Unfinished symphony: updating the systematics of Aeolidiidae (Nudibranchia, Gastropoda), with special focus on Aeolidiella Bergh, 1867.

Molecular phylogeny, morphology, and distribution of Polygordius (Polychaeta: Polygordiidae) in the Atlantic and Mediterranean

The genus Patella (Patellogastropoda, Mollusca) is represented by a group of species exclusive to the Northeast Atlantic Ocean (including Macaronesian archipelagos) and Mediterranean Sea. The species Patella ulyssiponensis and Patella aspera are common in European waters, with the first inhabiting continental coast, and the second endemic to Macaronesian archipelagos. However, the acceptance of these two lineages as separate species is still highly debated. The red coralline species algae Lithophyllum hibernicum, distributed from Northeast Atlantic to the Mediterranean, is usually found as epilithic crusts or unattached forms (named rhodolith beds), although it also forms epizoic crusts on other organisms, e.g., shell surfaces. In order to study the historic dispersal and migration routes of the Patella ulyssiponensis-aspera complex, taxonomic, genetic and biogeographic approaches were employed based on haplotype network analyses and estimations for the most common recent ancestor (TMRCA), using Cytochrome Oxydase I. A synonymy for these two species is proposed, with the presence of a shared haplotype between the continental (P. ulyssiponensis) and insular (P. aspera) lineages, and with basis of morphological and nomenclatural data. We propose an evolutionary scenario for its dispersal based on a high haplotype diversity for the Mediterranean regions, indicating its possible survival during the Messinian Salinity Crisis (6–5.3 Mya), followed by a colonization of the Proto-Macaronesian archipelagos. The epizoic association of L. hibernicum on P. ulyssiponensis shell adult surface is recorded in this study, likewise the promotion of settlement conditions provided by these coralline algae to P. ulyssiponensis larvae, may explain the reach of P. ulyssiponensis distribution through rhodolith transportation.

Pomfret, which are widely distributed throughout the western Pacific and Indian Oceans, are economically important fish species. As their similar external morphological characteristics can inhibit proper species identification, numerous errors exist in the morphological characterization and DNA barcoding data of pomfret. In this study, we extensively sampled pomfret from the Indian and Pacific Oceans. Using the sampled specimens, in combination with morphological assessments, DNA barcoding, and corrected sequences of the mitochondrial cytochrome c oxidase I (COI) gene in GenBank, we attempted to resolve the classification issues surrounding this group. We identified seven valid species in the genus Pampus, of which all seven are distributed in the western Pacific and three are distributed in the Indian Ocean. Pampus argenteus, Pampus cinereus, and Pampus sp. were identified as three valid species with relatively close genetic distances and sharing a common ancestor. Significant variation between Pampus chinensis specimens from the Arabian Sea and the northwestern Pacific suggest a possible species complex. Finally, we provide an identification key to facilitate the identification of pomfret based on the major diagnostic morphological characteristics of six Pampus species collected along the western Pacific coast. On the basis of the reports on the new record of “Pampus argenteus,” we found that the Lessepsian migration of pomfret was likely, with species from the Indian and Pacific Oceans spreading through the Mediterranean Sea into the waters of the eastern Atlantic. Further study is required to clarify the validity of the newly recorded “Pampus argenteus.”

Trapania is the second largest genus belonging to the family Goniodorididae, of which most of the species are reported from Indo‐Pacific waters. To date, there are nine species of Trapania distributed along the temperate coasts of the East Atlantic Ocean and Mediterranean Sea: Trapania fusca, Trapania graeffei, Trapania hispalensis, Trapania lineata, Trapania maculata, Trapania orteai, Trapania pallida, Trapania sanctipetrensis and Trapania tartanella. However, the validity of some of these species has been problematic due to uncertain taxonomic characteristics used for the differentiation of the species. The genus Trapania has a very uniformly external morphology and very similar internal anatomy. As a consequence, the features most commonly used to differentiate species have been the colour pattern of the body and the morphology of the radula. In the present study, we perform a morphological and molecular revision of the East Atlantic‐Mediterranean species of the genus Trapania. Morphological analyses include dissections and scanning electron microscope photographs of radulae, labial cuticles and penises. Molecular work includes phylogenetic, species delimitation and haplotype network analyses. Our results bring doubt on the taxonomic characteristics used so far, suggesting that the richness of the North Eastern Atlantic‐Mediterranean species has been overestimated. Trapania hispalensis, T. lineata and T. pallida are shown to belong to the same taxa, with Trapania lineata as senior synonym.

