Fossil Histiogaster mites and syninclusions from Eocene Rovno amber

Source image stacks of specimens, dataset for the paper<b>An exceptionally well-preserved Eocene </b><b>fossil mite, Histiogaster altilis sp. n. </b><b>(Acari: Astigmata), from tree sap: </b><b>Evidence of morphological and </b><b>ecological niche conservatism, with a </b><b>review of fossil Astigmata</b>Vasiliy B. Kolesnikov, Dmitry D. Vorontsov, Evgeny E. Perkovsky, Pavel B. KlimovWe describe <i>Histiogaster altilis</i> 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 <i>Histiogaster</i>. 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 <i>Histiogaster</i> 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 <i>Palaeotyroglyphus</i> Dubinin, 1962, from Astigmata.Images in JPEG or TIFF format, zipped per specimen.<br>Scalebars included as separate files, insert pixel to pixel to the photo. FastStone image viewer (freeware) is recommended for viewing the stacks.<br>Compound microscopes Nikon E-800 with dry (10x, 20x), water (40x and 60x) and oil (100x) immersion optics and Zeiss AxioImager A2 with dry (40x, 63x) and oil immersion optics (100x) were used, with brightfield, polarized, differential interference contrast and incident illumination. Stacks of images, comprising multiple focal planes, were obtained with Olympus OM-D E-M10-II digital camera. Images were treated for color, digital noise and sharpness with Adobe Lightroom.Fluorescence imaging was performed using a Zeiss LSM-880 confocal laser scanning microscope (CLSM) equipped with an Airyscan super-resolution detector.