Strait Of Gibraltar Research Articles

Origin and Evolution of Synoptic-Scale Vortices Initiated at Low Level Downwind of the Hoggar Mountains

Abstract Numerous low-level vortices are initiated downwind of the Hoggar Mountains and progress toward the Atlantic coast on the northern path of African easterly waves (AEWs). These vortices occur mostly in July and August and more specifically when the northern position of the Saharan heat low (SHL) generates stronger and vertically expanded easterly winds over the Hoggar Mountains. At synoptic time scales, a composite analysis reveals that vortex initiation and westward motion are also statistically triggered by a reinforcement of these easterly winds by a wide and persistent high pressure anomaly developing around the Strait of Gibraltar and by a weak wave trough approaching from the east. The vortices are generated in the lee of the Hoggar, about 1000 km west of this approaching trough, and intensify rapidly. The evolution of the vortex perturbation is afterward comparable with the known evolution of the AEWs of the northern path and suggest a growth due to dry barotropic and baroclinic processes induced in particular by the strong cyclonic shear between the reinforced easterly winds and the monsoon flow. These results show that vortex genesis promoted by changes in orographic forcing due to the strengthening of easterly winds over the Hoggar Mountains is a source of intensification of the northern path of AEWs in July and August. These results also provide a possible mechanism to explain the role of the SHL and of particular midlatitude intraseasonal disturbances on the intensity of these waves.

Phylogeny of Species, Infraspecific Taxa, and Forms in Iris Subgenus Xiphium (Iridaceae), From the Mediterranean Basin Biodiversity Hotspot

Abstract— Iris subgenus Xiphium is a small group of taxa that occur in the Mediterranean Basin, a long-recognized biodiversity hotspot. Phylogenetic relationships among these Iris were reconstructed based on sequence data from 110 nuclear markers (coding regions) and plastomes using Bayesian inference and maximum likelihood methods. Best trees based on plastome and combined datasets resolved Iris subgenus Xiphium and I. xiphium as not monophyletic while nuclear and all-gene (combined nuclear and plastid coding regions) datasets resolved the subgenus as monophyletic but I. xiphium as not monophyletic. Topology tests indicated the alternative hypothesis of a monophyletic subgenus is not rejected by the combined dataset while a monophyletic I. xiphium is rejected. Topology tests also showed the hypothesis of a polyphyletic subgenus is rejected by the nuclear and all-gene datasets, however, a monophyletic I. xiphium is not rejected by these two datasets. We hypothesize that the subgenus is monophyletic based on these analyses, morphology, and biogeography, and that uneven patterns of missing data is a likely reason for topological incongruence among datasets. A previously suggested informal group within the subgenus was supported. Patterns of relationships among species suggest multiple exchanges between the African and European continents but also the importance of the Strait of Gibraltar as a barrier to genetic exchange.

Analysis of internal soliton signals and their eastward propagation in the Alboran Sea: exploring the effect of subinertial forcing and fortnightly variability

Internal waves are commonly observed in oceans and lakes where high stratification exists. In the present study in the Strait of Gibraltar, we analyse internal soliton signals recorded in different locations in their eastward propagation from their release point (Camarinal Sill) to the continental slope of the northwestern Alboran Sea. Moreover, the effect of subinertial forcing on the release of solitons is also explored. The internal soliton activity was assessed from different approaches: (i) in-situ data (i.e., current and temperature measurements or High-Frequency Radar), (ii) numerical modelling, and (iii) an analytical approach. The arrival of solitons over the continental slope of the north-western Alboran Sea showed fortnightly variability in both number (occurrence) and amplitude during spring tides when compared with during neap tides. The observed arrival times of the solitons oscillated between 14 (spring tides) and 20 h (neap tides). Nevertheless, to provide a comprehensive explanation for the fluctuations in travel times, it is necessary to consider the subinertial variability driven by atmospheric forcing, which impacts both the flow in the Strait of Gibraltar and the mesoscale patterns in the Alboran Sea (e.g., the Coastal Cyclonic Gyre).