A southwestern Indian Ocean (SWIO) percoid fish Serranus knysnaensis Gilchrist, 1904, was long synonymised with the comber, Serranus cabrilla (Linnaeus, 1758), from the eastern Atlantic Ocean, Mediterranean and Black Sea. However, when the species was brought out of synonymy by Heemstra Heemstra (2004), reasons for this decision were not given. This study aims to revalidate the present taxonomic status of S. knysnaensis using morphological and molecular assessments. The two species are distinguished by the number of circumpeduncular scales (2634 in S. knysnaensis versus 3438 in S. cabrilla) and total gill rakers (1822 versus 2224). Serranus knysnaensis is also distinct from S. novemcinctus Kner, 1864, the other SWIO species of Serranus, based on total gill raker counts (1822 versus 3135). Genetic analysis of mitochondrial DNA barcode (COI) sequences for 17 Serranus species revealed three closely-related monophyletic clusters corresponding to S. cabrilla, S. novemcinctus and S. knysnaensis that were supported (P 0.001) by species delimitation methods. Even though the genetic distances among the three species were the lowest in the genus (1.60-1.99%), these species may be ecomorphs or lineages that have only recently diverged from each other. These three species also have allopatric distributions and our morphological and molecular data thus confirm that S. knysnaensis is a valid species.

Species delimitation within a taxonomically complex group: An example from the genus Apodemus (Rodentia: Muridae).

The Mediterranean Sea is recognized as a hot spot of biodiversity, but the ever-increasing commercial and recreational marine traffic and global warming pose significant threats to its fauna by enabling and facilitating, respectively, the introduction of non-indigenous species (NIS). To mitigate negative effects in the native communities, greater efforts are being made to generate updated lists of NIS and to monitor their spread over space and time. In this regard, Amathia verticillata (delle Chiaje, 1822), a worldwide distributed arborescent bryozoan, can play an important role as a vector of NIS due to its ability to be a species ‘carrier of other species’. Despite its importance, a detailed study on the highly specialized Nudibranchia molluscs associated with A. verticillata is still lacking. Given that some nudibranchs serve as powerful bioindicators of changes in the Mediterranean Sea, and considering that A. verticillata is an invasive species capable to facilitating the establishment and spread of NIS, a broad bibliographic study coupled with field investigations in different anthropized areas of the Central Mediterranean Sea were conducted. The nudibranch fauna associated with A. verticillata in the Mediterranean Sea was assessed for the first time. Nine species were found associated with this bryozoan, five of which were directly observed and analysed using morphological and molecular techniques. A case of cryptic diversity was revealed, with Polycerella recondita Schmekel, 1965 resurrected as a valid species, and the neglected Tenellia granosa (Schmekel, 1966) reported for the fourth time in the Mediterranean Sea. Notably, only three out of the nine species are Indo-Pacific, while the remaining six taxa have an Atlantic/Mediterranean distribution. This finding prompted further phylogenetic and haplotype network analyses on the two nudibranch species directly associated with A. verticillata: Bermudella polycerelloides and P. recondita. These analyses revealed different and previously unknown ecological traits of the spread of these two species.

The average wave steepness may be defined as the ratio between the significant wave height Hs and the wavelength associated to either the zero-up-crossing mean period Lm or the peak period Lp (Bitner Gregersen et al., 1998). This parameter may be calculated from wave data at fixed locations, as well as by starting from theoretical spectra. In this paper the average wave steepness is firstly analyzed by considering a JONSWAP spectrum. It is shown that for this spectrum the ratio Sm = Hs/Lm, as well as Sp = Hs/Lp, depends upon the values of the spectrum parameters. The theoretical values are then compared with wave data in the Mediterranean Sea, Pacific Ocean, Atlantic Ocean and North Sea. The values of Sm and Sp are deeply investigated for severe sea states, with large values of Hs. It is obtained that in severe sea state the observed values of wave steepness, defined as either Sm or Sp, are always in the range defined by theoretical spectra; therefore, the extreme values of Sm and Sp, which are of interest for naval architecture, may be obtained from theoretical analysis, as a function of extreme values of Hs.

