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Mud snails (family Nassariidae) represent a highly diversified lineage within the superfamily Buccinoidea. Recent molecular phylogenies contradicted in some instances the traditional nassariid classification and revealed important levels of homoplasy in phenotypic characters. In order to clarify the boundaries of the family Nassariidae, as well as to inquire on the diversification of the cosmopolitan Nassariinae, a robust phylogenetic framework is needed. Here, the near-complete mitogenomes of 31 species representing almost all lineages of Nassariidae plus several buccinoid outgroups were sequenced. All mitogenomes of buccinoids shared the same gene order, which is identical to the consensus reported for caenogastropods. The monophyly of Nassariidae as previously defined was not confirmed. The reconstructed phylogeny revealed distant relationships between the genera Cyllene, Anentome, Tomlinia, Engoniophos, Phos and Antillophos and the majority of nassariids, represented by Nassariinae + Bullia. Within Nassariinae, a robust phylogeny, which recognized a total of seven regional groups, was reconstructed. The West Atlantic/Mediterranean genus Tritia was divided into three clades. The biogeographical analysis together with the inferred chronogram suggested that Nassariinae might have originated during the late Paleocene in the Indo-Pacific region. Subsequent climate change and continental drift events triggered diversification within the subfamily, leading to the worldwide distribution of current genera. [ABSTRACT FROM AUTHOR]

Introduction: Information on the class Ophiuroidea is very scarce, despite it consisting of the highest number of species within the phylum Echinodermata, with up to 2 100 species. In particular, there are hardly any study focused specifically to ophiuroids found along the Pacific coast of Costa Rica. Objective: Morphological and genetic characterization of ophiuroids of the shallow intertidal and sublittoral areas of Las Baulas Marine National Park (Pacific coast of Costa Rica). Methods: Sampling was conducted between January and April of 2018 at seven locations: Punta del Morro, Playa Carbón, Playa Ventanas, Playa Grande, Playa Tamarindo Ciudad, Playa Tamarindo and Playa Langosta. A total of 214 ophiuroids were characterized using taxonomic keys and original descriptions and a molecular analysis of the mitochondrial Cytochrome oxidase I (COI) gene. Results: An analysis of morphological and genetic characters indicates that 11 species are present in the study site. Four may represent new species, nine constitute new records for the area and one (Ophiophragmus aff. stellatus) is recorded in Costa Rica for the first time. Additionally, juvenile individuals of different species were identified, and two cryptic species were detected. Conclusions: According to the molecular analysis, COI is useful to delimit ophiuroid species and to establish phylogenetic relationships at lower (genera and species) but not higher taxonomic levels. This study also provides images and morphological remarks for future comparative studies. [ABSTRACT FROM AUTHOR]

The porcelain crab Porcellana africana was originally identified as a subspecies of Porcellana platycheles , a species widely distributed in the eastern Atlantic Ocean and the Mediterranean Sea. A study characterizing the recent invasion of P. africana in South Africa places doubts on the identification and previously reported distribution of populations of the two species of Porcellana , which could have implications for the conservation and management of the species. Here, we aimed to delineate the Porcellana species from the East Atlantic to gain a better understanding of their distribution, which will help in conservation decision-making. Molecular analyses based on two mitochondrial genes and a nuclear gene confirmed that P. africana is a well-defined species and that its distribution extends further north, including the Canary Islands. A time divergence estimation indicates the cladogenesis between P. platycheles and P. africana occurred during the Neogene, likely linked to drastic climatic and environmental changes that took place during the Pliocene. Both species are morphologically very close, but can be distinguished by the shape of the third thoracic sternite. [ABSTRACT FROM AUTHOR]

