Radiation in sexual and parthenogenetic oribatid mites (Oribatida, Acari) as indicated by genetic divergence of closely related species

The D3 domain and its flanking regions of 28S rRNA of four pairs of closely related sexual species (Eupelops hirtus and E. torulosus; Oribatella calcarata and O. quadricornuta; Chamobates voigtsi and Ch. borealis; Liacarus coracinus and L. subterraneus) and four pairs of closely related parthenogenetic species (Nanhermannia nana and Na. coronata; Nothrus silvestris and No. palustris; Tectocepheus sarekensis and T. minor; Camisia spinifer and Ca. segnis) of oribatid mites were sequenced to investigate (1) if the D3 region can be used as a species marker and (2) if there is genetic variation among closely related species pairs and if its magnitude is related to reproductive mode. Furthermore, we investigated the world-wide genetic variation of the D3 region from the oribatid mite species Platynothrus peltifer. There was no intraspecific genetic variation in the D3 region in any of the species studied; it was even identical in two closely related parthenogenetic species (Na. nana and Na. coronata) and two closely related sexual species (E. hirtus and E. torulosus). The genetic differences of the other species pairs indicated that both parthenogenetic and sexual lineages have various ages. On average, however, the differences between the closely related parthenogenetic species were larger than those between closely related sexual species, indicating that parthenogenetic lineages exist historically and may radiate slower than sexual species. The findings of this study support the hypothesis that some of the parthenogenetic oribatid mite taxa (Tectocepheus, Nothrus) are ‘ancient asexuals’. The absence of intraspecific or intra-individual variation in the D3 region of parthenogenetic species is consistent with the presence of concerted evolution in the 28S rRNA gene. From this we infer the existence of a meiotic process, which is consistent with the automixy known from several other parthenogenetic oribatid species. This revised version was published online in July 2006 with corrections to the Cover Date.     

The influence of cadmium on life-history parameters and gut microflora of <Emphasis Type="Italic">Archegozetes longisetosus</Emphasis> (Acari: Oribatida) under laboratory conditions

We tested the effect of cadmium (25, 130 μg Cd g⁻¹), administered via Chinese cabbage (Brassica chinensis L.) as food on life-history parameters and gut microflora of tritonymphs and adults of the oribatid mite, Archegozetes longisetosus Aoki. Both concentrations of Cd had an adverse effect on offspring mortality, and the higher concentration also reduced female fecundity, as well as the number of bacteria, fungi and actinomycetes, and it changed the community structure of bacteria; the proportion of gram-negative bacteria increased while that of gram-positive bacteria declined. Interestingly, at the lower Cd concentration microflora was more abundant and diverse than in the control group, especially in the tritonymphs, although the mean activity of gut microflora was reduced. The higher Cd concentration reduced microflora activity both in the tritonymphs and adults.     

Two new species of oribatid mites of Lasiobelba (Acari,Oribatida, Oppiidae) from Nepal,including a key to all species of the genus

Two new species of oribatid mites of the genus Lasiobelba (Oribatida, Oppiidae), Lasiobelba (Lasiobelba) daamsae sp. n. and Lasiobelba (Antennoppia) nepalica sp. n., are described from eastern Nepal. Lasiobelba (L.) daamsae sp. n. is most similar to L. (L.) remota Aoki, 1959 and L. (L.) gibbosa (Mahunka, 1985), however, it differs from both by the anterior part of pedotecta I specifically curved, rostrum pointed and exobothridial setae not shorter than bothridial setae. Lasiobelba (Antennoppia) nepalica sp. n. is most similar to L. (A.) granulata (Mahunka, 1986), however, it differs from the latter by the larger body size, exobothridial setae longer than rostral setae and bothridial setae not longer than interlamellar setae. An identification key to known species of Lasiobelba is given.     

