Cold tolerance of alpine,Arctic, and Antarctic Collembola and mites

Because of their dominant role in the fauna of alpine, Arctic and Antarctic locations Collembola and mites are of particular interest regarding adaptations to low temperatures. No freezing-tolerant species have been found in these groups of terrestrial arthropods, and it appears that all species depend entirely on supercooling to survive the lower temperatures of their habitats. While summer animals have high supercooling points, an increase in supercooling ability occurs during autumn and early winter, and can be explained as a two-step process. Initially gut content has to be eliminated to avoid heterogeneous nucleation at high subzero temperatures due to foreign nucleating agents. Second, supercooling is further enhanced through accumulation of glycerol or other lowmolecular cryoprotective substances. Further studies are needed on the ability of such animals to avoid inoculative freezing in their microhabitats.     

Multiple convergent evolution of arboreal life in oribatid mites indicates the primacy of ecology

Frequent convergent evolution in phylogenetically unrelated taxa points to the importance of ecological factors during evolution, whereas convergent evolution in closely related taxa indicates the importance of favourable pre-existing characters (pre-adaptations). We investigated the transitions to arboreal life in oribatid mites (Oribatida, Acari), a group of mostly soil-living arthropods. We evaluated which general force—ecological factors, historical constraints or chance—was dominant in the evolution of arboreal life in oribatid mites. A phylogenetic study of 51 oribatid mite species and four outgroup taxa, using the ribosomal 18S rDNA region, indicates that arboreal life evolved at least 15 times independently. Arboreal oribatid mite species are not randomly distributed in the phylogenetic tree, but are concentrated among strongly sclerotized, sexual and evolutionary younger taxa. They convergently evolved a capitate sensillus, an anemoreceptor that either precludes overstimulation in the exposed bark habitat or functions as a gravity receptor. Sexual reproduction and strong sclerotization were important pre-adaptations for colonizing the bark of trees that facilitated the exploitation of living resources (e.g. lichens) and served as predator defence, respectively. Overall, our results indicate that ecological factors are most important for the observed pattern of convergent evolution of arboreal life in oribatid mites, supporting an adaptationist view of evolution.     

Chemical ecology of oribatid mites III. Chemical composition of oil gland exudates from two oribatid mites, Trhypochthoniellus sp. and Trhypochthonius japonicus (Acari: Trhypochthoniidae)

The composition of oil gland exudates from two oribatid mites, Trhypochthoniellus sp. and Trhypochthonius japonicus, was studied with reference to the related species Trhypochthoniellus crassus. Trhypochthoniellus sp. contained a mixture of seven compounds; (Z,Z)-6,9-heptadecadiene, geranial, 3-hydroxybenzene-1,2-dicarbaldehyde (γ-acaridial), neryl formate, neral, (Z)-8-heptadecene and geranyl formate in decreasing order of abundance. The profile of the components from T. japonicus consisted of two types depending on the locality of sampling with unknown reason; one possessing a mixture of eight compounds [(Z,E)-farnesal, γ-acaridial, (Z,Z)-6,9-heptadecadiene, (E,E)-farnesal, (Z)-8-heptadecene and geranial in decreasing order] together with two unknown compounds, and the other composed of the same set of compounds together with 2-hydroxy-6-methylbenzaldehyde as the most abundant component. Relative abundance among common components was consistent between the two types of T. japonicus. Profiles of components differed among three species including T. crasus. The phylogenetic relationship between Oribatida and Astigmata was discussed based on secretory compounds commonly distributed between these two suborders. This revised version was published online in July 2006 with corrections to the Cover Date.     

Community structure,trophic position and reproductive mode of soil and bark-living oribatid mites in an alpine grassland ecosystem

