Provision of astigmatid mites as supplementary food increases the density of the predatory mite Amblyseius swirskii in greenhouse crops, but does not support the omnivorous pest, western flower thrips

Astigmatid mites can be used as prey for mass rearing of phytoseiid predators, but also as a supplemental food source to support predator populations in crops. Here we evaluated the potential of six species of astigmatid mites (living or frozen) as alternative food for the predatory mite Amblyseius swirskii Athias-Henriot in greenhouse crops. All prey mites tested were suitable for predator oviposition. In general, oviposition was greater when prey mites were reared on dog food with yeast than when they were reared on wheat bran with yeast. Amongst prey items provided as frozen diet, larvae of Thyreophagus entomophagus (Laboulbene), Acarus siro L. and Lepidoglyphus destructor (Schrank) that had been reared on dog food with yeast, resulted in the highest oviposition rates of A. swirskii. T. entomophagus larvae as frozen diet resulted in the shortest preimaginal developmental time of A. swirskii. On chrysanthemum plants, we found that the greatest increase in predator density occurred when living mites of T. entomophagous were used as a food source. This increase was greater than when predators were fed cattail pollen, a commonly used supplemental food. Effects on predators of providing living A. siro and L. destructor, or frozen larvae of T. entomophagous as food, were comparable with provision of pollen. Use of supplemental food in crops can be a risk if it is also consumed by omnivorous pests such as western flower thrips, Frankliniella occidentalis Pergande. However, we showed that both frozen and living mites of T. entomophagous were unsuitable for thrips oviposition. Hence, we believe that provision of prey mite species increases A. swirskii density, supporting biological control of thrips and other pests in greenhouse crops.

Cheliceral chelal design in free-living astigmatid mites

Cheliceral chelal design in free-living astigmatid mites (Arthropoda: Acari) is reviewed within a mechanical model. Trophic access (body size and cheliceral reach) and food morsel handling (chelal gape and estimated static adductive crushing force) are morphologically investigated. Forty-seven commonly occurring astigmatid mite species from 20 genera (covering the Acaridae, Aeroglyphidae, Carpoglyphidae, Chortoglyphidae, Glycyphagidae, Lardoglyphidae, Pyroglyphidae, Suidasiidae, and Winterschmidtiidae) are categorised into functional groups using heuristics. Conclusions are confirmed with statistical tests and multivariate morphometrics. Despite these saprophagous acarines in general being simple ‘shrunken/swollen’ versions of each other, clear statistical correlations in the specifics of their mechanical design (cheliceral and chelal scale and general shape) with the type of habitat and food consumed (their ‘biome’) are found. Using multivariate analyses, macro- and microsaprophagous subtypes are delineated. Relative ratios of sizes on their own are not highly informative of adaptive syndromes. Sympatric resource competition is examined. Evidence for a maximum doubling of approximate body volume within nominal taxa is detected but larger mites are not more ‘generalist’ feeding types. Two contrasting types of basic ‘Bauplan’ are found differing in general scale: (i) a large, chunk-crunching, ‘demolition’-feeding omnivore design (comprising 10 macrosaprophagous astigmatid species), and (ii) a small selective picking, squashing/slicing or fragmentary/‘plankton’ feeding design (which may indicate obligate fungivory/microbivory) comprising 20 microsaprophagous acarid-shaped species. Seventeen other species appear to be specialists. Eleven of these are either: small (interstitial/burrowing) omnivores—or a derived form designed for processing large hard food morsels (debris durophagy, typified by the pyroglyphid Dermatophagoides farinae), or a specialist sub-type of particular surface gleaning/scraping fragmentary feeding. Six possible other minor specialist gleaning/scraping fragmentary feeders types each comprising one to two species are described. Details of these astigmatid trophic-processing functional groups need field validation and more corroborative comparative enzymology. Chelal velocity ratio in itself is not highly predictive of habitat but with cheliceral aspect ratio (or chelal adductive force) is indicative of life-style. Herbivores and pest species are typified by a predicted large chelal adductive force. Pest species may be ‘shredders’ derived from protein-seeking necrophages. Carpoglyphus lactis typifies a mite with tweezer-like chelae of very feeble adductive force. It is suggested that possible zoophagy (hypocarnivory) is associated with low chelal adductive force together with a small or large gape depending upon the size of the nematode being consumed. Kuzinia laevis typifies an oophagous durophage. Functional form is correlated with taxonomic position within the Astigmata—pyroglyphids and glycyphagids being distinct from acarids. A synthesis with mesostigmatid and oribatid feeding types is offered together with clarification of terminologies. The chelal lyrifissure in the daintiest chelicerae of these astigmatids is located similar to where the action of the chelal moveable digit folds the cheliceral shaft in uropodoids, suggesting mechanical similarities of function. Acarid astigmatids are trophically structured like microphytophagous/fragmentary feeding oribatids. Some larger astigmatids (Aleuroglyphus ovatus, Kuzinia laevis, Tyroborus lini) approximate, and Neosuidasia sp. matches, the design of macrophytophagous oribatids. Most astigmatid species reviewed appear to be positioned with other oribatid secondary decomposers. Only Dermatophagoides microceras might be a primary decomposer approximating a lichenivorous oribatid (Austrachipteria sp.) in trophic form. Astigmatid differences are consilient with the morphological trend from micro- to macrophytophagy in oribatids. The key competency in these actinotrichid mites is a type of ‘gnathosomisation’ through increased chelal and cheliceral height (i.e., a shape change that adjusts the chelal input effort arm and input adductive force) unrestricted by the dorsal constraint of a mesostigmatid-like gnathotectum. A predictive nomogram for ecologists to use on field samples is included. Future work is proposed in detail.

