Rovnopholcomma wunderlichi gen. et sp. nov. is described from Eocene Rovno amber (Ukraine). The new genus is the closest relative of Succinura Wunderlich, 2008, known from the Eocene Baltic (Gda & nacute;sk Bay), Danish and Bitterfeld ambers. The controversial theridiid subfamily Pholcommatinae Simon, 1894 is here delimited and divided into two tribes: 1) Pholcommatini Simon, 1894, which includes the extant genus Pholcomma Thorell, 1869 and eight extinct genera, all known from the Eocene of Europe; and 2) Theonoini Simon, 1894, which includes the extant genera Theonoe Simon, 1881, Carniella Thaler & Steinberger, 1988 and Robertus O. Pickard-Cambridge, 1879. One of the key diagnostic characters for the newly delimited Pholcommatinae is the presence of hooded trichobothrial bases, a unique feature within the family Theridiidae.

Here we describe two new fossil species and one new genus of pseudoscorpions, found in the late Eocene Baltic amber. Baltochthonius andrushchenkoi gen. et sp. nov. and Heterolophus eridanus sp. nov. are assigned to the subfamily Tridenchthoniinae (Pseudoscorpiones: Chthoniidae). We present an updated diagnostic key for the tribes, genera and subgenera of Tridenchthoniinae. The biogeographic, paleohabitat and ecological features of new species are presented and compared to the related extinct and extant species of the subfamily Tridenchthoniinae.

We describe Haplochthonius (Senilochthonius) nortoni sp. nov., the first fossil representative of the oribatid mite family Haplochthoniidae, discovered in mid-Cretaceous Kachin amber from Myanmar. Exceptional preservation enabled a detailed morphological study using confocal laser scanning microscopy, allowing confident placement of the new species within the subgenus Senilochthonius. Comparison with extant haplochthoniids, which are predominantly associated with xeric or periodically dry habitats, together with the presence of cerotegument, is consistent with the inference that dry or seasonally dry conditions were present in the Kachin amber forest.

We describe Histiogaster altilis sp. nov. (Acari: Astigmata: Acaridae), a newly identified species of mite from Eocene Rovno amber (34-37 Ma), based on both male and female specimens. The exceptional preservation of the fossils, coupled with advanced amber preparation and imaging techniques-including high-resolution microscopy, differential interference contrast (DIC) with transmitted light, and confocal laser scanning microscopy (CLSM) equipped with a super-resolution detector-enabled detailed examination of nearly all diagnostic features. These data allowed us to perform a comprehensive comparison between this fossil species and extant representatives of the genus Histiogaster. Based on morphological similarities with extant species of known biology, and the presence of syninclusions such as fossilized phloem sap emulsions and fungal or bacterial hyphae, we hypothesize that this fossil mite likely fed on fermented tree sap and associated microorganisms. Our findings indicate that species within the genus Histiogaster have undergone minimal morphological changes since the Eocene, while continuing to occupy their ancestral ecological niche. We also review fossil Astigmata and provide an annotated checklist of 14 fossil astigmatid records, and exclude 8 records, including the genus Palaeotyroglyphus Dubinin, 1962, from Astigmata.

A new subfamily, genus and species of pseudochiridiid pseudoscorpions is described from mid-Cretaceous Burmese amber (Myanmar), including a detailed diagnosis and illustrations: Palaeochiridium insolitum gen. et sp. nov. (Arachnida: Pseudoscorpiones) is the first valid species of the family Pseudochiridiidae from Burmese amber. Diagnostic, biogeographic, paleohabitat and ecological features of this new species are presented and discussed, and are compared to the related extinct and extant species of this family.

Acariform mites play a crucial role as primary soil decomposers, impacting the carbon cycle. However, the timing of their diversification is uncertain, with estimated dates ranging from the Precambrian (no land plants) to the Carboniferous (diverse terrestrial ecosystems). One factor affecting these time estimates is an uncertain phylogenetic position of the earliest unequivocal fossil mites from the Devonian Rhynie Chert, which have been classified in five modern families and three suborders. Here, we thoroughly examine these specimens, assign them to a single species Protacarus crani (family Protoacaridae, fam. nov., suborder Endeostigmata) and integrate this information into a time-calibrated phylogenetic analysis. Our phylogeny suggests a Cambrian basal divergence of Acariformes (508-486 Ma), coinciding with the land colonization by bryophytes. At this time, the mites' ecological niches were probably diversified beyond the upper soil. Our study provides temporal context, improves the accuracy of fossil dating, and underscores the importance of mites' diverse habitats and their potential roles in soil food webs.

