Dimitry M. Schepetov's research while affiliated with Lomonosov Moscow State University and other places

We studied the structure of digestive system of deep-sea torquaratorid Quatuoralisia malakhovi including the food-obtaining apparatus, microanatomy of all regions of digestive tract, and fine structure of various regions of the gut. The mouth of Q. malakhovi is surrounded by two symmetrical triangular lateral collar lips and one midventral collar lip, which may retract into the mouth. The ventral ciliary grooves run along the anterior- ventral edges of lateral lips and lead into the internal canals of the lips. The pharyngeal cavity is divided by left and right parabranchial ridges into the median pharyngeal zone with gill bars and two symmetrical peripheral canals, which fuse behind the site of genesis of new gill bars. The gill pharynx is followed by the hepatic region with metameric hepatic sacculations comprising cells with numerous large phagosomes indicating active intracellular digestion. The intestine is filled with undigested food residues including detritus flakes and remnants of various organisms. The intestine content was examined using SEM and histological studies. We analyzed the ratio of organic and mineral components of the bottom sediment from the habitat of Q. malakhovi, and the stable isotope composition of carbon and nitrogen in the intestine content, in the tissues, and in the sediment from the habitat of the studied acorn worm. Using the obtained data and the photographs and videotapes in situ, we have proposed a hypothesis explaining the feeding mechanism of Q. malakhovi. The width of the ventral ciliary groove of the lateral collar lips (100–200 μm) regulates the maximum size of particles that enter the pharynx of the animal. The minimum size of the sediment particles selected by Q. malakhovi is determined by the width of the gill pores and is 1–3 μm. The selected sediment particles move through the peripheral pharyngeal canals to the hepatic region, where the digestion of the food is carried out. In the posthepatic intestine, weight of the gut contents might serve as an anchor that holds the heavily watered jelly-like torquaratorid body at the bottom during the feeding.

In this study, we present the first integrative revision of the Boreal and Arctic calcareous sponges of the genus Leucosolenia with a specific focus on its biodiversity in the White Sea. The material for this work included a combination of newly collected specimens from different regions of the North-East Atlantic and the White Sea and historical museum collections. An integrative analysis was implemented based on vast morphological data (light microscopy, scanning and transmission electron microscopy), microbiome observations, ecological data, accompanied by molecular phylogenetic and species’ delimitation analyses based on three nuclear markers (28S rRNA, 18S rRNA, and histone 3). We demonstrate that Leucosolenia complicata, previously reported from Arctic waters, is restricted to the North-East Atlantic, while in the Arctic, Leucosolenia diversity is represented by at least four species: Leucosolenia corallorrhiza, Leucosolenia variabilis, and two new species, one of which is described herein under the name Leucosolenia creepae sp. nov.. The molecular phylogeny analysis supports the species identity of these species. In addition to conventional morphological characters, new informative fine morphological characters (skeleton and oscular crown organization; cytological structure, including morphotypes of symbiotic bacteria) were found, providing a baseline for further revision of this group in other regions.

Invasive plants are often released from herbivore pressure in their secondary range, but native herbivores can adapt to feed on them over time. Impatiens glandulifera and I. parviflora are two invasive species, whose leaves in the secondary range have been severely damaged by leaf miners in recent years. The leaf miner attack rates for these species and a native congener, I. noli-tangere, were examined. Molecular analysis shows that all three impatiens species are affected by the same leaf miner Phytoliriomyza melampyga (Agromyzidae) without signs of divergence between populations living on different plant species. The native I. noli-tangere is more often damaged by the leaf miner, whilst I. parviflora is attacked more often than I. glandulifera. The largest mined area was found in I. glandulifera leaves and the smallest in I. noli-tangere. The nitrogen content, indicative of food quality, was similar in all three species, and there were no differences in ¹⁵N enrichment between miners from three impatiens species. We suppose that observed differences in attack rates and mined area in P. melampyga on three Impatiens species can be explained mainly by different levels of antiherbivore defence and recent host shift from native species to invasive ones.

Onchidoris muricata (Gastropoda: Nudibranchia: Onchidorididae) is a well-known nudibranch species, which has a wide amphiboreal range confirmed by molecular data. However, O. muricata shows a high degree of variation in external morphology among distant populations, which may indicate the presence of cryptic diversity within this species. There are also two closely related species with an unconfirmed taxonomic status, which were recently described from the northwestern Pacific based on morphological data. In this paper we study the taxonomic status and population structure of O. muricata based on an integrative approach combining morphological and molecular data and using O. muricata as a model we explore issues of boreal marine fauna connectivity and glaciation-driven isolation. The external morphology, spicule composition, and features of the buccal armature and the reproductive system were studied using light microscopy, scanning electron microscopy and mCT scan technology. The molecular study included various population genetic analyses as well as divergence time estimation and ancestral area reconstruction analyses. Onchidoris muricata represents a true amphiboreal species, which shows a high degree of heterogeneity in morphological characters, especially in the radular morphology and in features of the reproductive system. Our new data question the validity of the North-West Pacific species O. macropompa and O. pavli as the morphology of both these species fall within the phenotypic diversity of O. muricata. Although our sampling does not include the type localities of these two species, the observed morphological variability in O. muricata and the lack of molecular data for the North Pacific species O. macropompa and O. pavli suggest the latter two species are in fact part of O. muricata morphological diversity. Phylogeographic analyses indicate a genetic separation of the North Pacific and North Atlantic-Arctic populations of O. muricata, suggesting restricted gene flow between these areas. We show that this divergence may be a result of glacial cycles during the late Pleistocene, which were a key factor in the reduction of gene flow across the Arctic Ocean. Our molecular results also suggest that the White Sea population experienced a bottleneck event during the last Glacial Maximum.

