Between March-May 2013 a massive Salpa maxima bloom was recorded by a citizen science study along the Ionian and Adriatic coast of the Salento peninsula (Italy). Citizen records were substantiated with field inspections along the coast and during an oceanographic campaign in the Otranto Channel. Salps clogged nets, impairing fishing activities along the coast. Swimmers were scared by the gelatinous appearance of the salps, and thought they were jellyfish. At the end of the bloom the dead bodies of the colonies, that were up to 6-7 m long, were accumulated along the coast and stirred by the waves, forming foams along dozens of kilometers of coast. The bloom also occurred at the Tremiti Islands, north of the Gargano Peninsula. The possible impacts of such events on the  functioning of pelagic systems are discussed.

The evolution of the upper water column in the Mediterranean Sea during more than 60 years is reconstructed in terms of few parameters describing the mixed layer and the seasonal thermocline. The analysis covers the period 1945–2011 using data from three public sources: MEDAR-MEDATLAS, World Ocean Database, MFS-VOS program. Five procedures for estimating the mixed layer depth are described, discussed and compared using the 20-year long time series of temperature profiles of the DYFAMED station in the Ligurian Sea. On this basis the so-called three segments profile model (which approximates the upper water column with three segments representing mixed layer, thermocline and deep layer) has been selected for a systematic analysis at Mediterranean scale. A widespread increase of the thickness and temperature of the mixed layer, increase of the depth and decrease of the temperature of the thermocline base have been observed in summer and autumn during the recent decades. It is shown that positive temperature extremes of the mixed layer and of its thickness are potential drivers of the mass mortalities of benthic invertebrates documented since 1983. Hotspots of mixed layer anomalies have been also identified. These results refine previous analyses showing that ongoing and future warming of upper Mediterranean is likely to increase mass mortalities by producing environmental conditions beyond the limit of tolerance of some benthic species.

Several hydroid species live associated with many organisms, including bacteria. Hydroid-bacteria associations were searched for in twenty Hydrozoa species that were collected in the northern Ionian Sea and observed under blue light excitation. Of these, six showed high fluorescence on the outer perisarc, five appeared medium fluorescent, four were slightly fluorescent, and five did not show any fluorescence. Luminous bacteria were isolated and counted from the surface of the fluorescent hydroids. Their association with hydrozoan species could be explained by their feeding activity on the chitinous structures of the perisarc, as previous research on the hydroid Aglaophenia octodonta showed. Moreover, microalgae were always recovered together with luminous bacteria in the strongly, medium and slightly fluorescent hydroids. Further studies will be undertaken to characterize the luminous bacteria isolated from the surface of the examined hydrozoans as well as to better understand whether their interaction with hydroids is only related to chitin utilization or if their coexistence with microalgae in hydrozoans has an ecological meaning.

A previously unknown association between a luminous Vibrio sp., taxonomically related to the species Vibrio harveyi and a common member of the shallow/mid water communities of the Mediterranean Sea, the hydrozoan Clytia linearis is described. All the specimens of C. linearis observed under blue light excitation showed both a natural luminescence appearing as a series of fine dots due to clytin, and a clear fluorescence on the external side of the perisarc around the colonies due to the presence of luminous bacteria. Luminous bacteria were isolated from the surface of C. linearis, their phenotypic characterization as isolates was performed by several morphological, biochemical, and cultural tests, completed with 16S rDNA sequence analysis. All the isolates were referred to a Vibrio sp. taxonomically related to V. harveyi. The association of the V. harveyi-related species with C. linearis, as already suggested for another hydroid, Aglaophenia octodonta, could be explained with the activity of these bacteria of feeding on the chitinous structures present in these hydroids. Moreover, the adhesion of the luminous bacterium (here referred to as Vibrio sp. CL1) on C. linearis may contribute to the survival of this Vibrio species in the marine environment providing a suitable growth habitat.

The biodiversity of the Santa Maria di Leuca (SML) coral bank is summarized and its description is updated using data collected by means of underwater video systems, benthic samplers and fishing gears. A total of 222 living species have been recorded within the coral bank area in the depth range 280-1121 m. The most abundant benthic taxa recorded are Porifera (36 species) followed by Mollusca (35) and Cnidaria (31). The scleractinian corals Madrepora oculata and Lophelia pertusa are the main colonial species in the structure of the SML bank. Annelida, Crustacea and Bryozoa have been found with 24, 23 and 19 species, respectively. A total of 40 species of demersal fish have been recorded. Other faunal taxa were found with small numbers of species. One hundred and thirty-five species are new for the SML bank, 31 of which represent new records for the north-western Ionian Sea (2 Porifera, 17 Cnidaria, 1 Mollusca, 3 Annelida, 2 Crustacea, 4 Bryozoa and 4 Echinodermata). The finding of the annelid Harrnothoe vesiculosa represents the first record for the Mediterranean Sea. The SML coral bank represents a biodiversity "hot-spot" on the bathyal bottoms of the Mediterranean Sea.

Abstract This volume contains the main results of the EC FP7 “The Ocean of Tomorrow” Project CoCoNet, divided in two sections: 1) a set of guidelines to design networks of Marine Protected Areas in the Mediterranean and the Black Seas; 2) a smart wind chart that will allow evaluating the possibility of installing Offshore Wind Farms in both seas. The concept of Cells of Ecosystem Functioning, based on connectivity, is introduced to define natural units of management and conservation. The definition of Good Environmental Status, as defined in the Marine Strategy Framework Directive, is fully embraced to set the objectives of the project, by adopting a holistic approach that integrates a full set of disciplines, ranging from physics to bio-ecology, economics, engineering and many sub-disciplines. The CoCoNet Consortium involved scientist sfrom 22 states, based in Africa, Asia, and Europe, contributing to build a coherent scientific community.

The patchy distribution pattern of benthic hydrozoans reflects high sensitivity of colonies to local and micro-scale environmental factors, which may affect the outcome of biodiversity inventories based on different sampling methodologies. We compared three quantitative sampling methods for benthic hydrozoans, differing for strategy (scraping standardized surfaces or picking visually located colonies) and tactics (extension of examined surface). Each of the three methods consisted of eight replicate samplings to compare relative and absolute method efficiencies, also in terms of minimum sampling area representative of the hydroid diversity in the study site. A single horizontal belt transect on a vertical rocky cliff was chosen at 15 m depth near Otranto (South Adriatic). A total of 37 species were identified by the three methods and their relative abundances were evaluated. The hydroid assemblage was dominated by generalist species with high polyp numbers able to colonize different substrata. We compared the outcomes of each of the three sampling methods, and by a cost-benefit analysis we identified the optimal sampling methods to be adopted according to the different targets of the investigations. On data standardized to the same total sampled areas, the three sampling methods did not originate significant differences in the number of polyps of each recorded species (PDA, Polyp Detection Ability), whereas the visually-oriented collection (VIS) and the scrapings over 20 × 20 cm standard surfaces (S20) were more effective in the detected number of species (SDA, Species Detection Ability) than over 10 × 10 cm squares (S10). For ecological purposes, samplings based on five S20 replicates can be considered an appropriate experimental design to get a statistically robust representation of the studied hydroid assemblage at Punta Palascia. However, variation in depth, exposure and geographical locations may require different sampling approaches, and pre-surveys should be always carried out before addressing taxonomical surveys of sessile organisms.