We present the first fossil evidence of pediculochelid mites, describing two new species: Paralycus ekaterinae sp. nov. (Eocene amber) and P. primus sp. nov. (Cretaceous amber). The exceptional preservation of the fossils, coupled with our newly developed methodological approach for examining minute arthropods in amber, has facilitated a detailed comparative morphological assessment at a resolution comparable to that of contemporary species, providing significant insights into their anatomical features. The observed morphological continuity between fossil and modern pediculochelid mites indicates the evolutionary stability of this lineage spanning at least 99 million years. These findings not only advance our knowledge of the evolutionary history of Pediculochelidae but also offer a broader perspective on the persistence of morphological traits over extensive geological timescales. We also address the phenomenon of phoresy within Paralycus and explore its potential implications for dispersal mechanisms. Furthermore, we evaluate the relationship between the dimensions of the amber imprints and the original size of the mites, contributing to our understanding of the mechanisms of microarthropod preservation in amber.

Cretaceous resins have preserved a remarkable diversity of sternorrhynchans. Burmese amber, formed in the mid-Cretaceous tropics, contains more numerous and diverse Psyllomorpha than all other fossil localities of the period together. The genus Dingla Szwedo et Drohojowska, 2020, previously placed into a separate family and infraorder, turned out to be similar in all essential characters to Mirala Burckhardt et Poinar, 2019 and Burmala Liu et al., 2021; therefore we synonymize Dinglidae Szwedo et Drohojowska, 2020 with Miralinae Shcherbakov, 2020 and raise the last subfamily to the full family status based on several unique apomorphies. A sister-group relationship between Dinglomorpha and Aleyrodomorpha was based on incorrect interpretation of characters. Pictala scorpioides gen. et sp. nov. from Burmese amber differs from other miralid genera by spotted forewings without pterostigma and the structure of terminalia in both sexes. In Miralidae, we discovered a long annulated labium and compound wax pores on the ventral side of the abdomendfor the first time among Hemiptera. The compound wax pores may have helped prevent miralids from sticking to the honeydew excreted. The long, flexible second labial segment, reinforced by sclerotized rings, probably allowed the protrusible length of the stylet bundle to be increased by arching the labium, as in mosquitoes. (c) 2024 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

We report the discovery of remarkable fossil mites referred to a new genus Punkochyzeria gen. nov. (Trombidiformes: Chyzeriidae) found in mid-Cretaceous Kachin amber from Myanmar. The postlarval stages of these mites possess unusually long tufts of dorsal opisthosomal setae. The mites were initially identified as Parachyzeria Hirst, 1926, but detailed morphological analysis revealed several key characters, including the absence of a paradont or basidonts on the palptibia, suggesting a new genus. We describe three new species, Punkochyzeria minaevi sp. nov., Punkochyzeria makolae sp. nov. and Punkochyzeria khoyi sp. nov., which are distinguished by the form of the dorsal opisthosomal setae, the odontus/palptarsus ratio and the number of setae on the palptibial ctenidium. We also present an identification key to the species of the genus Punkochyzeria and describe four specimens of this genus, which are difficult to attribute to any particular species, because of their poor state of preservation. We discuss the erectile function of the long dorsal setae. Notably, the individuals of P. makolae and P. khoyi carry other mites as syninclusions among the long tufts of setae, although phoretic relationship may be accidental. This discovery extends the known diversity of the family Chyzeriidae to the Cretaceous and provides new insights into their evolutionary history and ecological interactions.

A new species of chthonioid pseudoscorpion is described from Eocene Rovno amber (Ukraine), including a detailed diagnosis and illustrations: Chthonius marusiki sp. nov. (Arachnida, Pseudoscorpiones) is the first valid species of the family Chthoniidae from Rovno amber. Diagnostic, biogeographic, paleohabitat and ecological features of this new species are presented and discussed, and are compared to the related extinct and extant species of this genus.

The fossil representatives of the family Resinacaridae (Acari: Heterostigmata) from the Late Eocene Rovno amber are reviewed. Three new species are described in the genus Resinacarus Vitzthum, namely, R. longipilis sp. nov., R. vitzthumi sp. nov., and R. striatus sp. nov. A new genus and species, Pararesinacarus krczali gen. and sp. nov. are also described. The extant species Pararesinacarus aradii (Krczal) comb. nov. was moved from Resinacarus. All active stages of the extant type species of the genus Resinacarus, R. resinatus Vitzthum, are redescribed based on type material. A key to genera and species of Resinacaridae is also provided.

The female of a new fossil genus and species, Rhombometridium pankowskiorum gen. and sp. nov. (Acari: Trochometridiidae), is described from Cretaceous Kachin amber. The new genus is characterized by the presence of well-developed sporothecae anteriad legs III, each sporotheca containing several ovoid fungal spores. This is the oldest (ca. 100 Mya), evidence of symbiosis between mites and fungi and the first fossil record of the mite family Trochometridiidae. The new genus shares synapomorphies with the family Trochometridiidae (presence of sporothecae between bases of legs III and IV) and Caraboacaridae (rhombic body shape, absence of setae v2, absence of palpal solenidion, palps fused with distinctly widened gnathosomal capsule), and potentially represents a transitional form or a missing link between these two closely related families. We also compare the sporothecae of R. pankowskiorum with those of other heterostigmatic mites.

