Clarification of the diagnosis of the genus Loxosoma s.l. (Entoprocta; Loxosomatidae) based on morphological and molecular data.

Loxosomatidae are solitary entoprocts associated with various types of invertebrate hosts. Two genera are distinguished in the family Loxosomatidae, Loxosomella and Loxosoma, that have clear morphological differences in the attachment structures. Loxosoma attaches to the substratum by a muscular sucking pedal disk, which allows moving. Both kidneys and adults are thought to have a pedal disc throughout their lives. In August 2021, several specimens of loxosomatids were found in the White Sea at a depth of 3070 m on a polychaete Laonice sp. (Spionidae), which were investigated using light and electron microscopy as well as molecular phylogenetic analysis. These loxosomatids were identified as Loxosomella aripes Nielsen, although a stalk of large buds of the specimens from the White Sea terminate with a pedal disc typical of Loxosoma. Molecular phylogenetic analysis of two markers [28S rRNA (~380bp) and 18S rRNA (in three parts totaling ~1850bp)] confirms the affinity of the species to Loxosoma s.l. and does not confirm monophyly of the genera Loxosoma and Loxosomella, indicating that the entire system of loxosomatids requires revision. Here, we redescribe the species Loxosomella aripes as Loxosoma s.l. aripes. The diagnosis of the genus Loxosoma s.l. is supplemented with the observation that the structure of the attachment organ can change after anchoring to the substrate. A list of species currently assigned to Loxosomella that may in fact belong to the genus Loxosoma s.l. is also given.

Nematocyst sequestration within the family Fionidae (Gastropoda: Nudibranchia) considering ecological properties and evolution.

Aeolid nudibranchs are well-known for their ability to incorporate cnidarian nematocysts and use them for defense; this process is tightly linked with the feeding preferences of molluscs. As many nudibranch groups show signs of ecology-based adaptive radiation, studies of prey-based defensive mechanisms can provide valuable insight into details of nudibranch evolutionary history. The main goal of this study is to test the correlation of ecological traits, feeding mechanisms, and prey preferences with cnidosac fine morphology and to pinpoint the phylogenetic value of these traits. We study the cnidosac morphology in thirteen species-representatives of the main lineages within the family Fionidae s.l. The morphological analysis includes histological sections, transmission electron microscopy, confocal laser scanning microscopy, and scanning electron microscopy. For phylogenetic study, available molecular data from public repositories were used, and phylogenetic trees were produced based on Bayesian Inference and Maximum likelihood analysis for a concatenated dataset of three molecular markers (COI, 16S, H3). In general, fionid cnidosacs fit the common aeolid pattern, but among different species we detected a high variation in type of obtained nematocysts, their arrangement within cnidophages, and in number of cell types within cnidosacs. We report on presence of cellules speciale in the haemocoel of all studied species, and for the first time, we report on cells with chitinous spindles in the haemocoel of all fionids except Eubranchus. The function of both these cell types remains unknown. The loss of functional cnidosacs occurred at least three times within Fionidae, and in case of the genera Phestilla, Calma, and Fiona, this loss is linked to their non-cnidarian diet. The diversity of cnidosac fine structure within Fionidae s.l. correlates with that of the radular morphology and feeding preferences of each species. Prey shifts between cnidarian and non-cnidarian prey (both through evolutionary shifts and individual variation) rarely occur within Fionidae s.l.; however, microevolutionary shifts between different hydrozoan species within a single genus are more common. Cnidosac morphology demonstrates considerable resulting changes even when switching between similar hydrozoan species, or changing the feeding site on same prey species. These data indicate that cnidosac morphology likely follows microevolutionary prey shifts-in other words, it is affected by switches in prey species and changes in feeding sites with a single prey species. Thus, the cnidosac morphology may be a useful indicator when studying ecological features of particular species.

HOX-Gene Cluster Organization and Genome Duplications in Fishes and Mammals: Transcript Variant Distribution along the Anterior-Posterior Axis.

Hox genes play a crucial role in morphogenesis, especially in anterior-posterior body axis patterning. The organization of Hox clusters in vertebrates is a result of several genome duplications: two rounds of duplication in the ancestors of all vertebrates and a third round that was specific for teleost fishes. Teleostei cluster structure has been significantly modified in the evolutionary processes by Hox gene losses and co-options, while mammals show no such tendency. In mammals, the Hox gene number in a single cluster is stable and generally large, and the numbers are similar to those in the Chondrichthyes. Hox gene alternative splicing activity slightly differs between fishes and mammals. Fishes and mammals have differences in their known alternative splicing activity for Hox gene distribution along the anterior-posterior body axis. The analyzed fish groups-the Coelacanthiformes, Chondrichthyes, and Teleostei-all have higher known alternative mRNA numbers from the anterior and posterior regions, whereas mammals have a more uniform Hox transcript distribution along this axis. In fishes, most Hox transcripts produce functioning proteins, whereas mammals have significantly more known transcripts that do not produce functioning proteins.

