The moss mites of the Cheviot (Acari: Oribatei)

A faunal list of oribatid mites collected from the summit of the Cheviot, Northumberland, is given, together with notes on the taxonomy and distribution of several of the species. Special attention is paid to the Arctic-alpine and European-alpine species and the list provides further support for the view that the upland areas of Britain are characterized by a common group of oribatid species. It is suggested that these species may be cold hardy or cold tolerant with relatively high supercooling points, enabling them to survive the winter at these higher altitudes.     

The evolution and distribution of Calyptozetes sarekensis (Acari: Oribatei)

Calyptozetes sarekensis , an oribatid mite found predominantly, though not exclusively in lichens, inhabits regions within the arctic circle and subarctically between latitudes 60^o and 70^o (Swedish Lapland, Norway, Bear Island, Spitzbergen, Jan Mayen, Iceland, Greenland, northern Canada). In recent years, however, the species has been recorded from a number of montane sites in Great Britain and southern Europe. There would appear to be only two possible explanations for die discontinuous distribution of this mite. (1) The species has been transported from its main arctic and subarctic area of distribution to its southern montane outposts by some agent (driftwood, birds, wind), or (2) in Britain and southern Europe it represents a relict species of the Ice Age, left stranded on high ground after the final retreat of the ice. Evidence is presented in support of the second hypothesis. In addition, it is suggested that its presence on the different land masses of its main arctic and subarctic range, which are separated from each other by wide stretches of ocean, could be explained by die hypothesis that it is a very ancient species daring from the time Laurasia was in existence some 60 or more million years ago. The alternative hypothesis of transportation of the species between one or more of these areas, however, is by no means ruled out.     

A list of oribatid mites (Acari,Oribatida) of Vietnam

A species list of identified oribatid mite taxa (Acari, Oribatida) in the fauna of Vietnam is provided. During 1967–2015, a total of 535 species/subspecies from 222 genera and 81 families was registered. Of these, 194 species/subspecies were described as new for science from Vietnam.     

Light and electron microscope studies on Helicosporidium sp. parasitizing oribatid mites (Oribatei,Acarina) and collembola (Apterygota,Insecta) in forest soils

The life cycle of Helicosporidium sp. parasitizing natural populations of oribatid mites and collembolans in forest soils, is described by means of light, Nomarski interference, and electron microscopy. The ultrastructure of some early sporogonic stages (cysts), the young (maturing) spore, and the mature spore is discussed. Some data on the host-parasite relationships and prevalence of infection are presented.     

No evidence for the 'Meselson effect' in parthenogenetic oribatid mites (Oribatida, Acari)

It has been hypothesized that in ancient apomictic, nonrecombining lineages the two alleles of a single copy gene will become highly divergent as a result of the independent accumulation of mutations (Meselson effect). We used a partial sequence of the elongation factor-1alpha (ef-1alpha) and the heat shock protein 82 (hsp82) genes to test this hypothesis for putative ancient parthenogenetic oribatid mite lineages. In addition, we tested if the hsp82 gene is fully transcribed by sequencing the cDNA and we also tested if there is evidence for recombination and gene conversion in sexual and parthenogenetic oribatid mite species. The average maximum intra-specific divergence in the ef-1alpha was 2.7% in three parthenogenetic species and 8.6% in three sexual species; the average maximum intra-individual genetic divergence was 0.9% in the parthenogenetic and 6.0% in the sexual species. In the hsp82 gene the average maximum intra-individual genetic divergence in the sexual species Steganacarus magnus and in the parthenogenetic species Platynothrus peltifer was 1.1% and 1.2%, respectively. None of the differences were statistically significant. The cDNA data indicated that the hsp82 sequence is transcribed and intron-free. Likelihood permutation tests indicate that ef-1alpha has undergone recombination in all three studied sexual species and gene conversion in two of the sexual species, but neither process has occurred in any of the parthenogenetic species. No evidence for recombination or gene conversion was found for sexual or parthenogenetic oribatid mite species in the hsp 82 gene. There appears to be no Meselson effect in parthenogenetic oribatid mite species. Presumably, their low genetic divergence is due to automixis, other homogenizing mechanisms or strong selection to keep both the ef-1alpha and the hsp82 gene functioning.     

