Video surveys were carried out during the 75th cruise of the RV Akademik M.A. Lavrentyev (June 2016) along the northern slope of the Volcanologists Massif, in the south-western Bering Sea. The seafloor was explored using the ROV Comanche 18. Seven dives were performed in the depth range from 4,278 m to 349 m. Overall, about 180 species of megafauna were recognised. Fifteen types of megafauna communities corresponding to certain depth ranges were distinguished based on the most abundant taxa. Dominance changed with depth in the following order: the holothurian Kolga kamchatica at the maximum depth (4,277–4,278 m); the holothurian Scotoplanes kurilensis at 3,610–2,790 m; the ophiuroid Ophiura bathybia at 3,030–2,910 m; benthic shrimps of the family Crangonidae at 2,910–2,290 m; the holothurian Paelopatides solea at 2,650–2,290 m; benthic jellyfish from the family Rhopalonematidae at 2,470–2,130 m; the enteropneust Torquaratoridae at 2,290–1,830 m; the holothurian Synallactes chuni and the ophiuroid of the genera Ophiura and Ophiocantha at 1,830–1,750 m. At depths 1,750–720 m most of the megafauna was associated with live or dead colonies of the sponge Farrea spp. Depths 720–390 m were dominated by the coral Heteropolypus ritteri and/or Corallimorphus pilatus. At 390–350 m depth, the shallowest depth range, the dominant taxon was the zoantharian Epizoanthus sp. Soft sediment megafauna communities dominated by torquaratorid enteropneusts to our knowledge have not been observed before in the deep-sea, the same as communities with a dominance of benthopelagic rhopalonematid jellyfish. The depths of the largest community changes, or the largest turnover of dominant species, were revealed at ∼2,790 m between the bathyal and abyssal zones and ∼1,750 m and ∼720 m within the bathyal zone.

The first phylogenetic and phylogeographic studies of the cosmopolitan deep-sea species, Asteronyx loveni Müller and Troschel, 1842, were conducted, based on specimens collected from off the Pacific coast of Japan. Partial sequences of mitochondrial 16S (68 specimens) and COI ( 24specimens) genes were analyzed. Phylogenetic trees and network analyses revealed three lineages and five sub-lineages of A. loveni. Genetic distance and AMOVA (analysis of molecular variance)analyses suggested that the lineages should be considered three cryptic species. Skin on the aboral disc is partly thickened and forms a mesh-like pattern, which has never been reported in previous descriptions of Asteronyx; this is provided as a new taxonomic character. Based on absence/presence of mesh-like skin, one of the three lineages was assigned to A. loveni and another was described as Asteronyx reticulata new species. This new species can be distinguished from congeners by having reticulated external ossicles and small genital slits at the innermost position on the interradial oral disc.

The world’s most northern species of the nudibranch genus Adalaria rossica sp. nov. from Franz Josef Land and a new species of Onchidoris expectata sp. nov. from the north-west Pacific Matua Island (Kurile Islands) are described. Prior to this study the nudibranch fauna from Franz Josef Land was represented only by two common North Atlantic species. Molecular taxonomic data were not applied for the Franz Josef Land nudibranchs previously. Nudibranchs of Matua Island have never been investigated. Furthermore, a new North Pacific taxon, Adalaria ultima sp. nov., is described here. The taxonomy of the onchidoridid genera Adalaria and Onchidoris is discussed.

The key terms linking ontogeny and evolution are briefly reviewed. It is shown that their application and usage in the modern biology are often inconsistent and incorrectly understood even within the “evo-devo” field. For instance, the core modern reformulation that ontogeny not merely recapitulates, but produces phylogeny implies that ontogeny and phylogeny are closely interconnected. However, the vast modern phylogenetic and taxonomic fields largely omit ontogeny as a central concept. Instead, the common “clade-” and “tree-thinking” prevail, despite on the all achievements of the evo-devo. This is because the main conceptual basis of the modern biology is fundamentally ontogeny-free. In another words, in the Haeckel’s pair of “ontogeny and phylogeny,” ontogeny is still just a subsidiary for the evolutionary process (and hence, phylogeny), instead as in reality, its main driving force. The phylotypic periods is another important term of the evo-devo and represent a modern reformulation of Haeckel’s recapitulations and biogenetic law. However, surprisingly, this one of the most important biological evidence, based on the natural ontogenetic grounds, in the phylogenetic field that can be alleged as a “non-evolutionary concept.” All these observations clearly imply that a major revision of the main terms which are associated with the “ontogeny and phylogeny/evolution” field is urgently necessarily. Thus, “ontogenetic” is not just an endless addition to the term “systematics,” but instead a crucial term, without it neither systematics, nor biology have sense. To consistently employ the modern ontogenetic and epigenetic achievements, the concept of ontogenetic systematics is hereby refined. Ontogenetic systematics is not merely a “research program” but a key biological discipline which consistently links the enormous biological diversity with underlying fundamental process of ontogeny at both molecular and morphological levels. The paedomorphosis is another widespread ontogenetic-and-evolutionary process that is significantly underestimated or misinterpreted by the current phylogenetics and taxonomy. The term paedomorphosis is refined, as initially proposed to link ontogeny with evolution, whereas “neoteny” and “progenesis” are originally specific, narrow terms without evolutionary context, and should not be used as synonyms of paedomorphosis. Examples of application of the principles of ontogenetic systematics represented by such disparate animal groups as nudibranch molluscs and ophiuroid echinoderms clearly demonstrate that perseverance of the phylotypic periods is based not only on the classic examples in vertebrates, but it is a universal phenomenon in all organisms, including disparate animal phyla.

Background: Skin disease is the fourth most common disease among all diseases. The number of cases of skin diseases continues to increase, and people commonly use antibiotics to treat these diseases. Nevertheless, overuse of antibiotics can increase the resistance of these pathogens. Hence, the study of novel antibiotic compounds against multi-drug resistant (MDR) skin pathogens is urgently needed. Methods: This study describes the antimicrobial diversity of bacteria associated with three species of marine nudibranchs (Jorunna funebris, Gymnodoris rubropapulosa, and Glossodoris atromarginata) sampled from Jepara coastal waters, the North Java Sea in August 2020. A total of 115 bacterial strains were selected for their prospective antipathogenic compounds against the pathogens Cutibacterium acnes, Staphylococcus aureus, Candida albicans, and Malassezia furfur. Results: A total of 24 bacterial isolates (20.87%) exhibited antimicrobial activity against the pathogens that were selected and molecularly identified. Analyses of the gene of 16S rRNA discovered that these 24 isolates were associated with 11 genera of the phyla Firmicutes, Proteobacteria, and Actinobacteria, including Bacillus as the dominant genus, followed by Streptomyces, Gordonia, Salinicola, Thalassospira, Halomonas, Dietzia, Brevibacterium, Paracoccus, Pseudovibrio, Pseudoalteromonas, and Pseudomonas. None of the 24 antimicrobial bacterial strains possessed type-1 polyketide synthases (PKS-I). One strain possessed type II polyketide synthases (PKS-II), and five strains possessed non-ribosomal peptide synthetase (NRPS) genes. The amounts of bacterial genus and strains in the three nudibranchs differed significantly, as did the proportions of antimicrobial strains in each nudibranch species. The antibacterial strains isolated from G. atromarginata were the highest number (62.5%), followed by J. funebris (20.8%) and G. rubropapulosa (16.7%). Conclusions: These results demonstrate that nudibranch species harbor prominent and varied communities of bacteria and reveal that many nudibranch-associated bacteria have the potential for the advancement of broad-spectrum antibiotics.