A contribution to the systematics of the water mite Tiphys pistillifer (Koenike, 1908) (Acariformes, Pionidae)

Larva of the water mite Tiphys pistillifer (Koenike) is described for the first time. The morphology of this species is analyzed and male and female of the adult stage are re-described. Keys to females and males of the subgenus Acercopsis are provided.     

Functional morphology and ultrastructure of mouthparts in unfed water mite larvae Piona carnea (Koch, 1836) (Acariformes: Pionidae)

Mouthparts of unfed larvae Piona carnea (Koch, 1836) (Acariformes: Pionidae) were studied on whole-mount preparations, semi-thin sections and with TEM and SEM methods. The mouth apparatus is incorporated within the pseudotagma, gnathosoma, composed of the infracapitulum and of the chelicerae resting on the roof of the latter. The gnathosoma inclines to the long axis of the body and is inserted at its base into the idiosoma by the circumcapitular fold. The basal cheliceral segments are long and fused. An anterior projection, the proposed fused fixed digits, protrudes from the distal end of the basal cheliceral segment forward between the movable digits. The movable digits are always found in protruded position, strongly curved upward and show a groove on their inner sides. The ventral wall of the infracapitulum is made of the mentum posterior and the malapophyses anterior to the palp articulation. The malapophyses are squeezed between the large palps and envelope the distal portion of the chelicerae from the sides. The ventral portion of the fused malapophyses are provided with a characteristic ventral cuticular fork of unknown function. Each malapophysis terminates by a flexible lateral lip provided by several rigid jags looking posterad. The palps face downward and backward, and bear on the tibia the large curved palpal claws turned laterad. The palp femur bears on the ventral aspect a characteristic wide spade-like projection provided with its own muscles originating on the dorsal wall of the femur. The labrum is a thick cuticular arrow-like structure protruding forward into the preoral cavity, whereas the cervix is a thin weakly sclerotized plate. The particular labral valve projects forward from the dorsal basis of the labrum into the preoral cavity. The labrum and the cervix are provided by their own small labral and cervical muscles originating on the cervical apodemes. The pharynx is totally separated from the ventral wall of the infracapitulum and is devoid of ventral dilators. The dorsal pharyngeal dilators originate on the thick and sclerotized capitular apodeme and, posteriorly, on the paired cuticular branches, capitular apodemes, which end freely in the body cavity and are combined with the common salivary duct. The short sigmoid pieces serve for origin of the levator muscles of the chelicerae. Retraction of the gnathosoma and the chelicerae is mediated by several sets of muscles originating on the dorsal plate.     

Anatomy and ultrastructure of the salivary (prosomal) glands in unfed water mite larvae Piona carnea (C.L. Koch, 1836) (Acariformes: Pionidae)

Anatomy and ultrastructure of prosomal salivary glands in the unfed water mite larvae Piona carnea (C.L. Koch, 1836) were examined using serial semi-thin sections and transmission electron microscopy. Three pairs of alveolar salivary glands shown are termed lateral, ventro-lateral and medial in accordance with their spatial position. These glands belong to the podocephalic system and are situated on the common salivary duct from back to forth in the above mentioned sequence. The arrangement of the medial glands is unusual because they are situated one after another on the medial (axial) body line, therefore they are termed anterior and posterior medial glands. The secretory duct of the anterior medial gland mostly turns right, and the duct of the posterior gland turns left. The salivary glands are located in the body cavity partly inside the gnathosoma and in the idiosoma in front of the brain (synganglion). Each gland is represented by a single acinus (alveolus) and is composed of several cone shaped secretory cells arranged around the large central (intra-acinar) cavity with the secretory duct base. The cells of all glands are filled with secretory vesicles of different electron density. The remaining cell volume is occupied by elements of rough endoplasmic reticulum, and the membrane enveloping vesicles may have ribosomes on its external surface. Large nuclei provided with large nucleoli occupy the basal cell zones. The pronounced development of the prosomal salivary glands indicates their important role in extra-oral digestion of water mite larvae.     

Liacarus paraborealis, a new oribatid mite species (Acariformes, Oribatida) from Khabarovsk Territory

A new species, Liacarus paraborealis sp. n., was found in Khabarovsk Territory. It is characterized by the presence of a long, covering rostrum and connivent but completely divided lamellae with parallel inner margins; by the absence of translamella and the middle tooth between the lamellae; by the presence of a long spire of the trichobothrium; and by the presence of relatively short interlamellar hairs.     

