New water mites of the family Hygrobatidae (Acari,?Hydrachnidia) from Turkey

In this study, the findings of three water mite species of the family Hygrobatidae collected from different streams in Turkey were evaluated. Hygrobates (s. str.) anatolicus Esen & Pešić, sp. n. is described as new for science. Hygrobates (Rivobates) diversiporus Sokolow, 1927 and Atractides (s. str.) nikooae Pešić, 2004, which were illustrated and thoroughly discussed, are new records for the Turkish fauna.     

Can water mites control populations of planktonic Cladocera?

Predatory pelagic water mites, Piona sp., in a small subtropical lake of Argentina showed rapid numerical response and protection from fish consumption. In experiments, predation rates of Piona on cladocerans equalled those of the principle lake planktivore, Moenkhausia intermedia Eigenmann (about 100 prey · predator^–1 day^–1). As a result, the mites caused a summer depression in the dominant lake zooplankter, Daphnia laevis Birge, evidenced by the analysis of its population dynamics and simple modelling.     

Red, distasteful water mites: did fish make them that way?

Water mites (Acari: Hydrachnida) are unusual among the typically cryptic freshwater fauna in that many species are brightly colored red or orange, and also appear to be distasteful to fish. This apparent aposematism (use of color to warn predators) has been previously explained as the evolutionary end-product of pressure from fish predation. The fish-predation argument has been supported by observations that fish spit out red mites, powder made from red water mites is more distasteful to fish than powder made from non-red mites, and red mites appear to be more abundant than non-red mites in water bodies where fish are present. In this paper, we challenge the hypothesis that fish were the sole driving force behind the evolution of aposematism in water mites. We show that non-red mites actually dominate in water bodies with fish, and that red mites are more abundant in temporary, fishless water bodies. We also demonstrate that powder made from red, terrestrial velvet mites (Trombidiidae) was as distasteful to fish as powder made from red water mites. We suggest that the main role of red and orange carotenoid pigments may be to act as photoprotectants, and hypothesize that redness originated in the terrestrial ancestors of water mites and has been retained in certain lineages of water mites after the invasion of the aquatic habitat. We also suggest that distastefulness evolved subsequent to bright coloration in response to increased conspicuousness to predators. Relaxed selection for redness has occurred when adults and/or larvae are less exposed to sunlight, either through occupying more protected habitats, parasitizing more nocturnal hosts, or parasitizing hosts for a short period of time. Our ability to test this alternative hypothesis is hampered by lack of knowledge of the source and mode of action of distastefulness, and of phylogenetic relationships among the Parasitengona.     

Red, distasteful water mites: did fish make them that way?

Water mites (Acari: Hydrachnida) are unusual among the typically cryptic freshwater fauna in that many species are brightly colored red or orange, and also appear to be distasteful to fish. This apparent aposematism (use of color to warn predators) has been previously explained as the evolutionary end-product of pressure from fish predation. The fish-predation argument has been supported by observations that fish spit out red mites, powder made from red water mites is more distasteful to fish than powder made from non-red mites, and red mites appear to be more abundant than non-red mites in water bodies where fish are present. In this paper, we challenge the hypothesis that fish were the sole driving force behind the evolution of aposematism in water mites. We show that non-red mites actually dominate in water bodies with fish, and that red mites are more abundant in temporary, fishless water bodies. We also demonstrate that powder made from red, terrestrial velvet mites (Trombidiidae) was as distasteful to fish as powder made from red water mites. We suggest that the main role of red and orange carotenoid pigments may be to act as photoprotectants, and hypothesize that redness originated in the terrestrial ancestors of water mites and has been retained in certain lineages of water mites after the invasion of the aquatic habitat. We also suggest that distastefulness evolved subsequent to bright coloration in response to increased conspicuousness to predators. Relaxed selection for redness has occurred when adults and/or larvae are less exposed to sunlight, either through occupying more protected habitats, parasitizing more nocturnal hosts, or parasitizing hosts for a short period of time. Our ability to test this alternative hypothesis is hampered by lack of knowledge of the source and mode of action of distastefulness, and of phylogenetic relationships among the Parasitengona.     

Do plant mites commonly prefer the underside of leaves?