Seasonal and interannual variability of Mediterranean Sea overturning circulation

The overturning streamfunction is a widely used metric to monitor ocean circulation changes in the North Atlantic Ocean. Analogously, it is known that an overturning circulation develops in the Mediterranean Sea, although substantially weaker and smaller than in the Atlantic. In this work we use monthly mean fields from a high-resolution ocean reanalysis (1/16°×1/16°) to explore seasonal and interannual variability of Mediterranean Sea overturning circulation in depth and water mass parameter spaces (potential density, potential temperature, salinity) from 1987 to 2018 (both included). Results show a clear single zonal clockwise transport cell in all three spaces that extends from the Strait of Gibraltar to the Levantine Basin, in which water masses tend to densify as they move eastward. This densification is mainly controlled by salinity in the Eastern Mediterranean basin (EMED), while in the Western Mediterranean (WMED) both salinity and potential temperature variations should be taken into account. In contrast, the meridional overturning transport, much more complex, is able to better capture smaller-scale variations since it responds faster to perturbations in the circulation.Seasonal variations in overturning transport are reflected in the size and strength of overturning cells in all spaces, being cells remarkably narrower in winter than in summer. Regarding interannual changes, we show that the meridional overturning transport in density space is significantly correlated with the North Atlantic Oscillation, the Mediterranean Oscillation Index and the Scandinavian pattern during wintertime in the WMED, and with the Eastern Atlantic and the East Atlantic–Western Russian in the EMED. The overturning metric in density space captures well the Eastern Mediterranean Transient, that occurred during years 1992–1996. Finally, we explore the usefulness of overturning metric to detect and track water mass changes associated to shorter scale events, using as example the strong deep convection events of years 2004–2006 in the Gulf of Lion, which marked the beginning of the Western Mediterranean Transition.

Sustainability as a common goal: Regulatory compliance, stakeholder perspectives, and management implications of whale and dolphin watching in the Strait of Gibraltar

As the Whale and dolphin Watching (WW) industry grows, so does the need for better industry management. The present study aims to both evaluate the current compliance of WW operators with local WW statutory tools, as well as gain a multi-perspective overview of WW activities in the Strait of Gibraltar. To this end, a total of 637 questionnaires were filled out by stakeholders including WW customers and operators, researchers, environmental NGOs, technicians, and policy makers in Tarifa and Gibraltar between 2017 and 2019. A direct assessment of WW activities was also carried out in 2019. Results suggest that (1) local operators only partially follow rules, (2) customers prefer, and give higher ratings to operators when cetaceans are indifferent to or approach vessels and (3) stakeholders recognise the educational, scientific, and recreational values of WW. Suggestions for the improvement of compliance include the land-based monitoring of WW activities, the analysis of Automatic Identification System data and an increase in patrolling and enforcement (e.g., revoking of licenses). Moreover, the introduction of structured educational programmes during WW activities the designation of Marine Protected Areas, and of a regional shipping plan, together with an integrated management approach, could benefit the WW industry and improve its sustainability in the Strait.

Between Preventive Attack and Collaboration: British Military Planning on Spain, 1940–1944

In the early stages of the Second World War, Spanish dictator Francisco Franco and key regime figures were tempted to enter the war on the Axis side. This temptation was a serious concern for British wartime strategy. This article studies the British military operations prepared to confront the possibility of Spain entering the war between 1940 and 1944. These operations aimed to protect Gibraltar, maintain access through the Strait of Gibraltar, and reduce the Axis threat to maritime communications in the eastern Atlantic. The article sheds new light on three issues: the balance of advantages and disadvantages that the plans entailed and the preparations to carry them out; the simultaneity of planned operations to cooperate with the Spanish Armed Forces and ones to confront them; and the importance of Spanish non-belligerence as a differential factor with respect to other neutral European countries.

