Fish mitigate trophic depletion in marine cave ecosystems.

Dark marine habitats are often characterized by a food-limited condition. Peculiar dark habitats include marine caves, characterized by the absence of light and limited water flow, which lead to reduced fluxes of organic matter for cave-dwelling organisms. We investigated whether the most abundant and common cave-dwelling fish Apogon imberbis has the potential to play the role of trophic vector in Mediterranean marine caves. We first analysed stomach contents to check whether repletion changes according to a nycthemeral cycle. We then identified the prey items, to see whether they belong to species associated with cave habitats or not. Finally, we assessed whether A. imberbis moves outside marine caves at night to feed, by collecting visual census data on A. imberbis density both inside and outside caves, by day and by night. The stomach repletion of individuals sampled early in the morning was significantly higher than later in the day. Most prey were typical of habitats other than caves. A. imberbis was on average more abundant within caves during the day and outside during the night. Our study supports the hypothesis regarding the crucial trophic role of A. imberbis in connecting Mediterranean marine caves with external habitat

Diversity and distribution of the dinoflagellates Brachidinium, Asterodinium and Microceratium (Brachidiniales, Dinophyceae) in the open Mediterranean Sea

Brachidiniacean dinoflagellates have been investigated in the open waters of the Mediterranean Sea, along a transect from the south of France to the south of Cyprus (20 June–18 July 2008). Brachidinium and Karenia papilionacea often co-occurred, B. capitatum predominating in the surface waters. The highest abundance of Brachidinium were found in the upper 25min the western Mediterranean with a maximum (24 cells L–1) at a depth of 5 m in the Balearic Sea. Asterodinium (up to 4 cells L–1) was recorded below of deep chlorophyll maxima. The genus Microceratium, only known from the tropical Indo-Pacific region, is reported for the first time in the Mediterranean Sea. Microceratium was found below 100min the eastern Mediterranean Sea, with the highest abundance of 8 cells L–1 at 125 m depth, in the Levantine Basin. This study also illustrates for the first time specimens under the division of Brachidinium and Microceratium. This first occurrence of Microceratium in the Mediterranean Sea should be considered an indicator of climate warming. However, it should not be considered a non-indigenous taxon. Microceratium is the \u27tropical morphotype\u27, the adaptation of a local species (a life stage of Karenia – Brachidinium – Asterodinium) to the tropical environmental conditions that prevail in summer in the open Mediterranean Sea

A lionfish (Pterois miles) invasion has begun in the Mediterranean Sea

Until now, few sightings of the alien lionfish Pterois miles have been reported in the Mediterranean and it was questionable whether the species could invade this region like it has in the western Atlantic. Here, we present evidence from divers and fishermen that lionfish have recently increased in abundance and within a year colonised almost the entire south eastern coast of Cyprus, likely due to sea surface warming. At least 23 different fish are reported of which 6 were removed. Groups of lionfish exhibiting mating behaviour have been noted for the first time in the Mediterranean. Managers need this information and should alert stakeholders to the potential ecological and socio-economic impacts that may arise from a lionfish invasion. Actions could involve incentives to engage divers and fishermen in lionfish removal programmes, as these have worked well at shallow depths in the Caribbean. Given that the Suez Canal has recently been widened and deepened, measures will need to be put in place to help prevent further invasion

Invasión de ecosistemas fluviales por cangrejo rojo americano, Procambarus clarkii

