First record of the Atlantic bumper Chloroscombrus chrysurus (Teleostei: Carangidae) in the Mediterranean Sea

In December 1997, one specimen of the Atlantic bumper, Chloroscombrus chrysurus was recorded for the first time in the Mediterranean Sea, off Almuñécar (Granada, Spain: 36° 43′ 26″ N; 3° 41′ 39″ W). This species probably entered the Mediterranean Sea via the Strait of Gibraltar.     

Phylogeographic patterns of two tiger beetle species at both sides of the strait of Gibraltar (Coleoptera: Cicindelini)

The Strait of Gibraltar is one of the major barriers to gene flow between land masses of Europe and Africa at the western end of the Mediterranean. Since the opening of the Strait at the end of the Miocene 5.33 million years ago (Mya) it has exerted a strong influence on the dispersal and colonization of whole biotas, particularly with regard to the retreat of organisms during glaciation peaks and the northward colonization events during the warm periods of Pleistocene. The aim of this study is to elucidate the influence of the Strait of Gibraltar in the gene flow among populations of two tiger beetle species collected in Morocco, Cicindela campestris (L. 1758) and Lophyra flexuosa (Fabricius 1787), with regard to both new and published data from populations of southern Iberia. The phylogeographic analysis showed that Moroccan haplotypes of L. flexuosa belonged to a single coastal mitochondrial clade and that populations at both sides of` the Strait of Gibraltar were genetically well connected. The haplotype network of C. campestris showed that Moroccan populations made up a robust cluster clearly differentiated from those of Iberian and other European populations. These differences are thought to reflect the distinct evolutionary history (dispersal capacity, ecological strategies) of both species, as L. flexuosa shows an almost continuous distribution on the coasts located at both sides of the West Mediterranean, whereas C. campestris shows a patchy distribution and prefers montane habitats in the Western Palaearctic.     

Population Genetic Structure of a Sandstone Specialist and a Generalist Heath Species at Two Levels of Sandstone Patchiness across the Strait of Gibraltar

Many habitat specialist species are originally composed of small, discontinuous populations because their habitats are naturally fragmented or patchy. They may have suffered the long-term effects of natural patchiness. Mediterranean heathlands, a representative habitat in the Strait of Gibraltar region, are associated with nutrient-poor, acidic sandstone soils. Sandstone soil patches in the African side of the Strait (Tangier) are, in general, smaller and more scattered than in the European side (Algeciras). In this study, we analyze the effect of this sandstone patchiness on the population genetic diversity and structure of two Erica species from these Mediterranean heathlands that differ in their edaphic specificity, E. australis, sandstone specialist, and E. arborea, generalist. Average levels of within-population genetic diversity and gene flow between populations were significantly lower in Tangier (high sandstone patchiness) than in Algeciras (low patchiness) for the sandstone specialist, whereas no differences between both sides of the Strait were detected in the edaphic generalist. Since most endemic species in Mediterranean heathlands of the Strait of Gibraltar are sandstone specialists, these results highlight an increased vulnerability to loss of genetic diversity and local extinction of the heathland endemic flora in the Tangier side of the Strait of Gibraltar.     

Genetic diversity of the imperilled bath sponge Spongia officinalis Linnaeus, 1759 across the Mediterranean Sea: patterns of population differentiation and implications for taxonomy and conservation

The Mediterranean bath sponge Spongia officinalis is an iconic species with high socio‐economic value and precarious future owing to unregulated harvesting, mortality incidents and lack of established knowledge regarding its ecology. This study aims to assess genetic diversity and population structure of the species at different geographical scales throughout its distribution. For this purpose, 11 locations in the Eastern Mediterranean (Aegean Sea), Western Mediterranean (Provence coast) and the Strait of Gibraltar were sampled; specimens were analysed using partial mitochondrial cytochrome oxidase subunit I (COI) sequences, along with a set of eight microsatellite loci. According to our results (i) no genetic differentiation exists among the acknowledged Mediterranean morphotypes, and hence, S. officinalis can be viewed as a single, morphologically variable species; (ii) a notable divergence was recorded in the Gibraltar region, indicating the possible existence of a cryptic species; (iii) restriction to gene flow was evidenced between the Aegean Sea and Provence giving two well‐defined regional clusters, thus suggesting the existence of a phylogeographic break between the two systems; (iv) low levels of genetic structure, not correlated to geographical distance, were observed inside geographical sectors, implying mechanisms (natural or anthropogenic) that enhance dispersal and gene flow have promoted population connectivity; (v) the genetic diversity of S. officinalis is maintained high in most studied locations despite pressure from harvesting and the influence of devastating epidemics. These findings provide a basis towards the effective conservation and management of the species.     