The porcelain crab Porcellana africana was originally identified as a subspecies of Porcellana platycheles , a species widely distributed in the eastern Atlantic Ocean and the Mediterranean Sea. A study characterizing the recent invasion of P. africana in South Africa places doubts on the identification and previously reported distribution of populations of the two species of Porcellana , which could have implications for the conservation and management of the species. Here, we aimed to delineate the Porcellana species from the East Atlantic to gain a better understanding of their distribution, which will help in conservation decision-making. Molecular analyses based on two mitochondrial genes and a nuclear gene confirmed that P. africana is a well-defined species and that its distribution extends further north, including the Canary Islands. A time divergence estimation indicates the cladogenesis between P. platycheles and P. africana occurred during the Neogene, likely linked to drastic climatic and environmental changes that took place during the Pliocene. Both species are morphologically very close, but can be distinguished by the shape of the third thoracic sternite. [ABSTRACT FROM AUTHOR]

In order to further resolve the phylogenetic relationships within Caenogastropoda, the complete mitochondrial (mt) genomes of Cochlostoma hidalgoi (Cyclophoroidea), Naticarius hebraeus (Naticoidea), Galeodea echinophora (Tonnoidea), and Columbella adansoni (Buccinoidea), and the partial mt genome of Erosaria spurca (Cypraeoidea) were sequenced. All newly determined mt genomes conformed to the consensus gene order of caenogastropods, except that of C. hidalgoi , which differed in the relative positions of the trnD , trnQ , trnG , trnY , and trnT genes. Phylogenetic reconstruction of the caenogastropod tree was performed using probabilistic methods and based on the deduced amino acid sequences of concatenated mt protein coding genes. The reconstructed phylogeny recovered Architaenioglossa (superfamilies Cyclophoroidea, Ampullarioidea, and Viviparoidea) as a grade. The monophyly of Sorbeoconcha (all caenogastropods but Architaenioglossa) was supported by most but not all phylogenetic analyses (excluding Vermetoidea, which has a long branch). The relative phylogenetic position of Cerithioidea with respect to Hypsogastropoda remains unresolved. The monophyly of Hypsogastropoda (without Vermetoidea) is strongly supported. Within this clade, Littorinimorpha should be considered a grade. Several superfamilies (Abyssochrysoidea, Rissooidea, Truncatelloidea, and Naticoidea) branched off successively before a siphonate clade (Stromboidea, Cypraeoidea, Tonnoidea, Neogastropoda), which is strongly supported. The relative phylogenetic position of Vermetoidea could not be determined due to long-branch attraction artifacts. The superfamily Tonnoidea was recovered within Neogastropoda, which questions the monophyly of the latter as traditionally defined. The polyphyly of Muricoidea could be tentatively resolved excluding the families Volutidae and Babyloniidae, which would imply raising them to the rank of superfamilies. [ABSTRACT FROM AUTHOR]

The complete nucleotide sequence of the mitochondrial (mt) genome of the deep-sea vent snail Ifremeria nautilei (Gastropoda: Abyssochrysoidea) was determined. The double stranded circular molecule is 15,664 pb in length and encodes for the typical 37 metazoan mitochondrial genes. The gene arrangement of the Ifremeria mt genome is most similar to genome organization of caenogastropods and differs only on the relative position of the trnW gene. The deduced amino acid sequences of the mt protein coding genes of Ifremeria mt genome were aligned with orthologous sequences from representatives of the main lineages of gastropods and phylogenetic relationships were inferred. The reconstructed phylogeny supports that Ifremeria belongs to Caenogastropoda and that it is closely related to hypsogastropod superfamilies. Results were compared with a reconstructed nuclear-based phylogeny. Moreover, a relaxed molecular-clock timetree calibrated with fossils dated the divergence of Abyssochrysoidea in the Late Jurassic-Early Cretaceous indicating a relatively modern colonization of deep-sea environments by these snails. [ABSTRACT FROM AUTHOR]