Appendage development in embryos of the oribatid mite Archegozetes longisetosus (Acari, Oribatei, Trhypochthoniidae)

The development of reliable techniques to provide large numbers of fixed mite embryos free of their tough membranes has allowed us to produce scanning electron micrographs of oribatid embryos for the first time. Antibody staining for expression of the gene Distal-less demonstrates the formation of the labrum from a pair of regions in the ocular lobes, indicating a possible appendicular origin for the labrum. The chelicerae are followed from their initial postoral position through their anterior rotation to become preoral. The pedipalpal lobe, involved in the formation of the gnathosoma, is shown to be almost the size of the pedipalp at some stages, as well as expressing Distal-less . The fourth pair of walking limbs are not present in oribatid prelarvae and larvae, however, their anlage are visible in later embryonic stages but these do not express the gene Distal-less , suggesting that formation of distal structures is suppressed at this stage. Claparède's organs, present between coxae of legs I and II of larvae, are shown for the first time unequivocally to derive from the base of legs II. These are proposed to be homologous to the lateral organs of other arachnid groups.     

Setal variability of <Emphasis Type="Italic">Hydrozetes lemnae</Emphasis> and <Emphasis Type="Italic">H. thienemanni</Emphasis> (Acari: Oribatida: Hydrozetidae)

Setal variability and the other morphological characters of juvenile stages and adult of Hydrozetes lemnae (Coggi, 1897) and H. thienemanni Strenzke, 1943 were investigated. In the juveniles of both species the length and shape of some setae vary, especially in the gastronotic region, more so in H. lemnae, which is parthenogenetic and reproduces by thelytoky, than in H. thienemanni, which is dioecious. The former species usually has more thick setae in the anterior and medial regions of the gastronotum, especially in the larva, compared to the latter. In the juveniles of H. lemnae the prodorsal setae le and in are longer, and in the nymphs the gastronotal setae of the l-series are usually longer than in H. thienemanni. These species differ distinctly by the number of long setae in the posterior part of the nymphs; in H. lemnae three pairs of long setae occur, while in H. thienemanni only two pairs; the respective juvenile stages of H. lemnae are also smaller than those of H. thienemanni. In the adults the number of c-series setae varies, as seta c ₁ is lost, and in some individuals also seta c ₃, and only seta c ₂ remains.     

Mating and spermatophore morphology of water mites (Acari: Parasitengona)

In this paper I synthesize original and published studies of sperm transfer behaviour of 23 genera of water mites from 15 families. The morphology of spermatophores from 16 genera (12 families) is described. Behaviour and/or spermatophores are described for the first time for the following species: Hydrachna magniscutata Marshall, Hydrachna hesperia Lundblad, Hydrachna sp. nr. leegei Koenike, Limnochares americana Lundblad, Limnesia undulata (Müller), Neumania distincta Marshall, Unionicola (three species in the U. crassipes-complex), Thyas slolli Koenike, Lebertia annae Habeeb, Lebertia sp., Piona sp. nr. debilis (Wolcott), Tiphys vernalis (Habeeb), Arrenurus dentipetiolatus Marshall, Arrenurus marshalli Piersig and Arrenurus birgei Marshall. On the basis of proximity of male and female during sperm transfer, I divide water mites into four groups: complete dissociation, involving no physical or chemical contact between the sexes (nine genera); incomplete dissociation, requiring distance-or contact-chemoreception but not involving pairing behaviour (five genera); pairing with indirect transfer, involving pairing behaviour with females controlling sperm uptake (three genera); pairing with direct transfer (=copulation), involving pairing behaviour and male placement of sperm in the receiving structure of the female (12 genera). Four genera have representative species in more than one category of sperm transfer. Factors possibly leading to the diversity of water mite mating behaviour include an evolutionarily flexible mode of sperm transfer in the ancestral water mite, and the development of planktonic and endoparasitic habits in many mites. Morphological features of spermatophores that improve physical stability, probability of females taking up sperm and resistance against osmotic stress are discussed. Finally, I present implications of mating behaviour and spermatophore morphology for phylogenetic relationships within water mites and between this group and terrestrial Acari.     