The zooplankton community in bays of Toulon area (northwest Mediterranean Sea,France)

The abundance and the diversity of the zooplankton community were studied during an annual cycle in three shallow bays differently affected by anthropogenic inputs of Toulon area in the northwest Mediterranean Sea (France). Environmental variables of water quality were also considered. Our results discriminated Little Bay from the La Garonne and Niel Bay. Little Bay, heavely perturbed by anthropogenic inputs, had high chlorophyll a levels, abundant zooplankton, a low diversity index, a high dominance Index and a single dominant species (Oithona nana). La Garonne Bay and Niel Bay, much less polluted, had low chlorophyll a levels, low zooplankton abundance, low dominance Index and high diversity index and eveness. In addition, O. nana occurred rarely in the latter bays. Zooplankton successions were also different between Little Bay and the two other bays.     

Historical colonization of the Mediterranean Sea by Atlantic fishes: do biological traits matter?

Since its opening 5.33 million years ago, the Gibraltar Strait has always contributed to the Mediterranean fauna and flora. Despite the increasing importance of the phenomenon, ecological determinants underlying colonization success of Atlantic fishes in the Mediterranean Sea have been poorly investigated. Here we reconstruct the recent historical colonization of the whole Mediterranean Sea by Atlantic fishes and we aim to determine where Atlantic fishes preferentially establish and whether some biological traits and ecological factors can be correlated to the colonization success (climate match, position in the water column, maximum body length, propagules, confamilial resistance, depth). A database on Atlantic fish species records from 1810 to 2006 was built and the colonization rate of each introduced species was estimated. Analysis of Variance, Chi squared test and logistic regression were used to investigate the relationships between ecological variables and colonization success. In addition, an index of asymmetry was used to analyse the relative colonization on the two sides of the Mediterranean Sea. Overall 48.33% of Atlantic species introduced in the Mediterranean Sea succeeded in colonizing eastwards. We found that habitat depth of Atlantic species is significantly related to their colonization success due to the obstacle of the shallow depth of the Gibraltar Strait (300 m). It also appears that despite the cyclonic general water circulation on the North Western basin, the northern side is more colonized than the southern one: 70.40% of the studied species colonize the northern side, while only 29.62% colonize the southern one. Two hypotheses may explain this trend: the bottom-up process that enhances the colonization success of Atlantic fishes along the Spanish coast of Alboran Sea owning to its high productivity and the intensiveness of the scientific explorations along the northern Mediterranean side. We conclude that crossing the Gibraltar Strait does not guarantee the colonization success and that species life-history and functional traits are poor predictors. Instead we suggest that environmental factors may determine favourable locations for invasive species installation. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: J. Cambray.     

First record of red cornetfish Fistularia petimba (Syngnathiformes:Fistulariidae) from Antalya and İskenderun Bays along Turkish Coasts of the Mediterranean Sea

Here, we report the first occurrence of red cornetfish Fistularia petimba in the north‐eastern Mediterranean Sea. Altogether four specimens were captured; first two in Antalya Bay on 28 October 2016 and 26 November 2016, and the remaining two in ?skenderun Bay on 21 May 2017 during the bottom trawl surveys along the Mediterranean coast of Turkey. All specimens were young and more or less uniform in size (383, 335, 419 and 453 mm standard length). The possibility that F. petimba could become a new potential invader in the Mediterranean as its congeneric F. commersonii is cautioned against.     

