Atlantic Samples Research Articles

Cryptic Diversity of Mediterranean Neogoniolithon (Corallinales, Corallinophycidae, Rhodophyta)

ABSTRACTNeogoniolithon is a widespread genus of non‐geniculate coralline algae in the Mediterranean Sea. Three vaguely differentiated species have been reported in the region. This study examined the diversity of Neogoniolithon in the Mediterranean by inferring phylogenies using psbA and COI‐5P markers, applying delimitation algorithms and comparing morpho‐anatomies of putative species. In contrast to previous reports, 13 species were delimited from the Mediterranean in two distant clades. Initial observations suggested that tetrasporangial conceptacle size might be used to separate the two clades. Only three species showed fruticose morphologies. Further morpho‐anatomical differentiation was difficult. One species included Mediterranean, Pacific and Atlantic samples, while three other species occurred in the Mediterranean and the Canary Islands. The global tree revealed that most species were geographically restricted. Crypticity in multiple lineages implied a much higher diversity than currently reported, even lacking samples from the eastern Mediterranean. Only sequence data can be used to identify these cryptic lineages. High endemism emphasizes the importance of conservation of coralline algal bioconstructions to prevent extinctions. The presence of cryptic diversity also invites a reassessment of the knowledge on species distributions that are important in conservation planning and management.

Comparative analysis of phenotypes in the sea cucumber Cucumaria frondosa from the Arctic and the NW Atlantic

Research on ecologically and economically important sea cucumbers has been focused on temperate and tropical species, leaving those from higher latitudes, such as the Canadian Arctic, understudied. This study compared the phenotypic characters of the sea cucumber Cucumaria frondosa sampled from populations of the Arctic (Hudson Bay, Nunavut) and Northwest Atlantic (Newfoundland). Organ indices and external and internal tissue pigmentation, and various biochemical metrics (proximate composition, lipids, fatty acids, amino acids, lipid-soluble vitamins, carotenoids) were assessed. All sea cucumbers had similar total body weights, but those from Newfoundland had heavier gonads and body walls, while the tissue pigmentation of Nunavut individuals was distinctive (more red and yellow trivium, darker brown pigmentation). Moisture and ash contents of sea cucumbers were similar between locations; however, protein and lipid contents in Nunavut samples were 12 and 50% lower, respectively. Inversely, Nunavut samples contained more ω-3 fatty acids, a greater degree of lipid desaturation, double the concentration of proline and vitamin A, and more carbohydrates and astaxanthin than Northwest Atlantic samples. Examining phenotypic variability across latitudes and longitudes, including into the Arctic, highlights unique physical and biochemical features attributed to this specific environment and may support the sustainable development of sea cucumber fisheries.

Ecophenotypic variation or genetic differentiation? Ambiguity of morphological and molecular relationships presents uncertainty in host-specific plasticity of Chelonibia barnacles

The genus Chelonibia, informally referred to as the turtle barnacles, was historically subdivided into four species by both morphological differentiation and host affinity. More recent studies, however, hypothesized that three of these barnacle species – C. testudinaria, C. manati, and C. patula – comprise a single species, C. testudinaria, that exhibits host-specific ecophenotypic plasticity. In this study, we examined both morphological and molecular datasets to assess whether host attachment or genetic differentiation best explains the morphotypes assigned to C. testudinaria and C. manati. For morphology, we compared 11 mensural test and cirral characters from 71 C. testudinaria and 25 C. manati specimens identified by the previously established absence or presence of a ridged external dorsal surface. The two morphotypes overlapped in overall body size, although C. testudinaria averaged significantly larger and C. manati exhibited relatively longer cirri. Discriminant function analyses (DFA) showed strong but incomplete differentiation (92.6% classification success), with one C. manati morphotype collected from a sea turtle classified with high confidence as C. manati. Thus, the morphological data contradict the host-specificity hypothesis. Genetic analyses using three target loci (16s, 28s, COI) from the mitochondrial and nuclear genomes, as well as a single concatenated sequence of >1600 bp, likewise failed to support genetic differentiation between the two morphotypes within the Atlantic sample. With inclusion of a broader sample of Atlantic C. testudinaria and C. manati and Pacific C. testudinaria barnacles, we found strong population distinction between the ocean basins without morphotype separation. Results of the present study suggest that Balanomorph barnacle taxonomy, especially of endosymbiont species, requires further study, as neither phenotypic plasticity nor genetic differentiation accounted for existence of the two distinct morphotypes.