Jellyfish outbreaks are increasingly viewed as a deterministic response to escalating levels of environmental degradation and climate extremes. However, a comprehensive understanding of the influence of deterministic drivers and stochastic environmental variations favouring population renewal processes has remained elusive. This study quantifies the deterministic and stochastic components of environmental change that lead to outbreaks of the jellyfish Pelagia noctiluca in the Mediterranen Sea. Using data of jellyfish abundance collected at 241 sites along the Catalan coast from 2007 to 2010 we: (1) tested hypotheses about the influence of time-varying and spatial predictors of jellyfish outbreaks; (2) evaluated the relative importance of stochastic vs. deterministic forcing of outbreaks through the environmental bootstrap method; and (3) quantified return times of extreme events. Outbreaks were common in May and June and less likely in other summer months, which resulted in a negative relationship between outbreaks and SST. Cross- and along-shore advection by geostrophic flow were important concentrating forces of jellyfish, but most outbreaks occurred in the proximity of two canyons in the northern part of the study area. This result supported the recent hypothesis that canyons can funnel P. noctiluca blooms towards shore during upwelling. This can be a general, yet unappreciated mechanism leading to outbreaks of holoplanktonic jellyfish species. The environmental bootstrap indicated that stochastic environmental fluctuations have negligible effects on return times of outbreaks. Our analysis emphasized the importance of deterministic processes leading to jellyfish outbreaks compared to the stochastic component of environmental variation. A better understanding of how environmental drivers affect demographic and population processes in jellyfish species will increase the ability to anticipate jellyfish outbreaks in the future.

Surface-dwelling colonies ofVelella velellaoccur throughout tropical to cold-temperate oceans of the world and some-times are stranded in masses along hundreds of kilometers of beaches. Large-scale blooms in the WesternMediterranean Sea in 2013 and 2014 allowed the study of diet, prey digestion times and predation rates. Gastrozooidcontent analyses showed that 59% of the 769 identified prey were euphausiid larvae (calytopsis and furcilia) capturedat night. Copepods (41%), fish eggs (2.2%) and larvae (0.5%) were captured both at day and night. Digestion times atambient temperature (178C) of calytopsis, furcilia and copepods were estimated to be.6.5, 4.4 and 3.9 h, respect-ively. Estimated prey consumption was substantially lower in 2014 than in 2013 (41 vs. 75 prey day21colony21).Velella velellaand other gelatinous species bloomed in the Mediterranean Sea and the northeastern Atlantic and Pacificoceans in 2013 and 2014. Because of the wide distribution ofV. velellacolonies, their mass occurrences, potential im-portance as predators and competitors of fish, additional production from symbiotic zooxanthellae and stranding onbeaches, they could be important in open-ocean carbon cycling and in transport of pelagic production to landmasses.

Human activities determine dramatic changes in natural systems, especially in marine coastal areas. This is especially true when economic development is fast and scarcely regulated, representing a serious threat to biodiversity. Besides the obvious prediction of impairment of natural systems, forecasting the effects of human activities can be particularly challenging since they affect species and assemblages, the patterns of distribution and extent of which are often totally unknown. In Vlora Bay, we show through an interdisciplinary project that 15 y of coastal development can result in a loss of over 50% of seagrass cover and a decline in macroalgae cover such as Cystoseira spp., which are structurally and functionally crucial habitats that provide essential goods and services for local human communities and recreation. Furthermore, illegal fishery practices (date mussel fishery, trawling, and use of explosives) contribute to depict a scenario of fragmentation and loss of shallow species-rich assemblages. Large-scale changes in sedimentation patterns have been recognised as one of the main drivers of those changes. This model of development, associated with nearly irreversible environmental consequences, as observed in Albania, can serve as an example for many other Mediterranean areas, showing a combination of high biodiversity and low protection regime. We discuss the urgent need for ecosystem-based management to ensure sustainable development while conserving and managing natural biodiversity and resources.

Genetic drift and non-random mating seldom influence species with large breeding populations and high dispersal potential, characterized by unstructured gene pool and panmixia at a scale lower than the minimum dispersal range of individuals. In the present study, a set of nine microsatellite markers was developed and used to investigate the spatio-temporal genetic patterns of the holoplanktonic jellyfish Pelagia noctiluca (Scyphozoa) in the Southern Tyrrhenian Sea. Homozygote excess was detected at eight loci, and individuals exhibited intra-population relatedness higher than expected by chance in at least three samples. This result was supported by the presence of siblings in at least 5 out 8 samples, 4 of which contained full-sib in addition to half-sib dyads. Having tested and ruled out alternative explanations as null alleles, our results suggest the influence of reproductive and behavioural features in shaping the genetic structure of P. noctiluca, as outcomes of population genetics analyses pointed out. Indeed, the genetic differentiation among populations was globally small but highlighted: a) a spatial genetic patchiness uncorrelated with distance between sampling locations, and b) a significant genetic heterogeneity between samples collected in the same locations in different years. Therefore, despite its extreme dispersal potential, P. noctiluca does not maintain a single homogenous population, but rather these jellyfish appear to have intra-bloom localized recruitment and/or individual cohesiveness, whereby siblings more likely swarm together as a single group and remain close after spawning events. These findings provide the first evidence of family structures and consequent genetic patchiness in a species with highly dispersive potential throughout its whole life cycle, contributing to understanding the patterns of dispersal and connectivity in marine environments.