The community structure, stable isotope ratios (¹⁵N/¹⁴N, ¹³C/¹²C) and reproductive mode of oribatid mites (Acari, Oribatida) were investigated in four habitats (upper tree bark, lower tree bark, dry grassland soil, forest soil) at two sites in the Central Alps (Tyrol, Austria). We hypothesized that community structure and trophic position of oribatid mites of dry grassland soils and bark of trees are similar since these habitats have similar abiotic characteristics (open, dry) compared with forest soil. Further, we hypothesized that derived taxa of oribatid mites reproducing sexually dominate on the bark of trees since species in this habitat consume living resources such as lichens. In contrast to our hypothesis, the community structure of oribatid mites differed among grassland, forest and bark indicating the existence of niche differentiation in the respective oribatid mite species. In agreement with our hypothesis, sexually reproducing taxa of oribatid mites dominated on the bark of trees whereas parthenogenetic species were more frequent in soil. Several species of bark-living oribatid mites had stable isotope signatures that were similar to lichens indicating that they feed on lichens. However, nine species that frequently occurred on tree bark did not feed on lichens according to their stable isotope signatures. No oribatid mite species could be ascribed to moss feeding. We conclude that sexual reproduction served as preadaptation for oribatid mites allowing them to exploit new habitats and new resources on the bark of trees. Abiotic factors likely are of limited importance for bark-living oribatid mites since harsh abiotic conditions are assumed to favor parthenogenesis.     

The association of oribatid mites with lichens

Oribatei (Acari, Cryptostigmata) are found in a variety of terrestrial habitats, and many are associated with lichens; the relationship ranges from casual to highly dependent. Eighty-three species associated with lichens have been surveyed, and a tentative classification, based on their ecological requirements, is presented: Group A consists of species restricted to lichens as a biotope, though occasionally occurring as accidentals in other habitats; Group B consists of species which while preferring lichens as a habitat and feeding source are also adapted to existence on other plants (though in some cases their immatures may be lichen-restricted); Group C consists of species which, though frequently found on lichens, are equally common in other biotopes, particularly mosses, and must be regarded as much more generalized in their feeding habits. Certain aspects of oribatid-lichen specificity are discussed. The importance of oribatid-lichen associations from the point of view of soil fertility and energetics is emphasized.     

Dispersal patterns of oribatid mites across habitats and seasons

Oribatid mites are tiny arthropods that are common in all soils of the world; however, they also occur in microhabitats above the soil such as lichens, mosses, on the bark of trees and in suspended soils. For understanding oribatid mite community structure, it is important to know whether they are dispersal limited. The aim of this study was to investigate the importance of oribatid mite dispersal using Malaise traps to exclude sole passive wind-dispersal. Oribatid mite communities were collected over a 3-year period from five habitat types (coniferous forests, deciduous forests, mixed forests, meadows, bog/heathlands sites) and three seasons (spring, summer, autumn) in Sweden. Mites entered traps either by walking or by phoresy, i.e., by being attached to flying insects. We hypothesized (1) that oribatid mite communities in the traps differ between habitats, indicating habitat-limited dispersal, and (2) that oribatid mite communities differ among seasons suggesting that dispersal varies due to changing environmental conditions such as moisture or resource availability. The majority of the collected species were not typically soil-living species but rather from habitats such as trees, lichens and mosses (e.g., Carabodes labyrinthicus, Cymbaeremaeus cymba, Diapterobates humeralis and Phauloppia lucorum) indicating that walking into the traps or entering them via phoresy are of greater importance for aboveground than for soil-living species. Overall, oribatid mite communities collected in the traps likely originated from the surrounding local habitat suggesting that long distance dispersal of oribatid mites is scarce. Significant differences among seasons indicate higher dispersal during warm and dry periods of the year. Notably, 16 species of oribatid mites collected in our study were sampled for the first time in Sweden. This study also demonstrates that Malaise traps are a meaningful tool to investigate spatial and temporal patterns of oribatid mite communities.

     

Comparative water relations of sub-Antarctic and continental Antarctic oribatid mites

 Water availability, in addition to cold, is important in limiting biotic distribution in the Antarctic regions. In general, inland continental Antarctic habitats are dry, relative to maritime and sub-Antarctic habitats. This investigation compares the water relations of an endemic continental Antarctic oribatid mite, Maudheimia petronia Wallwork, and two sub-Antarctic oribatid mites, Halozetes fulvus Engelbrecht and Podacarus auberti Grandjean. M. petronia showed enhanced survival of dehydrating conditions, which may be attributable to both its greater resistance to and tolerance of water loss. The estimated lethal exposure times (LT₅₀) for M. petronia, P. auberti and H. fulvus held at 15°C and 0–5% RH were 250, 135 and 51 h, respectively. M. petronia lost water significantly more slowly than the sub-Antarctic mites (P<0.05), which did not differ in their rates of water loss (P>0.05). The mean losses of initial body water content after 45 h were 18.9, 27.3 and 29.3% for M. petronia, P. auberti and H. fulvus, respectively, and lethal water losses causing 50% of the sample to die were 65, 52, and 28%, respectively. These data suggest physiological adaptation by M. petronia for existence in periodically dry “chalikosystem” habitats at Antarctic nunataks. Comparisons of tolerance of submersion in freshwater showed P. auberti to be superior to M. petronia; the LT₅₀ values for submersion were >146 h and 32 h, respectively. Tolerance of submersion by P. auberti may be important for its existence in wet sub-Antarctic habitats. Conversely, the poor tolerance shown by M. petronia suggests that this mite has not been associated with moist environments. Received: 13 April 1995/Accepted: 4 August 1995     