Morphospecies<i>versus</i>Phylospecies Concepts for Evaluating Phytoplankton Diversity: The Case of the Coccolithophores

Haplotype phylogenies based on DNA sequence data are increasingly being used to test traditional species-level taxonomies based on morphology. However, few studies have critically compared species limits based on morphological and DNA data, and the methods used to delimit species using either type of data are only rarely explained. In this paper, we review three approaches for species delimitation (tree-based with DNA data and tree-based and character-based with morphological data) and propose explicit protocols for each. We then compare species limits inferred from these approaches, using morphological and mtDNA data for the Yarrow's spiny lizard (Sceloporus jarrovii), a traditionally polytypic species from the southwestern United States and Mexico. All three approaches support division of S. jarrovii into five species, but only two species are the same among the three approaches. We find the greatest support for the five species that are delimited based on mtDNA data, and we argue that mtDNA data may have important (and previously unappreciated) advantages for species delimitation. Because different data and approaches can disagree so extensively, our results demonstrate that the methodology of species delimitation is a critical issue in systematics.

The Atlantic bluefin tuna is a highly migratory species emblematic of the challenges associated with shared fisheries management. In an effort to resolve the species' stock dynamics, a genomewide search for spatially informative single nucleotide polymorphisms (SNPs) was undertaken, by way of sequencing reduced representation libraries. An allele frequency approach to SNP discovery was used, combining the data of 555 larvae and young-of-the-year (LYOY) into pools representing major geographical areas and mapping against a newly assembled genomic reference. From a set of 184,895 candidate loci, 384 were selected for validation using 167 LYOY. A highly discriminatory genotyping panel of 95 SNPs was ultimately developed by selecting loci with the most pronounced differences between western Atlantic and Mediterranean Sea LYOY. The panel was evaluated by genotyping a different set of LYOY (n=326), and from these, 77.8% and 82.1% were correctly assigned to western Atlantic and Mediterranean Sea origins, respectively. The panel revealed temporally persistent differentiation among LYOY from the western Atlantic and Mediterranean Sea (FST =0.008, p=.034). The composition of six mixed feeding aggregations in the Atlantic Ocean and Mediterranean Sea was characterized using genotypes from medium (n=184) and large (n=48) adults, applying population assignment and mixture analyses. The results provide evidence of persistent population structuring across broad geographic areas and extensive mixing in the Atlantic Ocean, particularly in the mid-Atlantic Bight and Gulf of St. Lawrence. The genomic reference and genotyping tools presented here constitute novel resources useful for future research and conservation efforts.

This paper describes a comprehensive online database of giant landslides on volcanic islands compiled by researchers from the Institute of Rock Structure and Mechanics, Czech Academy of Sciences, in the framework of IPL Project 212. The database was constructed from 2016 to 2018. It comprises a total of seventy-five events from the Atlantic Ocean and Mediterranean Sea, sixty-seven events from the Pacific Ocean, and forty events from the Indian Ocean. In this paper some of the main benefits of landslide inventories and thematic databases are outlined and the global distribution of giant landslides on volcanic islands is described in depth. The database is hosted on the website of the Institute of Rock Structure &amp; Mechanics and records can be downloaded as a spreadsheet or kml file for integration in a number of geospatial programs including ArcGIS and Google Earth. However, since completion of the database in 2018, a number of potentially significant studies of giant landslides on volcanic islands have been published from archipelagos in the Atlantic and Pacific Oceans while outstanding modern analogues for past events are represented by the collapse of Anak Krakatau on 22 December 2018 and the collapse of Hunga Tonga-Hunga Haʻapai on 15 January 2022. Consequently, the recent literature will be scrutinized with the aim of updating information already contained in the database while two new layers are planned: the first of these will provide information about recent volcanic collapses and the second will provide information about the long-term instrumental monitoring of giant landslides. It is intended that the second release of the database will be available online in early 2023.