The reef building vermetid gastropod Dendropoma petraeum inhabits the warmest waters of the Mediterranean Sea and is considered a threatened marine species. The aim of this study was to characterize its genetic structure throughout its whole distribution range using mitochondrial and nuclear sequence data. Because of its sessile adult lifestyle and lack of a pelagic larval stage, we expected a markedly subdivided population structure with limited levels of gene flow. Fragments of the mitochondrial genes cytochrome c oxidase subunit I (COI) and 16S rRNA (16S), were sequenced, along with the nuclear ribosomal cluster (internal transcribed spacer; ITS) in specimens from 18 localities. Our analyses identified four highly distinct phylogroups separated by a mean divergence of > 14% according to the COI sequence data or > 9% according to 16S, but differing only slightly in morphology. The nuclear data (ITS) indicated a lower substitution rate (divergence among groups of around 1%). These large genetic distances among the four lineages clearly point to the existence of a cryptic species complex within D. petraeum comprising at least four species. Differences in the characteristics of intracapsular larval development and protoconch were also detected among these lineages. The allopatric distribution of these cryptic species supports a predominantly vicariant-based cladogenetic pattern for the genus Dendropoma in the Mediterranean. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 898–912. [ABSTRACT FROM AUTHOR]

Background: Gastropod mitochondrial genomes exhibit an unusually great variety of gene orders compared to other metazoan mitochondrial genome such as e.g those of vertebrates. Hence, gastropod mitochondrial genomes constitute a good model system to study patterns, rates, and mechanisms of mitochondrial genome rearrangement. However, this kind of evolutionary comparative analysis requires a robust phylogenetic framework of the group under study, which has been elusive so far for gastropods in spite of the efforts carried out during the last two decades. Here, we report the complete nucleotide sequence of five mitochondrial genomes of gastropods (Pyramidella dolabrata, Ascobulla fragilis, Siphonaria pectinata, Onchidella celtica, and Myosotella myosotis), and we analyze them together with another ten complete mitochondrial genomes of gastropods currently available in molecular databases in order to reconstruct the phylogenetic relationships among the main lineages of gastropods. Results: Comparative analyses with other mollusk mitochondrial genomes allowed us to describe molecular features and general trends in the evolution of mitochondrial genome organization in gastropods. Phylogenetic reconstruction with commonly used methods of phylogenetic inference (ME, MP, ML, BI) arrived at a single topology, which was used to reconstruct the evolution of mitochondrial gene rearrangements in the group. Conclusion: Four main lineages were identified within gastropods: Caenogastropoda, Vetigastropoda, Patellogastropoda, and Heterobranchia. Caenogastropoda and Vetigastropoda are sister taxa, as well as, Patellogastropoda and Heterobranchia. This result rejects the validity of the derived clade Apogastropoda (Caenogastropoda + Heterobranchia). The position of Patellogastropoda remains unclear likely due to long-branch attraction biases. Within Heterobranchia, the most heterogeneous group of gastropods, neither Euthyneura (because of the inclusion of P. dolabrata) nor Pulmonata (polyphyletic) nor Opisthobranchia (because of the inclusion S. pectinata) were recovered as monophyletic groups. The gene order of the Vetigastropoda might represent the ancestral mitochondrial gene order for Gastropoda and we propose that at least three major rearrangements have taken place in the evolution of gastropods: one in the ancestor of Caenogastropoda, another in the ancestor of Patellogastropoda, and one more in the ancestor of Heterobranchia. [ABSTRACT FROM AUTHOR]

We report on a study of reproduction and development in the Mediterranean vermetid gastropod Vermetus triquetrus from the SE coast of Spain. It is a gonochoristic species. The egg capsules are attached to the inside of the shell, and females brood up to 22 capsules simultaneously (more often 4-10). The capsules hold 10-61 eggs or embryos; the uncleaved eggs are yolk-rich, with a mean diameter of 377.3 µm. A distinct polar lobe occurs during the first cleavage, and blastomere D has discernible qualities after the 4-cell stage. The formation of the mesentoblast 4d occurs at the transition from the 24-cell stage to the 25-cell stage. Gastrulation begins after the 36-cell stage. Internal yolk is the major source of nutrition for the encapsulated embryos, but some nurse eggs (∼12%) and some sibling larvae are also ingested by the developing embryos. Hatching occurs during the swimming/crawling pediveliger stage, and metamorphosis is completed outside the capsules soon after hatching. Hence, larval development in Vermetus triquetrus is lecithotrophic intracapsular, with a short free-swimming/crawling phase. [ABSTRACT FROM AUTHOR]