Articolo su invito a seguito del conferimento del titolo di Outstanding Faculty Member of the Year di Faculty of 1000

The origin of multicellular animals and how multicellularity evolved is one of those difficult and delicate biological problems that has been pondered over for centuries. This book attempts to summarize some of the more recent results in phylogenetics and developmental biology that address the evolution of key innovations in metazoans. The book has three main sections. The first section contains five chapters that address the phylogenetic issues involving this part of the tree of life. Even though modern genome technology has made it possible to study these issues using a vast information database the elucidation of the relationships in this part of the tree of life continues to be elusive. The second section of the book addresses some of the more prominent questions concerning the developmental biology of metazoan evolution. The topics in this section focus on nervous system development, sensory organ development and developmental systems. The third section of the book focuses on the evolution of pattern and process in the incredible forms of life that we call Metazoa. The topics covered in this part of the book include the evolution of life histories, ecological associations and the evolution of biogeochmical aspects of metazoa. The book has over 40 illustrations and an up to date bibliography of over 500 references. Each chapter concludes with a set of questions for study and discussion to assist instructors and students in delving more deeply into the topics covered by the seventeen chapters in the book. Table of Contents Introduction: A Phylogenomic Journey Through the Animal Tree of Life: Key Innovations in the Evolution of Metazoa; B. Schierwater and R. DeSalle Tangled Roots in the Animal Tree of Life Putting Animals in their Place Within a Context of Eukaryotic Innovations; D. Vazquez, L. Wegener Parfrey and L.A. Katz Elucidating Animal Phylogeny: Advances in Knowledge and Forthcoming Challenges; K.M. Kocot, J.T. Cannon and K.M. Halanych Key Transitions in Animal Evolution: a Mitochondrial DNA Perspective; D.V. Lavrov Pending Issues in Development and Phylogeny of Arthropods; J.S. Deutsch The Earliest Animals: From Genes to Transitions The Pre-nervous System and Beyond—Poriferan Milestones in the Early Evolution of the Metazoan Nervous System; M. Nickel A Key Innovation in Evolution, the Emergence of Neurogenesis: Cellular and Molecular Cues from Cnidarian Nervous Systems; B. Galliot, M. Quiquand, M. Miljkovic-Licina and S. Chera From Cnidaria to "Higher Metazoa" in One Step; F. Boero and S. Piraino Basal Metazoan Sensory Evolution; D.K. Jacobs, D.A. Gold, N. Nakanishi, D. Yuan, A. Camara, S.A. Nichols and V. Hartenstein Cnidarian Gene Expression Patterns and the Origins of Bilaterality—Are Cnidarians Reading the Same Game Plan as "Higher" Animals?; E.E. Ball, D.M. de Jong, B. Schierwater, C. Shinzato, D.C. Hayward and D.J. Miller Key Transitions During Animal Phototransduction Evolution: Co-duplication as a Null Hypothesis for the Evolutionary Origins of Novel Traits; T.H. Oakley and D.C. Plachetzki Vertebrate Hox Genes and Specializations in Mammals; C. Kappen Pattern and Process at the Base of the Metazoan Tree of Life Field Biology of Placozoans (Trichoplax): Distribution, Diversity, Biotic Interactions; V. Buchsbaum Pearse and O. Voigt Trichoplax and Placozoa: One of the Crucial Keys to Understanding Metazoan Evolution; B. Schierwater et al. A Food’s-Eye View of Animal Transitions; N.W. Blackstone Lost in Transition: The Biogeochemical Context of Animal Origins; E. Gaidos Redefining Stem Cells and Assembling Germ Plasm: Key Transitions in the Evolution of the Germ Line; J. Srouji and C. Extavour Questions and Discussion

The positive impressions described in the European Landscape Convention (ELC) simply identify beauty defined as follows in a popular dictionary: ‘a combination of qualities, such as shape, colour, or form that pleases the aesthetic senses, especially the sight’. The ELC is centred on the way the culture of a population perceives and modifies nature, somehow ‘improving’ it with wise management. Protecting beautiful places, and managing the habitats of European Community importance, is a first step towards recognizing the significance of the marine environment, inviting science to design an approach to its management and protection that goes beyond the biases of the current ‘culture’. Marine Protected Areas (MPAs) have been instituted to protect biodiversity and to enhance ecosystem functioning, and so adhere, at least in theory, to all the specifications of Good Environmental Status (GES). The assessment of the efficacy of MPA management should consider the attainment of GES

Satellite data show a steady increase, in the last decades, of the surface temperature (upper few millimetres of the water surface) of the Mediterranean Sea. Reports of mass mortalities of benthic marine invertebrates increased in the same period. Some local studies interpreted the two phenomena in a cause-effect fashion. However, a basin-wide picture of temperature changes combined with a systematic assessment on invertebrate mass mortalities was still lacking. Both the thermal structure of the water column in the Mediterranean Sea over the period 1945-2011 and all documented invertebrate mass mortality events in the basin are analysed to ascertain if: 1- documented mass mortalities occurred under conditions of positive temperature trends at basin scale, and 2- atypical thermal conditions were registered at the smaller spatial and temporal scale of mass mortality events. The thermal structure of the shallow water column over the last 67 years was reconstructed using data from three public sources: MEDAR-MEDATLAS, World Ocean Database, MFS-VOS programme. A review of the mass mortality events of benthic invertebrates at Mediterranean scale was also carried out. The analysis of in situ temperature profiles shows that the Mediterranean Sea changed in a non-homogeneous fashion. The frequency of mass mortalities is increasing. The areas subjected to these events correspond to positive thermal anomalies. Statistically significant temperature trends in the upper layers of the Mediterranean Sea show an increase of up to 0.07°C/yr for a large fraction of the basin. Mass mortalities are consistent with both the temperature increase at basin scale and the thermal changes at local scale, up to 5.2°C. Our research supports the existence of a causal link between positive thermal anomalies and observed invertebrate mass mortalities in the Mediterranean Sea, invoking focused mitigation initiatives in sensitive areas.

The aim of the present study was to determine the epidemiology of jellyfish stings in the Province of Lecce (Italy) in the bathing seasons of years 2007-2011, in order to estimate the presence of these organisms along the coast of the Salento and assess its socio-health implications. The study involved the gathering and processing of data on patients seeking medical treatment at summer first aid centres and hospitals along the coast of the Salento following contact with jellyfish. The analysis of reports showed that in the period 2007-2011 1733 stung bathers sought medical assistance, accounting for 3% of all medical services provided at first aid centres. In addition, jellyfish stings were observed to be the main cause of human pathologies arising from contact with marine organisms. 25.7% of total cases were reported in summer 2007, 22.5% in 2008, 24.7% in 2009, 17.6% in 2010 and 9.5% in 2011. The spatial distribution indicates a greater frequency of stings sustained along the Adriatic coast (65%); this trend is related to wind direction. Most of the injuries were seen in persons aged between 1 and 10. In the majority of cases the symptoms were not severe, being confined to local and cutaneous reactions. In 8.7% of cases however, there were complications, mainly allergic reactions (6.2%). The main drugs used are corticosteroids, locally applied and systemic (46% and 43%, respectively), while non-pharmacological treatments mainly consisted of rinsing with ammonia (74%). In the five-year period under study, an average of 8.1 cases/km of coastline was recorded, ranging from a maximum of 18.4 cases/km along the Adriatic coast to a minimum of 2.6 cases/km on the Lower Ionian, with an estimated cost of the health services provided of about 391,658 Euros. Overall, a slightly decreasing trend of jellyfish stings was observed from 2007 to 2011 along the coasts of Salento. Nevertheless, in the light of the significant economic costs and the socio-health impact reported in this study and given the importance of the bathing tourism in the Salento, there is a need to identify suitable strategies that will guarantee the best response in terms of both prevention and treatment.