First Record of the Northern Wolffish Anarhichas denticulatus Krøyer, 1845 (Anarhichadidae: Zoarcoidei: Perciformes) in the Siberian Arctic: Further Evidence of Atlantification?

A single specimen of the northern wolffish Anarhichas denticulatus Krøyer, 1845, 393 mm in length, was documented for the first time in the Siberian Arctic (Laptev Sea, Russia). Species identification was confirmed by an integrative taxonomic approach that included examination of external morphology and DNA barcoding using the COI mtDNA gene. This species is widely distributed in the North Atlantic, but records in the Arctic Ocean are limited to the Canadian and US coasts. This record might represent a significant range extension of about 7500 km for the species and may be associated with the eastward transport of a pelagic juvenile specimen from the Northeastern Atlantic to the Laptev Sea by the North Atlantic current, consistent with the hypothesis of Atlantification of the Arctic Ocean. X-ray images of the Laptev Sea specimen and photographs showing ontogenetic variations of species’ coloration are provided for reference. The Laptev Sea specimen had a more elongated shape, longer preorbital distance, and longer pectoral, dorsal, and anal fins, as well as a larger eye and wider caudal fin compared to North Atlantic samples. The size differences are likely associated with conditions experienced as a juvenile during the pelagic stage of the lifecycle.

Population structure discovered in juveniles of Greenland halibut (Reinhardtius hippoglossoidesWalbaum, 1792)

AbstractUnderstanding the genetic differentiation among populations of most marine fish requires investigating the differences among spawning grounds. However, this can be challenging as spawning grounds for some species are not well known, or spawning fish are difficult to collect. An alternative is to collect juvenile fish in nursery habitats closely associated with potential spawning grounds. Greenland halibut is a deep-dwelling, commercially important species with at least two identified major offshore spawning grounds in the North Atlantic and weak genetic differentiation across the Atlantic. In this study, we sampled juveniles from three sites representing the Davis Strait spawning area in the northwest Atlantic and one site in the northeast Atlantic representing the primary spawning area along the western slope of the Barents Sea. We applied genotype by sequencing and discovered 90 genetic markers that could be used to assess genetic differentiation among the four sites. The northeast and northwest Atlantic showed major genetic differentiation, supporting the existence of the two primary spawning clusters. Additionally, we found genetic differentiation between the three northwest Atlantic samples implying the existence of more than one spawning area in the northwest.

Stepping up to genome scan allows stock differentiation in the worldwide distributed blue shark Prionace glauca.

The blue shark Prionace glauca is a top predator with one of the widest geographical distributions of any shark species. It is classified as Critically Endangered in the Mediterranean Sea, and Near Threatened globally. Previous genetic studies did not reject the null hypothesis of a single global population. The blue shark was proposed as a possible archetype of the "grey zone of population differentiation," coined to designate cases where population structure may be too recent or too faint to be detected using a limited set of markers. Here, blue shark samples collected throughout its global range were sequenced using a specific RAD method (DArTseq), which recovered 37,655 genome-wide single nucleotide polymorphisms (SNPs). Two main groups emerged, with Mediterranean Sea and northern Atlantic samples (Northern population) differentiated significantly from the Indo-west Pacific samples (Southern population). Significant pairwise FST values indicated further genetic differentiation within the Atlantic Ocean, and between the Atlantic Ocean and the Mediterranean Sea. Reconstruction of recent demographic history suggested divergence between Northern and Southern populations occurred about 500 generations ago and revealed a drastic reduction in effective population size from a large ancestral population. Our results illustrate the power of genome scans to detect population structure and reconstruct demographic history in highly migratory marine species. Given that the management plans of the blue shark (targeted or bycatch) fisheries currently assume panmictic regional stocks, we strongly recommend that the results presented here be considered in future stock assessments and conservation strategies.