The article focuses on the spermatophores of three Mediterranean species of vermetid gastropods. It mentions the fertilization period of most basal gastropods which is correlated with the possession of primitive type of sperm. It describes the spermatophores which are oblong, gelatinous and transparent structures that range from 2.35 to three millimeters in length and from 0.97 to 1.50mm in width. Moreover, the study notes that the Serpulorbis arenarius produces the smallest euspermatozoa.

Oceanographic features such as currents, waves, temperature and salinity, together with life history traits, control patterns and rates of gene flow and contribute to shaping the population genetic structure of marine organisms. Seascape genetics is an emerging discipline that adopts a spatially explicit approach to examine biotic and abiotic factors that drive gene flow in marine environments. In this study, we examined factors that contribute to genetic differentiation in two coastal Mediterranean gastropods whose geographical ranges overlap but which inhabit different environments. The two species differ in several life history traits and in their dispersal capabilities. Genetic differentiation was relatively low for the trochid species Gibbula divaricata (FST =0.059), and high for the vermetid species Dendropoma lebeche (FST =0.410). Salinity emerged as the most important variable explaining the genetic structure of both species; sea surface temperature was also important for G. divaricata. For the more sessile D. lebeche, the coastline was predicted to provide important pathways for stepping‐stone connectivity and gene flow. Our results provide a greater understanding of the factors influencing marine population connectivity, which may be useful to guide marine conservation and management in the Mediterranean. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Slow-evolving mitochondrial genomes of Patellogastropoda were sequenced. • The mitochondrial gene order of Cellana radiata is closer to that of the ancestral gastropod. • Site-heterogeneous models avoided long branch attraction. • The monophylies of Orthogastropoda and Apogastropoda were recovered. Abstract Long-branch attraction (LBA) is a well-known artifact in phylogenetic reconstruction. Sparse taxon sampling and extreme heterogeneity of evolutionary rates among lineages generate propitious situations for LBA, even defying probabilistic methods of phylogenetic inference. A clear example illustrating LBA challenges is the difficulty of reconstructing the deep gastropod phylogeny, particularly using mitochondrial (mt) genomes. Previous studies consistently obtained unorthodox phylogenetic relationships due to the LBA between the mitogenomes of patellogastropods (true limpets, represented only by Lottia digitalis), heterobranchs, and outgroup taxa. Here, we use the reconstruction of the gastropod mitogenomic phylogeny as a case exercise to test the effect of key methodological approaches proposed to counteract LBA, including the selection of slow-evolving representatives, the use of different outgroups, the application of site-heterogeneous evolutionary models, and the removal of fast-evolving sites. In this regard, we sequenced three new patellogastropod mt genomes, which displayed shorter branches than the one of Lottia as well as gene organizations more similar to that of the hypothetical gastropod ancestor. Phylogenetic analyses incorporating the mt genomes of Patella ferruginea , Patella vulgata , and Cellana radiata allowed eliminating the artificial clustering of Patellogastropoda and Heterobranchia that had prevailed in previous studies. Furthermore, the use of site-heterogeneous models with certain combinations of lineages within the outgroup allowed eliminating also the LBA between Heterobranchia and the outgroup, and recovering Apogastropoda (i.e., Caenogastropoda + Heterobranchia). Hence, for the first time, we were able to obtain a mitogenomic phylogeny of gastropods that is congruent with both morphological and nuclear datasets. [ABSTRACT FROM AUTHOR]

