Morphology And Ultrastructure Of The Reproductive Systems In Aphrophoridae

Insects are extremely successful animals, based on their number of species and total biomass. Although other physiological systems contribute to their success, their reproductive systems are the basis of their reproductive potential. Research on the morphology and ultrastructure of insect reproductive systems contributes to the understanding of their reproductive cycle and their reproductive potential. In addition, changes in reproductive structures are critical to clarifying the evolution and phylogeny of insects, and to identifying taxa. Although froghoppers are plant-feeding insects that pose potential economic threats, few comparative studies of their reproductive systems have been published. Here, the morphology and ultrastructure of the reproductive systems were investigated for Philaenus spumarius(Linnaeus), Aphrophora oblique Uhler, Lepyronia coleopterata(Linnaeus), Aphrophora costalis Matsumura, Aphrophora shaanxiensis Liang and Philagra quadrimaculata Schmidt. Light microscopy and transmission electron microscopy were used to provide comparative data elucidating variation within the family Aphrophoridae and to provide information on traits that may be unique to this family but distinguish them from other froghopper families and from other HemipteraThe gross morphology of the male and female reproductive system in these six species is similar to those of related Auchenorrhyncha. The male reproductive system comprises a pair of symmetrical unsheathed testes, two vasa deferentia, paired seminal vesicles, a pair of accessory glands and a single common ejaculatory duct. The number of testicular follicles is variable among different species. Each testicular follicle forms a short and narrow vasa efferentia at the base, then gathers together and joins with the vas deferens. Part of the vas deferens expands to form the seminal vesicle, and a pair of seminal vesicles separates. A pair of developed accessory glands are divided into two distinct parts and merge with the posterior of the vas deferens and the ejaculatory duct. The common ejaculatory duct is usually pear-shaped, gradually narrowing posteriorly and connected to the phallus. The female reproductive system consists of a pair of symmetrical ovaries, a pair of lateral oviducts, one common oviduct, one bursa copulatrix and an accessory gland. The number of ovarioles is different among different species. Telotrophic ovarioles are divided into a terminal filament, germarium, vitellarium and ovary calyx. Numerous ovarioles form an ovary which goes through the lateral oviduct and the common oviduct and links with the valvulae through the vagina. Below the common oviduct is an inflated bursa copulatrix. A long tubular accessory gland is behind it.The ultrastructure of the reproductive system of these six species is similar. In the male reproductive system, the testicular follicle consists of the epithelium lying on a thick basal lamina surrounded by a muscular-connective sheath and a wide lumen filled with spermatids. Large numbers of vesicles, mitochondria and rough endoplasmic reticulum are observed in the epithelial cells. There are many spermcysts located in the testis, and different spermcysts contain spermatids at different developmental stages. Nebenkern appear near the nucleus at a certain stage in the developmental spermatids. The spermcyst is the unit of spermiogenesis; this process is accompanied by formation of an acrosome, extension of the nucleus, chromatin condensation, and so on. The seminal vesicle, from outside-inward, consists of: outer membrane, muscular-connective sheath, epithelium and lumen. There are several tracheoles and a large amount of circular granular materials in the outer membrane. Intercellular spaces are present between the outer membrane and muscle sheath in some regions. Numerous basal infoldings are located in the juncture of the epithelial cells and basal lamina. The epithelial cells contain a lot of rough endoplasmic reticulum, mitochondria, vesicles and multilamellar bodies. There are different forms of sperm storage in the lumen of the seminal vesicle. The male accessory glands are made up of outer membrane, muscular-connective sheath, the basal lamina and epithelial cells. Quantities of developed basal infoldings are present in the basal lamina. The epithelial cells are closely arranged with a large number of secretory substances, endoplasmic reticulum, and mitochondria. In female reproductive systems, the germarium contains mainly trophocytes. Egg chambers in the vitellarium are mainly composed of lamina propria, follicular epithelial cells and oocytes. The follicular epithelial cells are arranged surrounding the egg chamber. During the maturation of the oocytes, intercellular spaces emerge in follicle cells and lipid granules, protein granules, multilamellar bodies, yolks and microvilli are present in the cytoplasm of oocytes. The cell nucleus also changes over time, with a large number of electron granules, mitochondria and endoplasmic reticulum developing around it. The bursa copulatrix components are a muscular-connective sheath, epithelial cells and lumen. There are some tracheoles outside the muscular-connective sheath and many basal infoldings inside the basal lamina. Large amounts of endoplasmic reticulum, mitochondria and several Golgi bodies and cuticles are in the epithelium. The edge of the lumen has cuticles and numerous sperm are in it.The six species differ in the number of testicular follicles and ovarioles, and the shape of vas deferens. In the male reproductive system, there are 25 testicular follicles in Aphrophora oblique, 21 testicular follicles in Lepyronia coleopterata, 23 testicular follicles in Aphrophora costalis, and 30 testicular follicles in Aphrophora shaanxiensis. Vas deferens in Aphrophora oblique、Aphrophora costalis and Aphrophora shaanxiensis are very thin and long, the base of accessory gland is opaque and very thick, and the apical parts are translucent, very thin and highly curled. However, the vas deferens in Lepyronia coleopterata are short and thin, the base of the accessory glands is opaque and very thick and the apical parts are translucent, slightly thin and curled. In the female reproductive system, there are 12 ovarioles in Aphrophora oblique, 14 ovarioles in Lepyronia coleopterata, 18 ovarioles in Aphrophora costalis, and 16 ovarioles in Aphrophora shaanxiensis.There are some differences in the ultrastructure of the reproductive system among the six species. The nebenkern(Nk) in spermatids in Aphrophora oblique and Philagra quadrimaculata are made up of many mitochondria fused together into a maze of irregular shape, while the nebenkern of Lepyronia coleopterata is only gathered together by the diverse size of the mitochondria. In the seminal vesicle, vesicles of the epithelium are distributed close to the muscular-connective sheath. Sperm cells in the lumen are more concentrated with many embedded in the homogenous matrix. The matrix is also relatively abundant. Vesicles of epithelium in Aphrophora shaanxiensis are located near the lumen. Sperm cells in the lumen are relatively dispersed; the matrix is also limited. The ultrastructural structures of male accessory glands in Philaenus spumarius, Aphrophora oblique, Aphrophora shaanxiensis and Lepyronia coleopterata consist of a muscular-connective sheath and secretory epithelium. Secretory cells govern regulation; the mode of secretion is apocrine secretion. In Aphrophora costalis, the ultrastructure is mainly composed of epithelium and the cells are penetrated with intracellular canaliculi. The lumen of a canaliculus is almost completely filled with mitochondria, and the periphery is surrounded by secretory vacuoles and mitochondria. The mode of secretion is duct-forming secretion. While in the female reproductive system, we found black particulate matter in the epithelium of the bursa copulatrix in Philaenus spumarius, Aphrophora shaanxiensis and Philagra quadrimaculata, and the basal infoldings are developed. But in Aphrophora oblique and Lepyronia coleopterata, there is no black particulate matter in the epithelium and the basal infoldings are less developed. The cuticles in Lepyronia coleopterata and Philagra quadrimaculata are developed. In Philaenus spumarius and Aphrophora oblique they are less developed. And no one are found in Aphrophora shaanxiensis.The fine morphology and ultrastructure of the reproductive systems in these six species are illustrated, along with a brief discussion of the implications for classification and phylogenetic analyses of the subfamily. This report on the morphology and ultrastructure of the froghopper reproductive system provides a basis for future comparative study of related species and higher taxa.