Variability of the mitochondrial CO1 gene in native and invasive populations of Harmonia axyridis Pall. comparative analysis.

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.

Meloscaphander grandis (Heterobranchia: Cephalaspidea), a deep-water species from the North Pacific: Redescription and taxonomic remarks.

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).

Diet-driven ecological radiation and allopatric speciation result in high species diversity in a temperate-cold water marine genus Dendronotus (Gastropoda: Nudibranchia).

While the majority nudibranch clades are more species rich in the tropics, the genus Dendronotus is mainly represented in Arctic and boreal regions. This distribution pattern remains poorly understood. An integrative approach and novel data provided valuable insights into processes driving Dendronotus radiation and speciation. We propose an evolutionary scenario based on molecular phylogenetics and morphological, ecological, ontogenetic data, combined with data on complex geology and paleoclimatology of this region. Estimated phylogenetic relationships based on four molecular markers (COI, 16S, H3 and 28S) shows strong correlation with radular morphology, diet and biogeographical pattern. Ancestral area reconstruction (AAR) provides evidence for a tropical Pacific origin of the genus. Based on AAR and divergence time estimates we conclude that the evolution of Dendronotus has been shaped by different processes: initial migration out of the tropics, diet-driven adaptive radiation in the North Pacific influenced by Miocene climate change, and subsequent allopatric speciation resulting from successive closings of the Bering strait and cooling of the Arctic Ocean during the Pliocene-Pleistocene. At the same time, contemporary amphiboreal species appear to have dispersed into the Atlantic fairly recently.

A Radical Solution: The Phylogeny of the Nudibranch Family Fionidae.

Tergipedidae represents a diverse and successful group of aeolid nudibranchs, with approximately 200 species distributed throughout most marine ecosystems and spanning all biogeographical regions of the oceans. However, the systematics of this family remains poorly understood since no modern phylogenetic study has been undertaken to support any of the proposed classifications. The present study is the first molecular phylogeny of Tergipedidae based on partial sequences of two mitochondrial (COI and 16S) genes and one nuclear gene (H3). Maximum likelihood, maximum parsimony and Bayesian analysis were conducted in order to elucidate the systematics of this family. Our results do not recover the traditional Tergipedidae as monophyletic, since it belongs to a larger clade that includes the families Eubranchidae, Fionidae and Calmidae. This newly recovered clade is here referred to as Fionidae, the oldest name for this taxon. In addition, the present molecular phylogeny does not recover the traditional systematic relationships at a generic level, and therefore, systematic changes are required. We recognize the following clades within Fionidae: Calma, Cuthona, Cuthonella, Eubranchus, Fiona, Murmania, Tenellia, Tergipes, Tergiposacca gen. nov., Rubramoena gen. nov. and Abronica gen. nov. The type species of Tergiposacca, T. longicerata nov. sp. is described. The other two new genera have a previously described species as their type species. Most of these taxa, with the exceptions of Eubranchus, Tergipes and Fiona are composed of radically different constituent species from their traditional membership, but appear to be supported by morphological synapomorphies as well as molecular data. Aenigmastyletus, Catriona, Phestilla, Tenellia and Trinchesia are nested within other clades and, thus are here considered as synonyms of the larger clades. The phylogenetic position and validity of Myja, Guyvalvoria, Leostyletus and Subcuthona still need to be tested in future studies when material becomes available.

Cryptic diversity of the 'cosmopolitan' harpacticoid copepod Nannopus palustris: genetic and morphological evidence.

Nannopus palustris Brady, 1880 is a free-living widely distributed harpacticoid copepod, which has been formerly assumed to be a single, cosmopolitan but highly variable species. We compared several geographically distant N. palustris populations in terms of their morphology and genetics. Populations from the White Sea (WS), the North Sea (NS), the Black Sea (BS) and two sympatric morphs from South Carolina, USA (SC notched and SC straight morphs), were considered. The NS, BS and to a lesser extent SC notched specimens were morphologically similar and partly coincided to the 'canonical' description of the species. By contrast, WS population showed remarkable anatomical and morphometric peculiarities that correspond to some earlier descriptions. Genetic analyses of mitochondrial (cytochrome b) and nuclear (28S rDNA) genes demonstrated the significant distinctness among WS, both SC and (NS+BS) populations, the latter two being genetically indistinguishable. Concordance between mitochondrial and nuclear gene trees and morphological data supports that N. palustris is in fact composed of several pseudo-sibling species, which are genetically and morphologically divergent. Neither correlation between genetic divergence and geographical distance nor significant intrapopulation diversity was found for these species. Taxonomic status, distribution and phylogenetic relationships of the species within the Nannopus genus need to be reconsidered. A further subdivision of species complexes might have important implications for the analysis of biodiversity of benthic copepods and consequently for the interpretation of their (species-specific) ecological function.