Drivers and spread of non-native pests in forests: The case of Gonipterus platensis in Spanish Eucalyptus plantations

Plantations of Eucalyptus species have been widely used in Spain to meet the high demand for wood given their rapid growth and high wood production capacity. Defoliation induced by the invasive eucalypt weevil (Gonipterus platensis (Marelli)), however, has been causing significant economic damage to Spanish Eucalyptus spp. plantations since the 1990s. G. platensis is native to Tasmania, Australia, where populations are controlled by natural enemies including the egg parasitoid Anaphes nitens Girault. In this study, spatio-temporal Universal Kriging was applied to examine the dynamics of defoliation damage caused by G. platensis in Spanish Eucalyptus spp. plantations and to identify the main factors associated with the presence and spread of the pest. The data set combines the Spanish national plots belonging to the network of the European transnational survey of forest condition in Europe (ICP Forest Level I, 16 × 16 km grid) along with regional plots, measured using similar field protocols, in which Eucalyptus spp. are present. A total of 264 Eucalyptus plots were included in the study, G. platensis being present in 167 of these plots at some time during the observed period (2005–2020). Our results show that defoliation damage > 0% and defoliation damage > 5% caused by G. platensis increased over the period 2005–2010 and then decreased between 2010 and 2020. Defoliation damage > 15% incidence steadily decreased from 2005 to 2015, but showed an upturn in 2020. Stands belonging to the Atlantic region are more affected by this pest (76% of the Atlantic sampling plots affected versus just 4% of the Mediterranean plots). The species Eucalyptus globulus Labill. and monospecific stands, as well as spring precipitation of the current year were found to be positively associated with the incidence of G. platensis whereas the relationship with summer temperature of the previous year was negative. Finally, maps showing the degree of incidence over time have been produced to support decision-making for pest prevention and control. This study puts forward a methodology which allows the spread of this pest to be better understood and simulated, thus facilitating risk prevention.

Molecular and Biological Analysis on Ommastrephes caroli Findings in the Central Western Mediterranean Sea (Sardinian Waters) Including First Age Investigation Using Eye Lenses and Beaks

Molecular identifications based on two mitochondrial markers (cytochrome c oxidase subunit I -COI- and 16S ribosomal RNA gene -16S-) have been implemented to confirm the morphological identification of eight specimens collected in the Central western Mediterranean. Molecular data show they belonged to a recently resurrected species of the genus Ommastrephes, i.e., O. caroli, known to be distributed in the Atlantic Ocean and Mediterranean Sea. Despite this, molecular analyses of COI sequences evidenced the presence of potential genetic differentiation between Mediterranean and Atlantic samples, highlighting the need for further studies, with more individuals to investigate the connectivity between individuals living in the two areas. Furthermore, morphological, biometric and reproductive features here reported, could be useful in evaluating possible distinctive biological features between the Mediterranean and Atlantic individuals. Female mature size was larger than the male. The relationships obtained between the beak measurements and body sizes (DML; TW) were better described by a power model. Asynchronous oocytes development with relatively small oocytes (0.05–1.10 mm) and a protracted intermittent spawning with active feeding were observed. This study also reported for the specie O. caroli the first data on the potential fecundity estimated (840061 oocytes), the oviducal load (90000 ripe oocytes) as well as the number of seminal receptacles and the size and morphology of the spermatangia found in the buccal mass of all mated females. Even if on a low sample size, beaks and eye lenses were used for the first time in O. caroli for age estimation. The statistically significant relationship found between increments counted in eye lenses and beaks highlighted the reliability of the lenses to estimate age in O. caroli, even if further studies will be needed for its validation. Assuming a daily increment for both structures, a mean life span of about 12–13 months was estimated for both sexes, which is consistent with the sexual maturity condition observed in all the samples and the semelparity known for cephalopods coleoids.

Multi-element signature of cuttlefish and its potential for the discrimination of different geographical provenances and traceability

The measurement and analysis of fifty-two elements by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) and direct mercury analysis were applied to origin discrimination of Italian traditional cuttlefish (Chioggia, Venice lagoon) from Mediterranean and Atlantic samples. A total 68 specimens were analyzed in triplicates to generate 204 mass spectra profiles which were statistically processed by different chemometric techniques. Loading weights from principal component analysis as input for linear discriminant analysis (LW-LDA), stepwise-LDA (S-LDA) and variable influence of projection-partial least square discriminant analysis (VIP-PLS-DA) were used to classify samples while retaining the lowest possible number of key variables. VIP-PLS-DA was found to be the best variable selection-discriminant tool combo since the selected Na–Co–B–K–Cd–V–U–Rb–Ni–Ba–Cu–As–Sr–Mn–Mo–Li–Ca–Mg–Se–Bi–Cs–P–Y elemental pattern allowed the samples to be classified with 100% sensitivity, specificity and accuracy.