The great morphological and ecological diversity within the superfamily Trochoidea s. l. has in the past hindered the reconstruction of a robust phylogeny for the group based on morphology. Moreover, previous molecular phylogenies have disagreed on the monophyly and internal relationships of Trochoidea s. l., as well as on its relative phylogenetic position within Vetigastropoda. In order to further resolve the trochoidean and vetigastropod phylogenetic trees, we considerably increased the representation of trochoidean families for which no previous mitochondrial (mt) genomes were available: the complete mt genome of Cittarium pica (Tegulidae) and the nearly complete mt genomes of Tectus virgatus (Tegulidae), Gibbula umbilicaris (Trochidae) and Margarites vorticiferus (Margaritidae) were sequenced. In addition, the nucleotide sequences of all protein-coding and ribosomal RNA genes of Clanculus margaritarius (Trochidae) and of Calliostoma zizyphinum (Calliostomatidae) were derived from transcriptomic sequence data. The phylogenetic trees were reconstructed using probabilistic methods with Neomphalina as outgroup; these recovered with maximal support a clade of Trochoidea sensu Hickman & McLean (1990, Nat. Hist. Mus. Los Angeles County Sci. Series, 35: 1-169), which included superfamilies Angarioidea and Phasianelloidea deeply nested within superfamily Trochoidea sensu Williams (2012, Zool. Scripta, 41: 571-595). The families Trochidae + Calliostomatidae were the sister group to the remaining trochoidean lineages. Of these, the family Margaritidae was sister to a clade including Phasianelloidea + Angarioidea and Turbinidae + Tegulidae, this latter family being paraphyletic (Cittarium and Tectus need to be assigned to a new family). Gene order within the newly determined mt genomes was very stable (with only a few rearrangements, restricted to transfer RNA genes) and conformed to the vetigastropod and gastropod consensus genome organizations. [ABSTRACT FROM AUTHOR]

The subfamily Cantharidinae Gray, 1857 (Trochoidea: Trochidae) includes 23 recognized genera and over 200 known living species. These marine top shell snails are microphagous grazers that generally live in shallow rocky shores and in macroalgae and seagrass beds of sub-tropical and temperate waters from the Central and Western Indo-Pacific biogeographic regions to the Mediterranean Sea and the Eastern Atlantic Ocean. Recent molecular phylogenetic studies revising the family Trochidae supported the monophyly of the subfamily Cantharidinae and its sister group relationship to the subfamily Stomatellinae. These studies and others has thus far mostly focused on Indo-Pacific members of the subfamily Cantharidinae whereas here, we investigated phylogenetic relationships among their counterparts from the Mediterranean Sea and the North-eastern (NE) Atlantic Ocean including 33 species of genera Gibbula , Jujubinus , Phorcus , Clelandella , and Callumbonella . The Mediterranean and NE Atlantic taxa were supplemented with 30 Indo-Pacific Cantharidinae species plus 19 members of the sister group subfamily Stomatellinae. Phylogenetic trees were constructed using Bayesian inference and maximum likelihood with two datasets comprised of partial sequences of four or six mitochondrial ( cox1 , rrnL , rrnS , and cob ) and nuclear ( 28S rRNA and histone H3 ) genes. A clade comprised of all Mediterranean and NE Atlantic taxa was recovered with high support, but its sister group among the Indo-Pacific lineages could not be determined with confidence (although the assignment of “ Trochus ” kotschyi to Priotrochus could be rejected). Within the Mediterranean and NE Atlantic clade, genera Phorcus and Jujubinus were recovered as reciprocally monophyletic, and the deep-sea genera Clelandella and Callumbonella were placed with high support as sister to Jujubinus . However, the genus Gibbula as currently defined was not monophyletic and constituent species were divided into three major clades and two independent lineages. Phylogenetic relationships among Phorcus , Jujubinus (plus Clelandella and Callumbonella ), and the different clades of Gibbula were not fully resolved but received higher support in the phylogenetic analyses based on six genes. A first approach to resolve phylogenetic relationships within Stomatellinae was conducted showing that the diversity of the subfamily is highly underestimated at present, and that Calliotrochus is possibly a member of this subfamily. A chronogram was reconstructed using an uncorrelated relaxed lognormal molecular clock and the origin of the Mediterranean and NE Atlantic clade was dated right after the Azolla phase in the Middle Eocene about 48 million years ago whereas diversification of major clades (genera) followed the eastern closure of the Tethys Ocean in the Middle Miocene about 14 million years ago. [ABSTRACT FROM AUTHOR]