Hydroids, one of the dominant components of the zoobenthic communities, share comparable growth patterns with higher plants because of their modular body organization, high potential of asexual reproduction, and phenotypic plasticity. These features, together with the ability to enter dormancy to overcome unfavorable conditions, make hydroids successful organisms adaptable to a wide range of environmental scenarios. Depending on their wide range of shapes and sizes, hydroids form three-dimensional forests at different dimensional scales, establishing both trophic and non-trophic relationships with several other organisms, from virus to vertebrates. Despite numerous researches conducted to study the hydroid ecology, the putative importance of hydroids in structuring zoobenthic communities is underestimated. Here, information available about hydroid ecology is summarized, in order to emphasize the role of hydroids as forest formers, as well as their function in the bentho-pelagic coupling.

The Mediterranean hydrozoan fauna (Siphonophora excluded) comprises 400 species; most (68%) occur in the Atlantic Ocean, 20% are endemic to the Mediterranean, 8% are of Indo-Pacific origin, and 4% are non-classifiable. There are 69 nonindigenous (NIS) species in the basin: 44% of these are casual (recorded just one or very few times), 28% established (widely recorded in the basin), 6% invasive (established NIS that are able rapidly or largely to dissemi- nate away from the area of initial introduction, having a noticeable impact on the recipient community), and 22% questionable (of doubtful taxonomic sta- tus). Entry through the Suez Canal and range expansion through the Gibraltar Strait, often enhanced by ship traffic, appear to be the main processes for recent species introductions, but uncertainties remain for many NIS. Species additions immediately result in larger local or regional species pools, but the newcomers might impact on populations of native species, altering extinction probabilities. A more reliable evaluation of the species pool can be accom- plished by adding new species when they enter the taxonomic record (i.e. the records of any taxon in all types of literature), and by removing species that have not been found for a ‘reasonable’ time (e.g. several decades). Of the 400 non-siphonophoran hydrozoan species known to occur in the Mediterranean Sea, positive records in the last 10 years are available for 156 species (39%), whereas records of the remaining 244 species are older than a decade: 67 spe- cies have not been recorded for 41 years, 13 for 31–30 years, 79 for 21– 30 years, and 85 for 11–20 years.

Stinging jellyfish outbreaks represent a health hazard, causing contact dermatitis and systemic reactions. This study investigated the epidemiology, severity, and treatment protocols of jellyfish stings in a coastal area with high tourist development and frequent stinging jellyfish outbreaks of the central Mediterranean (Salento, Southern Italy), and the associated costs for the Italian National Health Service. In 2007–2011, 1,733 bathers (mostly children and females) sought medical assistance following jellyfish stings, the main cause of human pathologies due to contact with marine organisms. The majority of events were reported in the years 2007–2009, whereas the occurrence of cnidarian jellyfish outbreaks has been increasingly reported in the same area since summer 2010. Most symptoms were limited to local and cutaneous reactions; conversely, 8.7% of cases evoked complications, mainly due to allergic reactions. The main drugs used were corticosteroids, locally applied and systemic (46% and 43%, respectively), and with ammonia (74%) as the main non-pharmacological treatment. The estimated cost of jellyfish-related first-aid services along the Salento coastline over the 5-year period was approximately 400,000 Euros. Therefore the management of jellyfish outbreak phenomena need coordinated research efforts towards a better understanding of underlying ecological mechanisms, together with the adoption of effective prevention policy, mitigation strategies, and appropriate planning of health services at tourist hot spots.

Representatives of gelatinous zooplankton are increasingly reported in large numbers, with more than 1000 species worldwide, including Cnidaria, Ctenophora and Thaliacea, often collectively known as “jellyfish”. • The reasons for increasing jellyfish blooms are probably manifold, ranging from local to global. Climate change and overfishing are global phenomena, and are good candidates as primary drivers of the rise of gelatinous zooplankton, at least in some parts of the ocean. • Current evidence suggests that sea warming is forcing temperate marine biota towards the poles, with tropicalization of temperate marine ecosystems due to community phase shifts. Climate change is also negatively affecting tropical communities, as exemplified by the increasing frequency of coral bleaching events. Gelatinous zooplankton appear to be expanding their distributions, as seen in the Mediterranean Sea with the increased presence of tropical species, likely favoured by both temperature increases and the progressive enlargement of the Suez Canal. • There is no evidence that temperature rises are threatening tropical jellyfish species, as they are with corals, but this might be due to current lack of observations. • Increases in temperature may broaden the reproductive periods of mid-latitude jellyfish, and improve winter survival of tropical species expanding to temperate waters, therefore boosting both alien and native outbreaks. • Increases in temperature at high latitudes might be detrimental for indigenous species, reducing their reproductive outputs. So far, limited increases in temperature at high latitudes do not support the proliferation of warm-water, non-indigenous species. • The resulting patterns should see a stable situation at low and high latitudes, with no tendency to gelatinous plankton blooms, whereas these phenomena should increase at mid-latitudes, but this speculation needs to be substantiated by focused studies.

In recent years, jellyfish blooms have attracted considerable scientific interest for their potential impacts on human activities and ecosystem functioning, with much attention paid to jellyfish as predators and to gelatinous biomass as a carbon sink. Other than qualitative data and observations, few studies have quantified direct predation of fish on jellyfish to clarify whether they may represent a seasonally abundant food source. Here we estimate predation frequency by the commercially valuable Mediterranean bogue, Boops boops on the mauve stinger jellyfish, Pelagia noctiluca, in the Strait of Messina (NE Sicily). A total of 1054 jellyfish were sampled throughout one year to quantify predation by B. boops from bite marks on partially eaten jellyfish and energy density of the jellyfish. Predation by B. boops in summer was almost twice that in winter, and they selectively fed according to medusa gender and body part. Calorimetric analysis and biochemical composition showed that female jellyfish gonads had significantly higher energy content than male gonads due to more lipids and that gonads had six-fold higher energy content than the somatic tissues due to higher lipid and protein concentrations. Energetically, jellyfish gonads represent a highly rewarding food source, largely available to B. boops throughout spring and summer. During the remainder of the year, when gonads were not very evident, fish predation switched towards less-selective foraging on the somatic gelatinous biomass. P. noctiluca, the most abundant jellyfish species in the Mediterranean Sea and a key planktonic predator, may represent not only a nuisance for human leisure activities and a source of mortality for fish eggs and larvae, but also an important resource for fish species of commercial value, such as B. boops.