Transcriptional activity differentiates families of Marine Group II Euryarchaeota in the coastal ocean

Marine Group II Euryarchaeota (Candidatus Poseidoniales), abundant but yet-uncultivated members of marine microbial communities, are thought to be (photo)heterotrophs that metabolize dissolved organic matter (DOM), such as lipids and peptides. However, little is known about their transcriptional activity. We mapped reads from a metatranscriptomic time series collected at Sapelo Island (GA, USA) to metagenome-assembled genomes to determine the diversity of transcriptionally active Ca. Poseidoniales. Summer metatranscriptomes had the highest abundance of Ca. Poseidoniales transcripts, mostly from the O1 and O3 genera within Ca. Thalassarchaeaceae (MGIIb). In contrast, transcripts from fall and winter samples were predominantly from Ca. Poseidoniaceae (MGIIa). Genes encoding proteorhodopsin, membrane-bound pyrophosphatase, peptidase/proteases, and part of the ß-oxidation pathway were highly transcribed across abundant genera. Highly transcribed genes specific to Ca. Thalassarchaeaceae included xanthine/uracil permease and receptors for amino acid transporters. Enrichment of Ca. Thalassarchaeaceae transcript reads related to protein/peptide, nucleic acid, and amino acid transport and metabolism, as well as transcript depletion during dark incubations, provided further evidence of heterotrophic metabolism. Quantitative PCR analysis of South Atlantic Bight samples indicated consistently abundant Ca. Poseidoniales in nearshore and inshore waters. Together, our data suggest that Ca. Thalassarchaeaceae are important photoheterotrophs potentially linking DOM and nitrogen cycling in coastal waters.

Genetic population structure and tools for the management of European sprat (Sprattus sprattus)

AbstractThis study used RAD-seq-derived SNPs to explore population connectivity, local adaptation, and individual assignment in European sprat (Sprattus sprattus) and inform the alignment of management units with biological processes. FST, clustering, and outlier analyses support a genetically cohesive population spanning the Celtic Sea-English Channel-North Sea-Kattegat (NE Atlantic) region. The lack of structure among the NE Atlantic samples indicates connectivity across current management boundaries. However, the assumption of demographic panmixia is cautioned against unless verified by a multidisciplinary approach. The data confirm high genetic divergence of a Baltic population (average FST vs. NE Atlantic samples = 0.051) with signatures compatible with local adaptation in the form of outlier loci, some of which are shown to occur within exonic regions. The outliers permit diagnostic assignment of individuals between the NE Atlantic and Baltic populations and thus represent a “reduced panel” of markers for monitoring a potential mixed stock fishery within the western Baltic. Overall, this study provides information that may help refine spatial management boundaries of sprat and resources for genetic-assisted management.

Fin spine metals by LA-ICP-MS as a method for fish stock discrimination of Genidens barbus in anthropized estuaries

Metal:Ca ratios (Li:Ca, Cu:Ca, Fe:Ca, Na:Ca, Rb:Ca, Pb:Ca and Zn:Ca) in fin spines of Genidens barbus, an endangered catfish species, were used as possible habitat markers from three Southwestern Atlantic sampling areas (Paranaguá estuarine complex, Brazil; Paraná River Delta, Argentina-Uruguay; and Negro River, Patagonia). Significant differences (p < 0.05) among sites for metal:Ca ratios support the utility of two prospective indicators: (1) habitat – outer 45 μm of spine edge and, (2) fish stock – outer ∼600 μm of spine. Multivariate analysis (MANOVA and PERMANOVA, p < 0.05) and lineal discriminant function analysis (LDA) proved relatively effective for discriminating both habitat (classification rate: 73%) and fish stock (classification rate: 66%) between sampling sites. Classification success improved to 85% (habitat) and 86.3% (fish stock) when LDAs incorporating Sr:Ca, Ba:Ca, Mg:Ca and Mn:Ca) from previous research (same samples) were performed. These results support the use of metal:Ca ratios in G. barbus fin spines as a non-lethal tool for discriminating habitat use and stocks of this endangered catfish. This approach may be applicable to other vulnerable species in polluted habitats.

