells typical of epithelium, whose nuclei are relatively smaller than that of midgut. Relatively large muscle present at the well-defined and thick basement membrane, which presumably control the discharge of waste via the rectum and the anus. There are two pairs of Malpighian tubules. Numerous mitochondria and lamellar rough endoplasmic reticulum in the cells of anterior segment of the Malpighian tubules are observed; the sub-anterior segment of tubules resembles the distal segment, wave-like, amount vesicles are observed in the cells; numerous tightly packed large vacuoles vesicles contains two types brochosomes in the inflated segment of the Malpighian tubules.The salivary system of P. striatus contains one pair of salivary glands, which locate one on each side of the head and are made up of the primary and accessory gland, extending into mesothorax. The primary glands are divided into three portion, including anterior lobe, mid-lobe and posterior lobe. About nineteen acini are observed from the primary glands of P. striatus, varied in structure and colour. Five cellular types are found in the primary glands by transmission electron microscopy, which are rich in secretory granules, modified in size, electron-dense and shape. Rough endoplasmic reticulum in the shape of vesicular and lamellar, mitochondria and Golgi complexes are observed. The accessory gland has only an oval or a rod acinus. In the light of our studies, we confirmed that the primary glands are closely related to the synthesis of large amount of protein, while the accessory salivary gland as the source of water in the saliva.