Invasive plants form new ecological links with native biota that can affect soil animals. Giant goldenrod (Solidago gigantea Aiton) of the Asteraceae family originates in North America, but it is an invasive plant elsewhere in the world. We studied the belowground arthropod communities of invasive S. gigantea and native vegetation at three sites near Moscow, Russia. Molecular techniques allow for quick identification of the community composition but provide little information on the abundance of soil animals and should be verified by classical taxonomy methods. Thus, we identified soil arthropods using metabarcoding and morphological identification. The number of arthropod families identified by the two methods was comparable (53 and 56, respectively), with a significant correlation in the number of families detected in individual samples based on morphological and metabarcoding approaches. The structure of the belowground arthropod community was subtly different between the goldenrod and control sites. A goldenrod transplant experiment was designed to control the random factors that created site-specific variation. After one year, the abundance and diversity of soil arthropods remained the same in sites with transplanted goldenrod and the control plots, leading to the conclusion that invasive S. gigantea does not affect soil arthropod communities in this region.

Our study is focused on original and publicly accessible data on the intraspecific variability of the barcoding DNA fragment in ladybirds Harmonia axyridis Pall analysis. The complete dataset consists of 39 haplotypes, 16 of which we identified for the first time. The intra-population and geographical variability of the barcoding fragment was studied for seven populations of the western and eastern groups of the native range and in six invasive populations, in which 25 of the 39 haplotypes are found. Population structure inferred on base of molecular variability and haplotype frequencies showed a high level of differences between the eastern and western groups of native populations and confirm the hypothesis of the origin of all invasive populations from native populations of the eastern group. A comparative analysis of molecular variation indices testifies to various evolutionary scenarios of the formation of the western and eastern groups of native populations and confirms the hypothesis of the microevolutionary history of the species, previously suggested in morphological character based studies of the geographical variability of H. axyridis. A significant decrease in the molecular diversity of invasive populations confirms the hypothesis of a random nature of the primary invasion of this species in North America.

Studies on heterobranch fauna of Southern Vietnam are very fragmented. To date only two revisions of local species composition were conducted, however they were based on a sparse sampling in restricted areas. In total 150 species of heterobranchs were registered, among which about 120 species were nudibranchs. Nevertheless, this number is much lower than nudibranch diversity in adjacent areas (Thailand, Malaysia, Philippines). The main goal of our study was to observe and revise the species diversity of the suborder Cladobranchia, using molecular barcoding techniques and traditional morphological methods.

We propose three calibration scenarios of to date contemporary divergence of Anoplopomatidae (skilfish Erilepis zonifer and sablefish Anoplopoma fimbria ) for a data set of two mtDNA loci (СOI and Control Region). The first scenario is based upon a fossil record and the second and third ones upon major palaeogeological events 3.5 and 15 Mya. Estimated evolution speeds indicate that COI evolves faster in the skilfish mitochondrial genome. There is also evidence of skilfish going through a bottleneck event limiting its genetic diversity in the relatively recent past near Japan. Sablefish had two refugia on both sides of the Pacific Ocean. The contemporary haplotype divergence was formed ~450 thousand years ago during an ice age in the Pleistocene and contemporary populations display no apparent geographic differentiation.

Meloscaphander grandis is a little-known species missing from databases and papers on taxonomic revision and phylogenetic analysis of Scaphandridae. This species is redescribed herein, based on the type specimen and specimens from the abyssal plain adjacent to the Kuril-Kamchatka Trench. A phylogenetic analysis of COI, 16S, and 28S markers show M. grandis to nest within the Scaphander clade. Additionally, Scaphander lignarius and S. bathymophilus are suggested to be a complex of cryptic species. Morphological differences between the genera Meloscaphander and Scaphander are of dubious significance and, when coupled with molecular data, give a strong reason for reconsidering Meloscaphander as a junior synonym of Scaphander. Thus, according to an integrative taxonomic analysis, Meloscaphander grandis has been transferred to the genus Scaphander. The diagnosis of the genus Scaphander is expanded. We propose new combinations as follows: Scaphander grandis (Minichev, 1967) comb. n. for Meloscaphander grandis, Scaphander sibogae (Schepman, 1913) comb. n. for Meloscaphander sibogae, and Scaphander imperceptus (Bouchet, 1975) comb. n. for Meloscaphander imperceptus. Due to the homonymy of Scaphander sibogae Schepman, 1913 (with a sunken spire) and Scaphander sibogae (Schepman, 1913) comb. n. (with an elevated spire), the name S. attenuatus Schepman, 1913 becomes valid for the former species (with a sunken spire).