| Bradysia odoriphaga Yang et Zhang often called chive maggot, is the key native pest of chive. Since the 80's of last century, it has become an important pest of lily family vegetables as an key control target, on causing serious economic loss. This paper deals with the anatomy and histology of Bradysia odoriphaga larva, the activities of main digestive enzymes, including protease, esterase and amylase, pathogenic changes of tissues caused by toosendanin, an kind of botanical insecticide and the activities changes of three digestive enzymes. The main results are as follow: 1 Anatomy of the digestive system of Bradysia odoriphaga larvaThe alimentary canal of the larvae consists of foregut, midgut and hindgut. A pair of silk glands, arise from the lower of oral cavity. Foregut is a fine canal with no special changes. Midgut is wide in diameter and longer, with two long anteriorly-connected gastric caeca. According to the side and shapes of the cell, midgut has four parts. Hindgut is curved and changeable in width. Four malpighan tubes arise from between midgut and hindgut. In comparison with every parts of female alimentary canal, the male larva is short than the female larva.2 Histology of the alimentary canal Bradysia odoriphaga larva The technology of paraffin section and transmission electron microscope were used to study the histology of digestive system of Bradysia odoriphaga larva.Paraffin sections by light microscope showed that foregut have no visible cellar structure , the dorsal wall of midgut with smaller columnar cells is thinner than the ventral wall of midgut with bigger columnar cells , and hindgut have no obvious cell structure , but the wall of hindgut protrude in ridge to the cavity . Histological characters of the midgut with 4 regions showed the cells of the first region are smaller and columnar; the cells of the second region are bigger and wider with a big nuclear in each cell,and this region is thinner than the first region ; the third region with small columnar cells is thicker than the second region , just a transitional region from third region to fourth region ; the fourth region is thicker than other parts , with more narrow columnar cells than other regions. The cells of gastric caecas are mostly often cone-shaped, protruding to the cavity. The transmission electron microscope showed the microvilli of cells in the second region is short and columnar and arrange in order; mitochondria in the cells are oval or irregular, with many obvious ridges; nucleolus of the cells, with obvious double nuclear membrane, is round, in which much chromatin is distributed;smooth endoplasmic reticulum are rich between mitochondria around the nucleolus .In the fourth region , microvilli of cells are longer than that of the second region ; coarse endoplasmic reticulum with many ribosomes are rich ; and there are many mitochondria with different shapes , showing that this region is related to digestion and absorption . The ultrastracture of gastric caecas showed that there are much more fine and long microvilli arranged dense in the inner membrane of cells, and lots of mitochondria and endoplasmic reticulum gather around nucleolus, indicating gastric caecas is the main place where protein is synthesized and absorbed.3 The action machnisms of toosendanin on digestive system of Bradysia odoriphaga larva Stomach effect by immersion of food into series solutions of toosendanin was researched. After feeding the food, the symptoms of poisonous larva showed that the larva stopped feeding failed in crawling, shrunk turnend yellow, dehydrated and died of starvation at last. Some larvae could grow and develop, but died of disvitality or pupated and emergenced ahead of time.Pathological changes of histology of poisonous larvae were observed by light microscope and transmission electron microscope. Observations by light microscope showed that gut cells splited, separated between each other, and peritrophic membrane falled apart from the gut cells and splited. Observations from transmission electron mi... |
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