Contribution to the knowledge of Galumnoidea (Acari,Oribatida) of Cuba

An annotated checklist of identified oribatid mites of the superfamily Galumnoidea collected from Cuba, including ten species from four genera and two families, is provided. Galumna flabellifera Hammer, 1958, Pergalumna bifissurata Hammer, 1972, Pergalumna bryani (Jacot, 1934), Pergalumna decorata Balogh & Mahunka, 1977 and Galumnopsis secunda Sellnick, 1923 are recorded for the first time in the Cuban fauna. A new species of Pergalumna, Pergalumna cubaensis sp. n., is described; it is morphologically similar to Pergalumna decorata Balogh & Mahunka, 1977, but differs from the latter by the larger body size, heavily granulated prodorsum and well-developed interlamellar setae. The adult of Allogalumna cubana Balogh & Mahunka, 1979 is redescribed.     

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.     

Local–regional boundary shifts in oribatid mite (Acari: Oribatida) communities: species–area relationships in arboreal habitat islands of a coastal temperate rain forest, Vancouver Island, Canada

Aim This study investigates the species–area relationship (SAR) for oribatid mite communities of isolated suspended soil habitats, and compares the shape and slope of the SAR with a nested data set collected over three spatial scales (core, patch and tree level). We investigate whether scale dependence is exhibited in the nested sampling design, use multivariate regression models to elucidate factors affecting richness and abundance patterns, and ask whether the community composition of oribatid mites changes in suspended soil patches of different sizes. Location Walbran Valley, Vancouver Island, Canada. Methods A total of 216 core samples were collected from 72 small, medium and large isolated suspended soil habitats in six western redcedar trees in June 2005. The relationship between oribatid species richness and habitat volume was modelled for suspended soil habitat isolates (type 3) and a nested sampling design (type 1) over multiple spatial scales. Nonlinear estimation parameterized linear, power and Weibull function regression models for both SAR designs, and these were assessed for best fit using R² and Akaike's information criteria (ΔAIC) values. Factors affecting oribatid mite species richness and standardized abundance (number per g dry weight) were analysed by anova and linear regression models. Results Sixty‐seven species of oribatid mites were identified from 9064 adult specimens. Surface area and moisture content of suspended soils contributed to the variation in species richness, while overall oribatid mite abundance was explained by moisture and depth. A power‐law function best described the isolate SAR (S = 3.97 × A^0.12, R² = 0.247, F_1,70 = 22.450, P < 0.001), although linear and Weibull functions were also valid models. Oribatid mite species richness in nested samples closely fitted a power‐law model (S = 1.96 × A^0.39, R² = 0.854, F_1,18 = 2693.6, P < 0.001). The nested SAR constructed over spatial scales of core, patch and tree levels proved to be scale‐independent. Main conclusions Unique microhabitats provided by well developed suspended soil accumulations are a habitat template responsible for the diversity of canopy oribatid mites. Species–area relationships of isolate vs. nested species richness data differed in the rate of accumulation of species with increased area. We suggest that colonization history, stability of suspended soil environments, and structural habitat complexity at local and regional scales are major determinants of arboreal oribatid mite species richness.     

Contributions to the knowledge of oribatid mites (Acari,Oribatida) of Indonesia. 3. The genus Galumna (Galumnidae) with description of a new subgenus and seven new species

Seven new species of oribatid mites of the genus Galumna are described from litter and soil materials of Sumatra, Indonesia. A new subgenus, Galumna (Atypicogalumna) subgen. n., is proposed; it differs from all galumnid genera and subgenera by the simultaneous presence of porose areas and sacculi on the notogaster (vs. either porose areas or sacculi present). Galumna (Galumna) calva Starý, 1997 is recorded for the first time in the Oriental region, and Galumna (Galumna) sabahna Mahunka, 1995 is recorded for the first time in the Indonesian fauna.     