This study provides a comprehensive morphological analysis of ten fossil specimens from the genus Collohmannia, found in Eocene Baltic amber, with nine representing different species. Collohmanniidae, a unique monogeneric family of oribatid mites are among the largest oribatids. They feed on leaf litter and present significant sexual dimorphism and courtship behavior, which includes the transfer of nuptial food from male to female. Extant Collohmannia species inhabit isolated mountain forest areas. A fragmentation hypothesis has been proposed to account for their highly disjunctive distribution, suggesting that climate change divided a large forest area previously occupied by a parent species, leading to the allopatric evolution of several species of Collohmannia. However, with the discovery of a significant number of fossil species in Eocene Baltic amber we propose an alternate hypothesis with the Baltic amber forest serving as an arena for speciation of Collohmanniidae. According to it, the driving force of speciation was dietary and was based on gut microbiome specificity, reinforced by the female choice during the courtship ritual. In this paper we describe seven new fossil species of Collohmannia (C. sellnicki sp. nov., C. albertii sp. nov., C. nortoni sp. nov., C. groehni sp. nov., C. kerneggeri sp. nov., C. weiterschani sp. nov., C. clavata sp. nov.), re-describe C. schusteri based on study of the holotype, synonymize Embolacarus with Collohmannia, propose and describe the neotype of C. pergrata comb. nov., and provide a key to all described Collohmanniidae. Together with the hypotheses of speciation we propose verification experiments to be performed on extant Collohmannia mites.

We have recently shown that experience of flight remarkably enhanced subsequent terrestrial phonotaxis in females in response to the male calling song. Here, we elucidated the possible roles of octopamine and serotonin in the enhancing effect of flying on phonotactic behavior. Octopamine is known to be released into the hemolymph during flight in insects; however, the octopamine receptor antagonist epinastine did not abolish the effects of flight in our study. On the contrary, the drug significantly potentiated the influence of flying on phonotactic behavior. The octopamine receptor agonist chlordimeform, at a concentration of 2 mM, which was previously found to activate aggression in crickets, dramatically reduced the phonotactic response. However, at a 10-times-lower dose, chlordimeform produced a light but significant decrease in the time that females took to reach the source of the calling song. A similar effect was produced by octopamine itself, which hardly passes the blood–brain barrier in insects. The effect of flight was completely abolished in female crickets treated with alpha-methyl tryptophan (AMTP). AMPT suppresses the synthesis of serotonin, decreasing its content in the nervous systems of insects, including crickets. An activation of the serotonin synthesis with 5-hydroxytryptophan mimicked the effect of flight by increasing the number of visits to and the time spent in the zone near the source of the calling song. The 5-HT content in the third thoracic ganglion was significantly higher in flyers compared to the control group. In contrast, no changes in the octopamine level were observed in the third thoracic ganglion, which is known to play a crucial role in decision-making involved in intraspecific interactions. Therefore, the results suggest that although octopamine is known to be released into the hemolymph during flight, it is likely to inhibit rather than activate the central mechanisms related to phonotaxis. The weak facilitating effect of a low dose of chlordimeform can be attributed to the activation of peripheral octopaminergic receptors. Our results suggest that the serotoninergic system may contribute to the facilitation of female phonotactic behavior by flying. We suggest that both flying and serotonin enhance sexual motivation in females and, by these means, impact their behavioral response to the male calling song.

A new monotypic fossil family Unguicheylidae fam. nov. with type genus and species Unguicheylus quadriocellatus gen. nov., sp. nov. is described from the early-Cretaceous (Albian–lower Cenomanian) amber of northern Siberia (Taimyr amber, Baikura locality). The new family is provisionally placed in the superfamily Anystoidea and most similar to the family Pseudocheylidae, but differs mainly in having apomorphically adnate cheliceral bases (free, mobile bases in Pseudocheylidae), and the tarsi of all legs lacking annulated pretarsal stalks bearing reduced claws (present, apomorphic to Pseudocheylidae).