Could secondary flows have made possible the cross-strait transport and explosive invasion of Rugulopteryx okamurae algae in the Strait of Gibraltar?

Presently, the Strait of Gibraltar is undergoing an unprecedented invasion of the alien alga Rugulopteryx okamurae of North Pacific origin. According to the scarce literature, the algae first settled in the south shore, probably following commercial exchanges with French ports where it was accidentally introduced together with Japanese oysters imported for mariculture. There is no certainty, however, that the algae first colonized the south shore of the Strait and, from there, spread to the north. It could well have been the opposite. Whatever the case, it spread all over the Strait and surrounding areas with amazing rapidity. Human-mediated vectors (algae attached to ship hulls or fishing nets, for example) can be behind the spread from the shore initially settled to the algae-free shore on the opposite side. But it could also have happened by means of hydrodynamic processes without direct human intervention. This possibility is assessed in this paper by revisiting historical current meter profiles collected in the Strait of Gibraltar searching for secondary cross-strait flows. All the stations present an intermediate layer of northward cross-strait velocity near the interface of the mean baroclinic exchange along with a surface layer above of southward velocity, whose lower part also overlaps the interface zone. The first one would back the south-to-north transport of algal fragments, the second one, the north-to south. In both cases, algae must reach the depth of the interface. The vertical velocity field in the area, which far exceeds the small sedimentation velocity of the algae, allows their vertical displacements throughout the water column. Its endurance to survive under the weak or no light conditions that will prevail during the cross-strait transport and its capability of reactivating the metabolism after this unfavorable period, offers chances for colonizing the opposite shore. Therefore, the propagation of the algae by hydrodynamic processes, without human intervention, cannot be ruled out.

Towards the declaration of the strait of Gibraltar as an environmental controlled area

The emissions from maritime transportation, both greenhouse gases and traditional pollutants, are harmful to the ecosystem and human health. The large quantities of these pollutants emitted by shipping in the Strait of Gibraltar could be reduced if the Strait was declared an Emission Control Area (ECA). Using the SENEM1 emissions model, this study aims to compare the current situation and a possible future situation as an ECA. Unlike other models, SENEM1 includes all the variables – both ship and external conditions - that influence the calculation of emissions. Comparing only the 2017 emissions from ships sailing in the Strait of Gibraltar with the designated ECA simulation, reductions of up to 75.8 % in NOx, 73.4 % in PM2.5 and 94 % in SOx were collected. It would be a wakeup call for the International Maritime Organization (IMO) and the governments responsible to recommend that the Strait of Gibraltar be designated an ECA zone.

Euryalida (Echinodermata, Ophiuroidea) from Northwest Africa

From 2004 to 2012, ten multidisciplinary oceanographic surveys were conducted along the coast of Northwest Africa, between the Strait of Gibraltar and the northern border of Sierra Leone. A total of five species of Euryalida Lamarck, 1816 belonging to three families were captured at 29 of the 1298 stations sampled in the area. Among them, Astrodendrum juancarlosi sp. nov. is described and figured in this paper. Ophiocreas oedipus Lyman, 1879 is recorded for the first time on West African continental margin and Gorgonocephalus pustulatum (H.L. Clark, 1916), an Indo-Pacific species only known from South African coast in the Atlantic, is reported off Guinea-Bissau, greatly extending to the North its Atlantic distribution. In addition, Asteroschema inornatum Koehler, 1906, a northeast Atlantic species, is recorded for the first time in African waters, off Western Sahara, extending its range of distribution to the south. Our data also extend the bathymetric distribution of A. inornatum to shallower waters and of G. pustulatum to deeper waters. The association of some euryalids with certain species of pennatulaceans and gorgonians is also described.