Novel mitochondrial genes and gene reannotation: conservation of gene arrangements among available astigmatid mites

Background Mitochondrial genomes (mitogenomes) of metazoans typically contain 37 genes, comprising 13 protein-coding genes, two rRNA genes, and 22 tRNA genes. To date, complete mitogenome sequences of 15 species of Astigmatina are available, and they present variation in a number of features, such as gene arrangements, tRNA unconventional secondary structures, and the number and internal structures of control regions. Furthermore, 11 astigmatid mites from six superfamilies share the same gene arrangement. Two available species from the genus Histiostoma reportedly have different mitochondrial (mt) tRNA gene arrangements. Results We sequenced the mitogenomes of Lepidoglyphus destructor and Gohieria fusca, both from the superfamily Glycyphagoidea (Astigmatina). In total, 37 mt genes were identified in the two Glycyphagoidea species. Based on AT content and stem-loop structures, we divided the largest non-coding regions (LNRs) in L. destructor and G. fusca into two domains, respectively. The novel feature of two domains for the LNR was also found in Acalvolia sp. (Astigmatina, Hemisarcoptoidea). Using MITOS 2, tRNAScan, ARWEN, and manual approaches, we reannotated the mitogenomes of Histiostoma blomquisti, H. feroniarum, and Trouessartia rubecula. We reannotated six tRNA genes in H. blomquisti and four tRNA genes in H. feroniarum. We were able to identify all of the mt tRNA genes that were reported as lost in Tr. rubecula. The phylogenetic relationships found in our study were fairly consistent with previous studies of astigmatid mites phylogeny. Within Astigmatina, Glycyphagoidea was recovered as a monophyletic group. Conclusions A novel feature of the LNR was found in L. destructor, G. fusca and Acalvolia sp. (Astigmatina, Hemisarcoptoidea). This feature was not found in other available Astigmatina mitochondrial sequences. In the current study, most available astigmatid mitochondrial genomes shared the same consistent gene arrangement that could be the potential ancestral pattern in Astigmatina.

The complete mitochondrial genome of the storage mite pest Tyrophagus fanetzhangorum (Acari: Acaridae)

Mitochondrial (mt) genomes of astigmatid mites typically contain 37 genes for 13 proteins, two ribosomal RNA (rRNA) genes and 22 transfer RNA (tRNA) genes. However, two Tyrophagus mites (Tyrophagus putrescentiae and T. longior) were reported as having lost three tRNAs in their mt genomes. In this study, we sequenced the complete mitochondrial genome of Tyrophagus fanetzhangorum (14,257 bp) and found typical set of mt tRNA genes (22 tRNAs). The gene arrangement of T. fanetzhangorum is consistent with the pattern of possible common ancestor of astigmatid mites. Phylogenetic analyses were conducted using Maximum likelihood (ML) and Bayesian inference (BI) methods. Phylogenetic analysis shows that T. fanetzhangorum is more closely related to T. putrescentiae than to T. longior within the genus Tyrophagus.