Description of Scutovertex pileatus sp. nov. (Acari, Oribatida, Scutoverticidae) and molecular phylogenetic investigation of congeneric species in Austria

The oribatid mite Scutovertex pileatus sp. nov. is described on the basis of adult individuals originating from southern Austria (Carinthia). The new species shows the typical habitus of Scutovertex and is distinguished by the cerotegument and cuticle forming irregular nodules and bars over the entire body; the rostrum with two visor-like projections, with the ventral projection larger and arched ventrally; short lamellar setae; two pairs of converging ridges between the lamellae; small notogastral setae that are not broadened distally; and a sclerotized rib across the mentum. Furthermore, DNA sequences of the COI gene (region 2, 567 bp) of S. pileatus were compared with those of S. minutus, S. sculptus, using Cymbaeremaeus cymba as the outgroup. Molecular data unambiguously support the discreteness of all three species by placing them reciprocally monophyletic, as well as by large genetic divergences. Interspecific distances among C. cymba, S. minutus, S. pileatus and S. sculptus amounted to 13.7-29.9%.     

Peruvian oribatid mites (Acari,Oribatida) from the German Biological Expedition,with description of a new species of the genus Pergalumna

The present study is based on oribatid mite material (Acari, Oribatida) collected during the German Expedition in 2011 in Peru. An annotated checklist of identified oribatid mites, including 16 species from 14 genera and 8 families, is provided. Thirteen species and two genera (Notohermannia, Zetomimus) are recorded for the first time in Peru; the genus Notohermannia and species Notohermannia obtusa are recorded for the first time in the Neotropical region. A new species of the genus Pergalumna (Galumnidae), Pergalumna paraboliviana sp. n., is described. The new species is most similar to Pergalumna boliviana Ermilov, 2013 from Bolivia, however, it differs from the latter by the body size, morphology of porose areas A1 and the presence of interlamellar setae.     

The genus Scapheremaeus (Acari,Oribatida, Cymbaeremaeidae) in the oribatid mite fauna of New Zealand,with description of two new species

Two new species of oribatid mites of the genus Scapheremaeus (Oribatida, Cymbaeremaeidae), Scapheremaeus gibbus sp. n. and Scapheremaeus luxtoni sp. n., are described from New Zealand. Scapheremaeus gibbus sp. n. is morphologically most similar to Scapheremaeus humeratus Balogh & Mahunka, 1967, but differs from the latter by the number of notogastral, genital and adanal setae, morphology of bothridial setae, position of adanal lyrifissures and absence of humeral processes. Scapheremaeus luxtoni sp. n. is morphologically most similar to Scapheremaeus yamashitai Aoki, 1970, but differs from the latter by the morphology of notogastral and rostral setae, morphology of leg solenidia φ₂ and development of humeral processes. The species Scapheremaeus zephyrus Colloff, 2010 is recorded for the first time in New Zealand. An identification key to the known New Zealand species of Scapheremaeus is provided.     

Patterns of vertical stratification in a subtropical constructed wetland in south Florida (USA)

The South Florida Water Management District (District) has built large treatment wetlands, known as Stormwater Treatment Areas (STAs), to reduce excess phosphorus loading to the Everglades. The District conducted research in a prototype treatment wetland, the Everglades Nutrient Removal Project (ENRP), to study biogeochemical processes that are important to treatment performance. Vertical profile measurements of water temperature, dissolved oxygen, pH, conductivity and transmission of photosynthetically active radiation (PAR) were made in open-water areas and sites dominated by emergent, floating or submersed vegetation over an annual cycle. Relative thermal resistance to mixing was used to infer the strength of thermal stratification. Long-term diel variation in temperature at the surface and bottom of an open-water and a vegetated site also was measured. Open-water sites were nearly isothermal and had minimal thermal stratification, while vegetated sites were all thermally stratified to some degree. The highest surface water temperatures (>35 °C) occurred in submersed vegetation where much of the light absorbed by leaves and stems was reflected as heat. Oxygen was uniformly low (<4 mg L⁻¹) in emergent and floating vegetation and attributed to shading, high biological oxygen demand and limited reaeration at the surface. Depressed oxygen levels at open-water areas were attributed to high sediment oxygen demand. The highest oxygen concentrations occurred in submersed vegetation beds. Water column pH was unstratified and near circumneutral in the open water and at emergent and floating vegetation sites, while pH was markedly stratified in submersed vegetation, where surface values at times exceeded 9.0. High surface oxygen and pH levels in submersed vegetation were consistent with intense photosynthesis. Conductivity increased at the bottom of emergent and submersed vegetation but not at open-water or floating vegetation sites. PAR transmission was strongly reduced at all sites due to shading and/or absorption by dissolved organic carbon. Light extinction coefficients were markedly higher at vegetated sites compared to the open water. Peak irradiance shifted to longer wavelengths (538–643 nm) and both short (<400 nm) and long (>700 nm) wavelengths were largely attenuated at 60 cm relative to the surface. Long-term monitoring at a vegetated site revealed periods of inverse thermal stratification and dampened diel variation in temperatures at the bottom compared to open water.     