The species Dyschirius (Dyschiriodes) heydeni Fleischer, 1899 (Coleoptera: Carabidae) at both sides of the Strait of Gibraltar: update of its taxonomy, chorology and autoecology, with description of a new subspecies

Summary We report the first records of Dyschirius (Dyschiriodes) heydeni Fleischer, 1899 for the Iberian Peninsula. After comparative study of North African collection material, a new subspecies is proposed for Iberian populations: Dyschirius (Dyschiriodes) heydeni transcolumnalis n. ssp. We provide (re)descriptions and diagnoses of D. heydeni and its two subspecies, an update of the distribution range of the species and discussion on its autoecology. In addition, we assessed published data on the resembling species Dyschirius (Eudyschirius) globosus Herbst, 1784 in North Africa, and concluded that they result from incorrect identifications of D. heydeni. Reasons and implications of this finding are discussed.

Effects of environmental factors on the historical time serie of blackspot seabream commercial landings (1983 to 2015) in the strait of Gibraltar: A shared marine resource between the Spanish and Moroccan fleets

Effects of environmental factors on the historical time serie of blackspot seabream commercial landings (1983 to 2015) in the strait of Gibraltar: A shared marine resource between the Spanish and Moroccan fleets

Temporal and spatial variability in population traits of an intertidal fucoid reveals local-scale climatic refugia

Global change is imposing significant losses in the functional traits of marine organisms. Although areas of climatic refugia ameliorate local conditions and help them to persist, the extent to which mesoscale effects contribute for intraregional variability on population traits and conservation is uncertain. Here we assess patterns of conservation status of Fucus guiryi, the main intertidal habitat-forming seaweed in the Strait of Gibraltar (southern Spain and northern Morocco). We investigated the demography, reproductive phenology, and morphology at northern and southern side populations. Population traits were compared seasonally within populations from each side, and at spatial scale in early summer 2019. In the last decade three populations became extinct; two marginal populations had dispersed individuals with a narrower fertility season and miniaturized individuals below 3 cm; and five populations showed variable density and cover with more than 20% of reproductive individuals over the seasons. Highest density, cover, morphology, and reproductive potential was detected at one population from each side, suggesting local-scale climatic refugia in upwelling areas located inside marine protected areas. Southern recruits were more warm-tolerant but grew less at colder conditions than northern ones, revealing a mesoscale heterogeneity in thermal affinities. This study evidenced functional losses and distinct reproductive strategies experienced by F. guiryi at peripheral locations and urges to prioritize its conservation and restoration at contemporary climatic refugia.

Implication of middle Eocene to early Miocene ostracodes from the N. El Faras-1X Well, Qattara Depression, Egypt, for paleobathymetry and paleobiogeographic reconstruction

The subsurface middle Eocene - early Miocene succession in the N. El Faras - 1X Well, drilled in the Qattara Depression at the northern part of the Western Desert, Egypt (Southern Tethyan Province, STP), was studied for its ostracode content to infer changes in paleobathymetry as well as paleobiogeographic reconstructions. This succession is composed mainly of three lithostratigraphic units, as the upper part of the Apollonia Formation (middle to late Eocene), the Dabaa Formation (late Eocene and Oligocene) and the lower part of the Moghra Formation (early Miocene). The stratigraphical distribution, paleoenvironmental and paleobiogeographical significance of the ostracode faunas from the Oligocene interval of the study area are documented for the first time. Fifty seven ostracode species belonging to 36 genera were identified in this succession. Among them, two new species were described. The vertical distribution of these ostracode species enabled the recognition of seven local biozones. Qualitative and quantitative statistical analysis of ostracode associations revealed a depositional depth ranging from the inner to outer neritic setting. Considering the CONISS cluster analysis, six ecozones were established. During the middle and late Eocene, the paleobiogeographical affinities of the Egyptian ostracodes from N. El Faras-1X× Well succession with that of the Southern Tethyan countries suggest a direct connection between Egypt and the countries of the Southern Tethyan Province. This connection facilitated the dispersal and exchange within this province. The low ostracode similarity between the STP and the Northern Tethyan Province (NTP) suggests a slight connection and exchange between them. The in common occurrence of these ostracodes with that of Somalia is attributed to the connection between the STP and Somalia via the Tethyan Seaway, which facilitated the dispersal and exchange of the middle Eocene ostracodes. The similarity between the Egyptian ostracodes (STP) and that of South America and the Caribbean Sub-Province indicates a direct connection between those provinces across the Gibraltar Strait and through the North Equatorial Oceanic Water Current during that time. During the Oligocene, the low ostracode similarity between the STP and the NTP may be attributed to a more or less restricted connection. Also, the low similarity indicates a continuation of the mild connection between the STP and the South America and Caribbean Sub-Province across the Gibraltar Strait and through the North Equatorial Current. During the early Miocene, the similarity of the recorded ostracodes of the STP with that of the NTP suggests a continuous connection between the two provinces. Also, there was a connection between the South America and Caribbean Sub-Province and the North American Province through the North Equatorial Current and the warm Gulf Stream within the Caribbean Sea.

