Opisthobranch molluscs of the Sudanese Red Sea

Eighteen opisthobranch species are described and illustrated from the Sudanese Red Sea, including seven new species, one new subspecies and three species for which this is the first Red Sea record. Eleven bullomorphs, four pleurobranchomorphs, four sacoglossans and four phyllidiid mudibranchs are now known from the Red Sea. There appears to be a high percentage of endemic species in the Red Sea. This is what one might expect, in view of the conditions of near isolation, low temperatures and high salinity that prevailed in this sea 13000 23000 years ago. Of the groups discussed in this paper, one Red Sea species has invaded the Mediterranean Sea, and one Mediterranean species has invaded the Red Sea, since the opening of the Suez Canal in 1867. Many Red Sea species are very colourful, in comparison to Mediterranean ones. This could perhaps be because Red Sea waters are cleaner, thereby favouring the evolution of greater precision in colour markings.     

Opisthobranch molluscs of the Sudanese Red Sea

Eighteen opisthobranch species are described and illustrated from the Sudanese Red Sea, including seven new species, one new subspecies and three species for which this is the first Red Sea record. Eleven bullomorphs, four pleurobranchomorphs, four sacoglossans and four phyllidiid mudibranchs are now known from the Red Sea.
There appears to be a high percentage of endemic species in the Red Sea. This is what one might expect, in view of the conditions of near isolation, low temperatures and high salinity that prevailed in this sea 13000 23000 years ago.
Of the groups discussed in this paper, one Red Sea species has invaded the Mediterranean Sea, and one Mediterranean species has invaded the Red Sea, since the opening of the Suez Canal in 1867.
Many Red Sea species are very colourful, in comparison to Mediterranean ones. This could perhaps be because Red Sea waters are cleaner, thereby favouring the evolution of greater precision in colour markings.     

First record of the dog snapper Lutjanus jocu in the Mediterranean Sea

The capture of a single specimen of the dog snapper Lutjanus jocu from the Ligurian Sea (north‐west Mediterranean Sea) in November 2005 is reported. This finding constitutes the first record of this species from the Mediterranean Sea.     

Increasing southern invasion enhances congruence between endemic and exotic Mediterranean fish fauna

Species movements in relation with global warming may increase the spatial overlap between exotic and endemic species, which is a critical issue for the conservation of biodiversity. The Mediterranean Sea, which is a receptacle for exotic species while being a hotspot for endemism, provides exceptional material for a case study. The aim of our study was to quantify (i) the increasing invasion from southern fish exotic species (Red Sea and Atlantic Ocean) that the Mediterranean biota is experiencing and (ii) the spatial overlap between exotic and endemic Mediterranean fish fauna following the northward movement of exotic species within the Mediterranean Sea in the context of global warming. The historical invasion dynamic of exotic fish species and the sea surface temperature series were reconstructed from 1810 to 2006 in order to estimate the correlation between invasion rate and climate. The geographical distributions of exotic and endemic fish richness before and after the period of global warming were used to assess the dynamic of spatial congruence. The results revealed (i) an acceleration of successful introductions from the Red Sea and (ii) the introduction of Atlantic species from lower latitudes in correlation with the increasing temperature of the Mediterranean Sea. We also showed an increasing overlap between the spatial distributions of endemic and exotic species richness. Taken together, our results suggest that endemic fish species are facing a growing number of exotic species because the Mediterranean Sea is acting as a catchment basin for southern species.     

Phylogeography of the planktonic chaetognath Sagitta setosa reveals isolation in European seas

Numerous planktonic species have disjunct distribution patterns in the world's oceans. However, it is unclear whether these are truly unconnected by gene flow, or whether they are composed of morphologically cryptic species. The marine planktonic chaetognath Sagitta setosa Müller has a discontinuous geographic distribution over the continental shelf in the northeastern Atlantic, Mediterranean Sea, and Black Sea. Morphological variation between these populations has been described, but overlaps and is therefore unsuitable to determine the degree of isolation between populations. To test whether disjunct populations are also genetically disjunct, we sequenced a 504-bp fragment of mitochondrial DNA comprising the cytochrome oxidase II region of 86 individuals. Sequences were highly variable; each represented a different haplotype. Within S. setosa, sequence divergence ranged from 0.2 to 8.1% and strong phylogeographic structure was found, with four main groups corresponding to the northeastern Atlantic, Mediterranean Sea (including Ligurian Sea, Tyrrhenian Sea and Gulf of Gabes), Adriatic Sea, and Black Sea. Two of these (Atlantic and Black Sea) were resolved as monophyletic clades, thus gene flow between disjunct populations of S. setosa has been extremely limited and lineage sorting has taken place. The deepest divergence was between Atlantic and Mediterranean/Black Sea populations followed by a split between Mediterranean and Black Sea populations. The Mediterranean/Black Sea clade comprised three groups, with the Adriatic Sea as the most likely sister clade of the Black Sea. These data are consistent with a colonization of the Black Sea from the Mediterranean. Furthermore, a possible cryptic species was found in the Black Sea with 23.1% sequence divergence from S. setosa. Two possibilities for the evolutionary origin of this species are proposed, namely, that it represents a relict species from the ancient Paratethys, or that it represents another chaetognath species that colonized the Black Sea more recently. Even though the exact timing of disjunction of S. setosa populations remains unclear, on the basis of the geological and paleoclimatic history of the European basins and our estimates of net nucleotide divergence, we suggest that disjunct populations arose through vicariance resulting from the cyclical changes in temperature and sea levels during the Pleistocene. We conclude that these populations have remained disjunct, not because of limited dispersal ability, but because of the inability to maintain viable populations in suboptimal, geographically intermediate areas.     