Anatomy and ultrastructure of dermal glands in an adult water mite,Teutonia cometes (Koch, 1837) (Acariformes: Hydrachnidia: Teutoniidae)

Organization of dermal glands in adult water mites Teutonia cometes (Koch, 1837) was studied using light-optical, SEM and TEM methods for the first time. These glands are large and occur in a total number of ten pairs at the dorsal, ventral and lateral sides of the body. The slit-like external openings of the glands (glandularia) are provided with a cone-shaped sclerite, and are combined with a single small trichoid seta (hair sensillum), which is always situated slightly apart from the anterior aspect of the gland opening. Each gland is formed by an epithelium encompassing a very large lumen (central cavity) normally filled with secretion that stains in varying intensity on toluidine blue stained sections. The epithelium is composed of irregularly shaped secretory cells with an electron-dense cytoplasm and infolded basal portions. The cells possess a large irregularly shaped nucleus and are filled with tightly packed slightly dilated cisterns and vesicles of rough endoplasmic reticulum (RER) with electron lucent contents. Dense vesicles are also present in the apical cell zone. Some cells undergo dissolution, occupy an upper position within the epithelium and have a lighter cytoplasm with disorganized RER. Muscle fibers are regularly present in the deep folds of the basal cell portions and may serve to squeeze the gland and eject the secretion into the external milieu. The structure of these dermal glands is compared with the previously described idiosomal glands of the same species and a tentative correlation with the glandularia system of water mites is given. Possible functions of the dermal glands of T. cometes are discussed.     

A new mite superfamily Cloacaroidea and its position within the Prostigmata (Acariformes)

The external morphology of 2 closely related mite families, Cloacaridae and Epimyodicidae (Acari: Prostigmata), comprising highly specialized endoparasites of vertebrates, is analyzed. These mites exhibit strong regression of many structures ancestrally present in other Prostigmata as a consequence of their endoparasitic mode of life. The relationships of these 2 families with other taxa in the infraorder Eleutherengona are still not clear. Our reinterpretation of the chelicerae as unfused precludes inclusion of this lineage in the Cheyletoidea as proposed previously. A new superfamily, Cloacaroidea superfam, nov., incertae sedis, within the infraorder Eleutherengona is established for these 2 families, and their host-parasite relationships are briefly discussed. A new cloacarid species, Caminacarus dawsoni n. sp., from Graptemys pseudogeographica (Testudines: Emydidae) from the United States is also described.     

New species of the primitive oribatid mite families Brachychthoniidae and Phthiracaridae (Acariformes, Oribatida) from the Caucasus

Seven new species and a new subspecies of the families Brachychthoniidae Thor, 1934 and Phthiracaridae Perty, 1841 from the Caucasus are described: Liochthonius murtazalievi sp. n., Sellnickochthonius ilyinae sp. n., Atropacarus achmedovi sp. n., A. kremenitsai sp. n., A. yarovenkoi sp. n., A. chernovae sp. n., A. obesus minimus ssp. n., and Steganacarus (Tropacarus) adelaidae sp. n., and also the species Synchthonius elegans Forsslund, 1957, Atopochthonius maimaensis Grishina, 1971, and Atopochthonius artiodactylus Grandjean, 1949 from the Caucasus are figured.     

The parasitism of the itch mite Sarcoptes scabiei (Acariformes: Sarcoptidae)]

The life cycle of the itch mite Sarcoptes scabiei (L.), an intracutaneous parasite of man and animals, has been studied. The paper concerns morphological adaptations, embryonal and postembryonal development, life cycle pattern, scabious passage as a reproductive formation, invasive stages, feeding, reproduction and topical relationships with the host, distribution and survival in the environment.     

Morphological variablility in the chigger mite species Neotrombicula sympatrica (Acariformes: Trombiculidae) from Kyrgyzstan

Aberrations (quantitative chaetotactic deviations, i.e. decreasing or increasing of setae numbers and variations in arrangement of setae) and anomalies (qualitative chaetotactic deviations, for example, partial reduction of scutum, shortening of a seta more than 1.5-2 times, merging of setae) were recorded for 13 taxonomically important morphological structures in the chigger mite species Neotrombicula sympatrica Stekolnikov, 2001. 3308 specimens were studied as a total. 17.2% of them had various morphological deviations. The most common types of aberrations were observed in the number and positions of genualae I (94 specimens), AM seta (79 spec.) and sternal setae (77 spec.). The aberrations of sternal and coxal setae were usually interrelated: the sternal seta was "transferred" from the sternal area onto the coxa, or the other way round take place. The specimens having aberrations of sternal setae were twice as numerous as the specimens with aberrations of coxal setae (77 against 35). The specimens with aberrations of dorsal setae and mastitarsala were very rare (2 spec. each). Among anomalies, the presence of nude galeal seta (91 spec.) and scutal anomalies (66 spec.) were prevalent. The most frequently one form of deviation only was observed in one specimen of N. sympatrica. Nevertheless, the specimens simultaneously having several aberrations or anomalies were also found. 17 types of such combinations were observed, that counts 20.6% of all specimens with deviations. Symmetric deviations, namely the presence of two nude galeal setae (31 spec.), presence of 2 genualae on both legs I (4 spec.), presence of 2 AM (2 spec.) and symmetric reduction of scutal angles (1 spec.), sometimes cause troubles in diagnostics. The quarter of variance in N. sympatrica and in the species N. monticola Schluger et Davydov, 1967 formerly studied by the author turned out as almost identical. The specimens with deviations counted 14.5% of all studied specimens in the latter species. However, the structures of variance in these species is different. In N. monticola, the aberrations of humeral setae were dominant (71.6%) (Kharadov, Chirov, 2001), while in N. sympatrica, the aberrations of other structures were prevalent: genualae I (24.8%), AM (20.9%) and sternal setae (20.4%).     