Insights into the genetic structure of the rabbitfish Chimaera monstrosa (Holocephali) across the Atlantic‐Mediterranean transition zone

A comparison of the genetic structure of Chimaera monstrosa populations from the Atlantic Ocean and the Mediterranean Sea was carried out using mitochondrial DNA analysis. Results indicate high and significant pairwise Φ_ST values with no shared haplotypes between the two areas. Furthermore, migration rate estimates suggested absence of gene flow between the two basins. These findings, coupled with the species vertical distribution, suggest that the shallow depth of the Strait of Gibraltar may act as a barrier limiting the dispersal capabilities of these populations, which likely became separated at the end of the middle Pleistocene.     

Fin whale (Balaenoptera physalus) population identity in the western Mediterranean Sea

Archival bottom‐mounted audio recorders were deployed in nine different areas of the western Mediterranean Sea, Strait of Gibraltar, and adjacent North Atlantic waters during 2006–2009 to study fin whale (Balaenoptera physalus) seasonal presence and population structure. Analysis of 29,822 recording hours revealed typical long, patterned sequences of 20 Hz notes (here called “song”), back‐beats, 135–140 Hz notes, and downsweeps. Acoustic parameters (internote interval, note duration, frequency range, center and peak frequencies) were statistically compared among songs and song notes recorded in all areas. Fin whale singers producing songs attributable to the northeastern North Atlantic subpopulation were detected crossing the Strait of Gibraltar and wintering in the southwestern Mediterranean Sea (Alboran basin), while songs attributed to the Mediterranean were detected in the northwest Mediterranean basin. These results suggest that the northeastern North Atlantic fin whale distribution extends into the southwest Mediterranean basin, and spatial and temporal overlap may exist between this subpopulation and the Mediterranean subpopulation. This new interpretation of the fin whale population structure in the western Mediterranean Sea has important ecological and conservation implications. The conventionally accepted distribution ranges of northeastern North Atlantic and Mediterranean fin whale subpopulations should be reconsidered in light of the results from this study.     

Zoogeography and life cycle patterns of Mediterranean hydromedusae (Gnidaria)

The distribution of the 346 hydromedusan species hitherto recorded from the Mediterranean is considered, dividing the species into zoogeographical groups. The consequences for dispersal due to possession or lack of a medusa stage in the life cycle are discussed, and related to actual known distributions. There is contradictory evidence for an influence of life cycle patterns on species distribution. The Mediterranean hydromedusan fauna is composed of 19.5% endemic species. Their origin is debatable. The majority of the remaining Mediterranean species is present in the Atlantic, with various world distributions, and could have entered the Mediterranean from Gibraltar after the Messinian crisis. Only 8.0% of the fauna is classified as Indo-Pacific, the species being mainly restricted to the eastern basin, some of which have presumably migrated from the Red Sea via the Suez Canal, being then classifiable as Lessepsian migrants. The importance of historical and climatic factors in determining the composition of the Mediterranean fauna of hydromedusae is discussed.     

Presence of Caulerpa racemosa (Forsskål) J. Agardh in Ceuta (Northern Africa, Gibraltar Area)

Caulerpa racemosa (Forsskål) J. Agardh has been recorded along the Mediterranean Sea since the 1920s, and since then has continually invaded its coasts moving westward towards the Atlantic. In recent years, authors have revealed the negative effect of the species on the Mediterranean’s benthic communities. Taking into account that the latest reference placed the species in Murcia (Southeastern Spain) in 2005, we now give evidence here of the presence of this invasive algae in Ceuta, a Spanish city located in the Strait of Gibraltar on the North Africa Coast. This is the first and westernmost recorded presence of the species in the area. Characteristics of the located patches are given.     

Harpacticoiden (Crustacea, Copepoda) aus dem Küstengrundwasser der französischen Mittelmeerküste

Investigations of the ground water of the French Mediterranean coast gave 28 different species of harpacticoid copepods. Among them, six species are new to the French coast and three species and one form are described as new, viz. Ectinosoma mediterraneum sp.n., Sigmatidium rouchi sp.n., Ameira atlántica mediterránea forma n., and Taurocletodes gallicus sp.n. Comparison of the harpacticoid fauna of the French coast with other marine districts shows close relations to the fauna of the Black Sea, while the relations to the Atlantic coast (Portugal) and the Baltic Sea (Bay of Kiel) are only remote. A genus is established, Taurocletodes gen.n. Sigmatidium noodti sp.n. is described from the Sea of Marmara.     