Ecological traits and environmental affinity explain Red Sea fish introduction into the Mediterranean

Alien species are considered one of the prime threats to biodiversity, driving major changes in ecosystem structure and function. Identifying the traits associated with alien introduction has been largely restricted to comparing indigenous and alien species or comparing alien species that differ in abundance or impact. However, a more complete understanding may emerge when the entire pool of potential alien species is used as a control, information that is rarely available. In the eastern Mediterranean, the marine environment is undergoing an unparalleled species composition transformation, as a flood of aliens have entered from the Red Sea following the opening of the Suez Canal in 1869. In this study, we compile data on species traits, geographical distribution, and environmental affinity of the entire pool of reef‐associated fish species in the Red Sea and more generally across the Indo‐Pacific. We use this extensive data to identify the prime characteristics separating Red Sea species that have become alien in the Mediterranean from those that have not. We find that alien species occupy a larger range of environments in their native ranges, explaining their ability to colonize the seasonal Mediterranean. Red Sea species that naturally experience high maximum temperatures in their native range have a high probability of becoming alien. Thus, contrary to predictions of an accelerating number of aliens following increased water temperatures, hotter summers in this region may prevent the establishment of many alien species. We further find that ecological trait diversity of alien species is substantially more evenly spaced and more divergent than random samples from the pool of Red Sea species, pointing at additional processes, such as competition, promoting ecological diversity among alien species. We use these results to provide a first quantitative ranking of the potential of Red Sea species to become established in the eastern Mediterranean.     

Molecular analysis of the recently described lizardfish Saurida lessepsianus (Synodontidae) from the Red Sea and the Mediterranean,with remarks on its phylogeny and genetic bottleneck effect

The opening of the Suez Canal in 1869 led to a massive influx of Red Sea species that invaded the Mediterranean; this was termed ‘Lessepsian migration'. Among these species was a species of lizardfish, identified by some authors as Saurida undosquamis and by others as S. macrolepis. Recently, the Red Sea and the Mediterranean populations were described according to external characteristics as a unique taxon, Saurida lessepsianus. Our molecular study confirms this finding and determines that all previous records of S. undosquamis and S. macrolepis in the Red Sea and the Mediterranean are misidentifications of S. lessepsianus. The Mediterranean population of S. lessepsianus exhibits a lower genetic variability than that of the Red Sea population, suggesting a bottleneck effect.     

Endemic and Indo-Pacific plankton in the Mediterranean Sea: a study based on dinoflagellate records

Aim To investigate biogeographical patterns based on published dinoflagellate records from the Mediterranean and Black Seas, and to provide a tentative list of endemic and Indo‐Pacific dinoflagellates in the Mediterranean Sea. Location Mediterranean Sea, Black Sea. Methods Checklists of dinoflagellates of the Mediterranean and Black Seas were compared with worldwide literature records. Only species reported in the Indo‐Pacific Ocean or exclusively known in the Mediterranean Sea were selected for biogeographical analysis. Results Dinoflagellates in the Mediterranean Sea comprised c. 43% of the world marine species and c. 88% of the dinoflagellate genera. Species richness among the Mediterranean sub‐basins showed marked differences due to the less reliable records of unarmoured (athecate) and rare dinoflagellates. These differences disappeared when only the more easily identifiable taxa were considered. Of the 673 dinoflagellates cited in the Mediterranean, 87% were also reported in the Atlantic Ocean. Only 40 taxa (6% of the total) were considered to be potential Indo‐Pacific species. Most were reported from the Ligurian Sea (21), and only two species from the Levantine basin. The other 48 taxa (7% of total) were known exclusively from the Mediterranean Sea, mainly from the Ligurian Sea. Half of these taxa were reported by a single author. Main conclusions Substantial dinoflagellates species richness can be attributed, in part, to the historical tradition of taxonomic studies in the Mediterranean Sea. The list of species of both Indo‐Pacific and exclusively Mediterranean species included taxa of dubious taxonomic validity or that were insufficiently known. The exclusion of these questionable taxa revealed the near absence of endemic dinoflagellates in the Mediterranean Sea compared with macroscopic organisms. This could be related to: (1) continuous replenishment of the plankton populations by the inflow of Atlantic water through the Strait of Gibraltar, (2) the possibility that species introduced during the Pliocenic flooding after the Messinian salinity crisis have not had enough time to diverge from their Atlantic ancestors, and/or (3) the reliance on traditional taxonomy based on morphological characters, which precludes the detection of cryptic speciation.     