Geology and stratigraphy of the Neogene section along the Oued Beth between Dar bel Hamri and El Kansera (Rharb Basin, northwestern Morocco) and its otolith-based fish fauna: a faunal inventory for the Early Pliocene remigration into the Mediterranean

The coquina on the banks of the Oued Beth in the Rharb Basin in northwestern Morocco has long been known to be exceptionally rich in fossils. The stratigraphic position ranging from the Late Miocene to the Pliocene has been controversial, however. In the course of my master’s degree field work in 1975/76, I mapped the right bank of the Oued Beth from Dar bel Hamri to El Kansera. Following multiple recent studies in the general region, I here review my results and present an updated comprehensive stratigraphic and geologic frame for the first time. The coquina near Dar bel Hamri is interpreted to be of Early Pliocene age, possibly containing some reworking of Late Miocene fossils. The coquina and other locations along the Oued Beth have yielded a rich otolith assemblage, which is described in this article. It represents the first fossil otolith-based fish fauna described from Northwest Africa and contains 96 species, 16 of which are new. The new species in the order of their description are Diaphus maghrebensis n. sp., Ophidion tuseti n. sp., Centroberyx vonderhochti n. sp., Myripristis ouarredi n. sp., Deltentosteus planus n. sp., Caranx rharbensis n. sp., Trachurus insectus n. sp., Parapristipoma bethensis n. sp., Pomadasys zemmourensis n. sp., Cepola lombartei n. sp., Trachinus maroccanus n. sp., Trachinus wernlii n. sp., Uranoscopus hoedemakersi n. sp., Uranoscopus vanhinsberghi n. sp., Spondyliosoma tingitana n. sp., and Opsodentex mordax n. sp. In addition, a new species is described from the Tortonian and Zanclean of Italy: Rhynchoconger carnevalei n. sp. Some additional otoliths are described from another Northwest Moroccan location of Early Pliocene age near Asilah, 50 km south of the Strait of Gibraltar. The Early Pliocene fish fauna from Dar bel Hamri in the Rharb Basin is also of interest, because it constitutes the nearest Atlantic fauna of the time of the reconnection of the Mediterranean with the Atlantic and may have acted as a hosting area for the remigration of fishes into the Mediterranean. Indeed, the correlation is high between the Northwest Moroccan and the well-known time-equivalent Mediterranean fish fauna, but the Moroccan fauna also contains a good proportion of putative endemic taxa and taxa with tropical West African affinities that apparently did not migrate into the Mediterranean. Thus, the Early Pliocene fish fauna from the Rharb Basin represents a unique assemblage for which I propose the biogeographic term “Maghrebian bioprovince.”