Paranthias furcifer (Perciformes: Serranidae), a new alien fish in the Mediterranean Sea

A specimen of a creole fish Paranthias furcifer (285 mm total length) was captured in Marina Bay (Croatian coast) in the eastern Adriatic Sea. This is the first Mediterranean record of this species. The possible modes of introduction of species are discussed.     

Retracted: A new species in town: New record of Hexanchus nakamurai Teng, 1962 from the Levantine Sea

Hexanchus nakamurai is a deep-water species, with very little scientific information. This study confirms the distribution of the species in the most eastern region of the Mediterranean Sea, Levantine Sea, in addition to providing some biological information from four pregnant individuals, which is being reported for the first time in the Mediterranean Sea. A total of four individuals were bycaught, in two sets on opposite coasts, three on the 13th of May 2020 from the western coast, and an individual on the 14th June 2020 from east coast of the island of Cyprus. The four specimens, all pregnant females, measured between 107 and 116 cm in total length and between 4,330 and 4,960 g in weight. All specimens were in early pregnancy according to the level of embryo development, which confirms that the size at maturity is smaller than previously reported. In the stomachs, remains of the hake Merluccius merluccius, the cephalopod Loligo vulgaris and two unidentified species of Hirudinea (Annelida) were found. This study provides important new information on the Mediterranean distribution of a globally rare and data deficient species, including an expansion of its known range, dietary preferences and insights of its reproduction biology; the first pregnant females reported in the Mediterranean Sea.     

Feeding ecology of Mediterranean common dolphins: The importance of mesopelagic fish in the diet of an endangered subpopulation

The Mediterranean subpopulation of common dolphin (Delphinus delphis) is classified as endangered by the IUCN. Still, information about their diet in the Mediterranean is scarce. Stomach contents of 37 common dolphins stranded in the Alboran Sea and Strait of Gibraltar were analyzed. A total of 13,634 individual prey of 28 different taxa were identified. For fish, Myctophidae was the most important family as indicated by the highest index of relative importance (IRI = 8,470), followed by the family Sparidae (IRI = 609). The most important Myctophidae species was Madeira lantern fish (Ceratoscopelus maderensis) and for Sparids, the bogue (Boops boops). Cephalopods, instead, were found in low quantities only with 31 prey from the Loliginidae, Ommastrephidae, and Sepiolidae families. Overall, our results indicate that common dolphins are mainly piscivorous (99.77%N, 94.59%O, 99.73%W), feeding mostly on mesopelagic prey. Although common dolphins inhabit mainly coastal waters in the study area, the narrow continental shelf seems to facilitate the availability of Myctophids and other members of the mesopelagic assemblage to dolphins when the assemblage migrates to the surface at night. Our results represent the first attempt at quantifying the diet of this predator in the Alboran Sea and Strait of Gibraltar.     

The impacts of the Messinian Salinity Crisis on the biogeography of three Mediterranean sandfly (Diptera: Psychodidae) species

The desiccation of the Mediterranean Basin at the end of the Miocene was a milestone in the evolution of the Mediterranean sandfly fauna. This severe environmental change should have notably influenced their paleobiogeography as well as paleoecology and might have triggered the rapid speciation of the ancestors of the extant European sandfly species. The aim of this study was to explore how the Messinian Salinity Crisis could influence the distribution and migration routes of the ancient Mediterranean sandfly species. The unknown ecological requirements of this ancient species were replaced by the distribution-limiting climatic values of three species of extant European phlebotomine sandflies which represent the three ecological types of European sandfly fauna. The former potential occurrence patterns were determined by Climate Envelope Modelling Method. As a climate model for the Messinian Period in the Mediterranean Basin, the modified mid-Pliocene warm period model was used. The thermal surplus of the desiccated seafloor was reconstructed based on the atmospheric lapse rate. It was found that the extraordinary hot climate of the Mediterranean abyssal plain did not allow the direct cross-migration of the ancient sandfly species anywhere between Europe and North Africa neither through Gibraltar nor the Strait of Sicily. While Phlebotomus neglectus and Phlebotomus papatasi could colonize the Adriatic Plain, Phlebotomus ariasi could not. The results indicate that the Messinian played an important role in the speciation rather than migration of the ancestors of present-day Mediterranean sandflies.     