In spite of considerable research effort on the “immortal jellyfish” Turritopsis dohrnii (Weismann, 1883), a comprehensive account including the ontogenetic stages throughout its normal life cycle is still missing. Here, we report the development of the medusa morph, with description of four consecutive stages distinguished by the morphology of the umbrellar apex and the number of marginal tentacles. Medusae reared at two different temperatures (14 and 25°C) showed identical morphological features, but with shorter developmental time at higher temperature. Additional information on the morphology of the polyp stage is also provided. The implications for an easy morphological identification of T. dohrnii medusae from other congeneric species are discussed.

Key messages  Marine ecosystem degradation involves the loss of benefits to society; it can occur as a result of natural causes or human activity.  Impacts of climate change, including ocean acidification, are inherently global. Widespread local activities can also have cumulative global effects. The many components of both kinds of impacts interact.  The rate of marine ecosystem degradation is accelerating due to economic growth and population growth.  Improved assessments of ecosystem state should be based on integrated, interdisciplinary observations that include biodiversity and ecosystem functioning.  Further international policy action is needed to reduce the drivers of marine degradation, improve marine literacy and develop a global approach to marine conservation.

Oceans and seas are essential components of the biosphere. Marine sustainability and human society are intrinsically interlinked. The oceans are crucial for global food security, human health and regulation of climate. The livelihoods of over 3 billion people worldwide depend upon services from marine and coastal biodiversity. Under the EU’s blue growth strategy, new marine goods and services, such as marine renewable energy, marine biotechnology and marine minerals, are seen as important sources of employment, economic security and sustainable development. Over the past 10 years there has been increasing focus on marine and maritime governance both within the European Union and beyond. The fundamental challenge that European policymakers must address is how to achieve a sustainable use of the oceans that ensures that marine goods and services are available for future generations, while meeting the demands of human population growth and economic growth.

Hydrozoa of the Mediterranean Sea are well known and a recent monograph covers 457 species. Mediterranean non-Siphonophoran Hydrozoa comprises 398 species, an increasing number due to continuous updates, representing about 10 % of the 3,702 currently valid species reported in a recent world assessment of hydrozoan diversity. Many new records are non indigenous species, previously described species that occurred elsewhere and whose arrival was presumably caused by human activities. However, many species reported in the past are not recorded in recent times. Realistic assessments of species pools require addition of new species, but also subtraction of species not found since a certain period. With the confidence of extinction index, cases of putative extinction can be raised. Out of the 398 known species, only 162 (41 %) have been reported in the last decade, while 53 (13 %) are not recorded in the literature since at least 41 years. According to the confidence of extinction index, 60 % of the 53 missing species are extinct, and 11 % are putatively extinct from the basin. From a biogeographical point of view, the missing species are: 34 % endemic, 19 % boreal, 15 % Mediterranean-Atlantic, 11 % Indo-Pacific, 11 % circumtropical, 4 % cosmopolitan, 2 % tropical-Atlantic, 4 % non-classifiable. Fluctuations in species composition into a certain area cause heavy variability in the expression of both structural and functional biodiversity. As consequence, the regional biodiversity should be analyzed through its temporal evolution, to detect changes and their possible causes. This approach has profound consequences on biodiversity assessments and also on the compilation of red lists.

The monograph reviews the recent trends in marine sciences and identifies research priorities that will characterize marine research in Europe in the next decade.

Thirty-eight nonindigenous marine species (NIS) (macroalgae, sponges, hydrozoans, molluscs, polychaetes, crustaceans, ascidiaceans and fish), are reported from the Apulian coast of Italy. Shipping, aquaculture and migration through the Suez Canal are the main pathways of introduction of the NIS. In Apulian waters, 21% of NIS are occasional, 18% are invasive and 61% are well-established. It is highly probable that more NIS will arrive from warm-water regions, because Mediterranean waters are warming. Furthermore, some of the successful NIS must have the ability to become dormant in order to survive adverse conditions, either seasonal or during long journeys in ballast waters. The identification of NIS depends greatly on the available taxonomic expertise; hence the paucity of taxonomists hinders our knowledge of NIS in our seas. We propose the creation and maintenance of a network of observatories across the Mediterranean to monitor the changes that take place along its coasts.

A bloom of an unknown semaestome jellyfish species was recorded in the North Adriatic Sea from September 2013 to early 2014. Morphological analysis of several specimens showed distinct differences from other known semaestome species in the Mediterranean Sea and unquestionably identified them as belonging to a new pelagiid species within genus Pelagia. The new species is morphologically distinct from P. noctiluca, currently the only recognized valid species in the genus, and from other doubtful Pelagia species recorded from other areas of the world. Molecular analyses of mitochondrial cytochrome c oxidase subunit I (COI) and nuclear 28S ribosomal DNA genes corroborate its specific distinction from P. noctiluca and other pelagiid taxa, supporting the monophyly of Pelagiidae. Thus, we describe Pelagia benovici sp. nov. Piraino, Aglieri, Scorrano & Boero.

Over recent decades, man’s expanding infl uence on the oceans has begun to cause change in some regions, including in the Mediterranean Sea. New proliferations of jellyfi sh may be occurring in the Mediterranean Sea, possibly in response to the cumulative effects of some of these anthropogenic impacts. In the Mediterranean Sea, many of these “proliferation events” are due to Pelagia noctiluca , an oceanic scyphozoan that has become very abundant along the coasts. Pelagia noctiluca is usually considered to be the most important jellyfi sh species in the Mediterranean Sea due to its widespread distribution, abundance, and ecological role and also because of its negative interaction with humans. Climatic conditions that favor enhanced reproduction by P. noctiluca and probably also determine optimal conditions for the formation of blooms are characterized by mild winters, low rainfall, high temperature, and high-atmospheric pressure. The Medusa Project in Catalonia aims to understand the spatiotemporal dynamics of the jellyfi sh populations in the NW Mediterranean Sea by undertaking daily sampling during summer (May to September) of 243 beaches, covering more than 500 km of coast. Data on beach strandings along the Spanish Catalan coast revealed that jellyfi sh occur in greatest concentrations along the northern Catalan coast and on beaches located close to marine canyons. The arrival of P. noctiluca to the coast depends fi rstly on the offshore production of jellyfi sh. Oceanographic structures like fronts, which enhance and maintain high levels of biological production and provide ideal conditions for feeding, growth, and reproduction of the jellyfi sh are present in the NW Mediterranean. The weakening of the front results in large numbers of P. noctiluca being driven into the coast by southeast winds. In the NW Mediterranean Sea P. noctiluca exert top-down control over a variety of prey including fi sh eggs and possibly the invasive ctenophore Mnemiopsis leidyi . P. noctiluca is also responsible for the majority of the stings incurred by bathers along the Catalan coast. Finally, we recommend that similar sampling programs should be done elsewhere to better understand changes in the distribution, abundance, and blooming patterns of dangerous jellyfi sh species.