Land-sea linkages on the Algerian Margin over the last 14 kyrs BP: Climate variability at orbital to centennial timescales

Past and present environmental conditions over the Holocene along the Algerian coast involve complex atmosphere-hydrosphere-biosphere interactions and anthropogenic activities on adjacent watersheds. Atlantic Ocean surface waters entering the western Mediterranean Sea at the Gibraltar Strait create the Algerian Current, which flows along the North African coast in a succession of strong and large-scale eddies. Deep-water upwelling plumes are other recurrent hydrological features of the Algerian margin affecting regional environmental features. However, vegetation and paleohydrological changes that have occurred over the Holocene have not yet been described. To bridge this gap, a suite of paleoclimate proxies was analysed in marine core MD04–2801 (2067 m water depth) at a secular-scale resolution over the last 14 kyrs BP. Terrestrial (pollen grains) and marine (dinoflagellate cysts or dinocysts) palynological assemblages, as well as sedimentological (grain-size analysis and XRD-based quantitative analysis of clay minerals) and biomarkers (alkenones and n-alkanes), were determined to explore the links between past sea surface hydrological conditions and regional environmental changes on nearby watersheds.The over-representation of heterotrophic dinocyst taxa (Brigantedinium spp.) indicates strong planktonic productivity in the study area. Results shows that the links between dryness on land and surface hydrological conditions are expressed by: (i) recurrent upwelling cells during the relatively dry climate conditions of the Younger Dryas (12.7 to 11.7 ka BP), the Early Holocene (11.7 to 8.2 ka BP) and from 6 ka BP onwards, (ii) enhanced fluvial discharges between 8.2 and 6 ka BP during the African Humid Period concomitant with the colonization of coastal lands by Mediterranean forest. Middle to Late Holocene transition around 4.2 ka BP characterizes by the intense event reffered to here as the Algerian Mega Drought (4.3 to 3.9 ka BP).

Baseline genetic distinctiveness supports structured populations of thornback ray in the Mediterranean Sea

Abstract The thornback ray (Raja clavata) is the most important chondrichthyan in terms of landings in the Mediterranean Sea. Intense harvesting may induce negative genetic effects reducing the resilience of overfished species. For this reason, genetic diversity information should be considered in fisheries management and conservation policies. Microsatellite markers were used to unravel the genetic features (variability, connectivity, sex‐biased dispersal) of R. clavata populations, both at the small (around the coast of Sardinia, western Mediterranean Sea) and larger spatial scales (at the pan‐Mediterranean level, and between the Atlantic Ocean and the Mediterranean Sea). Individual clustering, multivariate and variance analyses rejected the hypothesis of genetic homogeneity, with significant genetic differences between Mediterranean and Atlantic rays, as well as within the Mediterranean Sea between its western and eastern basins. The data indicated that both the Strait of Gibraltar and the Sicilian Channel seem to be effective in limiting the dispersal of thornback ray individuals, but a further structuring was identified, with the significant genetic differentiation of the populations located in the Algero‐Provençal and Tyrrhenian basins. Such a fine‐scale arrangement suggests the occurrence of additional barriers to species dispersal. A lack of significant genetic differentiation, stable over the years, was measured at a local scale among R. clavata Sardinian samples. Several possible mechanisms, both biological and abiotic (e.g. migratory behaviour, waterfronts and oceanographic discontinuities), are discussed. Overall, the genetic data presented, both at the local and regional level, could represent the baseline information for the temporal monitoring of populations and assessing the effects of present or future fisheries‐related management actions. The data obtained are information of paramount importance for minimizing the gaps in our current knowledge of the genetic diversity of thornback rays and maximizing the information needed for the correct protection of R. clavata populations.

