Morpho-functional variety of the coxal glands in cheyletoid mites (Prostigmata). II. Cheyletidae.

Trombidiform mites are characterized by the presence of several paired glands in the anterior body portion united by a common conducting duct (podocephalic canal). Apart from the acinous (salivary) glands the podocephalic system includes a pair of tubular coxal glands (CGs) responsible for osmoregulation. The aim of the present study was to figure out how functional changes of acinous glands reflect on the corresponding CG. For this purpose, the anatomy and fine structure of the CG were analyzed in two mite species, Bakericheyla chanayi and Ornithocheyletia sp. (Cheyletidae), which have a different composition of their single acinous gland. The results showed that in both species the CG lacks a filtering saccule. It is composed of the proximal and distal tubes and leads into a cuticle-lined excretory duct. Both tubes demonstrate a similar species-specific fine structure. They are characterized by an extensive system of apical membrane invaginations (internal canals) associated with numerous large mitochondria. Local areas of modified internal canals were regularly observed in both species. They contain structures resembling those constituting filtering slit diaphragms of other animals. In O. sp., CG cells in addition demonstrate features characteristic of protein-like secretion. Apparently this correlates with the loss of true salivary glands in this species, as its acinous gland was previously assumed as silk producing. Contrary to this, the CG of B. chanayi shows no kind of granulation, which coincides with the presence of a salivary portion in its complex acinous gland. The microtubule-rich intercalary cells at the base of the excretory duct were associated with special muscles presumably regulating the dilation of the duct lumen. These cells might represent a basic feature common to different types of podocephalic glands.

[The quill mite Syringophilopsis fringilla (Fritsch) (Acari: Trombidiformes: Syringophilidae): The structure of receptor organs providing feeding of the parasite inside the feather quill].

The structure of sensory organs situated on palps and inside the cheliceral stylet of the quill mite Sringophilopsis fringilla (Fritsch, 1958) was examined in scanning and transmitting electron microscopes. Eight sensilla of 3 types were revealed on palptarsus, including two contact chemo-mechanosensory sensilla, a single distant chemosensory (probably olfactory) sensillum, and 5 tactile mechanosensitive sensilla. All other sensilla situated on basas parts of the palp and on the outer surface of gnathosoma are represented by tactile mechanoreceptors. A proprioceptor sensillum was revealed in the movable digit of the chelicera; modified cilia of dendrites of 5 sensory neurons run in the inner non-sclerotized core of the stylet, ending at different levels as electron-dense rods connected with the sclerotized wall of the stylet. The authors assume that the proprioceptor sensillum of the stylet detects the pressing force of the movable digit on the inner wall of the quill during piercing process, while papal sensilla determine the optimal place for piercing.

Morpho-functional variety of the coxal glands in cheyletoid mites (Prostigmata). I. Syringophilidae.

The anatomy and fine structure of the osmoregulatory coxal glands have been investigated in the parasitic quill mites, Syringophylopsis fringilla (Fritsch) and Torotrogla cardueli Bochkov & Mironov (Syringophilidae). In both species, tubular coxal organs are the only pair of propodosomal glands, whereas in most Prostigmata, several acinous (salivary) glands are also present entering a pair of podocephalic canals, which are continuations of the coxal glands' excretory ducts. In the adults and tritonymphs of the quill mites, the coxal glands show the same basic morphology with slight differences in their packing mode between the studied species. A filtering sacculus is absent. Each gland consists of a long tubular gland body comprising 4 to 6 longitudinal trunks and a cuticle-lined excretory duct continuous into the podocephalic canal. The gland body is composed of 4 morphologically distinct regions: proximal and distal tubes followed by the two granule-containing regions denoted as the "violet" and "green" gland portions. Electron microscopy showed the epithelium of the proximal and distal tubes to be rich in deep apical membrane invaginations associated with branched pinocytotic canals or vacuoles, especially extensive in the distal tube. A number of large mitochondria are concentrated basally to maintain ionic and water transport. The enlarged penultimate "violet" portion is composed of high epithelial cells that show certain endocytotic activity and also produce a large amount of uniform secretory granules derived from numerous small Golgi bodies. The terminal "green" portion produces dense protein-like inclusions and might functionally substitute lost salivary glands. The fine structure of the podocephalic canal is also thoroughly described and compared to the information available in the literature.