Trabajo presentado en las Jornadas españolas sobre conservación del cangrejo de río autóctono, celebradas el 21 y 22 de septiembre de 2015.Las invasiones biológicas son una de las mayores amenazas para la biodiversidad y conservación de las especies autóctonas, jugando un papel clave en el cambio global. Para intentar controlarlas, es importante entender dos tipos de fenómenos: los mecanismos que permiten a una especie establecerse con éxito en un nuevo ambiente, y las consecuencias ecológicas, evolutivas y económicas de una invasión. Nosotros abordaremos ambos tipos de fenómenos usando un enfoque multidisciplinar y un estudio multiescala, empleando como modelo de estudio una de las especies invasoras con mayor importancia global, la cual ya ha invadido la mayoría de aguas continentales: el cangrejo rojo americano, Procambarus clarkii. En su área nativa, esta especie vive principalmente en marismas; sin embargo, en las áreas invadidas ha sido capaz de invadir un nuevo ambiente, los arroyos, (en nuestro caso: el oeste de Andalucía en el suroeste de España). Desde su introducción hace unos 40 años, esta invasión está causando importantes daños a las especies autóctonas como el cangrejo de río, Austropotamobius pallipes. En este estudio, nos planteamos los siguientes cinco objetivos: (1) comparar la diversidad genética de las poblaciones invasoras con las de las áreas nativas, identificando patrones de introducción, propagación y flujo génico; (2) determinar qué mecanismos (a nivel de expresión de genes en diferentes tejidos) permiten que P. clarkii se adapte a nuevas condiciones o estrés ambiental: identificando genes y loci responsables para la adaptación local; (3) explorar los efectos ecológicos de P. clarkii en arroyos, en términos de estructura y funcionamiento del ecosistema, además de las interacciones con poblaciones nativas, tanto de cangrejo de río (A. pallipes) como de anfibios y peces autóctonos. Para hacer esto, compararemos los efectos ecológicos de las poblaciones de arroyo (las cuales potencialmente han evolucionado en respuesta a nuevos ambientes) con aquellas de poblaciones fundadoras desde las marismas; (4) comparar los efectos ecológicos de P. clarkii con aquellos de A. pallipes y determinar si la especie invasora está ocupando el mismo nicho ecológico que la especie nativa a la cual ha desplazado; y (5) examinar la prevalencia de Aphanomyces astaci en el cangrejo rojo americano, dado que esta especie invasora es portadora de la peste del cangrejo, afanomicosis, causando la muerte del cangrejo de río autóctono; y también la del hongo que causa la quitridiomicosis en anfibios. Con este proyecto, pretendemos dilucidar los mecanismos que permiten al cangrejo rojo americano establecerse exitosamente en un nuevo ambiente y las consecuencias que esto conlleva para las especies autóctonas.Peer reviewe

Invasion of fluvial ecosystems by red swamp crayfish, Procambarus clarkii

Trabajo presentado en el International Symposium on Conservation of Native European Freshwater Crayfish, celebrado en Olot (Girona) del 23 al 25 de septiembre de 2015.Biological invasions are one of the biggest threats to biodiversity and conservation of native species, playing a key role in global change. To try to control them, it is important to understand two types of phenomena: mechanisms that allow a species to successfully establish in a new environment, and the ecological, evolutionary and socio-economic consequences of an invasion. We will address both types of phenomena using a multidisciplinary approach and multi-scale research, employing as study model an invasive species of global importance, which has invaded many inland waters: the red swamp crayfish, Procambarus clarkii. In its native area, this species mainly lives in marshes; nevertheless, it has been able to invade a new environment, streams, in invaded areas (in our case: West Andalusia in South Western Spain). Since its introduction over 40 years ago, this invasion is causing serious damage to native species like the European freshwater crayfish, Austropotamobius pallipes. We have five main objectives in this study: (1) to compare the genetic diversity of invasive populations with the native area, identifying patterns of introduction, propagation and gene flow; (2) to determine what mechanisms (at the level of gene expression in different tissues) allow P. clarkii to adapt to new conditions or environmental stress: identify genes and loci responsible for local adaptation; (3) to explore the ecological effects of P. clarkii in streams, in terms of structure and ecosystem functioning, and interactions with populations of native crayfish (A. pallipes) and native amphibians and fishes. To do this, we will compare the ecological effects of stream populations (which have potentially evolved in response to the new environment) with those of founding populations from marshes; (4) to compare the ecological effects of P. clarkii with those of A. pallipes and determine whether the invasive species is occupying the same ecological niche as the native species which has displaced; and (5) to examine the prevalence of Aphanomyces astaci in the red swamp crayfish, given that this invasive species is a chronic carrier of the crayfish plague, aphanomycosis, causing the death of European freshwater crayfish; and that of the fungus that causes chytridiomycosis in amphibians. In this project, we expect to find mechanisms that allow the red swamp crayfish to successfully establish in a new environment and the consequences that this entails for native species.Peer reviewe

The Whereabouts of an Ancient Wanderer: Global Phylogeography of the Solitary Ascidian Styela plicata