Length–weight relationships for six fish species in Iskenderun Bay (Eastern Mediterranean Sea coast of Turkey)

The length–weight relationships (LWRs) were estimated for six non‐indigenous fish species, namely, Apogon smithi (Kotthaus, 1970); Ostorhinchus fasciatus (White, 1790); Pomadasys stridens (Forsskål, 1775); Champsodon capensis Regan, 1908; Torquigener flavimaculosus Hardy & Randall, 1983; and Tylerius spinosissimus (Regan, 1908) from Iskenderun Bay, eastern Mediterranean Sea. Their length–weight relationship b values ranged from 2.902 to 3.501, and all regressions were found to be significant for all six species (P < 0.001). This study is the first reference on length–weight relationships for these six non‐indigenous fish species from the Eastern Mediterranean Sea coast of Turkey.     

Phylogeography of the marbled crab Pachygrapsus marmoratus (Decapoda,Grapsidae) along part of the African Mediterranean coast reveals genetic homogeneity across the Siculo-Tunisian Strait versus heterogeneity across the Gibraltar Strait

We investigate the influence of previously postulated biogeographic barriers in the Mediterranean Sea on the population genetic structure of a highly dispersive and continuously distributed coastal species. In particular, we examine nuclear and mitochondrial genetic variation in the marbled crab, Pachygrapsus marmoratus, across part of the African Mediterranean coast in order to assess the influence of the Siculo-Tunisian Strait on its population genetic structure. Four polymorphic microsatellite loci were genotyped for 110 individuals, collected from eight locations covering parts of the Algerian, Tunisian and Libyan coasts. In addition, mtDNA corresponding to the Cox1 gene was sequenced for 80 samples. The corresponding results show contrasting patterns of genetic differentiation. While mtDNA results revealed a homogeneous haplotype composition in our study area, microsatellite data depicted genetic differentiation among populations, but not associated with any geographic barrier. This pattern, already recorded for this species from different geographic regions, may hint at the involvement of a complex series of abiotic and biotic factors in determining genetic structure. Demographic history reconstruction, inferred from mtDNA data, supports demographic and spatial expansion for the North African metapopulation dating back to the Mid-Pleistocene and following an historical bottleneck. Comparison of these African mitochondrial sequences with new sequences from a Turkish population and previously published sequences revealed a weak but significant separation of Atlantic and Mediterranean populations across the Gibraltar Strait, which was not recorded in previous studies of this grapsid species.     

Spread of Microcosmus squamiger (Ascidiacea: Pyuridae) in the Mediterranean Sea and adjacent waters

The Mediterranean Sea is subject to an ever-increasing arrival of non-indigenous marine organisms. Microcosmus squamiger is a solitary ascidian that inhabits shallow rocky littoral habitats. It probably originated in Australia and it has shown great invasive potential in other parts of the world. In the Mediterranean, M. squamiger has only been reported at a few sites in Spain and Italy. However, the closely related species Microcosmus exasperatus has been reported in several areas of the western Mediterranean. As these species can be easily confused, we re-examined most of the material from previous studies and our personal collections. In addition, sampling was done at several sites along the western Mediterranean and Atlantic coasts. The results showed that the majority of the M. exasperatus reports correspond to M. squamiger, and that M. squamiger is common on the Atlantic shores. This suggests that M. squamiger has entered the Mediterranean through the Gibraltar Strait, while the restricted distribution in the eastern Mediterranean of M. exasperatus suggests that this species is probably a Lessepsian migrant. In the Mediterranean Sea, M. squamiger has the ability to occupy extensive areas of hard substrata and to outcompete native species. Further studies are necessary to assess what impacts this invasive species have on native communities.