Identification And Morphology Of The Fourth-stage Larvae Of Eustrongylides Ignotus And Histopathology Of Infected Fish In Freshwater Lake

Because nematode has many kinds and similar morphology,it can't be identified by naked eye.Us in a month in October 2017,the Shanghai some freshwater lakes fish survey found that Culter alburnus Basilewsky and Hemibarbus maculatus Bleeker intraperitoneal infection nematodes,but was unable to determine the specific type.In order to find out the specific species and classification status of the nematode,molecular biological analysis was conducted on Culter alburnus Basilewsky and Hemibarbus maculatus Bleeker,collected from the abdominal cavity of the fish.Through comparison of 18 S rDNA sequences,it was found that the similarity between the nematode and Eustrongylides ignotus 18 S rDNA sequences in the abdominal cavity of Hypomesus transpacificus nipponensis was up to 100%.The rDNA sequence of Eustrongylides ignotus 18 S rDNA parasitic in the abdominal cavity of Gambusia affinis was 99.87%.The results showed that both Culter alburnus Basilewsky and Hemibarbus maculatus Bleeker were Eustrongylides ignotus(Login number :MK340916).On the basis of determining the nematode as E.ignotus according to the 18 S rDNA sequence,the ITS rDNA sequence of this nematode was determined.By naked eye and microscope and scanning electron microscope,the main characteristics of the nematode worm pink,round barrel,the central body even thickness,it is fine,a conical head,mouth cracks shaped,polypidehas two laps mastoid head,inner ring six spinous papilla,outer ring 6 papillary papilla,anal opening in polypide brought correct central and reported at the end of the figure,the stomach tumor nematodes,external form and insect body has three layer,to determine the nematodes as part of the figure,brought Eustrongylides ignotus ? stage larvae.On both sides of the body surface of the newly discovered polypide,there are side macules,with straight concave lines,and small spotty microprocesses in the center.In addition,the size of body length,esophagus length,oral cavity length,spinous papilla,papillary papilla,side body macular process,and tail body macular process and other data were measured.The morphological characteristics of the internal structure of the polypide,such as the esophagus,intestinal tract and reproductive system,were supplemented by observing the internal structure of the polypide through light microscope and bodysection.The mouth is conical,the front part of the esophagus is thin,and the back part is thick.The length of the esophagus accounts for about one-fifth of the polypide length.The esophagus is divided into a dorsal gland and two lower abdominal glands.The enclosed esophageal cavity is in a tri-radial shape.The intestinal tract is composed of the foregut,the midgut and the hindgut.The intestinal tract is connected to the body wall through the mesentery and consists of a single layer of columnar epithelial cells.The body muscle of the outer part of the intestinal tract is a single layer of spindle longitudinal muscle cells,which are generally divided into four cable regions.The muscle cells are attached to the subcortex,and the other end extends into the body cavity.The extended end is connected with other body muscle ends or some specialized muscles.The reproductive system of the female insect is composed of ovaries and fallopian tubes.The outer layer of the ovary is connective tissue composed of fibroblasts Surrounded by tissue,the internal oocyte,oviduct in the body cavity there are many roundabout,the outer layer of the oviduct for fibroblast composed of connective tissue,the inner layer for short columnar epithelial cells,no mature eggs were found.Male reproductive system is mainly composed of the testis and vas deferens long,testis outer layer is a list of the thin layer of connective tissue that fibroblasts,the inner layer of spermatocyte,vas deferens from polypide central backward outspread,the outer layer of fibroblasts of connective tissue and lining for short columnar epithelium cells,did not see out of acicular structure.Histopathological damage of stage ? larvae of E.ignotus on fish body was studied by tissue sector.the results showed that except some nematodes attached to the surface of internal organs in the abdominal cavity of fish,other nematodes parasitized in liver and mesentery in the form of enveloped cysts.Cysts are pink,usually oval,the development and stimulation of the worm body in the early stage,fibroblasts in the tissues and organs near the parasite increase in value,forming connective tissue layer,and encase the worm body;In the middle stage,fibroblasts and other cells in the connective tissue of the tomont wall show necrosis,and the necrotic cells gradually fall off from the inner surface of the tomont wall and enter the tomont cavity.At anaphase of cyst,necrotic cells in cyst wall increased,leading to rupture of cyst wall.The cysts formed in the liver have no obvious effect on the liver at the initial stage.With the thickening of the cyst wall,eosinophilic leukocyte infiltration often occurs at the close junction between the cyst and the liver,and liver tissue hyperemia and hemosiderin pigmentation and other phenomena occur.The cysts formed in the spleen cause a small amount of ischemia and hemosiderin in the spleen.The presence of several nematode worms in the mesentery results in a large number of eosinophilic white blood cells and secretory granules in the pancreatic tissue.In this article,through analysis and study of molecular biology,morphology and pathology,determine the nematode species,classification status,characteristics and its fish tissue pathological damage,for the host to supplement and enrich the relevant knowledge of the nematodes and master its organization to Culter alburnus Basilewsky and Hemibarbus maculatus Bleeker is of great significance in such aspects as pathological damage.