The non-indigenous hydrozoan Clytia hummelincki, recorded for the first time in the Mediterranean Sea in 1996, has now become established on barren grounds where conditions of low diversity, high grazing pressure and low levels of competition occur. The mechanisms of persistence of this species, as well as its population dynamics in this habitat and in species-rich, algae-dominated shallow rocky communities were investigated in situ at four sampling sites in the Northern Ionian Sea from October 2012 to September 2014. Multivariate analyses were conducted to assess the differences in population dynamics of this species in both contrasting habitats. Clytia hummelincki reached peak abundance during summer, with numerous reproductive structures observed in August and September. A remarkable regression period was evident in the cold season, when colonies were largely reduced to dormant tissue in the coenosarc of the hydrorhiza and were often covered by encrusting algae. Both regeneration of colonies from resting hydrorhizae and recruitment of new planulae are involved in the maintenance of the populations. Colonies regrew from hydrorhizae less than half of the time. Population dynamics in sea-urchin barren grounds and algae-dominated communities did not differ significantly, suggesting that populations of this hydrozoan are now well established in the central Mediterranean Sea. This species is no longer confined to low diversity, highly grazed, low competition environments.

Fisheries exploitation has caused widespread declines in marine predators. Theory predicts that predator depletion will destabilise lower trophic levels, making natural communities more vulnerable to environmental perturbations. However, empirical evidence has been limited. Using a community matrix model, we empirically assessed trends in the stability of a multispecies coastal fish community over the course of predator depletion. Three indices of community stability (resistance, resilience and reactivity) revealed significantly decreasing stability concurrent with declining predator abundance. The trophically downgraded community exhibited weaker top-down control, leading to predator-release processes in lower trophic levels and increased susceptibility to perturbation. At the community level, our results suggest that high predator abundance acts as a stabilising force to the naturally stochastic and highly autocorrelated dynamics in low trophic species. These findings have important implications for the conservation and management of predators in marine ecosystems and provide empirical support for the theory of predatory control.

Investigations on sexual reproduction of jellyfish are essential to understanding mechanisms and patterns of outbreaks formation. Pelagia noctiluca (Forskål, 1775) (Scyphozoa) is known as the predominant jellyfish species with direct development in Western and Central Mediterranean Sea. In this paper we used integrated morphometric, histological, and biochemical approaches to investigate the annual reproductive biology of P. noctiluca from the Strait of Messina (South Thyrrenian Sea), a key proliferation area for this species due to favourable temperatures and high productivity. From November 2011 to September 2012, P. noctiluca sexual reproduction occurred throughout the year, with two seasonal peaks (autumn, spring) of spawning and embryonic development. Gonads of female P. noctiluca were characterized by a large amount of mature eggs of small size (diameter < 200 mm) during high food availability, whereas fewer, larger eggs (diameter > 200 mm) were detected during low availability of prey. Two morphometric indexes were applied: the Gonad-Somatic Index (GSI, gonadal/somatic tissue dry weight ratio) and Fecundity Index (FI, n eggs mm2 * gonadal dry weight). The FI showed longer spawning periods than the GSI, providing a better causal-mechanistic explanation for the year-round occurrence of P. noctiluca in the Strait of Messina. Protein contents of the gonads changed seasonally, with the highest concentrations during the pre-spawning periods. We suggest that investigations on jellyfish sexual reproduction can provide biological information relevant for understanding mechanisms of jellyfish blooms as well as for the management of coastal zones affected by outbreaks of gelatinous species.

Gelatinous plankton is formed by representatives of Cnidaria (true jellyfish), Ctenophora (comb jellies) and Tunicata (salps). The life cycles of gelatinous plankters are conducive to bloom events, with huge populations that are occasionally built up whenever conditions are favorable. Such events have been known since ancient times and are part of the normal functioning of the oceans. In the last decade, however, the media are reporting on an increasingly high number of gelatinous plankton blooms. The reasons for these reports is that thousands of tourists are stung, fisheries are harmed or even impaired by jellyfish that eat fish eggs and larvae, coastal plants are stopped by gelatinous masses. The scientific literature seldom reports on these events, so time is ripe to cope with this mismatch between what is happening and what is being studied. Fisheries scientists seldom considered gelatinous plankton both in their field-work and in their computer-generated models, aimed at managing fish populations. Jellyfish are an important cause of fish mortality since they are predators of fish eggs and larvae, furthermore they compete with fish larvae and juveniles by feeding on their crustacean food. The Black Sea case of the impact of the ctenophore Mnemiopsis leydi on the fish populations, and then on the fisheries, showed that gelatinous plankton is an important variable in fisheries science and that it cannot be overlooked. The aim of this report is to review current knowledge on gelatinous plankton in the Mediterranean and Black Sea, so as to provide a framework to include this important component of marine ecosystems in fisheries science and in the management of other human activities such as tourism and coastal development. Fact sheets on the most important gelatinous plankters of the Mediterranean and Black Seas are in cluded as an appendix.

The shallow-water hydrozoan Antarctic fauna is still poorly studied, and available knowledge mostly refers to samples gathered by traditional ship-operated gears. By scuba diving in the coastal areas off the Italian Antarctic station "Mario Zucchelli" (Ross Sea, Terra Nova Bay), in the austral summer 2002-2003, a total of 20 hydrozoan species were found, belonging to 10 families and 13 genera. As hypothesized, Anthoathecata (11 species), usually under-represented in collections from indirect sampling gears, are common as also are Leptothecata (9 species). Hydractiniidae and Hydractinia are the dominant family and genus, followed by Haleciidae and Halecium. A new species to science, Halecium exaggeratum sp. nov. is also described. Most species are either endemic to Antarctic waters or restricted to Antarctic/sub-Antarctic areas; only two species have a wider distribution. Material reared in aquaria at the Italian Antarctic Base Mario Zucchelli facilitated knowledge of the life cycle and reproductive biology of several species. In particular, Opercularella belgicae was found to liberate a medusa stage referable to Phialella, and the species is assigned here to that genus, as Phialella belgicae. Also, extraordinary is the complete absence or scant representation of the most typical Antarctic benthic hydroid genera (Antarctoscyphus, Oswaldella, Schizotricha, Staurotheca, and Symplectoscyphus), likely related to the shallow limits of sampling (down to 48 m).