Different colonization patterns of phytophagous and predatory mites (Acari: Tetranychidae, Phytoseiidae) on three grape varieties: a case study

In a vineyard having three varieties of grape (Merlot, Trebbiano and Garganega) differently colonized by two phytoseiid species,Typhlodromus pyri Scheuten andAmblyseius andersoni (Chant), the dynamics of mite populations were monitored over 5 years (1989–1993) in order to study their colonization, interspecific competition and the control of spider mites, i.e.Panonychus ulmi (Koch). These aspects were also investigated by releasingT. pyri, A. andersoni andAmblyseius aberrans (Oudemans) on some of the above varieties. In most of the experimental years (1989–1992), selective pesticides were used in order to allow a successful release of phytoseiids, in particularA. aberrans. The use of non-selective insecticides was re-established during 1993 in order to test its effect on the new mite communities originating from 1989 onwards. In the first years of the experiments an apparent relationship between grape variety and phytoseiid species was observed: in the control plots,A. andersoni occurred on Merlot whereT. pyri was rare, while the latter species was largely dominant overA. andersoni on Trebbiano and Garganega.Panonychus ulmi populations reached moderate levels only on Merlot and in the first part of experiments. The variety-phytoseiid species relationship was temporary as, at the end of experiments,T. pyri was completely dominant on all varieties. This new situation started when prey occurrence and interspecific competition decreased in importance. The moderate success of theT. pyri release on Merlot contrasts with the results of previous experiments. Two factors could be involved in this phenomenon: low interspecific competition by phytoseiids and predation by macropredators.Amblyseius aberrans was able to displaceA. andersoni andT. pyri on grape varieties where the two species were more abundant and reached higher population densities on varieties with pubescent leaf undersurfaces. In the first experimental year, spider mite densities were reduced more effectively inA. aberrans release plots than in the control or inT. pyri release plots. One year later,P. ulmi reached lower levels in the release treatments than in the control.Typhlodromus pyri andA. aberrans persisted in conditions of prey scarcity. The high competitivity ofA. aberrans over the remaining two phytoseiid species constitutes a major factor in selecting predatory species for inoculative releases in vineyards.     

The water mites (Acari: Hydrachnidia) of streams in The Netherlands: Distribution and ecological aspects on a regional scale

The water mites of running waters in The Netherlands have been surveyed for the period 1987–1992. The aims were to investigate their present distribution, to make a comparison with historical data and to identify differences in water mite assemblages on a regional scale. The investigation covered 821 sites in eight different drainage areas. In spite of the scarcity of historical data, it may be concluded that in the course of this century about 40% of rheophilic water mites have become extinct. In canalized streams lentic species are dominant. In springs and spring streams, lotic species can survive, but the assemblages consist mainly of euryoecious water mite species.Multivariate techniques were used to show regional differences. These differences are mainly determined by stream hydraulics. The area of Zuid-Limburg can easily be demarcated by its relatively high number of rheophilic species. The man-made streams (sprengen) at the east side of the Veluwe area are characterized by a number of species which indicate undisturbed circumstances. The response of water mites to pollution of running waters is discussed.     

Water mites of the genus Sperchon Kramer (Acari: Hydrachnidia: Sperchontidae) from Turkey,with description of a new species from Taurus Mountains (southern Turkey)

A new water mite species Sperchon (Hispidosperchon) serapae n. sp. is described. The material was collected from a slow-flowing stream during field study on the water mite fauna of the Lakes region in southwestern Turkey. An updated list of hitherto known species of Sperchon Kramer from Turkey, including nomenclatural changes and numerous new locality records to the species, is also given.     