An efficient and non-destructive DNA extraction method for oribatid mites

Molecular methods play an important role in systematic acarology and DNA extraction is the first step in this ground. Nowadays, the varieties of methods are being used for extraction of DNA, but most of them destroy the important external characters that are essential for morphological identification. In order to overcome the problem of associating molecular and morphological information, we have developed a simple, efficient and non-destructive DNA extraction method for oribatid mites. The non-destructive method was tested on three different species [Oppia nitens C.L. Koch, 1836 (Oppiidae), Acrotritia ardua C.L. Koch, 1841 (Euphthiracaridae), and Amerus polonicus Kulczynski, 1902 (Ameridae)] and exoskeleton of specimens were preserved in Hoyer’s medium on glass microscopic slides for further identification via morphological studies. This method is more time consuming than commercial kits, but is easier and cheaper, meanwhile, allows systematic analysis with linking the morphological and genetic traits from a single mite. The most important advantage of TNES method is that after using this non-destructive method, specimens preserve all of their morphological features.     

Positive correlation of trophic level and proportion of sexual taxa of oribatid mites (Acari: Oribatida) in alpine soil systems

We investigated community structure, trophic ecology (using stable isotope ratios; ¹⁵N/¹⁴N, ¹³C/¹²C) and reproductive mode of oribatid mites (Acari, Oribatida) along an altitudinal gradient (2,050–2,900 m) in the Central Alps (Obergurgl, Austria). We hypothesized that (1) the community structure changes with altitude, (2) oribatid mites span over four trophic levels, (3) the proportion of sexual taxa increases with altitude, and (4) the proportion of sexual taxa increases with trophic level, i.e. is positively correlated with the δ¹⁵N signatures. Oribatid mite community structure changed with altitude indicating that oribatid mites occupy different niches at different altitudes. Oribatid mites spanned over 12 δ¹⁵N units, i.e. about four trophic levels, which is similar to lowland forest ecosystems. The proportion of sexually reproducing taxa increased from 2,050 to 2,900 m suggesting that limited resource availability at high altitudes favors sexual reproduction. Sexual taxa more frequently occurred higher in the food web indicating that the reproductive mode is related to nutrition of oribatid mites. Generally, oribatid mite community structure changed from being decomposer dominated at lower altitude to being dominated by fungal and lichen feeders, and predators at higher altitude. This supports the view that resources from dead organic material become less available with increasing altitude forcing species to feed on living resources such as fungi, lichens and nematodes. Our findings support the hypothesis that limited resource accessibility (at high altitudes) favors sexually reproducing species whereas ample resource supply (at lower altitudes) favors parthenogenetic species.     

Temperature effects on locomotor activity rates of sub-Antarctic oribatid mites

The influence of temperature on locomotor activity was determined for the sub-Antarctic mites, Halozetes fulvus Engelbrecht and Podacarus auberti Grandjean. In both species walking was severely impaired at below-freezing temperatures. Above zero, locomotor activity rates increased with a rise in temperature over a wide temperature range (for example, this was 2–30°C for H. fulvus), and they showed a biologically normal level of sensitivity to change in temperature. All the calculated Q₁₀ values for mean rates over 5° intervals varied between 1.3 and 2.9. The present data are compared with some rate functions of maritime and continental Antarctic micro-arthropods, and they confirm the relative enhancement of the physiological rate by a continental Antarctic mite. One explanation for the less temperature-sensitive rates in H. fulvus and P. auberti may be that they have relatively more time available for normal biological activity.     