Vibrio harveyi is the major causal organism of vibriosis, causing potential devastation to diverse ranges of marine invertebrates over a wide geographical area. These microorganisms, however, are phenotypically diverse, and many of the isolates are also resistant to multiple antibiotics. In a previous study, we described a previously unknown association between Vibrio sp. AO1, a luminous bacterium related to the species V. harveyi, and the benthic hydrozoan Aglaophenia octodonta. In this study, we analyzed the susceptibility to antibiotics (ampicillin, streptomycin, tetracycline, or co-trimoxazole = mix of sulfamethoxazole and trimetoprim) of Vibrio sp. AO1 growing in pure culture or in association with its hydroid host by using microcosm experiments. The results of minimum inhibitory concentration (MIC) experiments demonstrated that Vibrio sp. AO1 was highly resistant to ampicillin and streptomycin in pure culture. Nevertheless, these antibiotics, when used at sub-MIC values, significantly reduced the hydroid fluorescence. Co-trimoxazole showed the highest inhibitory effect on fluorescence of A. octodonta. However, in all treatments, the fluorescence was reduced after 48 h, but never disappeared completely around the folds along the hydrocaulus and at the base of the hydrothecae of A. octodonta when the antibiotic was used at concentration completely inhibiting growth in vitro. The apparent discrepancy between the MIC data and the fluorescence patterns may be due to either heterogeneity of the bacterial population in terms of antibiotic susceptibility or specific chemical-physical conditions of the hydroid microenvironment that may decrease the antibiotic susceptibility of the whole population. The latter hypothesis is supported by scanning electron microscope evidence for development of bacterial biofilm on the hydroid surface. On the basis of the results obtained, we infer that A. octodonta might behave as a reservoir of antibiotic multiresistant bacteria, increasing the risk of their transfer into aquaculture farms.

1. Taxonomic sufficiency concerns the use of higher-taxon diversity as a surrogate for species diversity. It represents a fast and cost-effective method to assess community responses to natural and anthropogenic environmental drivers. In spite of the potential applications of using higher taxa as surrogates for species, little research has been carried out to determine the underlying reasons that might make taxonomic surrogacy effective for detecting diversity changes. 2. Here, we determine whether the effectiveness of higher taxa as species surrogates relies mostly on taxonomic relatedness of species (i.e. the relative closeness of species in the Linnaean taxonomic hierarchy) or depends simply on the numerical ratio between species and higher taxa (i.e. the degree of species aggregation). We reviewed the current literature on taxonomic sufficiency to check for any correlation between the effectiveness of higher taxa and the degree of species aggregation across different types of organisms. Tests based on random simulations from diverse marine mollusc assemblages were also carried out to ascertain whether the ability of higher taxa to detect variation in the multivariate structure of assemblages depended on the degree of species aggregation. 3. Mollusc data showed that information loss and the ensuing decrease in statistical power to detect natural or human-driven changes in assemblages at higher taxonomic levels depend on the degree of species aggregation, rather than on the taxonomic resolution employed. Analyses of the literature suggested that such outcomes could be generalizable to a wide range of organisms and environmental settings. 4. Our findings do not support the idea of a direct relationship between taxonomic relatedness and ecological similarity among species. This indicates that taxonomic ranks higher than species may not provide ecologically meaningful information, because higher taxa can behave as random groups of species unlikely to convey consistent responses to natural or human-driven environmental changes. 5. Synthesis and applications. Surrogates of species-level information can be based on the ‘highest practicable aggregation’ of species, irrespective of their taxonomic relatedness. Our findings cast doubt on static taxonomical groupings, legitimizing the use of alternative ways to aggregate species to maximize the use of species surrogacy. Key-words: biodiversity, conservation, higher-taxon approach, impact assessment, marine molluscs, natural environmental variations, phylogenetic relatedness, taxonomic surrogates, taxonomy

The Suez Canal is one of the most important waterways in the world – during the last year 17,148 ships passed through the Canal – reducing emissions, saving time, and operating costs to shippers. The rapid increase in ship size from the “Post-Suezmax” (> 12,000 TEU) to the latest container vessels (> 19,000 TEU) now requires enlargements of port facilities and canals. A project of this magnitude, and with potentially negative environmental outcomes, requires a transparent and scientifically sound “Environmental Impact Assessment” (EIA). An explicit obligation on Parties to the Convention on Biological Diversity (https://www.cbd.int/doc/ legal/cbd-en.pdf) was made to consider transboundary impacts on biodiversity, particularly those associated with invasive non-indigenous species.

The structure and function of the Mediterranean Sea Ecosystems (MSE) are rapidly changing. Global warming is the main driver of change, and the MSE responses are dramatic. The establishment of non-indigenous species, heavily influenced ecosystem functioning; human pressures such as overfishing, triggered regime shifts such as that from fish to jellyfish; the Eastern Mediterranean Transient changed the circulation patterns of the Eastern Mediterranean basin. Models did not predict these changes. Science, so far, focused much on the constraints that lead to regular sequences of events, allowing for predictions. In periods of rapid change, though, the historical nature of ecology becomes prominent, and contingencies acquire an overwhelming importance. This calls for new approaches to the study of complex systems, for instance with a shift from monitoring to observation, with a revival of natural history. The identification of cells of ecosystem functioning, based on oceanographic processes that enhance production at different levels of marine food webs in specific areas, is a challenge for future studies that will eventually lead to better management and protection of the marine natural heritage. Even if historical systems do not allow for predictions, some trends are clear and a set of possible scenarios of what will happen in the future Mediterranean Sea can be proposed.

