| Trypophloeus klimeschi Eggers is a devastating pest of Populus alba var.pyramidalis Bunge.It was first discovered in Kyrgyz Republic in 1915.After an outbreak in 2003 in Xinjiang Province,it is now seriously harmful in Dunhuang of Gansu Province,and gradually spread to the surrounding area.Although the biological characteristics,occurrence regularity,host selection and intestinal microbial community of T.klimeschi have been systematically studied,the characteristics and ultrastructure of the alimentary canal and reproductive systems,which are closely related to population reproduction and nutrient metabolism,remain unclear.Therefore,the aim of this paper is to study the alimentary canal and reproductive systems of the adult T.klimeschi by applying light and electron microscopy techniques.The research obtained the following results:1.The male reproductive system of T.klimeschi is comprised of a pair of testes,a pair of seminal vesicles,a pair of vasa deferentia,a pair of multilobulated accessory glands,a pair of tubular accessory glands and an ejaculatory duct.Each testis consists of 2 follicles surrounded by a fat layer,and there are a lot of cysts in the follicles.There are 350 to 512 spermatozoa in a cyst.The mature spermatozoa are scattered in the seminal vesicles.The female reproductive system of T.klimeschi is comprised of a pair of ovaries,a pair of lateral oviducts,a common oviduct,a spermatheca,a pair of accessory glands and a bursa copulatrix.Each ovary has two ovarioles.The spermatheca is comprised of a spermathecal duct,a spermathecal sac and a spermathecal pump.The spermathecal sac is a cavity surrounded by the basal lamina,the epithelium and the inner cuticle,its epithelium contains a lot of secretory cells and ductforming cells.The spermathecal pump is comprised of the basal lamina,the epithelium and the inner cuticle,its epithelial cells are flat and inner cuticle is thicker than that of the spermathecal sac.The accessory gland is comprised of the basal lamina,the epithelium and the inner cuticle.Because there are no abundant endoplasmic reticulum and Golgi apparatus in the epithelial cells of the accessory glands,its main function is storage.The overall morphology of the male and female reproductive system of T.klimeschi and spermatheca structure are similar to that of Dendroctonus.But the secretion function of the male multilobulated accessory glands of T.klimeschi is very strong,and the female accessory glands of which are a pair of prolate sac-like structures.2.The spermatozoa of T.klimeschi are about 77 μm in length and 0.5 μm in width.It is comprised of a three-layer acrosome complex,a nucleus,a 9 + 9 + 2 axoneme,two mitochondrial derivatives of different sizes,two accessory bodies of different sizes and a“puff”-like expansion.In early spermiogenesis,an preacrosomal vesicle is present at the flank of the Golgi apparatus,but the preacrosomal vesicle of T.klimeschi is oval.In spermiogenesis,the nuclear chromatin condenses into two different patterns(one homogeneously compact,the other fibrillar).3.The ovariole of T.klimeschi is comprised of terminal filament,tropharium,vitellarium and pedicel.The entire ovariole is surrounded by peritoneal sheath,and the tropharium and vitellarium is surrounded by the basal lamina.The terminal filament is comprised of peritoneal sheath.There are floded basal lamina at the bottom of the terminal filament.The tropharium conrains several clusters of nurse cells,and there are no differences in the content of free ribosomes among different nurse cell clusters.The programmed cell death is present in the posterior tropharium.There is a group of follicular plug cells at the pedicel of ovariole,and the follicular plug cells can secrete coralloid substances.The ovarioles of T.klimeschi conform to the transition stage of Polyphaga-type,which is different from the known secondary stage of Polyphaga-type of Curculionidae.4.The alimentary canal of T.klimeschi is comprised of foregut,midgut and hindgut.The foregut and hindgut have a cuticle(intima)on the inner surface,while the midgut does not.The total length of the alimentary canal is about 6 mm,which is about 3 times as much as the body length.The foregut accounts for 18% of the total length,the midgut accounts for 47%,and the hindgut accounts for 35%.(1)The foregut is comprised of oral cavity,pharynx,esophagus,crop and proventriculus.The crop is well developed and its inner surface is covered with spines.The proventriculus contains 8 chitinous plates,each plates is divided into the anterior part and the posterior part.The anterior part accounts for about 1/5 of the length of the entire plate,the raised surface has2 symmetrical scaly tooth;the posterior part accounts for about 4/5 of the length of the entire plate,with elongated bristles and leaf-like bristles.The foregut and midgut are bounded by the stomodeal valve which has a gradually thinning cuticle.(2)The midgut of T.klimeschi is comprised of the expanded anterior part and the tubular posterior part.The epithelial cells of the expanded anterior part are columnar and formed microvilli on the side close to the intestinal lumen.There are 2 rows of 18 to 30 gastric caeca on both sides of the tubular posterior part.The gastric caeca have two forms: slender and stubby.The gastric caeca is composed of the muscle layer and the epithelium which forms long microvilli that absorb nutrients by contacting food particles in the center of the gastric caeca lumen.At the insertion site of the gastric caeca,the epithelial cells first formed columnar protrusions on the side close to the intestinal lumen,and then formed short and sparse microvilli on the protrusions.There are 2 groups of 6 Malpighian tubules at the end of the midgut,2 in one group and 4 in the other group.The 6 Malpighian tubules eventually gather together and enter the perinephric membrane of the rectum forming the cryptonephric system.The perinephric chamber consists of an anterior part that is parallel to the rectum and a hemispherical posterior part.The gastric caeca and its surrounding specialized midgut epithelial cells provide an important structural basis for efficient nutrient metabolism and absorption in T.klimeschi.(3)The hindgut of T.klimeschi is comprised of the pyloric valve,ileum,colon and rectum.The pyloric valve is close to the base of the Malpighian tubules.The cell of the pyloric valve filled with a large number aggregates of low electron density form intima on the side of the intestinal lumen.The ileum is short and has spines on inner surface that point toward the colon.There is a clear constriction between the ileum and colon.The colon is slender and curved and surrounded by the circular muscles,with severely folded epithelium and intima.The rectum is thick,long and straight,with the thickest intima.The end of the rectum is surrounded by abundant circular muscles,its diameter is rapidly reduced,and there are many depressions on the surface of intima.Spines on the surface of the ileum of T.klimeschi are associated with symbiotic microorganisms that contribute to intestinal metabolism and absorption.Although the male and female reproductive system,sperm structure and spermatogenesis,ovary structure and development and alimentary canal structure of T.klimeschi are similar to that of Curculionidae,but there are significant specificities in spermatogenesis,ovarian development and other aspects,which enables the beetle to effectively utilize the host’s nutrients and achieve stable population density and efficient reproduction. |
PDF Full Text Request