The nucleotide sequences of the complete or nearly complete mitochondrial (mt) genomes of seven vetigastropods were determined: Angaria neglecta (Angarioidea), Phasianella solida (Phasianelloidea), Granata lyrata (Seguenzioidea), Tegula lividomaculata and Bolma rugosa (Trochoidea), Diodora graeca (Fissurelloidea) and Lepetodrilus schrolli (Lepetodriloidea). While the mt genomes of the superfamilies Angarioidea, Phasianelloidea, Seguenzioidea and Trochoidea conform generally to the ancestral gene order of Vetigastropoda and Gastropoda, those of the superfamilies Fissurelloidea and Lepetodriloidea have suffered important rearrangements. The gene order of the mt DNA of Chrysomallon squamiferum, a representative of Neomphalina, was also analysed since it has been proposed to be closely related to Vetigastropoda, and showed a distinct arrangement. The reconstructed phylogenies recovered Neomphalina as a distinct gastropod lineage that is the sister group (only with moderate bootstrap support) of a clade including Vetigastropoda and Neritimorpha + Caeno-gastropoda while the relative position of Heterobranchia and Patellogastropoda in the gastropod tree could not be determined definitively due to their long branches. Within the monophyletic Vetigastropoda, the superfamily Fissurelloidea was recovered as the sister group of two lineages, one including Lepetodriloidea as the sister group of Seguenzioidea + Halitoidea, the other including Phasianelloidea, Angarioidea and Trochoidea without resolved relationships. The long branches of Fissurelloidea were found to introduce significant tree instability in phylogenetic reconstruction. The new phylogeny supports that the loss of the right pallial gill occurred multiple times in vetigastropod evolution as previously suggested and that Phasianelloidea, Angarioidea and Trochoidea radiated from a common asymmetric (single-gilled) ancestor that lived in the middle Palaeozoic. [ABSTRACT FROM AUTHOR]

Aim: How historical and contemporary eco‐evolutionary processes shape the patterns of genetic diversity and differentiation across species' distribution range remains an open question with strong conservation implications. Focusing on the orange stony coral, Astroides calycularis, we (a) characterized the pattern of neutral genetic diversity across the distribution range; (b) gave insights into the underlying processes; and (c) discussed conservation implications with emphasis on a national park located on a hotspot of genetic diversity. Location: South Mediterranean Sea and Zembra National Park. Methods: We combined new data from 12 microsatellites in 13 populations located in the Centre and in the Western Periphery of the distribution range with a published dataset including 16 populations from the Western and Eastern Peripheries. We analysed the relationship among parameters of genetic diversity (He, Ar(g)) and structure (population‐specific FST) and two measures of geographic peripherality. We compared two estimators of pairwise genetic structure (GST, DEST) across the distribution range. The evolutionary and demographic history of the populations following the Last Glacial Maximum was reconstructed using approximate Bayesian computations and maximum‐likelihood analyses. We inferred the contemporary connectivity among populations from Zembra National Park and with the neighbouring area of Cap Bon. Results: We demonstrate a decrease in genetic diversity and an increase in genetic differentiation from the Centre to the Eastern and Western Peripheries of the distribution range. Populations from Zembra show the highest genetic diversity reported in the species. We identified a spillover effect towards Cap Bon. Main conclusions: The patterns of genetic diversity and differentiation are most likely explained by "the postglacial range expansion hypothesis" rather than the "central–peripheral hypothesis." Enforcement of conservation measures should be considered to protect this genetic diversity pattern, in particular when considering the low effective population size inferred at many sites. [ABSTRACT FROM AUTHOR]