Molecular and morphological differentiation between steganacarid mites (Acari: Oribatida) from the Canary islands

Two steganacarid species, Steganacarus ( Steganacarus ) tenerifensis and S . ( S .) carlosi , the first endemic to Tenerife and the second to La Gomera and Tenerife, were found to have such wide morphological variability as to cast doubt on their specific limits. Cluster analysis and MDS ordering were used to quantify morphological variation, and biochemical procedures were used to assess genetic variation in the two entities. The results revealed disagreement between the morphological and genetic data as reported in previous studies on steganacarid mites. Morphological traits were highly heterogeneous in the Canary island populations and genetic structure was homogeneous with very low heterozygosity. The separation of the two Canary island species, not to mention the phenotypes close to carlosi , is difficult to justify due to their very high genetic identity. The presence of morphological intermediates suggests the same conclusion. However, the sympatry of some phenotypes and previous data on this animal group are a source of doubt and suggest that further investigations are needed before conclusions can be reached in this regard. Correlations between morphological differentiation and known palaeogeographic events are suggested in the light of the possible evolutionary history of the steganacarid mites on the Canary islands.     

Morphology of Hydrozetes confervae () and H. parisiensis (Acari: Oribatida: Hydrozetidae), and keys to European species of Hydrozetes Berlese, 1902

Hydrozetes confervae [Schrank, F.P., 1781. Enumeratio insectorum Austriae indigenorum. Augustae Vindeliciorum, 1-552] and Hydrozetes parisiensis [Grandjean, F., 1948. Sur les Hydrozetes (Acariens) de l’Europe occidentale. Bull. Mus. Nat. Hist. nat., Paris, ser. 2(20), 328-335] are common European species of the aquatic oribatid mite family Hydrozetidae, but their external morphology is incompletely known. We describe and illustrate their larvae for the first time, and the nymphs of both species are redescribed and illustrated. Juveniles of the two species differ mainly by the position of gastronotal seta lm in relation to the opisthonotal gland opening (gla) and by the number of extremely long posterior hysterosomal setae in nymphs. In H. confervae seta lm inserts anteromedial to gla, but posterior to gla in H. parisiensis; nymphs of H. confervae have three pairs of long hysterosomal setae, while H. parisiensis has a larger, but variable number. Separate identification keys for the larvae, nymphs and adults of all known European species of Hydrozetes Berlese, 1902, are presented.     

Evaluation of astigmatid mites as factitious food for rearing four predaceous phytoseiid mites (Acari: Astigmatina; Phytoseiidae)

Phytoseiids are possibly the most important mites used in biological control and are usually produced using a tritrophic system that, although efficient, is expensive and laborious. Mites of the cohort Astigmatina (Sarcoptiformes) have been used as factitious prey in the mass rearing of phytoseiids and may allow a much simpler production system. This research evaluated the potential of ten Astigmatina species to serve as factitious food sources for Euseius concordis (Chant), Iphiseiodes zuluagai Denmark and Muma, Neoseiulus barkeri Hughes and Neoseiulus californicus McGregor, all phytoseiid species commonly found in different countries. The high fecundity and survival rates obtained suggest that Thyreophagus n. sp. is a suitable prey for rearing N. barkeri and that Austroglycyphagus lukoschusi (Fain) and Blomia tropicalis is suitable for rearing N. californicus. Oviposition by E. concordis was negligible, but survivorship was high on most prey species, suggesting that these species may be useful for maintenance of the predator. I. zuluagai had low fecundity and survival on all the astigmatid species evaluated and none were suitable for its rearing.     

Microhabitat selection and coexistence in feather mites (Acari: Analgoidea) on Alaskan seabirds

Summary Two species of feather mites, Alloptes (A.) sp. and Laronyssus martini, coexisted on the flight feathers of kittiwakes, while Alloptes (C.) sp. occurred alone on murres. All three species were found mostly on the ventral surface of mid-wing regions. On individual feathers, the mites were attached to the distal sides of barbs on the trailing vanes. The two species coexisted on kittiwakes but occupied different portions of feathers. The results suggest that the two species compete for the attachment site on the feather and Alloptes (A.) sp. is excluded by L. martini from the preferred microhabitat.     

