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.     

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.     

Biodiversity and distribution of water mites (Acari, Hydrachnidia) in spring habitats

1. The distribution, species richness and ecology of spring‐dwelling water mites in Italy were investigated with the aim to better elucidate the role of spring habitats to sustain high levels of biodiversity and their contribution to freshwater biodiversity at a local and regional scale. 2. More than 300 springs in different geographic areas (Alps, Central and Southern Apennines, Sicily and Sardinia), were examined with a total of 163 water mite species recorded. 3. Species richness in each area ranged from 33 species on Sardinia to 77 on Sicily. The highest diversity was found in the Gran Sasso (Central Apennines). The proportion of crenobionts (species strictly bound to this type of habitat) exceeded 50% in almost all the areas investigated. 4. A diverse (up to 20 species per spring) and highly specialised mite fauna was observed in undisturbed rheocrenes and in natural springs of intermediate typology (rheohelocrenes and rheopsammocrenes). In springs subjected to human impacts (pasture, deforestation, alteration and transformation of spring sources) species richness declined and crenobionts were replaced by unspecialised crenoxenes. 5. The zoogeographic importance of spring habitats is confirmed by the presence of 18 endemic species and by members of genera with an interesting disjunct and relict distribution. 6. A comparison with other geographic areas suggests that springs contain a significant fraction of the total number of species found in freshwater habitats and may contribute almost one third of regional freshwater biodiversity. The presence of endemic crenobionts and rare taxa highlights the importance of these habitats in maintaining high levels of biodiversity as well as their contribution to a better understanding of biodiversity patterns in freshwaters.     

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.     

Origin and higher-level relationships of psoroptidian mites (Acari: Astigmata: Psoroptidia): evidence from three nuclear genes

Phylogenic relationships of the Psoroptidia, a group of primarily parasitic mites of vertebrates, were investigated based on sequences from three nuclear genes (4.2 kb aligned) sampled from 126 taxa. Several morphological classification schemes and a recent molecular analysis, suggesting that the group may not be monophyletic were statistically rejected by newly generated molecular data, and the results are robust under a range of analytical and partition strategies. Six families Psoroptidae, Lobalgidae (mammalian parasites), Pyroglyphidae (house dust mites and parasites inside feather calamus), Turbinoptidae (upper respiratory track parasites of birds), Psoroptoididae (downy feather mites), and Epidermoptidae (skin parasites of birds) form a well-supported monophyletic group (the epidermoptid-psoroptid complex). These relationships, recovered by combined and separate analyses of all gene partitions, were previously suspected based on some morphological evidence, but evidence has been dismissed as resulting from convergence based on similar parasitic ecologies. The existence of the epidermoptid-psoroptid complex and the statistical rejection of Sarcoptoidea (the morphology-based group joining all mammal-associated mites) indicate that current classification criteria, influenced as they are by host preferences, need to be reassessed for non-pterolichoid superfamilies. However, two of our findings remain sensitive to analytical methods and assumptions: (i) the families Heterocoptidae and Hypoderatidae as the first and second closest outgroups of Psoroptidia, respectively, and (ii) the superfamily Pterolichoidea (including Freyanoidea) forming a sister clade to the remaining psoroptidian superfamilies. Our findings suggest that (i) house dust mites (Pyroglyphidae: Dermatophagoidinae) originated from a parasitic ancestor within the core of Psoroptidia, violating a basic principle of evolution that it is virtually impossible for a permanent parasite to become free-living, and (ii) there were at least two shifts from presumably avian to mammalian hosts.     