The mud snails endemic to the East Atlantic/Mediterranean region (genus Tritia; subfamily Nassariinae) account for the second highest diversity within the family Nassariidae (Gastropoda: Buccinoidea). In order to understand how the diversity of species, shell morphologies and ecological traits evolved within this genus, a robust phylogenetic framework is needed, yet still unavailable due to high levels of homoplasy in shell morphology, the main trait used for their taxonomic classification. Here, the near‐complete mitogenomes of 20 species representing more than half of the diversity of Tritia were sequenced. All mitogenomes of Tritia shared the same gene order, which is identical to the consensus reported for caenogastropods. The reconstructed phylogeny indicates that all analysed Tritia species formed a natural group except Tritia vaucheri, which was sister to an early diverging clade within subfamily Nassariinae that includes species of genus Reticunassa sister to Nassarius jacksonianus and Nassarius sp. Within Tritia, the North‐west Atlantic species Tritia obsoleta was placed as the sister group of three mostly East Atlantic/Mediterranean clades (I‐III), prompting the reinstatement of the genus Ilyanassa. The latter three clades corresponded to different shell features (I, shell mostly with marked sculpture; II, shell with strong nodules and small size; and III, smooth shell). For Tritia incrassata, the analysed specimens from Norway and from the Spanish Mediterranean coasts showed notable genetic divergence, which may indicate the existence of cryptic species. The ancestral character state reconstruction of protoconch inferred that the ancestor of Tritia had planktotrophic larvae and that a transition to lecithotrophy occurred independently at least three times within Nassariinae. The reconstructed chronogram dated the origin of Tritia in the Oligocene and main diversification events during the Miocene to Pleistocene, correlated with drastic shifts in local paleoecosystems caused by cooling events, eustatic sea level changes and the Messinian Salinity Crisis that favoured temperate taxa. [ABSTRACT FROM AUTHOR]

Three species of the genus Asterina are known to inhabit the Mediterranean Sea and the north-eastern Atlantic Ocean: Asterina gibbosa (Pennant, 1777), A. pancerii (Gasco, 1870) and A. phylactica Emson & Crump, 1979. Differentiation of these species has primarily been based only on subtle characters (some highly debatable), such as colour or size. Therefore, this study aimed to review the morphological data characterising members of the genus, to incorporate new characters that may clarify morphological analyses and to couple morphological data with molecular evidence of differentiation based on the analysis of partial sequences of the cytochrome c oxidase subunit I (COI) and 18S rDNA (18S) genes and two anonymous nuclear loci (AgX2 and AgX5). The different lineages and cryptic species identified from the molecular analysis were then morphologically characterised, which was challenging given the limited number of diagnostic characters. Two of the five monophyletic lineages obtained molecularly (COI divergence >4%), further supported by differences in morphological characters and reproductive behaviour, are proposed as new species: Asterina martinbarriosi, sp. nov. from the Canary Islands, Spain (eastern central Atlantic Ocean) and Asterina vicentae, sp. nov. from Tarragona, north-eastern Spain (western Mediterranean Sea). [ABSTRACT FROM AUTHOR]