Salmon species identification via direct DNA sequencing of single amplicons

For Pacific salmonids, a key fisheries forensics and management goal is to identify individuals to specific species and potentially specific populations or geographic regions within species. Genetic variation can be used for both species and individual identification, and variation at single nucleotide polymorphisms (SNPs) within two specific DNA amplicons was used to distinguish among coho salmon (Oncorhynchus kisutch), Chinook salmon (Oncorhynchus tshawytscha), sockeye salmon (Oncorhynchus nerka), chum salmon (Oncorhynchus keta), pink salmon (Oncorhynchus gorbuscha), masu salmon (Oncorhynchus masou), steelhead/rainbow trout (Oncorhynchus mykiss), cutthroat trout (Oncorhynchus clarkii), and Atlantic salmon (Salmo salar). A total of 2510 individuals was evaluated from a Pacific rim distribution of populations for sockeye salmon, chum salmon, and pink salmon, whereas masu salmon samples were genotyped only from Japanese populations. Coho salmon, Chinook salmon, steehead trout, cutthroat trout, and Atlantic salmon samples were genotyped only from North American populations. All individual salmonids genotyped were assigned with 100% accuracy to their respective species via diagnostic homozygous SNP genotypes for each species except for cutthroat trout, where no diagnostic SNP genotypes were observed in the two amplicons evaluated.

Assessment of genetic diversity and population structure of the common littoral shrimp Palaemon serratus (Pennant, 1777) by microsatellites: Towards a sustainable management

Abstract The common littoral shrimp Palaemon serratus is an ecologically and economically important decapod crustacean. Understanding the spatial structure of its populations is crucial to implement effective management strategies. In this study, 17 polymorphic microsatellite nuclear markers were examined in 252 individuals to explore the genetic diversity and the population structure underlying the geographical distribution of this crustacean in European waters. Basic genetic descriptors, population genetic analyses based on FST, analysis of the molecular variance (AMOVA), Bayesian clustering and the Mantel test were performed. Genetic differentiation was significant among sampling sites. AMOVAs and Bayesian assignment tests showed genetic differentiation among localities from the Atlantic coast and those belonging to the area of the Strait of Gibraltar and the Mediterranean Sea. The Guadalquivir estuary was significantly different from the remaining localities. A biogeographical break was detected to the west of the Strait of Gibraltar, and evidence of isolation by distance was obtained. Localities on both sides of the English Channel showed genetic differentiation with the rest of the Atlantic sampling sites, indicating a biogeographical break in this area. These results will contribute towards the better understanding of the biology and ecology of this shrimp and management of the valuable fishery. Two priority areas were delimited: the Atlantic and the Gibraltar–Mediterranean. The Guadalquivir estuary, Anglesey and Calais should also be considered as different genetic stocks.

Why is electric vehicle uptake low in Atlantic Canada? A comparison to leading adoption provinces

This paper investigates potential electric vehicle (EV) adoption among households in Atlantic Canada, a region lagging in terms of EV uptake. The data come from a 2015 Survey for Preferences and Attitudes of Canadians towards Electric Vehicles or SPACE, with an intent to investigate electric mobility prospects in Canada through a series of socioeconomic, attitudinal, and stated preference (SP) questions. A latent class (LC) random utility model is used to segment Atlantic respondents based on their sociodemographic and environmental attitudes, and to estimate their willingness-to-pay for different vehicular features. A separate model is estimated for leading adoption provinces (Ontario and British Columbia), and compared to the Atlantic model. Results indicate that cash incentives and the quality of battery warranty are important features shaping the choice of vehicle powertrain in the Atlantic sample. Contrary to the model obtained from the leading provinces, electric range, maintenance cost, free parking, and access to high occupancy vehicle lanes are not significant attributes in the Atlantic model. With respect to segmentation, the adoption of EVs in the Atlantic model increases with youth, education, and progressive attitudes towards the environment, while income is not a determining factor. Our results imply some support for EVs among Atlantic consumers, though at less advanced levels than the leading adoption provinces in Canada. However, the high purchase price of EVs, lack of financial incentives, and limited public charging infrastructure are seen as key reasons for low EV deployment in Atlantic Canada. The demographic profiles of the plug-in oriented group, found in this study, suggest targeted decisions regarding policy and marketing.