In this study, we explored the population genetic structure and its relation to environmental adaptations of the dolphinfish ( Coryphaena hippurus ) in the western Atlantic Ocean and Mediterranean Sea. Although previously two populations within the Mediterranean Sea were identified, recent evidence suggests more complex structuring. We employed 3RAD sequencing on 138 samples from the Atlantic and Mediterranean, obtaining a total of 20,072 SNPs of which 24 SNPs were strongly associated with temperature and salinity variables (putative adaptive outlier loci). Results revealed a clear genetic differentiation between the Atlantic and Mediterranean basins, with practically no connectivity between them, confirming the Mediterranean basin's long‐term isolation. Within the Mediterranean basin, subtle genetic differences were detected between eastern and western Mediterranean sub‐basins based on neutral loci with an increased signal of differences in the outlier loci associated with temperature and salinity that identified further differences into three genetically distinct groups, despite an overall high genetic connectivity. Environmental–genetic association analyses identified salinity, temperature and nitrate as major drivers of genetic variation. The most informative dataset (outlier SNPs related to temperature and salinity) explained over 80% of the genetic variation through a model incorporating multiple oceanographic variables. Overall, this research underscores how high‐resolution genomic tools can detect hidden genetic structure and adaptation, even in highly dispersive marine species. These findings are essential for fisheries management, particularly in the Mediterranean Sea, where distinct local adaptations may be at risk from global environmental change. Recognizing and preserving this genetic diversity is crucial for the long‐term sustainability of dolphinfish populations under climate and anthropogenic pressures.

Natural markers (δ13C and δ18O stable isotopes) in the cuttlebones of the European common cuttlefish (Sepia officinalis) were determined for individuals collected across a substantial portion of their range in the Northeast Atlantic Ocean (NEAO) and Mediterranean Sea. Cuttlebone δ13C and δ18O were quantified for core and edge material to characterize geochemical signatures associated with early (juvenile) and recent (sub-adult/adult) life-history periods, respectively. Regional shifts in cuttlebone δ13C and δ18O values were detected across the 12 sites investigated. Individuals collected from sites in the NEAO displayed more enriched δ13C and δ18O values relative to sites in the Mediterranean Sea, with the latter also showing salient differences in both markers among western, central and eastern collection areas. Classification success based on cuttlebone δ13C and δ18O values to four geographical regions (NEAO, western, central and eastern Mediterranean Sea) was relatively high, suggesting that environmental conditions in each region were distinct and produced area-specific geochemical signatures on the cuttlebones of S. officinalis. A modified δ13C and δ18O baseline was developed from sites proximal to the Strait of Gibraltar in both the NEAO and Mediterranean Sea to assess potential mixing through this corridor. Nearly, all (95%) of δ13C and δ18O signatures of S. officinalis collected in the area of the NEAO closest to the Strait of Gibraltar (Gulf of Cadiz) matched the signatures of specimens collected in the western Mediterranean, signifying potential movement and mixing of individuals through this passageway. This study extends the current application of these geochemical markers for assessing the natal origin and population connectivity of this species and potentially other taxa that inhabit this geographical area.

The bearded fireworm Hermodice carunculata is a conspicuous omnivorous benthic invertebrate distributed in the wider Atlantic Ocean, Mediterranean Sea and the Red Sea. Questions were raised in the past regarding the taxonomic status of amphiatlantic fireworm specimens but subsequent analysis of morphological data with new molecular data reconfirmed the presence of only one species, H. carunculata with amphiatlantic distribution. Hermodice carunculata has been the subject of several taxonomic and genetic studies but there are still questions regarding the genetic diversity and population structure of the species throughout its range. We contributed to the genetic studies of H. carunculata with ~200 new samples from over 20 locations in the Caribbean, Eastern Atlantic Ocean and the Mediterranean Sea. We sequenced the mitochondrial markers Cytochrome c oxidase Subunit I (COI) and Cytochrome b (Cytb) from each polychaete to examine the patterns of genetic diversity of H. carunculata. Our data revealed a significant population structure between the Caribbean H. carunculata including those from Brazil compared with those from the eastern Atlantic (Tenerife, Canary Islands) and eastern Mediterranean (Greece and Malta). We inferred rates of gene flow between eastern and western Atlantic populations by estimating the bidirectional effective migration rate (Nem). We corroborate previous studies indicating the existence of one species with genetically distinct populations. However, the biological significance of the observed population divergence should be evaluated with cross-breeding experiments.