Global diversity of water mites (Acari,Hydrachnidia; Arachnida) in freshwater

The Hydrachnidia (water mites) represent the most important group of the Arachnida in fresh water. Over 6,000 species have been described worldwide, representing 57 families, 81 subfamilies and more than 400 genera. The article analyzes extant water mite diversity and biogeography. Data on distribution and species richness of water mites are substantial but still far from complete. Many parts of the world are poorly investigated, Oriental and Afrotropical regions in particular. Moreover, information among different freshwater habitats is unbalanced with springs and interstitial waters disproportionately unrepresented. Therefore, more than 10,000 species could be reasonably expected to occur in inland waters worldwide. Based on available information, the Palaearctic region represents one of the better investigated areas with the highest number of species recorded (1,642 species). More than 1,000 species have been recorded in each of the Neotropical (1,305 species) and Nearctic regions (1,025 species). Known species richness is lower in Afrotropical (787 species) and Australasian (694 species) regions, and lowest in the Oriental region (554 species). The total number of genera is not correlated with species richness and is distinctly higher in the Neotropical (164 genera); genus richness is similar in the Palaearctic, Nearctic and Australasian regions (128–131 genera) and is lower in the Afrotropical and Oriental regions with 110 and 94 genera, respectively. A mean number of about three genera per family occur in the Palaeartic, Nearctic and Oriental while an average of more than four genera characterizes the families of Australasian and Afrotropical regions and more than five genera those of the Neotropical. Australasian fauna is also characterized by the highest percentage of endemic genera (62%), followed by Neotropical (50.6%) and Afrotropical (47.2%) regions. Lower values are recorded for the Palaearctic (26.9%), Oriental (24.4%) and Nearctic (21.4%). The Palaearctic and Nearctic have the highest faunistic similarity, some minor affinities are also evident for the generic diversification of Holarctic and Oriental families. The faunas of Southern Hemisphere bioregions are more distinct and characterized by the presence of ancient Gondwanan clades with a regional diversification particularly evident in the Neotropics and Australasia. This scenario of water mite diversity and distribution reflect the basic vicariance pattern, isolation, phylogenetic diversification, recent climatic vicissitudes and episodes of dispersal between adjacent land masses together with extant ecological factors can be evoked to explain distribution patterns at a global scale. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Experimental evidence for a female sex pheromone in Arrenurus manubriator (Acari: Hydrachnida; Arrenuridae)

We present experimental evidence for a water-borne female-produced sex pheromone in aquatic parasitengonine mites. Water that has contained adult female Arrenurus manubriator Marshall will elicit arrestant behaviour in conspecific adult males, and if the cue is sufficiently strong, the males will assume a readiness posture (with 4th pair of legs held over the back, bent anteromedially at the genuotibial joint) that is typically a precursor to coupling. Water that has not been exposed to female mites does not induce any behavioural response from male mites. Female-conditioned water that has been passed through a C-18 column does not elicit any response from male A. manubriator, while the rehydrated residue from the column does induce arrestant behaviour and may result in the readiness posture. The results from the C-18 extraction indicate that the pheromone is nonpolar in nature. This revised version was published online in July 2006 with corrections to the Cover Date.     

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.     

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.     

Competitive interactions among four pest species of earth mites (Acari: Penthaleidae)

Earth mites are major winter pests of a variety of crops and pastures in southern Australia. Competition between four earth mite species was investigated using field and shadehouse experiments. The influence of different plant hosts on the frequency and intensity of competitive interactions also were examined. This information is important, because control attempts that eradicate one species of mite could be directly followed by an increase in abundance of another earth mite species. There were strong effects of intraspecific competition on the reproductive rate of species, while interspecific interactions between Halotydeus destructor (Tucker) and Penthaleus species and between the three Penthaleus species also were detected. Competitive abilities were altered on the different plant types. On pasture, the competitive advantage swayed between Penthaleus major (Dugés), H. destructor, and Penthaleus falcatus (Qin & Halliday). Penthaleus sp. x was the strongest competitor in a mixture of wheat, Triticum aestivum (L.), and oats, Avena sativa (L.), whereas on canola, Brassica napus (L.), and bristly ox-tongue, Picris echioides (L.), P. falcatus, and H. destructor were superior competitors. These results suggest that competition is a strong force influencing the abundance of earth mites in the field and that host plant factors are important in shaping the type of interactions. This highlights the importance of identifying mite species when considering control options and suggests that effective control recommendations need to be developed for each individual species.     