A new water mite species of the genus <Emphasis Type="Italic">Georgella</Emphasis> (Acariformes,Gydryphantidae)

The larva, deutonymph, female, and male of a new water mite species, Georgella samaraensis, are described and illustrated. Larvae of Georgella are similar to larvae of the genus Hydryphantes, differing in the following characters: basal cheliceral segments have no longitudinal ribs, dorso-distal prominences of the pedipalpal tibia are undeveloped, and the excretory pore is partly surrounded by the anal sclerite. The larva known as G. koenikei (Münchberg, 1936) is erroneously treated as a larva of fresh-water Georgella (Hydrachnidia). The morphology of all the active developmental phases of Georgella strongly differs from that in mites of the genus Hydryphantes. Therefore, the generic status of Georgella should be restored.     

The ultrastructure and possible functions of nephrocytes in the trombiculid mite Hirsutiella zachvatkini (Acariformes: Trombiculidae)

The ultrastructure of nephrocytes during the post-larval development of the trombiculid mite Hirsutiella zachvatkini (Schluger) was investigated by means of transmission electron microscopy. Nephrocytes are situated either individually or in groups inside the haemocoelic space and are always ensheathed by a basal membrane. They contain numerous tubular elements, electron-dense inclusions and sometimes electron-lucent vacuoles. Invaginations of the plasma membrane, often in the form of labyrinthine channels, with coated pits of plasma membrane and characteristic slit diaphragms linking adjacent pedicels, typically occupy the peripheral parts of the cells. However, no distinct zonation of organelles in the nephrocytes of trombiculids was observed. The number of nephrocytes in the haemocoel and the intensity of development of their tubular elements and in particular of labyrinthine channels vary significantly during the ontogenesis of mites. The possible functions of nephrocytes and their structure and differentiation in comparison with other arachnids are discussed.     

A new subgenus and three new species of the Oribatid mite families hermanniellidae,Oribatellidae, and Scheloribatidae (Acariformes,Oribatida) from the Caucasus

A new subgenus, Sacculoribatella subgen. n., of Oribatella and 3 new species the families Hermanniellidae (Hermanniella aliverdievae sp. n.), Oribatellidae (Oribatella caspica sp. n.), and Scheloribatidae (Pachygena makarovae sp. n.) are described from the Caucasus.     

Phylogenetic taxonomy of the marine mite genus Rhombognathides (Acari: Halacaridae: Rhombognathinae)

This study examined the impacts of the alien waterweed, water hyacinth, on the abundance and diversity of aquatic macroinvertebrates in the littoral areas of northern Lake Victoria in Uganda. The weed had undergone explosive growth on the lake causing serious disruption to people, the economy and the ecosystem. This study was confined to impact of the weed in the littoral zone, not to the large floating mats of vegetation which float across the lake and clog large areas of shoreline.The littoral area studied comprised of fringing mats of Eichhornia crassipes (Mart) Solms (water hyacinth) to the lakeward of Cyperus papyrus; water hyacinth mats undergoing colonisation by Vossia cuspidata (Roxb.) Griff.; and a typical Cyperus papyrus L shore with no outer floating mat of water hyacinth. Numerical abundance (Nos. m^–2) and diversity (No. of taxa) of macroinvertebrates recovered from pure Eichhornia crassipes and the Eichhornia-Vossia succession increased from the fringe of the Cyperus papyrus towards the open water. In the typical Cyperus papyrus fringe, in the absence of water hyacinth, abundance was highest at the papyrus/open water interface and dropped off sharply towards open water. The Shannon–Weaver diversity index (H) of macroinvertebrates decreased progressively from pure Eichhornia crassipes stands, to Vossia/Eichhornia beds and Cyperus papyrus stands (H=0.56, 0.54 and 0.34, respectively) but were not significantly different. Dissolved oxygen decreased from open water into vegetation where it approached anoxia. Water hyacinth appeared to enhance the abundance and diversity of aquatic macroinvertebrates at the interface with the open water. The impoverished abundance and diversity of the macroinvertebrates deeper into the vegetation mats suggested negative environmental impacts of the water hyacinth when the fringe is too wide. Further research is recommended to establish the optimum width of the fringe of stationery water hyacinth that promotes maximum abundance and diversity of aquatic macroinvertebrates and, possibly, of other aquatic life. Since this study in 1997, there has been a dramatic decrease in Eichhornia infestations and by June 2000 it appeared largely to exist only as fringing vegetation in bays and inlets.     