We examined three astigmatic mite specimens phoretic on the beetle Glesoconomorphus ekaterinae from Eocene Rovno amber. Due to the precious nature of this amber piece, housing the name-bearing holotype of the host beetle, traditional trimming for the application of high-resolution imaging techniques at small focal distances was unfeasible. To overcome this challenge, we employed a combination of confocal microscopy relying on the autofluorescence properties of the mite chitinous exoskeleton and long working distance / water immersion objectives. This innovative approach successfully resolved the minute mite features from a considerable distance (700 μm). Based on these data, we describe many taxonomically important characters and identify these mites as a new species, Congovidia glesoconomorphi sp. nov., within the family Hemisarcoptidae. This represents the first fossil record for the mite family. Additionally, we provide a key for phoretic deutonymphs of all known species of Congovidia. As larvae of many extant Eurypinae live in subcortical spaces of decomposing tree trunks, we suggest that the mite C. glesoconomorphi similarly occupied subcortical niches in decayed wood and utilized adult beetles of G. ekaterinae for dispersal.

The task of directional hearing faces most animals that possess ears. They approach this task in different ways, but a common trait is the use of binaural cues to find the direction to the source of sound. In insects, the task is further complicated by their small size and, hence, minute temporal and level differences between two ears. A single symmetric flagellar particle velocity receiver, such as the antenna of a mosquito, should not be able to discriminate between the two opposite directions along the vector of the sound wave. Paired antennae of mosquitoes presume the usage of binaural hearing, but its mechanisms are expected to be significantly different from the ones typical for the pressure receivers. However, the directionality of flagellar auditory organs has received little attention. Here, we measured the in-flight orientation of antennae in female Culex pipiens pipiens mosquitoes and obtained a detailed physiological mapping of the Johnston’s organ directionality at the level of individual sensory units. By combining these data, we created a three-dimensional model of the mosquito’s auditory space. The orientation of the antennae was found to be coordinated with the neuronal asymmetry of the Johnston’s organs to maintain a uniformly shaped auditory space, symmetric relative to a flying mosquito. The overlap of the directional characteristics of the left and right sensory units was found to be optimal for binaural hearing focused primarily in front of, above and below a flying mosquito.

Intense species-specific locomotion changes the behavioural and cognitive states of various vertebrates and invertebrates. However, whether and how reproductive behaviour is affected by previous increased motor activity remains largely unknown. We addressed this question using a model organism, the pond snail Lymnaea stagnalis. Intense crawling in shallow water for two hours had previously been shown to affect orienting behaviour in a new environment as well as the state of the serotonergic system in L. stagnalis. We found that the same behaviour resulted in an increased number of egg clutches and the total number of eggs laid in the following 24 h. However, the number of eggs per clutch was not affected. This effect was significantly stronger from January to May, in contrast to the September-December period. Transcripts of the egg-laying prohormone gene and the tryptophan hydroxylase gene, which codes for the rate-limiting enzyme in serotonin synthesis, were significantly higher in the central nervous system of snails that rested in clean water for two hours after intense crawling. Additionally, the neurons of the left (but not the right) caudo-dorsal cluster (CDC), which produce the ovulation hormone and play a key role in oviposition, responded to stimulation with a higher number of spikes, although there were no differences in their resting membrane potentials. We speculate that the left-right asymmetry of the response was due to the asymmetric (right) location of the male reproductive neurons having an antagonistic influence on the female hormonal system in the hermaphrodite mollusc. Serotonin, which is known to enhance oviposition in L. stagnalis, had no direct effect on the membrane potential or electrical activity of CDC neurons. Our data suggest that (i) two-hour crawling in shallow water enhances oviposition in L. stagnalis, (ii) the effect depends on the season, and (iii) the underlying mechanisms may include increased excitability of the CDC neurons and increased expression of the egg-laying prohormone gene.

The first record is presented of the sejoid genus Uropodella (family Uropodellidae, suborder Sejida) from Baltic amber, based on a well-preserved adult male. Morphologically, the specimen is as modern in structure as adults of the six known extant species of Uropodella. The diagnosis of the fossil in distinction to the extant species justifies naming it as a new species. This record traces the genus back to the Eocene, representing the oldest validated age for a mesostigmatan genus. A key to species of the genus Uropodella is given.

Amber is known as one of the best sources of fossil organisms preserved with exceptional fidelity. Historically, different methods of imaging have been applied to amber, including optical microscopy and microtomography. These methods are sufficient to resolve millimeter-scaled fossils. However, microfossils, such as microarthropods, require another resolution. Here, we describe a non-destructive method of super resolution confocal microscopy (sCLSM) to study amber-preserved microfossils, using a novel astigmatid mite species (genus Histiogaster, Acaridae) from Eocene Rovno amber as a model. We show that the resolution obtained with sCLSM is comparable to that of scanning electron microscopy (SEM) routinely used to study modern mites. We compare sCLSM imaging to other methods that are used to study amber inclusions and emphasize its advantages in examination of unique fossil specimens. Furthermore, we show that the deterioration of amber, which manifests in its darkening, positively correlates with its increased fluorescence. Our results demonstrate a great potential of the sCLSM method for imaging of the tiniest organisms preserved in amber.