Review of oribatid mites as intermediate hosts of tapeworms of the Anoplocephalidae

A list of oribatid mites acting as intermediate hosts of tapeworms of the Anoplocephaldae is provided. to date, 127 species of oribatids included in 27 families, are implicated as intermediate hosts of the 14 genera and 27 species of anoplocephalid tapeworms. The most cited mites families are Oribatulidae with 35 species, Galumnidae with 22 species and Ceratozetidae with 15 species. Scheloribates laevigatus (Oribatulidae) is the species that demonstrated most susceptibility, both natural and experimental, to develop larval forms of anoplocephalid tapeworms. A theoretical-methodological model for parasitology based on the trophic characteristics of the intermediate and definitive mammalian hosts is reviewed.     

Additional notes on taxonomy and ecology of Anuraeopsis miracleae Koste, 1991 (Rotatoria:Monogononta) from an Austrian alpine lake

Although closely resembling Anuraeopsis fissa, Anuraeopsis miracleae constitutes a well defined species, being more highly adapted to microaerobic, cold environments. Our observations on the Austrian population are compared with information available on specimens from the type locality in Spain. Morphological discrepancies, especially concerning characteristics of Weber's organ and shape of the eggs are described and discussed. General ecological features indicate that the species is not restricted to meromictic or stratified lakes. To agree with the provisions of the International Code of Zoological Nomenclature the original spelling of A. miraclei Koste, 1991 is emended to A. miracleae Koste, 1991.     

A review of oribatid mites of the family Suctobelbidae (Acariformes,Oribatida) from the caucasus

This paper summarizes the data on the oribatid mite fauna of the family Suctobelbidae Grandjean, 1954, recorded from the Caucasus. The distribution of 47 species of the genera Suctobelba Paoli, 1908, Suctobelbella Jacot, 1937, and Suctobelbila Jacot, 1937 in the territory of the Caucasus is shown. The following five new species and four new subspecies are described: Suctobelba cornigera sp. n., S. flagelliseta sp. n., S. scalpellata caucasica ssp. n., Suctobelbella (Suctobelbella) liacariformis sp. n., S. (S.) acutidens pilososetosa ssp. n., S. (S.) subcornigera maculata ssp. n., S. (Flagrosuctobelba) diversosetosa arilloi ssp. n., S. (F.) nana sp. n., and S. (F.) sensillinuda sp. n. Four species belonging to the genus Suctobelbella changed their status: S. (S.) acutidens duplex (Strenzke, 1950) stat. n., S. (S.) acutidens sarekensis (Forsslund, 1941) stat. n., S. (S.) subcornigera vera (Moritz, 1964) stat. n. and S. (Flagrosuctobelba) forsslundi moritzi Mahunka, 1987 stat. n. S. (S.) hammerae (Krivolutsky, 1965) was synonymized to S. (S.) acutidens duplex. The genus Suctobelbila and the species Suctobelbila dentata europaea Moritz, 1974, Suctobelba altvateri Moritz, 1970, S. atomaria Moritz, 1970, S. secta Moritz, 1970, Suctobelbella (S.) acutidens sarekensis, S. (S.) hastata Pankow, 1986, S. (S.) subcornigera vera stat. n., S. (Flagrosuctobelba) ancorhina Chinone, 2003, S. (F.) elegantula (Hammer, 1958), S (F.) flagellifera Chinone, 2003, S (F.) granifera Chinone, 2003, S. (F.) forsslundi moritzi Mahunka, 1987 stat. n., and S. (F.) multiplumosa (Hammer, 1979) are recorded from the Caucasus for the first time. A key to the species is given.     

New Data on the fauna of oribatid mites (Acari,Oribatida) from the polar Urals

The fauna of oribatid mites in soils of the polar Ural mountains (the lower Malaya Paipudyna River, Labytnangi District, Yamal-Nenets Autonomous Area, 67°06′N, 65°20′E) was studied. Samples from the upper soil layer and litter were collected along a transect running from the floodplain to the mountain lichen tundra (from 150 to 520 m a.s.l.. A total of about 10 thousand mites belonging to 82 species of 34 families were collected, and the distribution of some species in various biotopes was recorded. 46 species and 11 families (Hypochthoniidae, Euphthiracaridae, Phthiracaridae, Nanhermanniidae, Trhypochthoniidae, Cepheidae, Eremaeidae, Thyrisomidae, Micreremidae, Passalozetidae, and Scutoverticidae) are new to the fauna of the polar Urals. Together with these new taxa, the oribatid fauna of the polar Urals comprises not less than 106 species of 34 families. This fauna consists mainly of species with the wide polyzonal geographical distribution.