Morphological aspects of blood digestion in a parasitic mite Bakericheyla chanayi.

All life stages of B. chanayi (Acariformes: Cheyletidae) are characterized by occasional bloodsucking and a long period of digestion. No newly engorged mites were found during the period of their host birds' migration. The fine structure of the digestive tract of a blood-feeding acariform mite is described for the first time. The anterior midgut (AMG) is a place of blood digestion, while the posterior midgut (PMG) is involved in nitrogen metabolism forming guanine crystals as the main end-product. The AMG epithelium consists of digestive cells that probably arise from mitotically active basal cells with high synthesizing activity. As observed in ticks, blood digestion is accompanied by the formation of huge endosomes that serve as places of storage and sorting of ingested material. Digestive cells show different types of endocytotic activity as well as various late endosomes, which implies different subcellular pathways for different blood components. In both midgut regions, elimination of the excretory material occurs by apocrine secretion or by discharging of apical cell fragments (loaded with lysosomes) into the gut lumen. The formation of guanine granules occurs inside the lysosomes of PMG epithelial cells thus having much in common with intracellular digestion. Peculiarities of intracellular blood digestion were analyzed according to the modern hypothesis of endocytosis and compared to what is known in ticks.

The ultrastructural investigation of the midgut in the quill mite Syringophilopsis fringilla (Acari, Trombidiformes: Syringophilidae).

The midgut of the females of Syringophilopsis fringilla (Fritsch) composed of anterior midgut and excretory organ (=posterior midgut) was investigated by means of light and transmission electron microscopy. The anterior midgut includes the ventriculus and two pairs of midgut caeca. These organs are lined by a similar epithelium except for the region adjacent to the coxal glands. Four cell subtypes were distinguished in the epithelium of the anterior midgut. All of them evidently represent physiological states of a single cell type. The digestive cells are most abundant. These cells are rich in rough endoplasmic reticulum and participate both in secretion and intracellular digestion. They form macropinocytotic vesicles in the apical region and a lot of secondary lysosomes in the central cytoplasm. After accumulating various residual bodies and spherites, the digestive cells transform into the excretory cells. The latter can be either extruded into the gut lumen or bud off their apical region and enter a new digestive cycle. The secretory cells were not found in all specimens examined. They are characterized by the presence of dense membrane-bounded granules, 2-4 microm in diameter, as well as by an extensive rough endoplasmic reticulum and Golgi bodies. The ventricular wall adjacent to the coxal glands demonstrates features of transporting epithelia. The cells are characterized by irregularly branched apical processes and a high concentration of mitochondria. The main function of the excretory organ (posterior midgut) is the elimination of nitrogenous waste. Formation of guanine-containing granules in the cytoplasm of the epithelial cells was shown to be associated with Golgi activity. The excretory granules are released into the gut lumen by means of eccrine or apocrine secretion. Evacuation of the fecal masses occurs periodically. Mitotic figures have been observed occasionally in the epithelial cells of the anterior midgut.

[Peculiarities of the internal anatomy in the mite family Syringophilidae by the example of Syringophilopsis fringilla--a parasite of chaffinch].

Internal anatomy of the female Syringophilopsis fringilla (Fritsch, 1958) was investigated by light microscope using electron microscope to control the results for some body regions. The digestive tract is open. The anterior midgut includes the stomach and two pairs of caeca. The posterior midgut is represented by a long tubular excretory organ being connected to the stomach via a small opening. The opening is provided by a muscular sphincter. The short hind gut ends in the anal opening at the terminal side of the body. The unpaired tubular gland occupies medial region of the body between the brain and the mouth parts. Paired coxal glands lack typical sacculi. Each of them, in addition to long filtering tubules, contains two glandular regions producing different secretory products. The cuticul-lined excretory duct of each coxal gland opens into the podocephalic canal, running from the base of leg coxae I to the front side of the rostrum The female reproductive system of S. fringilla is composed of the unpaired ovary, large oviduct, and cuticular vaginal cavity with extensively folded walls. Vagina leads to the separate opening, situated in the deep body invagination ventrally to the anus. The oviduct consists of highly folded proximal portion and enlarged distal one. The distal portion of the oviduct is characterized by the glandular epithelial lining producing special secretory product into the lumen of the organ. All females examined contain numerous long spermia inside the large receptaculum seminis. The latter runs into the oviduct at the junction of its two parts. Large granulocytes were observed in the body cavity of the mites. Neither nephrocytes nor typical fat body cells were found.

