No abstract

No abstract

Anatomy and ultrastructure of the female and male reproductive system in Acarus siro L. were investigated by light and electron microscopy. The female system consists of paired ovaries of nutrimentary type in which oogonia and oocytes are connected by bridges with a large central cell. The oviducts empty into the uterus, which passes into preoviporal duct lined by cuticle, and opening as a longitudinal slit (oviporus). An elongated accessory gland composed of one type of secretory cell is located along each oviduct. The copulatory opening occurs at the posterior margin of the body and leads, via the inseminatory canal, to the receptaculum seminis, consisting of the basal and saccular part. Both inseminatory canal and basal part of receptaculum seminis are lined by cuticle, whereas the wall of the sac is formed by cells covered only by long, numerous microvilli. The basal part of the receptaculum seminis joins the ovaries via two lumenless transitory cones. The male reproductive system contains paired testes, in which spermatogonia tightly surround the central cell. The proximal part of the paired vasa deferentia serves as a sperm reservoir, while the distal one has a glandular character. An unpaired, cuticle-lined ejaculatory duct opens into the apex of the aedeagus. The single accessory gland is located asymmetrically at the level of, or slightly posterior to, coxae IV. The structure of the genital papillae, which are topographically related to the genital opening in both sexes, is also briefly described.

Witalifiski, W., 1993. Egg shells in mites: vitelline envelope and chorion in Acaridida (Acari). Exp.Appl. Acarol., 17: 321-.344.This study deals with the formation of vitelline envelope (VE) and chonon compartments in several free living and parasitic acaridid mites. In all investigated mites, the VE is of primary origin (produced by oocyte itself), whereas exochorion material is of tertiary, origin (oviduct or chorion gland .secretion).In acarid mites Acarus siro and Tyrophagus perniciosus, VE formation starts with the oviductal oocytes in which vitellogenesis already proceeds. It is characterized by stratification (Acarus) or coarse fibrillar texture (Tyrophag~). Oocyte microvilli penetrating VE material were not observed. When the vitellogenesis terminates, VE becomes homogeneous and is transformed into chorion. This is the only layer protecting the deposited egg in A. siro, whereas in T. perniciosus the chorion-coated eggs passing through the distal portion of the oviduct are additionally covered by exochorion material deposited in three distinct forms: dense patches, granules, and most conspicuous tocular chambers.In Tyrophagus longior, the egg surface closely resembles that of T. perniciosus, but the locular chambers are smaller. In Aleuroglyphus ovatus the exochorion material forms tiny spherical patches instead of locnlar chambers.In Sarcoptes scabiei, Notoedres cati and Falculifer rostratus, flocculent VE appears on vitellogenic oocytes in the oviduct. VE development is characterized by formation of numerous lenticular perivitelline spaces, which initially grow to disappear later. Then VE material transforms into fully homogeneous chorion. Chorion glands in Sarcoptes and Notoedres produce multivesicular secretory bodies; their content is released onto the egg surface to form a vesicular monolayer (exochorion) during the egg passage. The chorion gland in Falculifer is composed of two secretory cell types. Its secretion possibly glues the eggs to the host feather barb during highly ordered deposition, and forms the appendage ending with a fibbed plate, here considered to be a print of female undulate lamina acting as an ovipositor. The hatching suture is present. Neither distinct micropyle nor aeropyles have been found in eggs of species under study.The exochorion is proposed to be an adhesive layer which fixes the eggs to the substratum. The same role plays the chorion gland secretion in F. rostrat~. It can be argued, however, that locular chambers of Tyrophagus exochorion may participate in reduction of water loss rather than in egg adherence or plastron respiration, as previously suggested in the literature.

No abstract

No abstract

Astigmatans are a large group of mites living in nearly every environment and exhibiting very diverse reproductive strategies. In spite of an uniform anatomical organization of their reproductive systems, gametogenesis in each sex is highly variable, leading to gamete formation showing many peculiar features and emphasizing the distinct position of Astigmata. This review summarizes the contemporary knowledge on the structure of ovaries and testes in astigmatic mites, the peculiarities of oogenesis and spermatogenesis, as well as provides new data on several species not studied previously. New questions are discussed and approaches for future studies are proposed.

The Astigmata, a large and variable group, is still a subject of taxonomic dispute. Particularly, their origin from ancestors of the lower oribatid mites (e.g., Malaconothroidea) seems well documented by many lines of evidence. The structure of spermatozoa has been successfully applied to phylogenetic investigations in many animal groups. The aim of our study was to provide new data on spermatozoon structure in Astigmata and to consider its appropriateness in phylogenetic studies. The study reveals information on spermatozoa in 17 species of Astigmata (11 species studied for the first time) extending our knowledge to 18 species (one species known only from the literature) representing 12 families and 7 superfamilies. Spermatozoa have the same basic structure in all species: cells are multiform and the chromatin forms thin threads embedded directly in the cytoplasm; the acrosome is absent. The cytoplasm in most species contains electron-dense lamellae, varying in both number and arrangement within the cell. In Sarcoptoidea, electron-dense tubules in contact with lamellae margins were also observed in Psoroptidae (Psoroptes equi), whereas in two representatives of Sarcoptidae (Notoedres cati and Sarcoptes scabiei), only electron-dense tubules were found. In two species, Canestrinia sellnicki (Canestrinioidea: Canestriniidae) and Scutulanyssus obscurus (Analgoidea: Pteronyssidae), neither lamellae nor tubules were present. The mitochondria in a spermatozoon are usually gathered at the cell periphery and their structure is usually modified to form so-called mitochondrial derivatives. The chromatin threads are an autapomorphy strongly supporting the monophyly of Astigmata. As spermatozoa vary considerably between species in Astigmata, we deduce that sperm structure may be useful for phylogenetic analyses within the group. Several conclusions concerning the affinities within Astigmata are presented. Spermatology seems to be unhelpful, however, in questions on the origin of Astigmata (particularly for Astigmata-Oribatida relationships), since their sperm do not possess synapomorphies with sperm of the remaining groups of Acariformes, i.e., Endeostigmata, Prostigmata, and Oribatida.