Ultrastructure of the integument during moulting of the quiescent tritonymphal instar of trombiculid mite Hirsutiella zachvatkini (Acariformes: Trombiculidae)

The ultrastructure of the integument of the quiescent reduced tritonymph of the trombiculid mite Hirsutiella zachvatkini (Schluger) was investigated by means of transmission electron microscopy. Mites were investigated daily during the 14–16 day tritonymphal period (imagochrysalis). This period includes the deutonymphal moult (1–3 days), the quiescent tritonymph period (2–4 days), and the tritonymphal moult into the adult mite (6–10 days). A distinct recognizable feature of the tritonymphal moulting cycle is a sequence of events independent of precise time intervals. This process involves partial destruction and reorganization of the hypodermis of the previous instar, and formation of a new hypodermis of the subsequent instar from islands of rudimentary hypodermal cells. The integument of the reduced tritonymph differs greatly from that of both larva and active deutonymph and adult. It consists of a simply organized hypodermal layer of varying thickness and a thick clear poorly lamellate cuticle with curved pore canals, and lacking setae. The epicuticle is very thin and without a clear protein layer. The tritonymphal instar as such with its own cuticle situated near the hypodermis is encased within the detached covering of the previous active deutonymph, and may be considered a calyptostasic and entirely pharate instar. There is a tendency for reduced tritonymphal stage to be eliminated from ontogenesis and this stage is not homologous to the pupa of insects.     

Phylogenetic position of the mite family Myobiidae within the infraorder Eleutherengona (Acariformes) and origins of parasitism in eleutherengone mites

The position of the family Myobiidae in the infraorder Eleutherengona (Prostigmata) was analyzed with a cladistic parsimony approach for the first time. Species of the genera Anystis von Heyden (Anystidae), Pomerantzia Baker (Pomerantziidae), and Walytydeus Kuznetzov (Paratydeidae) were selected as outgroups. Among Eleutherengona, species of the following genera were selected as ingroup taxa: Hirstiella Berlese (Pterygosomatidae), Eucheyletia Baker, Cheyletiella Canestrini (Cheyletidae), Syringophilus Heller (Syringophilidae), Tarsocheylus Berlese (Tarsocheylidae), Heterocheylus Lombardini (Heterocheylidae), Pygmephorus Kramer (Pygmephoridae), Raphignathus Dugès (Raphignathidae), Neognathus Willmann (Caligonellidae), Storchia Oudemans (Stigmaeidae), and Tuckerella Womersley (Tuckerellidae). Three most parsimonious trees with similar topology were obtained. In all these trees, the family Myobiidae is situated outside of the clade joining the higher Raphignathae (Raphignathoidea and Cheyletoidea) and represents a branch within the earlier derivative Raphignathae. This result is based primarily on characters from leg setation and postembryonic development. The conclusion from this topology is that myobiid mites have developed some gnathosomal structures convergently with Cheyletoidea, including the stylet-like chelicerae and stylophore fused with the subcapitulum. The evolution of animal eleutherengone parasitism is discussed. Parasitism arisen independently in numerous phyletic lineages or superfamilies of Eleutherengona. The representatives of some phylogenetically distant eleutherengone lineages developed similar adaptations to predation and parasitism. However, in spite of some similarities in these adaptations, the evolutionary trends and pathways for switching to a parasitic mode of life are quite different in particular eleutherengone lineages.     

New data on the water mite fauna (Acari,Hydrachnidia, Halacaroidea) of the Sakha Republic (Yakutia)

Examination of the water mite collection made by the authors in the territory of the Sakha Republic (Yakutia) in 2006 has revealed 43 mite species of the phalanx Hydrachnidia, belonging to 19 genera and 12 families, 1 species of the phalanx Trombidia, and 2 freshwater species of the superfamily Halacaroidea, belonging to 2 genera and 1 family. All the species registered, except for two species of the phalanx Hydrachnidia (Mixobates processifer and Lebertia porosa), were recorded in the Sakha Republic for the first time. The species Aturus miyashitai Uchida, 1934 and A. parapilosus Kim et Chung, 1993 (Hydrachnidia) and the family Johnstonianidae Thor, 1935 (Trombidia) are new for the Russian fauna. The female of A. parapilosus is described for the first time.