Differentiation of body form of Gustavioidea (Acari: Oribatida) in the light of ontogeny of three species

Differentiation of body form of Gustavioidea in the light of ontogeny of Dorycranosus curtipilis (Liacaridae), Ceratoppia sphaerica and Ceratoppiaquadridentata (Peloppiidae) was investigated, and morphology of juveniles of these species was described and illustrated for the first time. The juveniles of D. curtipilis differ distinctly from those of Ceratoppia species mainly by stronger chelicerae, more elongated body, and convex gastronotum, oval cross section, small and clavate sensillus, and rather thin, and pliable setae. The protonymphs of all these species lose gastronotal setae of d-series, and these setae are absent in subsequent nymphs and adult. The adult loses further notogastral setae, such that 11 pairs remain in D. curtipilis, but only two pairs in Ceratoppia species. Diagnoses of these species are enriched with morphological characters of juveniles, and the morphology of Ceratoppiabipilis is briefly compared, as are aspects of Gustaviafusifer (Gustaviidae).     

中国三甲螨科1新记录属及2新记录种

记述我国三甲螨科1新记录属：印三甲螨属Indotritia Jacot,1928及中国2新记录种：爪哇印三甲螨Indotritia javensis（Sellnick,1923）和波状印三甲螨Indotritia undulata Bayoumi ＆ Mahunka,1979,给出了形态描述和特征图。所有标本材料均保存在中国科学院动物研究所国家动物博物馆。     

Stand structure and woody species diversity in relation to stand stratification in a subtropical evergreen broadleaf forest, Okinawa Island

Stand structure and woody species diversity in a subtropical evergreen broadleaf forest grown in a silicate habitat, Okinawa Island, have been investigated on the basis of stand stratification. The forest stand consisted of four layers. The floristic composition of the top and the lower three layers was only slightly similar, although approximately one-third of the species were common to them. Mean tree weight decreased from the top toward the bottom layer whereas tree density increased from the top downward. This trend resembled the mean weight–density trajectory of self-thinning plant populations. The relationship between mean tree height and tree density for the upper two layers supported Yamakuras quasi –1/2 power law of tree height. The values of the Shannon–Wiener index, H, and the equitability index, J, tended to increase from the top layer downward except for the bottom layer. The values of H and J were, respectively, 4.83 bit and 0.82 for trees taller than 0.10 m. The lower layers contained many species of smaller height. High species diversity of the forest depended on small trees in the lower layers. Conservation of small trees in the lower layers, especially the bottom layer, is indispensable for sound maintenance of Okinawan evergreen broadleaf forests.     

Natural hybridization between a deciduous (Nothofagus antarctica, Nothofagaceae) and an evergreen (N. dombeyi) forest tree species: evidence from morphological and isoenzymatic traits