Potential of TROPOMI for understanding spatio-temporal variations in surface NO2 and their dependencies upon land use over the Iberian Peninsula

Abstract. In orbit since late 2017, the Tropospheric Monitoring Instrument (TROPOMI) is offering new outstanding opportunities for better understanding the emission and fate of nitrogen dioxide (NO2) pollution in the troposphere. In this study, we provide a comprehensive analysis of the spatio-temporal variability of TROPOMI NO2 tropospheric columns (TrC-NO2) over the Iberian Peninsula during 2018–2021, considering the recently developed Product Algorithm Laboratory (PAL) product. We complement our analysis with estimates of NOx anthropogenic and natural soil emissions. Closely related to cloud cover, the data availability of TROPOMI observations ranges from 30 %–45 % during April and November to 70 %–80 % during summertime, with strong variations between northern and southern Spain. Strongest TrC-NO2 hotspots are located over Madrid and Barcelona, while TrC-NO2 enhancements are also observed along international maritime routes close the strait of Gibraltar, and to a lesser extent along specific major highways. TROPOMI TrC-NO2 appear reasonably well correlated with collocated surface NO2 mixing ratios, with correlations around 0.7–0.8 depending on the averaging time. We investigate the changes of weekly and monthly variability of TROPOMI TrC-NO2 depending on the urban cover fraction. Weekly profiles show a reduction of TrC-NO2 during the weekend ranging from −10 % to −40 % from least to most urbanized areas, in reasonable agreement with surface NO2. In the largest agglomerations like Madrid or Barcelona, this weekend effect peaks not in the city center but in specific suburban areas/cities, suggesting a larger relative contribution of commuting to total NOx anthropogenic emissions. The TROPOMI TrC-NO2 monthly variability also strongly varies with the level of urbanization, with monthly differences relative to annual mean ranging from −40 % in summer to +60 % in winter in the most urbanized areas, and from −10 % to +20 % in the least urbanized areas. When focusing on agricultural areas, TROPOMI observations depict an enhancement in June–July that could come from natural soil NO emissions. Some specific analysis of surface NO2 observations in Madrid show that the relatively sharp NO2 minimum used to occur in August (drop of road transport during holidays) has now evolved into a much broader minimum partly de-coupled from the observed local road traffic counting; this change started in 2018, thus before the COVID-19 outbreak. Over 2019–2021, a reasonable consistency of the inter-annual variability of NO2 is also found between both datasets. Our study illustrates the strong potential of TROPOMI TrC-NO2 observations for complementing the existing surface NO2 monitoring stations, especially in the poorly covered rural and maritime areas where NOx can play a key role, notably for the production of tropospheric O3.

Italian and German Submarine Passage of the Straits of Gibraltar in the Second World War

Italian and German Submarine Passage of the Straits of Gibraltar in the Second World War

Diversified pottery use across 5th and 4th millennium cal BC Neolithic coastal communities along the Strait of Gibraltar

Diversified pottery use across 5th and 4th millennium cal BC Neolithic coastal communities along the Strait of Gibraltar

How tiny species can be overlooked: the finding of Eudendrium capillaroides (Cnidaria, Hydrozoa) in the Strait of Gibraltar

Eudendrium capillaroides Schuchert, 2008 has not been reported since its original description. The new and abundant material found in Ceuta, southern coast of the Strait of Gibraltar, allows us to refine the morphological diagnosis of this species. Eudendrium capillaroides is characterized by small monosiphonic colonies, a dense ring at the base of the hydranth, and it seems to have a preference for growing on other hydroids. Male gonophores on atrophied polyps, two-chambered (occasionally one chamber), and female gonophores on reduced polyps in the initial stages of development but hydrants later completely atrophied. Nematocysts are heterotrichous microbasic euryteles of two size classes, a larger size densely distributed in a band on the hydrant body basally and a smaller size abundant mainly on the tentacles. Furthermore, we carried out molecular analyses to assess the status of E. capillaroides and its most similar congener E. capillare within the genus Eudendrium. The use of few morphological characters or incomplete descriptions may thus lead to an incorrect wide distribution of a nominal species that actually represents a species complex. This can particularly be the case in less conspicuous species, such as many hydroids, where the degree of diversity might be underestimated. The accurate description of tiny, inconspicuous and/or cryptic species is important in order to better estimate global marine diversity as well as to understand marine communities and the relationships between their components.