Alexander A. Khaustov’s research while affiliated with Tyumen State Medical University and other places

The mite Thyreophagus entomophagus is a cosmopolitan species of significant economic importance in biocontrol applications, serving as a factitious prey for the mass rearing of predatory mites. This species has been reported from a variety of habitats. However, the taxonomic reliability of its name is questionable due to inconsistencies in historical species identifications, the absence of type specimens, and misidentified GenBank sequences. Here, to address these issues and to standardize the nomenclature, we redescribe Thyreophagus entomophagus based on a commercial culture with known COX1 barcoding sequence data and designate a neotype from this culture. As part of delimiting the species boundaries of Th. entomophagus, the question of whether this species forms heteromorphic deutonymphs is particularly important. While the literature suggests that most populations lack them, at least one population in Germany has been reported to produce heteromorphic deutonymphs. However, after careful examination, we identified this population as a new species, Thyreophagus holda, indicating that previous identifications of this population as Th. entomophagus were incorrect. The absence of the heteromorphic deutonymphal stage is a beneficial trait for mass production, as it simplifies the life cycle by eliminating the energetically costly heteromorphic deutonymph. Our preliminary molecular phylogenetic analyses of Th. entomophagus and other species of Thyreophagus indicate that the loss of heteromorphic deutonymphs and the emergence of asexual reproduction (another beneficial trait for mass production) are derived traits that arose after the divergence of the most recent common ancestor of Thyreophagus. These insights enhance our understanding of the evolutionary traits that increase the effectiveness of Th. entomophagus and related species in biocontrol settings. Our study points to the need for additional bioprospecting efforts to identify new candidate species for biocontrol that possess both asexual reproduction and the absence of heteromorphic deutonymphs.

Phoretic deutonymphs of Winterschmidtia tawantinsuyuca sp. n. (Acari: Winterschmidtiidae) are described from Peru. This is the fourth species of the genus recorded in the Neotropical realm. Similar to the three other Peruvian species, the new species is phoretic on bark beetles, but this is the first finding of Winterschmidtia on the beetles of the genus Xyleborus (Coleoptera: Curculionidae: Scolytinae). The new species differs from all others in the ornamentation on of its prodorsal shield.

Simple Summary In recent years, there has been a growing interest in finding sustainable and environmentally friendly solutions to combat agricultural pests while minimizing the adverse impacts of chemical pesticides. Species of the genus Thyreophagus have emerged as a valuable asset in this pursuit. These mites are utilized as factitious prey for the mass rearing of predatory mites. Predatory mites, in turn, play a crucial role in biological pest control—they feed on a variety of agricultural pests such as spider mites, thrips and other small arthropods that harm crops. Despite their significance, we do not know much about Thyreophagus mites because many species live in hidden habitats and are difficult to study. As part of our survey, we discovered a new species, Thyreophagus tauricus, and provide detailed descriptions of its different life stages. Genetic sequencing was also performed to identify this new species and compare it with others: Thyreophagus corticalis (broadly distributed Palearcic species), Th. calusorum, Th. entomophagus (economically important factitious prey mites). We also correct some mistakes in mite identification, particularly the economically important species Th. entomophagus, which can be crucial for future studies and biocontrol applications. Abstract As part of a survey of the subcortical astigmatic mites of Crimea, we discovered a new sexual acarid species, Thyreophagus tauricus sp. n. This species was cultured in the laboratory to correlate the adult and deutonymphal stages. Using specimens obtained by these rearing experiments, we provide a detailed description of Th. tauricus (light microscopy, SEM) based on females, males and heteromorphic deutonymphs. Furthermore, to facilitate molecular identification, the entire COX1 gene was also sequenced for this and three other Palearctic species reared in the lab as pure cultures. Adults of Th. tauricus sp. n. are distinct among all other species of the genus by the presence of flattened, button-shaped or minute spiniform setae s III and IV, which are well-developed spiniform in all other known species of Thyreophagus. Heteromorphic deutonymphs of Th. tauricus are distinct from all other species of Thyreophagus by the presence of well-developed setae cm on the dorsal part of the subcapitular remnant (absent all other species). Th. tauricus is morphologically very similar to Th. corticalis; however, COX1 K2P distances between these two species were large, 19.8%. COX1 K2P distances between Th. tauricus and other species (Th. entomophagus, Th. “entomophagus” NC 066986.1, Th. calusorum, Th. corticalis) ranged between 20.1 and 24.3%. We show that the GenBank sequence of Th. “entomophagus” from China (NC 066986.1) was probably misidentified.