The adaxial (upper) and abaxial (lower) surfaces of a plant leaf provide heterogeneous habitats for small arthropods with different environmental conditions, such as light, humidity, and surface morphology. As for plant mites, some agricultural pest species and their natural enemies have been observed to favor the abaxial leaf surface, which is considered an adaptation to avoid rain or solar ultraviolet radiation. However, whether such a preference for the leaf underside is a common behavioral trait in mites on wild vegetation remains unknown. The authors conducted a 2-year survey on the foliar mite assemblage found on Viburnum erosum var. punctatum, a deciduous shrub on which several mite taxa occur throughout the seasons, and 14 sympatric tree or shrub species in secondary broadleaf-forest sites in Kyoto, west–central Japan. We compared adaxial–abaxial surface distributions of mites among mite taxa, seasons, and morphology of host leaves (presence/absence of hairs and domatia). On V. erosum var. punctatum, seven of 11 distinguished mite taxa were significantly distributed in favor of abaxial leaf surfaces and the trend was seasonally stable, except for Eriophyoidea. Mite assemblages on 15 plant species were significantly biased towards the abaxial leaf surfaces, regardless of surface morphology. Our data suggest that many mite taxa commonly prefer to stay on abaxial leaf surfaces in wild vegetation. Oribatida displayed a relatively neutral distribution, and in Tenuipalpidae, the ratio of eggs collected from the adaxial versus the abaxial side was significantly higher than the ratio of the motile individuals, implying that some mite taxa exploit adaxial leaf surfaces as habitat.     

Freezing: how do water mites (Acari: Hydrachnidia) survive exposure to sub-zero temperatures?

Experimental and Applied Acarology - Until now, very little is known about the ability of adult and deutonymph water mites (Acari, Hydrachnidia) to survive in sub-zero temperatures. Information...     

“Forms” of water mites (Acari: Hydrachnidia): intraspecific variation or valid species?

In many groups of organisms, especially in the older literature, it has been common practice to recognize sympatrically occurring phenotypic variants of a species as “forms”. However, what these forms really represent often remains unclear, especially in poorly studied groups. With new algorithms for DNA‐based species delimitation, the status of forms can be explicitly tested with molecular data. In this study, we test a number of what is now recognized as valid species of water mites (Hydrachnidia), but have in the past been treated as forms sympatrically occurring with their nominate species. We also test a form without prior taxonomical status, using DNA and morphometrics. The barcoding fragment of COI, nuclear 28S and quantitative analyses of morphological data were used to test whether these taxa merit species status, as suggested by several taxonomists. Our results confirm valid species. Genetic distances between the form and nominate species (Piona dispersa and Piona variabilis, COI 11%), as well as likelihood ratio tests under the general mixed‐Yule coalescent model, supported that these are separately evolving lineages as defined by the unified species concept. In addition, they can be diagnosed with morphological characters. The study also reveals that some taxa genetically represent more than one species. We propose that P. dispersa are recognized as valid taxa at the species level. Unionicola minor (which may consist of several species), Piona stjordalensis, P. imminuta s. lat., and P. rotundoides are confirmed as species using this model. The results also imply that future studies of other water mite species complexes are likely to reveal many more genetically and morphologically distinct species.     

Does pollen availability mitigate the impact of pesticides on generalist predatory mites?

The effect of the provision of pollen on the impact of pesticides on the predatory mite Kampimodromus aberrans was assessed at individual and population levels. In the laboratory we evaluated the influence of pollen amount and pollen application frequency on lethal and sub-lethal effects of chlorpyrifos and spinosad. In a potted plant experiment, the effects of pesticides and pollen were assessed on predatory mite population abundance. In the laboratory, survival and fecundity of predatory mites were reduced by insecticides, and spinosad was more toxic than chlorpyrifos. In the same experiment, high pollen application frequency alleviated the sub-lethal effect induced by chlorpyrifos. On potted plants, pollen applications reduced the impact of chlorpyrifos on K. aberrans, whereas without pollen applications the impact of spinosad and chlorpyrifos on the predatory mite population was similar. Results obtained here highlight that the provision of fresh pollen is of particular importance for predatory mites when pesticides are applied.     

A molecular dynamics simulation study of the effect of water–graphene interaction on the properties of confined water

The role of water in determining the structure and stability of biomacromolecules has been well studied. In this work, molecular dynamics simulations have been applied to investigate the effect of surface hydrophobicity on the structure and dynamics of water confined between graphene surfaces. In order to evaluate this effect, we apply various attractive/repulsive water–graphene interaction potentials (hydrophobicity). The properties of confined water are studied by applying a purely repulsive interaction potential between water–graphene (modelled as a repulsive r^?12 potential) and repulsive–attractive forces (modelled as an LJ(12-6) potential). Compared to the case of a purely repulsive graphene–water potential, the inclusion of repulsive–attractive forces leads to formation of sharp peaks for density and the number of hydrogen bonds. Also, it was found that repulsive–attractive graphene–water potential caused slower hydrogen bonds dynamics and restricted the diffusion coefficient of water. Consequently, it was found that hydrogen bond breakage and formation rate with the repulsive r^?12 potential model, will increase compared to the corresponding water confined with the LJ(12-6) potential.     