Phylogenetic Analysis of Astigmatid Mites Sarcoptes scabiei and Dermatophagoides farinae using ITS-2 as a Genetic Marker

Objective: The coding of astigmatid mites based on their morphological and developmental characteristics often leads to uncertainty in the results. The ribosomal internal transcribed spacer (ITS-2) region, being highly conserved in eukaryotes is commonly employed as a barcode for identification of mite species. The present study was an attempt to characterize the gene sequences of astigmatid mites i.e. Sarcoptes scabiei (S. scabiei), Dermatophagoides farinae (D. farinae) using ITS-2 as a genetic marker. Place and Duration of Study: The study was conducted at Department of Dermatology, Military Hospital (MH), Rawalpindi from September 2012 to October 2013. Materials and Methods: In order to characterize relationship of astigmatid mites, the ITS-2 marker was successfully amplified and sequenced. The resulting ITS-2 gene sequences were aligned using Clustal W. MEGA 7 was used to construct phylogenetic tree of the aligned sequence. Results: The phylogenetic tree showed an overall genetic distance of 0.53 indicating close genetic relationship among astigmatid mite species. Pairwise distance was calculated for the ITS-2 gene and low genetic diversity values were observed within S. scabiei and D. farinae that range from 0.003-0.008 and 0.006-0.038 respectively. Conclusion: The study supports the view that the ITS-2 region can be used to identify morphologically difficult astigmatid mites but is not useful in characterization of different species based on the geographical distribution. This study has important implication in our understanding of the epidemiology of S. scabiei and D. farinae and development of control strategies in human transmission.

Mitochondrial genome reorganization provides insights into the relationship between oribatid mites and astigmatid mites (Acari: Sarcoptiformes: Oribatida)

Oribatida s.l. represents one of the most species-rich mite lineages, including two recognized groups: oribatid mites (Oribatida s.s., non-astigmatan oribatids) and astigmatid mites (Astigmata). However, the relationship between these two groups has been debated. Here, we sequenced the complete mitochondrial (mt) genome of one oribatid mite and one astigmatid mite, retrieved complete mt genomes of three oribatid mites, and compared them with two other oribatid mites and 12 astigmatid mites sequenced previously. We find that gene orders in the mt genomes of both oribatid mites and astigmatid mites are rearranged relative to the hypothetical ancestral arrangement of the arthropods. Based on the shared derived gene clusters in each mt genome group, rearranged mt genomes are roughly divided into two groups corresponding to each mite group (oribatid mites or astigmatid mites). Phylogenetic results show that Astigmata nested in Oribatida. The monophyly of Astigmata is recovered, while paraphyly of Oribatida s.s. is observed. Our results show that rearranged gene orders in the mt genomes characterize various lineages of oribatid mites and astigmatid mites, and have potential phylogenetic information for resolving the high-level (cohort or supercohort) phylogeny of Oribatida.

Feather mites (Acari: Astigmata) of captive Psittaciformes in Brazil

ABSTRACT Feather samples were obtained from the following Psittaciformes birds: Amazona amazonica, Amazona aestiva, Aratinga jandaya, Brotogeris spp., Ara ararauna and Ara chloropterus (total of 37 individuals). These birds were housed at the Wild Animal Screening Center of Maranhão, São Luís, Brazil. Four feathers were taken from the following regions: head, back, wings, belly/breast, thighs, and tail/covert. Mites were found on 17 birds (45.94%). Astigmatid mites belonging to the genera Fainalges (Xolalgidae), Chiasmalges (Psoroptoididae) and Tanyaralichus (Pterolichidae) were identified. The highest dominance coefficient was for the mite Fainalges sp. (DC= 96.29). Chiasmalges sp. was obtained only from Ara chloropterus, and Tanyaralichus was found in A. aestiva. The genus Fainalges was obtained from all the species of Psittaciformes studied, except for A. ararauna. In evaluating mite density according to body region, statistical differences were found between the back and wing regions (P= 0.041), back and thighs (P= 0.02), wings and tail (P= 0.002), belly and tail (P= 0.031) and thighs and tail (P= 0.001). The morphological variations observed in Fainalges spp. suggested the existence of three species that probably have not been described yet. This was the first record of the genus Tanyaralichus in Brazil.