[Ultrastructure of the testes and spermatogenesis in the mite Anystis baccarum].

The epithelial lining of testes in Anystis baccarum is glandular and produces a secretory product necessary to form spermatophores. The main stages of spermatogenesis occur in the lumen of the testis in groups of synchronously developing sister cells. Spermatogonia and late spermatids are encircled by glandular cells. Reorganization of developing spermatids is typical of the trombidiform mites and includes formation of the acrosomal complex, cytoplasm elimination, disappearance of the nuclear envelope and formation of invaginations of plasmalemma. The chromatin material condensation is not followed by the entire chromatin body formation. In mature spermatoza, dense chromatin strands (80b nm in diameter) lie along the cell in the peripheral layer of the cytoplasm. Mature spermatozoa lack axonema or any protrusions. A layer of microtubules, visible underneath the outer membrane, may serve for sperm movement in the female genital duct. The acrosomal complex consists of acromal granule, acrosomal filament and subacrosomal substance. This, as well as two aggregates of typical mitochondria, looks plesiomorphic.

[Formation of the peritrophic membrane in the gut of Colicoides punctatus (Diptera: Ceratopogonidae)]. / Obrazovanie peritrofitseskoi membrany v kishechnike Culicoides punctatus (Diptera: Ceratopogonidae).

Using light and electron microscopy, the structure of the peritrophic membrane (PM) was studied in females of the biting midge Culicoides punctatus (Mg.) during the process of blood meal digestion. The PM formation occurs in the posterior part of midgut and lasts during the most time of the digestive cycle. The PM precursors are probably not associated with any intracellular granules. The PM consists of two main components: light structural component and dark amorphous matrix, both of which are directly released from the entire microvillar surface. The aggregation of secreted components takes place in the gut lumen to form gel-like multilayered PM up to 6 microns thickness with bundles of microfibrills situated in the PM surface facing the lumen. Similarities and differences of the PM formation in most groups of blood-sucking insects are discussed.

[The organization of the female reproductive system in the parasitic mite Myobia murismusculi (Trombidiformes: Myobiidae)]. / Organizatsiia zhenskoi reproduktivnoi sistemy paraziticheskikh kleshchei Myobia murismusculi (Trombidiformes: Myobiidae).

The general morphology of the internal genital organs in Myobia murismusculi females have been studied by means of light and electron microscopy. It is shown, that their reproductive system is composed of the single ovary, long complex oviduct, cuticular vagina and receptaculum seminis. The apical region of the ovary is formed by the numerous processes of gonadian somatic cells. These cells generate the ovarian sheath and probably take place in oocyte's metabolism. Any nutritive cells in the Myobia ovary are absent. The vitellogenetic oocytes develop in the ovarian pouches like in other trombidiform mites. The oviduct consists of three parts, each of them has a specific ultrastructure and type of secretory product. Two proximal parts of the oviduct produce the egg-shell components, while the third distal part never contains oocytes. It could be suggested that this part produces a special secret onto the oocyte surface to glue the oocytes to the hairs of host.

[A morphologic analysis of digestion in Leptopsylla segnis (Siphonaptera: Leptopsyllidae) fleas]. / Morfologicheskii analiz pishchevareniia u blokh Leptopsylla segnis (Siphonaptera: Leptopsyllidae).

Changes in the ultrastructure of cells of the intestinal epithelium during the digestion of one blood portion were traced in the fleas L. segnis. It is shown that alongside with the cavity digestion take place elements of intracellular digestion. Hypothetic scheme of the digestive cell functioning is given.