Biodiversity issues for the forthcoming tropical Mediterranean Sea

Present-day Mediterranean marine biodiversity is undergoing rapid alteration. Because of the increased occurrence of warm-water biota, it has been said that the Mediterranean is under a process of ‘tropicalization’. This paper analyses the main patterns of the Mediterranean Sea tropicalization and considers briefly its extent and consequences. As happened during previous interglacial phases of the Quaternary, Atlantic water, entering via the Straits of Gibraltar, carries into the Mediterranean species that are prevalently of (sub)tropical affinity. On the other side of the basin, Red Sea species penetrate through the Suez Canal, a phenomenon called lessepsian migration from the name of F. de Lesseps, the French engineer who promoted the cutting of the Canal. Also the many exotic species introduced by humans voluntarily or involuntarily are nearly always typical of warm waters. Climate change combines with Atlantic influx, lessepsian migration and the introduction of exotic species by humans to the establishment of tropical marine biota in the Mediterranean Sea. Present-day warming ultimately favours the spread of warm-water species through direct and indirect effects, and especially by changing water circulation. It is impossible at present to foresee to what extent the exuberance of warm-water species will affect the trophic web and the functioning of marine ecosystems in the Mediterranean Sea of tomorrow. While Mediterranean Sea communities are modifying their pattern of species composition, they do not seem to be acquiring a more marked tropical physiognomy: Mediterranean coastal marine ecosystems are still dominated by frondose algae (even if the species that are gaining ascendancy are of tropical origin) and not by corals as is normal in tropical seas.     

Alien species in the Mediterranean Sea—which, when, where, why?

A critical evaluation of more than 2,200 publications, some dating back to the late 1800s, established the presence, and traced the spatio-temporal spread, of 558 alien metazoan species in the Mediterranean Sea. The majority of aliens in the eastern Mediterranean entered through the Suez Canal, whereas mariculture and shipping are powerful means of introduction in the northwestern Mediterranean and in the Adriatic Sea. Most aliens are thermophilic species. The possible causes for the epic scale of invasion in the Mediterranean Sea are discussed. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: J. Davenport, G. Burnell, T. Cross, M. Emmerson, R. McAllen, R. Ramsay & E. Rogan Challenges to Marine Ecosystems     

Genetic validation of the unexpected presence of a tropical tuna,bigeye tuna (Thunnus obesus), in the Mediterranean

Bigeye tuna (Thunnus obesus, Lowe, 1839) is one of the eight recognized species of the genus Thunnus. It is considered a tropical species distributed in the Atlantic, Pacific and Indian Oceans. To date, no validated presence of this species has been reported inside the Mediterranean Sea. This study, however, confirms, for the first time, the presence of three young individuals of this species within the Mediterranean Sea.     

Redescription of Fabriciola tonerella Banse, 1959, and a new record of Novafabricia infratorquata (Fitzhugh, 1983) from the Mediterranean Sea, with a key for the Fabriciinae (Annelida: Polychaeta) of the Mediterranean Sea and the north-east Atlantic

The fabriciin sabellid species Fabriciola tonerella Banse, 1959 living on gastropod shells inhabited by hermit crabs collected in the western Mediterranean Sea is redescribed. Another species of Fabriciinae, Novafabricia infratorquata (Fitzhugh, 1983), is recorded for the first time from the Mediterranean Sea and found in the same habitat is described as well. The variability of characters depending on size and geographical distribution is given for both species. Moreover, selected characters for all known species of Fabriciola and Novafabricia as well as a simple key for all Fabriciinae of the Mediterranean Sea and the north-east Atlantic are provided.     