BACKGROUND AND AIMS: Trees with a partial leaf-shedding pattern and other morphological features a priori considered intermediate between those of the deciduous Nothofagus antarctica (G. Forster) Oersted and the evergreen N. dombeyi (Mirb.) Oersted (Nothofagaceae) were found in natural stands. The hybridization between a deciduous and an evergreen species of Nothofagus has not been reported so far in natural communities. METHODS: The putative hybrids and the two presumed parental species were compared using 14 enzyme systems as well as shoot, leaf and reproductive morphology. KEY RESULTS: Six enzyme systems showed good resolution (MDH-B, IDH, SKDH, 6-PGDH, GOT and PGI) and in four of them (PGI, MDH-B, SKDH and 6-PGDH) the putative hybrids showed intermediate zymogram patterns between N. antarctica and N. dombeyi. Both principal coordinates analysis on isozyme data and principal components analysis (PCA) on quantitative morphological traits of shoots and leaves separated both parental species and located the putative hybrids closer to N. antarctica than to N. dombeyi. In the PCA, the number of basal cataphylls and the length : width ratio of leaves were the variables most discriminating among shoots of the three entities. The putative hybrids were intermediate between both species regarding leaf vernation, outline and venation, variation in leaf shape (length/width) with position on the parent shoot and in staminate inflorescence and cupule morphology. For other morphological traits, the putative hybrids resembled one of the parental species or differed from both species (e.g. valve morphology). CONCLUSIONS: Isoenzymatic and morphological data sets support the idea of the hybrid nature (probably F1 generation) of the semi-deciduous trees found. Nothofagus antarctica and N. dombeyi are probably more closely related than previously assumed. The relevance of pollen type in revealing evolutionary relationships between Nothofagus species is supported, and that of leaf-shedding pattern is rejected.     

Consumption rate of phytonematodes by <Emphasis Type="Italic">Pergalumna</Emphasis> sp. (Acari: Oribatida: Galumnidae) under laboratory conditions determined by a new method

Although several generalist species of Pergalumna are known to be nematode predators, the potential of oribatid mites as natural enemies of phytonematodes has been underestimated. The objective of this work was to estimate the consumption rate of a Pergalumna sp. when feeding on two major pest nematodes, Meloidogyne javanica and Pratylenchus coffeae, under laboratory conditions. A new method was used, in which live nematodes are offered to mites and subsequently consumption is quantified based on the sclerotized, well preserved structures in the mite's fecal pellets. The assay was evaluated during 5 days, at 25 degrees C and 96% relative humidity, with three replicates for each nematode species. Every replicate consisted of a group of four mites isolated in an arena, to which 400 nematodes were transferred daily. The daily produced fecal pellets were mounted in Hoyer's medium for examination under a microscope. The nematode buccal stylets and cephalic frameworks were counted to estimate the number of nematodes consumed. It was estimated that a single mite daily ingested 18.3 +/- 0.8 (mean +/- SE) M. javanica (J(2) juveniles) or 41.6 +/- 7.2 P. coffeae (juveniles + adults), the maximal daily consumption being 34 M. javanica and 73 P. coffeae. The method showed to be practical, precise and suitable for laboratory studies in which nematophagous mites classified as engulfers are included.     

Diversity of soil oribatid mites (Acari: Oribatida) from High Katanga (Democratic Republic of Congo): a multiscale and multifactor approach

Although the soil is a major reservoir of biodiversity, our knowledge ofits mesofauna remains scanty, especially in the tropics. The diversity oforibatids (149 adult oribatid mite species) is analyzed for the first time in anAfrican soil and studied in three ecosystems of a regressive sere: forest,woodland and savanna. Savanna is the richest ecosystem overall, with 105collected species, whereas the mean number of species per relevé (diversity) is highest in forest. In barren soils, the number of species observedalong the sere drops regularly from the typical forest to the savanna. However,this pattern is complicated by other factors acting at different scales. Theincrease of oribatid richness parallels that of habitat complexity, from barrensoil to termitaria colonized by grasses and trees. On a finer scale, soilproperties also influence species richness, either indirectly through density(water content) or directly (total nitrogen, C/N ratio, organic matter), buttheir importance varies in relation to seasons. Most exclusive species (nearly90%) are housed in the two extreme types of vegetation, forest and savanna. On afiner scale, two habitats, the typical forest and the termitaria in the savanna,are remarkable by the number of exclusive species and are worth protectingthrough effective conservation measures.