Reproducibility of species recognition in modern planktonic foraminifera and its implications for analyses of community structure

Abstract. Applications of planktonic foraminifera in Quaternary palaeoceanographic and palaeobiological studies require consistency in species identification. Yet the degree of taxonomic consistency among the practitioners and the effects of any potential deviations on community structure metrics have never been quantitatively assessed. Here we present the results of an experiment in taxonomic consistency involving 21 researchers representing a range of experience and taxonomic schools from around the world. Participants were asked to identify the same two sets of 300 specimens from a modern subtropical North Atlantic sample, one sieved at &gt;125 µm and one at &gt; 150 µm. The identification was carried out either on actual specimens (slide test) or their digital images (digital test). The specimens were fixed so the identifications could be directly compared. In all tests, only between one-quarter and one-eighth of the specimens achieved absolute agreement. Therefore, the identifications across the participants were used to determine a consensus ID for each specimen. Since no strict consensus (&gt;50 % agreement) could be achieved for 20–30 % of the specimens, we used a “soft consensus” based on the most common identification. The average percentage agreement relative to the consensus of the slide test was 77 % in the &gt;150 µm and 69 % in the &gt;125 µm test. These values were 7 % lower for the digital analyses. We find that taxonomic consistency is enhanced when researchers have been trained within a taxonomic school and when they regularly perform community analyses. There is an almost negligible effect of taxonomic inconsistency on sea surface temperature estimates based on transfer function conversion of the census counts, indicating the temperature signal in foraminiferal assemblages is correctly represented even if only two-thirds of the assemblage is consistently identified. The same does not apply to measures of diversity and community structure within the assemblage, and here we advise caution in using compound datasets for such studies. The decrease in the level of consistency when specimens are identified from digital images is significant and species-specific, with implications for the development of training sets for automated identification systems.

Population structure of North Atlantic and North Pacific sei whales (Balaenoptera borealis) inferred from mitochondrial control region DNA sequences and microsatellite genotypes

Currently, three stocks of sei whales (Balaenoptera borealis) are defined in the North Atlantic; the Nova Scotian, Iceland-Denmark Strait and Eastern North Atlantic stocks, which are mainly based upon historical catch and sighting data. We analyzed mitochondrial control region DNA (mtDNA) sequences and genotypes from 7 to 11 microsatellite loci in 87 samples from three sites in the North Atlantic; Iceland, the Gulf of Maine and the Azores, and compared against the North Pacific using 489 previously published samples. No statistically significant deviations from homogeneity were detected among the North Atlantic samples at mtDNA or microsatellite loci. The genealogy estimated from the mtDNA sequences revealed a clear division of the haplotypes into a North Atlantic and a North Pacific clade, with the exception of one haplotype detected in a single sample from the Azores, which was included in the North Pacific clade. Significant genetic divergence between the North Atlantic and North Pacific Oceans was detected (mtDNA ΦST = 0.72, microsatellite Weir and Cockerham’s ϴ = 0.20; p < 0.001). The coalescent-based estimate of the population divergence time between the North Atlantic and North Pacific populations from the sequence variation among the mtDNA sequences was at 163,000 years ago. However, the inference was limited by an absence of samples from the Southern Hemisphere and uncertainty regarding mutation rates and generation times. The estimates of inter-oceanic migration rates were low (Nm at 0.007 into the North Pacific and at 0.248 in the opposite direction). Although estimates of genetic divergence among the current North Atlantic stocks were low and consistent with the extensive range of movement observed in satellite tagged sei whales, the high uncertainty of the genetic divergence estimates precludes rejection of multiple stocks in the North Atlantic.

Identification of a New Mullet Species Complex Based on an Integrative Molecular and Cytogenetic Investigation of Mugil hospes (Mugilidae: Mugiliformes).

Mullets are very common fishes included in the family Mugilidae, (Mugiliformes), which are characterized by both a remarkably uniform external morphology and internal anatomy. Recently, within this family, different species complexes were molecularly identified within Mugil, a genus which is characterized by lineages that sometimes show very different karyotypes. Here we report the results of cytogenetic and molecular analyses conducted on Mugil hospes, commonly known as the hospe mullet, from Ecuador. The study aims to verify whether the original described species from the Pacific Ocean corresponds to that identified in the Atlantic Ocean, and to identify species-specific chromosome markers that can add new comparative data about Mugilidae karyotype evolution. The karyotype of M. hospes from Ecuador is composed of 48 acrocentric chromosomes and shows two active nucleolar organizer regions (NORs). In situ hybridization, using different types of repetitive sequences (rDNAs, U1 snDNA, telomeric repeats) as probes, identified species-specific chromosome markers that have been compared with those of other species of the genus Mugil. Cytochrome c oxidase subunit I (COI) sequence analysis shows only 92–93% similarity with sequences previously deposited under this species name in GenBank, all of which were from the Atlantic Ocean. Phylogenetic reconstructions indicate the presence of three well-supported hospe mullet lineages whose molecular divergence is compatible with the presence of distinct species. Indeed, the first lineage includes samples from Ecuador, whereas the other two lineages include the Atlantic samples and correspond to M. brevirostris from Brazil and Mugil sp. R from Belize/Venezuela. Results here provided reiterate the pivotal importance of an integrative molecular and cytogenetic approach in the reconstruction of the relationships within Mugilidae.