Chemoreception in four species of water mites (Acari: Hydrachnida): behavioural and morphological evidence

Silver nitrate staining of the solenidial and eupathidial sensilla on the palpi, tarsi and tibiae of legs I and II of Arrenurus acutus, Geayia ovata, Mideopsis reelfootensis and Albia caerulea, along with ultrastructural studies, showed that these setae have a porous shaft cuticle. These setae are hollow and contain dendrites in their lumens and more than one neuron is associated with each setae. Behavioural experiments supported the involvement of these sensilla in the perception of chemical cues from prey and sexual partners.     

Chemoreception in four species of water mites (Acari: Hydrachnida): behavioural and morphological evidence

Silver nitrate staining of the solenidial and eupathidial sensilla on the palpi, tarsi and tibiae of legs I and II of Arrenurus acutus, Geayia ovata, Mideopsis reelfootensis and Albia caerulea, along with ultrastructural studies, showed that these setae have a porous shaft cuticle. These setae are hollow and contain dendrites in their lumens and more than one neuron is associated with each setae. Behavioural experiments supported the involvement of these sensilla in the perception of chemical cues from prey and sexual partners.     

Oribatid mites reveal that competition for resources and trophic structure combine to regulate the assembly of diverse soil animal communities

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Population dynamics of phytophagous and predatory mites (Acari: Tetranychidae, Eriophyidae, Phytoseiidae) on bamboo plants in Fujian, China

The seasonal cycle and population dynamics of Schizotetranychus nanjingensis Ma and Yuan, Aponychus corpuzae Rimando (Tetranychidae), Aculus bambusae Kuang (Eriophyidae) and their natural enemy Typhlodromus bambusae Ehara (Phytoseiidae) were studied during 1996–1998 in moso bamboo forests in Nanping, Fujian, China. Damage to bamboo leaves was often caused by mixed populations of the three phytophagous species, which displayed different seasonal dynamics: S. nanjingensis fed actively and reproduced in May and from late July to late October (aestivating from June to mid July), Ap. corpuzae was active and reproduced from mid July to late November, and Ac. bambusae from July to next February. During Spring S. nanjingensis was the dominant species with the greatest niche width, but in Summer Ac. bambusae and Ap. corpuzae became dominant and had greater niche widths. In Autumn, Ac. bambusae decreased but both S. nanjingensis and Ap. corpuzae mites increased and the latter became dominant. In winter all species decreased sharply in number. The two spider mite species (S. nanjingensis and Ap. corpuzae) had high niche overlaps in all four seasons. Niche overlaps between the eriophyid Ac. bambusae and the two spider mites were similarly high except during the spring when Ac. bambusae was absent. The predatory mite (T. bambusae) had higher niche overlap with Ap. corpuzae than with others during Autumn and Winter, but during Spring and Summer niche overlap was higher with S. nanjingensis.     

Fine structure of the genital system in the females of Pergamasus mites (Acari: Gamasida: Pergamasidae)

The female reproductive system in Pergamasus mites consists of an unpaired vagina, vaginal duct, uterus, and ovary. Additionally, there are paired vaginal glands, as well as unpaired ventral and paired lateromedial glandular complexes. The vagina and vaginal duct are cuticle‐lined. In the dorsal wall of the vagina, this lining forms the endogynium which possesses a “sac” and two conspicuous “spherules” and is armed with “stipula” and other cuticular protrusions. The endogynium functions as a spermatheca, being a storing site for the spermatophore. The spherule procuticle is perforated by microvilli of underlying cells that are structurally very unusual. The lining of the vaginal duct forms numerous cuticular fibers directed toward the vagina. There is an external layer of muscles, supposedly functioning as a sphincter. The uterus is an organ in which the fertilized egg is stored for some time and starts embryonic development. Its wall is composed of glandular epithelial cells. The ovary consists of inner and outer parts. The former part is formed by a nutritive syncytium, whereas the latter contains growing oocytes. Two groups of glands connect with the genital tract. Paired vaginal glands are composed of glandular and secretion‐storing parts and open into the vagina. Paired lateromedial and unpaired ventral glandular complexes empty into the genital tract between the vaginal duct and uterus. The structure of the female genital system is discussed in terms of its function and phylogeny. J. Morphol. 240:195–223, 1999. © 1999 Wiley‐Liss, Inc.