Water mites (Acari, Hydrachnidia) from Baishih River drainage in Northern Taiwan, with description of two new species

NEW RECORDS OF WATER MITES (ACARI: Hydrachnidia) from Baishih River drainage of north Taiwan, are presented. Twelve species are recorded, of which ten are new for Taiwan; two of them, Torrenticola projectura and Hygrobates taiwanicus are described as new for science.     

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.     

Review Geographic differences in host specialization between the symbiotic water mites Unionicola formosa and Unionicola foili (Acari: Unionicolidae)

The host specificity and population genetic structure of the symbiotic water mites Unionicola foili from the host mussel Utterbackia imbecillis and Unionicola formosa from the mussels Pyganodon cataracta, Pyganodon grandis and Anodonta suborbiculata were examined over a broad geographical scale in order to determine the extent to which specialization by these water mites is structured geographically. The behavioural responses of U. foili and U. formosa were highly host-species specific, with adults of both species exhibiting negative phototaxis in the presence of a chemical factor from the species of mussel with which the mites had been associated in the field. The photobehaviour of these water mites in the presence of water from a non-host mussel varied depending on the species in question. Although U. foili from U. imbecillis exhibited negative phototaxis in water modified by A. suborbiculata, mites from this latter host did not exhibit a directional response in U. imbecillis water. Unionicola foili and U. formosa from A. suborbiculata were positively phototactic when they were exposed to water modified by either species of Pyganodon. The photoresponse of U. formosa from P. cataracta and P. grandis was positive in the presence of water modified by U. imbecillis and A. suborbiculta. However, these mussel-mites showed no directional response in water modified by their alternate species of Pyganodon. Unionicola foili and the host-associated populations of U. formosa were examined for allozyme variation at eight loci to determine the pattern and degree of genetic variation. There was a high degree of genetic differentiation when mite populations from the two species of Pyganodon were compared with U. foili or U. formosa from A. suborbiculata. These populational groupings were fixed for different alleles at two enzyme loci. The results of this study indicate that populations of U. formosa from P. cataracta and P. grandis are reproductively isolated from U. foili from U. imbecillis and from U. formosa from A. suborbiculata and contend that host specificity is an important mechanism in restricting gene flow among these populational groupings. Furthermore, this study indicates that specialization among unionicolid water mites can vary geographically, owing to differences in geographic distribution of available hosts and differences in host use.Exp Appl Acarol 22: 683697 © 1998 Kluwer Academic Publishers     

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.     

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.     

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.     

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.     

Communication via sex pheromones within and among Arrenurus spp. mites (Acari: Hydrachnida; Arrenuridae)

We present direct experimental evidence of pheromone use in six species of Arrenurus and indirect evidence for four species, including members of the subgenera Megaluracarus, Truncaturus, and Arrenurus. Water in which females were housed elicited arrestant behaviour in males, males oriented to the source, and at least some individuals in each species assumed the male readiness posture, a precursor to coupling. Most species responded to water treated with conspecific females, but there was also interspecific sex pheromone responsiveness. Arrenurus manubriator and A. megalurus demonstrated reciprocal pheromone cross-attractancy. Males of A. major, A. marshallae, and A. birgei responded to water from females of related species from within their subgenera. Arrenurus apetiolatus males failed to respond to conspecific female-treated water, but the same water elicited arrestant behaviour and orientation in A. manubriator. Heterospecific reactions to female-conditioned water were limited to cases involving members of the same species group and were not seen between species representing different species groups or different subgenera. The species for which cross-attractancy has been demonstrated commonly co-occur in nature, so apparently these pheromones are of limited value for species recognition. Shared reaction to sex pheromones provides additional evidence for inferring close phylogenetic relationship among species, and thus far, corresponds with morphological evidence based on adult males and larvae.