Do brassinosteroids mediate the water stress response?

Brassinosteroids (BRs) have been suggested to increase the resistance of plants to a variety of stresses, including water stress. This is based on application studies, where exogenously applied bioactive BRs have been shown to improve various aspects of plant growth under water stress conditions. However, it is not known whether changes in endogenous BR levels are normally involved in mediating the plant's response to stress. We have utilized BR mutants in pea ( Pisum sativum L.) to determine whether changes in endogenous BR levels are part of the plant's response to water stress and whether low endogenous BR levels alter the plant's ability to cope with water stress. In wild-type (WT) plants, we show that while water stress causes a significant increase in ABA levels, it does not result in altered BR levels in either apical, internode or leaf tissue. Furthermore, the plant's ability to increase ABA levels in response to water stress is not affected by BR deficiency, as there was no significant difference in ABA levels between WT, lkb (a BR-deficient mutant) and lka (a BR-perception mutant) plants before or 14 days after the cessation of watering. In addition, the effect of water stress on traits such as height, leaf size and water potential in lkb and lka was similar to that observed in WT plants. Therefore, it appears that, at least in pea, changes in endogenous BR levels are not normally part of the plant's response to water stress.     

Do phytoseiid mites select the best prey species in terms of reproductive success?

Optimal foraging theory predicts that predators prefer those prey species that are most rewarding in terms of reproductive success, which is dependent on prey quality and prey availability. To investigate which selection pressures may have moulded prey preference in an acarine system consisting of two prey species and three predator species, we tested whether prey preference of the predators is matched by the associated reproductive success.The predators involved areAmblyseius finlandicus (Oudemans),Am. potentillae (Garman) andTyphlodromus pyri Scheuten. The prey species are the apple rust mite (Aculus schlechtendali (Nalepa)) and the fruit-tree red spider mite (Panonychus ulmi (Koch)).Reproductive success was assessed in terms of intrinsic rate of increase and for one predator also in terms of diapause induction. All three predator species reached highest reproductive success on the same prey species: apple rust mite. This was most pronounced for the predatorAm. finlandicus, because its larval stage suffered severe mortality when feeding onP. ulmi.An independent study on prey preference of the three predator species (Dicke et al., 1988) revealed thatAm. finlandicus prefersAc. schlechtendali toP. ulmi, whereas the other two predator species have the reverse preference.Thus, on the basis of current data, prey preference ofAm. finlandicus can be understood in terms of reproductive success. However, this is not so for prey preference ofT. pyri andAm. potentillae. Investigations needed for a better understanding of prey preference of the last-named two predator species are discussed.     

Review Oribatid mites of the Galápagos Islands – faunistics, ecology and speciation

The results from investigations on oribatid mites of the Galápagos archipelago during 10 years are presented. Samples were taken on all larger and most smaller islands of the archipelago, as well as in all vegetation zones and some special habitats such as grass or cactus litter and fumaroles. A total of 202 oribatid species belonging to 64 families were encountered; among them 81 species are new to science. The Oribatida occur from the littoral zone to the summit of the volcanoes. Diversity and abundance increases from the arid to the moister zones at higher elevations. Most species prefer moist habitats at medium to higher elevations of the islands, in some parts reaching remarkably high abundances (in the Scalesia zone of Santa Cruz approximately 18 000 individuals m–2). The species richness of an island depends on the altitude and number of available habitats rather than the area of the island. Many oribatid species on the Galápagos Islands have a wide biogeographical distribution. The majority originate from the Central and South American mainland, but several Pacific and even Holarctic elements were also found. In comparison with the species composition of the adjacent mainland, the oribatid mite fauna of the Galápagos Islands can be regarded as disharmonic. Sea surface transportation has been proved at least between the islands, which also applies to oribatid species living at higher elevations. Long distance dispersal can be assumed to be mainly hydrochorous. The oribatid fauna of the littoral and arid vegetation zones is presented in detail. Some species even inhabit such extreme habitats as warm fern litter in fumaroles or hot volcanic soils. Others were mainly found in or near agricultural areas, suggesting human introduction. Striking distribution patterns within the archipelago are discussed. The distribution of endemic forms in the genera Aeroppia, Scapheremaeus, Scheloribates and Cultrobates indicates both speciation on different islands, as well as speciation on the same island by occupying different habitats.     