Population genetics,gene flow,and biogeographical boundaries of Carcinus aestuarii (Crustacea: Brachyura: Carcinidae) along the European Mediterranean coast

Carcinus aestuarii Nardo, 1847 is a widespread coastal crab species throughout the Mediterranean Sea with a pelagic larval phase. This species tolerates a wide range of environmental conditions and typically inhabits fragmented habitats, such as embayments, lagoons and estuaries. It is therefore a good candidate species for studying and testing different phylogeographical hypotheses in the Mediterranean Sea. By contrast to its Atlantic sister species, Carcinus maenas, studies on the population genetic structure of C. aestuarii in its native range are still scarce. In the present study, specimens from along the European Mediterranean Sea were collected and DNA‐sequenced and analyses were applied to discriminate between present day and historical factors influencing the population genetic structure of this species. The results obtained demonstrate the existence of two genetically distinct geographical groups, corresponding to the eastern and western Mediterranean, with further subdivision within the East Mediterranean Basin. A strong asymmetric gene flow was recorded toward the Eastern Basin, which may play a crucial role in shaping the present day biogeographical patterns of this species and potentially other sympatric ones with pelagic larvae. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 109 , 771–790.     

Why is the mediterranean more readily colonized than the Red Sea,by organisms using the Suez Canal as a passageway?

Summary Since the opening of the Suez Canal, more than 120 Red Sea species colonized the eastern Mediterranean, whereas less than 10 Mediterranean species colonized the Red Sea. For most of the species involved in this colonization, the mode of dispersal from the source to the colonized area is through free-drifting propagules. In order to examine whether the current regime of the Suez Canal may be involved in this assymetry in colonization, a mathematical hydraulic model that forecasts the direction and velocity of water currents through the year, along the length of the Canal, was utilized. The movements of free-floating propagules that occur at either entrance of the Canal, was simulated on a computer, and it was found that the completion of a Mediterranean-bound passage of Red Sea propagules is far faster and much more likely than a completion of a Red Sea-bound passage of Mediterranean propagules.Paper No. 7 in the series Colonization of the Eastern Mediterranean by Red Sea species immigrating through the Suez Canal     

An annotated checklist of dinoflagellates in the Black Sea

An annotated checklist of free-living dinoflagellates (Dinophyceae) of the Black Sea, based on literature records, is reported and compared to the Mediterranean Sea and world oceans. Toxic species and/or responsible of harmful algal blooms (HAB) are marked in the checklist. From the 267 species (54 genera) listed nearly all taxa can be considered as cosmopolitan and no species as endemic. Several typically Arctic-boreal species (non recorded from the Mediterranean Sea) are reported from the Black Sea. The taxonomy and the biogeography of the taxa are discussed.     

A Sea Under Siege – Alien Species in the Mediterranean

Exotic macrophytes, invertebrates and fish are found in most coastal habitats in the Mediterranean Sea. The Mediterranean Sea has been subjected to introductions of non-indigenous species by ship traffic since the opening of interoceanic maritime routes five centuries ago. The Sea, a hub of shipping, is exceptionally susceptible to invaders that arrive in fouling communities or ballast. The Suez Canal has been the largest pathway for the entry of these species: more than 300 Erythrean species – principally molluscs, fish, decapod crustaceans, polychaetes and algae – have become established in the eastern Mediterranean, primarily along the Levantine coasts. Mariculture of nonindigenous shellfish predominates in the northern Mediterranean lagoonar environments. Unrestricted transport of commercially important exotic shellfish has resulted in numerous unintentional introductions of pathogens, parasites and pest species. Some invaders have outcompeted or replaced native species locally, severely reducing biodiversity; some other invaders are so abundant they are exploited commercially. The rate of these biotic invasions has increased in recent decades, and they collectively have significant ecological and economic impacts in the Mediterranean Sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

First record of the bluespotted cornetfish from the Mediterranean Sea

Three specimens of the Indo-Pacific Bluespotted cornetfish Fistularia commersonii are recorded for the first time from the Mediterranean. The presence of this species in the Mediterranean is due to migration from the Red Sea via the Suez Canal.     

Untersuchungen zur Zoogeographie der Euphausiaceen (Crustacea) des Roten Meeres

A joint programme on “Biota of the Red Sea and the Eastern Mediterranean” has been carried out by the Hebrew University of Jerusalem and the Smithsonian Institution of Washington between 1967 and 1972 in order to study the role played by the Suez Canal as a route for faunal exchanges between the Red Sea and Eastern Mediterranean. The euphausiids of this material have been examined and additional samples of zooplankton have been taken in the Gulf of Elat (Aqaba) in 1973 in order to study the vertical distribution of the euphausiids. Four species have been found to occur in the Northern Red Sea and the Gulf of Elat:Euphausia diomedeae, E. sanzoi, Stylocheiron affine andS. abbreviatum. Seven species were found in the Eastern Mediterranean of whichEuphausia brevis is the dominant species. The present studies revealed that an exchange of Euphausiacea through the Suez Canal does not take place. The species of the Red Sea belong to the Indopacific fauna. Despite the particular historic-geographical and ecological situation of the Red Sea, no endemisms or subspecies have evolved there within the Euphausiacea.