Four genetically distinct clades were recently described under the name Dendropoma petraeum , a Mediterranean endemic vermetid gastropod. The aim of this work is to date the processes that drove to the diversification within this taxon and to relate them to the corresponding historical events occurred in the Mediterranean Sea. Sequences from mitochondrial and nuclear markers were obtained from specimens collected in 29 localities spanning over 4000 km across the entire distribution range of D. petraeum species complex. The phylogenetic and coalescent-based analyses confirmed the four well-supported and largely differentiated lineages of D. petraeum , clearly delimited geographically along a west–east axis within the Mediterranean Sea: Western, Tyrrhenian–Sicilian, Ionian–Aegean and Levantine lineages. Divergence time estimates, obtained using a range of known substitution rates for other marine gastropods, indicated two main stages of diversification . In the first period (between 9.5 and 4.5 mya), the ancestral D. petraeum diverged into the current four lineages. The most recent period occurred between 3.72 and 0.66 mya in the late Pliocene–early Pleistocene, and included the main within-lineage diversification events. Therefore, if the divergence time between the major lineages of Dendropoma in the Mediterranean actually predated or coincided with the Messinian Salinity Crisis, then they should have survived to this dramatic period within the Mediterranean, as supported by Bayes Factors model comparison. Conversely, if the divergence started after the crisis, congruent with the idea that no true marine organism survived the Messinian Salinity Crisis, then our results indicate substitution rates of Dendropoma much higher than usual (5.16% per million years for COI, 3.04% for 16S). More recent climate changes seem to have conditioned the demographic history of each lineage differently. While Western and Tyrrhenian–Sicilian lineages both underwent an increase in their effective population sizes from 1.5 to 0.6 mya coinciding with a long interglacial period, the Ionian–Aegean and Levantine lineages showed constant effective population sizes since 2–2.5 mya, suggesting that these eastern lineages might represent small and relict populations surviving the subsequent Quaternary glaciations in isolated refugia. [ABSTRACT FROM AUTHOR]

Cladocora caespitosa is a reef-building zooxanthellate scleractinian coral in the Mediterranean Sea. Mortality events have recurrently affected this species during the last decade. Thus, knowledge of its genetic structure, population diversity, and connectivity is needed to accomplish suitable conservation plans. In order to obtain a better understanding of the population genetics of this species, 13 highly variable microsatellites markers were developed from a naturally bleached colony. The developed primers failed to amplify zooxanthella DNA, isolated from C. caespitosa, verifying that these markers were of the coral and not algal symbiont origin. The degree of polymorphism of these loci was tested on tissue samples from 28 colonies. The allele number for each loci ranged from 2 to 13 (mean Na = 5.4), with an average observed heterozygosity of 0.42 (He = 0.43) and all loci were in Hardy–Weinberg equilibrium. These new markers should be useful in future conservation genetic studies and will help to improve the resolution of the individual identification within this coral species. Primers were also tested in Oculina patagonica, with successful amplifications of several loci. [ABSTRACT FROM PUBLISHER]

The Mediterranean Sea is losing its biological distinctiveness, and the same phenomenon is occurring in other seas. It gives urgency to a better understanding of the factors that affect marine biological invasions. A chemoecological approach is proposed here to define biotic conditions that promote biological invasions in terms of enemy escape and resource opportunities. Research has focusid on the secondary metabolite composition of three exotic sea slugs found in Greece that have most probably entered the Mediterranean basin by Lessepsian migration, an exchange that contributes significantly to Mediterranean biodiversity. We have found toxic compounds with significant activity as feeding deterrents both in the cephalaspidean Haminoea cyanomarginata and in the nudibranch Melibe viridis. These findings led us to propose aposematism in the former and dietary autonomy in producing defensive metabolites in the latter case, as predisposing factors to the migration. In the third mollusk investigated, the anaspidean Syphonota geographica, the topic of marine invasions has been approached through a study of its feeding biology. The identification of the same compounds from both the viscera of each individual, separately analyzed, and their food, the seagrass Halophila stipulacea, implies a dietary dependency. The survival of S. geographica in the Mediterranean seems to be related to the presence of H. stipulacea. The initial invasion of this exotic pest would seem to have paved the way for the subsequent invasion of a trophic specialist that takes advantage of niche opportunities. [ABSTRACT FROM AUTHOR]