Seascape genetics of a flatfish reveals local selection under high levels of gene flow

Local adaptation is often found to be in a delicate balance with gene flow in marine species with high dispersal potential. Genotyping with mapped transcriptome-derived markers and advanced seascape statistical analyses are proven tools to uncover the genomic basis of biologically relevant traits under environmental selection. Using a panel of 426 gene-linked single nucleotide polymorphisms (SNPs), we scanned 17 samples (n¼539) of sole (Solea solea L.) from the Northeast Atlantic Ocean and applied a node-based seascape analysis. Neutral loci confirmed a clear distinction between the North Sea–Baltic Sea transition zone and the other Eastern Atlantic samples. At a more subtle level, the latter unit split in an English Channel and North Sea group, and a Bay of Biscay and Atlantic Iberian coast group. A fourth group, the Irish and Celtic Sea, was identified with 19 outlier loci. A pattern of isolation by distance (IBD) characterized the latitudinal distribution. Seascape analyses identified winter seawater temperature, food availability and coastal currents to explain a significant component of geographically distributed genetic variation, suggesting that these factors act as drivers of local adaptation. The evidence for local adaptation is in line with the current understanding on the impact of two key ecological factors, the life-history trait winter mortality and the behaviour of inshore/offshore spawning. We conclude that the subtle differentiation between two metapopulations (North Sea and Bay of Biscay) mirrors local adaptation. At least three genomic regions with strong population differentiation point to locally divergent selection. Further functional characterization of these genomic regions should help with formulating adaptive management policies.

Anisakis species composition and infection characteristics in Atlantic mackerel, Scomber scombrus, from major European fishing grounds — reflecting changing fish host distribution and migration pattern

Atlantic mackerel (Scomber scombrus) ranks among the most valuable fish species in Europe. The NE Atlantic mackerel population is considered to comprise three main stocks (southern, western and North Sea), with variable proportions of these three intermixing at the northerly feeding grounds. The southern and western mackerel stocks have moved over the past 4–5 years further north- and westward. Consequently, large-scale mackerel fishing and processing have become thriving industries in Iceland and the Faroe Islands in just a few years. The mackerel population structure in the Mediterranean Sea is less well known but seems to comprise at least one, more or less isolated, spawning component. Although mackerel is an important food resource, systematic and concerted epidemiological surveys of Anisakis species in Atlantic mackerel from European fishing grounds have been lacking. As part of the EU FP7 PARASITE project (GA no. 312068), occurrence and specific identity of Anisakis spp. from 1801 mackerel from Northeast Atlantic and Mediterranean waters was investigated. In general, mackerel caught at the Atlantic fishing grounds exhibited markedly higher Anisakis spp. infection levels than fish from the Mediterranean localities. Mackerel caught off NW Spain and Portugal (ICES VIIIc, IXa) showed highest overall and muscular prevalence, reaching 87% and 52%, respectively, which differed significantly from all other Atlantic samples. Lowest overall Anisakis spp. prevalence and abundance was recorded in mackerel from Faroe Isles waters, while lowest muscular infection levels were found in the samples from the North Sea. Genetic nematode species identification showed that A. simplex (sensu stricto) is the dominating species in mackerel from the Atlantic areas, while A. pegreffii dominated in the samples from the Mediterranean Sea. The latter species showed generally low prevalence and intensity in the flesh, not exceeding 6% and one larva, respectively. While A. simplex (s. s.) and A. pegreffii seem to co-occur in mackerel from off NW Spain and Portugal, several A. pegreffii were also recorded in mackerel from the North- and Norwegian Seas. These findings imply that the actual mackerel started their feeding migration in waters south to the British Isles, which include parts of the sympatric area of the two sibling species. Thus, A. pegreffii could prove a useful supplementary marker to track migration routes of the different mackerel stock components in NE Atlantic waters.