The majority of Hydrozoa is represented by not readily noticeable, small species. In recent decades, however, taxonomic knowledge of the group has increased worldwide, with a significant number of investigations focused on the Mediterranean Sea. Over more than two decades, 115 species of hydrozoans were recorded from coastal waters along nearly 300 km of the Salento Peninsula (Apulia, Italy). For each species, records from different collections were merged into single sheets of a general database.        For each species, the following information is reported: description, cnidome, biology, occurrence in Salento, worldwide distribution, and bibliography. Descriptions refer to the benthic hydroid stage and, when present, also to the planktonic medusa stage. The 115 species of Hydrozoa, recorded along the Salento coastline, represent 25% of the Mediterranean Hydrozoa fauna (totaling 461 species), and nearly 3% of 3,702 world's known species covered in a recent monograph. Four species are non-indigenous, three of them with invasive behavior (Clytia hummelincki, Clytia linearis, and Eudendrium carneum), and one species now very common (Eudendrium merulum) in Salento. The complete life cycle of Clytia paulensis (Vanhöffen, 1910) is described for the first time. 

The majority of Hydrozoa is represented by not readily noticeable, small species. In recent decades, however, taxonomic knowledge of the group has increased worldwide, with a significant number of investigations focused on the Mediterranean Sea. Over more than two decades, 115 species of hydrozoans were recorded from coastal waters along nearly 300 km of the Salento Peninsula (Apulia, Italy). For each species, records from different collections were merged into single sheets of a general database. For each species, the following information is reported: description, cnidome, biology, occurrence in Salento, worldwide distribution, and bibliography. Descriptions refer to the benthic hydroid stage and, when present, also to the planktonic medusa stage. The 115 species of Hydrozoa, recorded along the Salento coastline, represent 25% of the Mediterranean Hydrozoa fauna (totaling 461 species), and nearly 3% of 3,702 world's known species covered in a recent monograph. Four species are non-indigenous, three of them with invasive behavior (Clytia hummelincki, Clytia linearis, and Eudendrium carneum), and one species now very common (Eudendrium merulum) in Salento. The complete life cycle of Clytia paulensis (Vanhöffen, 1910) is described for the first time.

The Strait of Messina is certainly a focal area for the biological cycle of the jellyfish Pelagia noctiluca in the Western Mediterranean Sea. By means of both original and literature data, a conceptual model outlining the biological cycle of this species is proposed. P. noctiluca reproduces from late winter to late spring in the Aeolian Island Archipelago. From late spring to early summer, currents transport newly produced young individuals (20-30 mm bell diameter) eastwards, towards the Strait. The Strait of Messina ecosystem is not a suitable reproduction area for its intense hydrodynamism that would surely lead to a very low reproductive success due to gamete dispersion. This area, however, represents an optimal site for growth, due to its intensive primary and secondary production, but also for an optimal temperature range, lower in summer and higher in winter in respect to the surrounding basins. Pelagia remains all the summer inside the Strait, increasing in bell diameter (50-70 mm) and biomass. Subsequently, in late summer-early autumn, the mature specimens, taking advantage of a typical autumnal downwelling transport, move to deep Tyrrhenian waters where overwinter, to upwell in the Aeolian Archipelago by late winter to start a new cycle.

Research policies ensuing from the Convention on Biological Diversity made huge funds available to study biodiversity. These were mostly dedicated to projects aimed at providing services to taxonomy via information and technology, or to develop “modern”, i.e., molecular, approaches to taxonomy. Traditional taxonomy was overly neglected and is in serious distress all over the world. It is argued that both novel and traditional ways to study biodiversity are essential and that the demise of traditional taxonomy (based on phenotypes) in the era of biodiversity is the result of an unwise policy, mainly fostered by portions of the scientific community that aim at taking total advantage of the funds dedicated to the study of biodiversity.

Ecological systems depend on both constraints and historical contingencies, both of which shape their present observable system state. In contrast to ahistorical systems, which are governed solely by constraints (i.e. laws), historical systems and their dynamics can be understood only if properly described, in the course of time. Describing these dynamics and understanding long-termvariability can be seen as themission of long time series measuring not only simple abiotic features but also complex biological variables, such as species diversity and abundances, allowing deep insights in the functioning of food webs and ecosystems in general. Long timeseries are irreplaceable for understanding change, and crucially inherent system variability and thus envisaging future scenarios. This notwithstanding current policies in funding and evaluating scientific research discourage the maintenance of long term series, despite a clear need for long-term strategies to cope with climate change. Time series are crucial for a pursuit of the much invoked Ecosystem Approach and to the passage from simple monitoring programs of large-scale and long-termEarth observatories — thus promoting a better understanding of the causes and effects of change in ecosystems. The few ongoing long time series in European waters must be integrated and networked so as to facilitate the formation of nodes of a series of observatories which, together, should allowthe long-termmanagement of the features and characteristics of European waters. Human capacity building in this region of expertise and a stronger societal involvement are also urgently needed, since the expertise in recognizing and describing species and therefore recording them reliably in the context of time series is rapidly vanishing from the European Scientific community.

Molecular analyses have led to an increased knowledge of the number and distribution of morphologically cryptic species in the world's oceans and, concomitantly, to the identification of non-indigenous species (NIS). Traditional taxonomy and accurate delimitation of species’ life histories and autecology lag far behind, however, even for the most widely distributed taxa, such as the moon jellyfish Aurelia (Cnidaria, Scyphozoa) species complex. Here we analysed mitochondrial cytochrome c oxidase subunit I (COI) and nuclear 28S ribosomal RNA (28S) gene sequences to assign polyps, ephyrae, and medusae collected in the Mediterranean Sea to different phylogenetic species. We find evidence for three Aurelia species, none of which are referable to the type species of the genus, Aurelia aurita (Linnaeus, 1758), and describe the anatomical, morphometric, and developmental variation within and between them. We identify Aurelia coerulea von Lendenfeld, 1884 and Aurelia solida Browne, 1905 as established non-indigenous species in the Mediterranean Sea. We describe Aurelia relicta sp. nov., an endemic species currently unique to a population in the marine lake of Mljet (Croatia). These results demonstrate the usefulness of integrative approaches in resolving taxonomic uncertainty surrounding cryptic species complexes, identifying patterns of marine biodiversity, and recognizing non-indigenous species in marine ecosystems.

Whether jellyfish are increasing or not in the global ocean is a subject of some debate, but the fact remains that when they bloom, jellyfish can negatively affect local economies. Despite this, there has been no robust debate about the idea of deliberately removing jellyfish as a means of population control. Here,wediscuss the effects of fishing for jellyfish, either as a sustainable resource and/or as away to simply reduce their nuisance value, on both individual jellyfish populations and the ecosystem. Given that the drivers influencing each local bloom are different, or that the effects of more widespread drivers may be manifested differently at each locale, our priority at population control/use needs to be more basic research on jellyfish. While we do not advocate a no-fishing approach, we emphasize the need to be cautious in embracing jellyfish fisheries as a panacea and we need to consider the management of each bloom on a case-by-case basis.