Venus: Where has all the water gone?

Conditions on the surface of venus are reviewed and evidence for the existence of a hydrosphere assessed. Escape mechanisms are examined and found to be insufficient to explain the presumed absence of liquid water on venus. The consequences of a hot, acidic hydrosphere are explored as is marginal evidence for biological activity.Supported by research grants from National Aeronautics and Space Administration NGR 012-001-042, the Life Insurance Medical Research Foundation, and the University of Hawaii.     

Temporary forest pools: can we see the water for the trees?

Temporary waters, in general, are fascinating habitats in which to study the properties of species adapted to living in highly variable environments. Species display a remarkable array of strategies for dealing with the periodic loss of their primary medium that sets them apart from the inhabitants of permanent water bodies. Survival of individuals typically depends on exceptional physiological tolerance or effective migrational abilities, and communities have their own, distinctive hallmarks. This paper will broadly overview the biology of temporary ponds, but will emphasize those in temperate forests. In particular, links will be sought between aquatic community properties, the nature of the riparian vegetation, and forestry practices. Quite apart from their inherent biological interest, temporary waters are now in the limelight both from a conservation perspective, as these habitats come more into conflict with human activities, and a health-control perspective, as breeding habitats for vectors of arboviruses. Traditionally, many temporary waters, be they pools, streams or wetlands, have been considered to be ȁ8wastedȁ9 areas of land, potentially convertible to agriculture/silviculture once drained. In reality, they are natural features of the global landscape representing distinct and unique habitats for many species – some that are found nowhere else, others that reach their maximum abundance there. To be effective, conservation measures must preserve the full, hydroseral range of wetland types.     

What are the driving forces for water lifting in the xylem conduit?

After Renner had shown convincingly in 1925 that the transpirational water loss generates tensions larger than 0.1 MPa (i.e. negative pressures) in the xylem of cut leafy twigs the Cohesion Theory proposed by Böhm, Askenasy, Dixon and Joly at the end of the 19th century was immediately accepted by plant physiologists. Introduction of the pressure chamber technique by Scholander et al. in 1965 enforced the general belief that tension is the only driving force for water lifting although substantial criticism regarding the technique and/or the Cohesion Theory was published by several authors. As typical for scientific disciplines, the advent of minimal‐ and non‐invasive techniques in the last decade as well as the development of a new, reliable method for xylem sap sampling have challenged this view. Today, xylem pressure gradients, potentials, ion concentrations and volume flows as well as cell turgor pressure gradients can be monitored online in intact transpiring higher plants, and within a given physiological context by using the pressure probe technique and high‐resolution NMR imaging techniques, respectively. Application of the pressure probe technique to transpiring plants has shown that negative absolute pressures (down to ? 0.6 MPa) and pressure gradients can exist temporarily in the xylem conduit, but that the magnitude and (occasionally) direction of gradients contrasts frequently the belief that tension is the only driving force. This seems to be particularly the case for plants faced with problems of height, drought, freezing and salinity as well as with cavitation of the tensile water. Reviewing the current data base shows that other forces come into operation when exclusively tension fails to lift water against gravity due to environmental conditions. Possible candidates are longitudinal cellular and xylem osmotic pressure gradients, axial potential gradients in the vessels as well as gel‐ and gas bubble‐supported interfacial gradients. The multiforce theory overcomes the problem of the Cohesion Theory that life on earth depends on water being in a highly metastable state.     

Investigation of the active site of Escherichia coli Cu,Zn superoxide dismutase reveals the absence of the copper-coordinated water molecule. is the water molecule really necessary for the enzymatic mechanism?

The active site of the Cu,Zn superoxide dismutase from Escherichia coli in the oxidized Cu(II) state has been studied by nuclear magnetic relaxation dispersion (NMRD), optical and nuclear magnetic resonance spectroscopy. The orientation of some metal ligands is different with respect to all the other Cu,Zn superoxide dismutases. Moreover, NMRD measurements demonstrate the lack of a copper-coordinated water molecule. In spite of these differences the enzymatic activity is still high. Azide also binds copper with normal affinity and induces modifications in the active site comparable to those previously observed in the eukaryotic enzymes. Our results suggest that, in this enzyme, the copper-coordinated water molecule appears not necessary for the enzymatic reaction. A role for the copper-coordinated water molecule is discussed in the light of recent crystallographic studies.