A template for the future: digitizing and databasing a taxonomic illustration collection

This is the first iconographic taxonomic database intended as an everyday tool for the practising taxonomist, that allows access to the original drawings used to describe species. We demonstrate the system with water mites (Acari, Parasitengona, Hydrachnidia) but it may be used with any other plant or animal group. Query by genus or species leads to the original drawings and any additional images associated to that particular name. At present, the database includes images from more than 4,000 species (around 38,000 illustrations) and is easily expandable. Copyright does not allow the database to be used in an open WWW context, but it can be an extremely useful tool in private taxonomic applications.     

A thermocline as an obstacle to the spread of water mites (Acari: Hydrachnidia) across the lake profile

The aim of the study was to determine whether a thermocline may constitute a barrier discouraging vertical migration of water mites. The research was carried out in May, June, July, and August 1999 in Lake Lubie, and a total of 3252 water mites (1880 females and 1178 males) belonging to 29 species were collected. A strong negative correlation was observed between the drop in temperature in the thermocline and the abundance and number of water mite species living beneath the thermocline. The negative correlation resulted from a considerable limitation of vertical migration of water mites by factors such as: low temperature below the thermocline, large difference between temperatures above and below the thermocline, and considerable thickness of the thermocline. During summer season, lower layers of the lake were increasingly penetrated by water mites as the temperatures above and below the thermocline were becoming more uniform. Lake species displayed the greatest ability to penetrate lower water layers and were present below the thermocline during the whole study period; moreover, their numbers were quite steady. On the contrary, the species, which are characteristic for small water bodies, crossed the thermocline in comparatively large numbers in June when the thermocline was of the lowest thickness.     

Water mites as potential long-term bioindicators in formerly drained and rewetted raised bogs

Many environmental studies of restored peatlands focus on biogeochemical cycles, productivity and decomposition. However, changes in the composition and structure of invertebrate assemblages in restored bogs have received little attention. In the present study we describe effects of rewetting on the water mite faunas (Acari: Hydrachnidia) of four raised bogs located in northwestern Germany. All examined peatlands had been drained in the past, and two of them had been subjected to peat extraction. The examined sites had been rewetted 2, 12, 14 and 25 years prior to our surveys, and currently represent different stages of plant succession. With increasing age after rewetting, the vegetation developed more complex structure as defined by Sphagnum status, and water mite fauna became somewhat similar to the fauna in an undisturbed raised reference bog. Water mites were found almost exclusively in bogs 25 years after wetting, and in these bogs they occurred in sites with more complex vegetation structure. Because water mites have high demands on abiotic and biotic factors due to their complex life cycle (i.e., the larvae are parasites, and the nymphs and adults are predators), we can infer that their mere presence irrespective of species abundance and richness reflects positive effects of the rewetting measures conducted in peat bogs.     

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     

Descriptions of Atractides aprojectus sp.nov.and male of A.huaxiensis Yi & Jin (Acari: Hydrachnidia) from China

A water mite species is described as new to science, Atractides(Tympanomegapus) aprojectus sp. nov. The male of Atractides(Tympanomegapus) huaxiensis Yi & Jin, 2010 is described for the first time from Guizhou Province, China. The materials were collected during a survey in 2011 from the rivers in Guizhou. The specimens are deposited in the Institute of Entomology, Guizhou University(GUGC).     

Attachment site and infestation parameters of parasitic water mites on the whirligig beetle Dineutus nigrior Roberts (Coleoptera: Gyrinidae)

Larval water mites parasitise a wide range of aquatic insects and may have a negative impact on host fitness. One host taxon susceptible to water mite parasitism is the whirligig beetle (Coleoptera: Gyrinidae). We made 11 collections of the whirligig beetle Dineutus nigrior Roberts from May to October of 2006 to investigate patterns of water mite parasitism on that host species. Mites were identified as of the genus Eylais. Mite intensity ranged from 1 to 11. Median intensity was 1.0 and ranged from 1.0 to 3.0 for individual samples. There did not appear to be temporal patterns in mite intensity. Prevalence was 30.9% but varied substantially over the sampling period ranging from 2.5 to 63.3%. Mites were attached to the metathoracic wings and the body tergites under the elytra. When all samples were considered there was equal use of wings and body tergites but there was temporal variation in the use of attachment sites.     

Allocation of reproductive effort in female Arrenurus spp. water mites (Acari: Hydrachnidia; Arrenuridae)

Summary Twenty-seven species of water mites of the genus Arrenurus were compared with respect to allocation of reproductive effort. Clutch volume was positively correlated to female volume, female volume was positively correlated with clutch size and with larval volume, while clutch size and larval volume were negatively correlated. In threespace, corresponding to female volume, clutch size and larval volume, species were arranged along two trajectories representing separate reproductive strategies. The strategy characterized by small larvae, large clutches and large females corresponded to species of the subgenus Arrenurus, known to be larval parasites of adult Odonata. Members of three subgenera, known to be larval parasites of adult Diptera, followed the second strategy of small clutch size and alrge larvae. Of nine species of mites tested for intraspecific relationships, only one significant relationship was found, between female volume and clutch size for A. (Megaluracarus) bartonensis.