Genetic tools have greatly aided in tracing the sources and colonization history of introduced species. However, recurrent introductions and repeated shuffling of populations may have blurred some of the genetic signals left by ancient introductions. Styela plicata is a solitary ascidian distributed worldwide. Although its origin remains unclear, this species is believed to have spread worldwide by travelling on ship's hulls. The goals of this study were to infer the genetic structure and global phylogeography of S. plicata and to look for present-day and historical genetic patterns. Two genetic markers were used: a fragment of the mitochondrial gene Cytochrome Oxidase subunit I (COI) and a fragment of the nuclear gene Adenine Nucleotide Transporter/ADP-ATP Translocase (ANT). A total of 368 individuals for COI and 315 for ANT were sequenced from 17 locations worldwide. The levels of gene diversity were moderate for COI to high for ANT. The Mediterranean populations showed the least diversity and allelic richness for both markers, while the Indian, Atlantic and Pacific Oceans had the highest gene and nucleotide diversities. Network and phylogenetic analyses with COI and ANT revealed two groups of alleles separated by 15 and 4 mutational steps, respectively. The existence of different lineages suggested an ancient population split. However, the geographic distributions of these groups did not show any consistent pattern, indicating different phylogeographic histories for each gene. Genetic divergence was significant for many population-pairs irrespective of the geographic distance among them. Stochastic introduction events are reflected in the uneven distribution of COI and ANT allele frequencies and groups among many populations. Our results confirmed that S. plicata has been present in all studied oceans for a long time, and that recurrent colonization events and occasional shuffling among populations have determined the actual genetic structure of this species

Interpopulation differences in expression of candidate genes for salinity tolerance in winter migrating anadromous brown trout (Salmo trutta L.)

<p>Abstract</p> <p>Background</p> <p>Winter migration of immature brown trout (<it>Salmo trutta</it>) into freshwater rivers has been hypothesized to result from physiologically stressful combinations of high salinity and low temperature in the sea.</p> <p>Results</p> <p>We sampled brown trout from two Danish populations entering different saline conditions and quantified expression of the <it>hsp70 </it>and <it>Na/K-ATPases α 1b </it>genes following acclimation to freshwater and full-strength seawater at 2°C and 10°C. An interaction effect of low temperature and high salinity on expression of both <it>hsp70 </it>and <it>Na/K-ATPase α 1b </it>was found in trout from the river entering high saline conditions, while a temperature independent up-regulation of both genes in full-strength seawater was found for trout entering marine conditions with lower salinities.</p> <p>Conclusion</p> <p>Overall our results support the hypothesis that physiologically stressful conditions in the sea drive sea-run brown trout into freshwater rivers in winter. However, our results also demonstrate intra-specific differences in expression of important stress and osmoregulative genes most likely reflecting adaptive differences between trout populations on a regional scale, thus strongly suggesting local adaptations driven by the local marine environment.</p

A Phylogenetic Perspective on the Evolution of Mediterranean Teleost Fishes

The Mediterranean Sea is a highly diverse, highly studied, and highly impacted biogeographic region, yet no phylogenetic reconstruction of fish diversity in this area has been published to date. Here, we infer the timing and geographic origins of Mediterranean teleost species diversity using nucleotide sequences collected from GenBank. We assembled a DNA supermatrix composed of four mitochondrial genes (12S ribosomal DNA, 16S ribosomal DNA, cytochrome c oxidase subunit I and cytochrome b) and two nuclear genes (rhodopsin and recombination activating gene I), including 62% of Mediterranean teleost species plus 9 outgroups. Maximum likelihood and Bayesian phylogenetic and dating analyses were calibrated using 20 fossil constraints. An additional 124 species were grafted onto the chronogram according to their taxonomic affinity, checking for the effects of taxonomic coverage in subsequent diversification analyses. We then interpreted the time-line of teleost diversification in light of Mediterranean historical biogeography, distinguishing non-endemic natives, endemics and exotic species. Results show that the major Mediterranean orders are of Cretaceous origin, specifically ∼100–80 Mya, and most Perciformes families originated 80–50 Mya. Two important clade origin events were detected. The first at 100–80 Mya, affected native and exotic species, and reflects a global diversification period at a time when the Mediterranean Sea did not yet exist. The second occurred during the last 50 Mya, and is noticeable among endemic and native species, but not among exotic species. This period corresponds to isolation of the Mediterranean from Indo-Pacific waters before the Messinian salinity crisis. The Mediterranean fish fauna illustrates well the assembly of regional faunas through origination and immigration, where dispersal and isolation have shaped the emergence of a biodiversity hotspot

Growth and Demography of the Solitary Scleractinian Coral Leptopsammia pruvoti along a Sea Surface Temperature Gradient in the Mediterranean Sea

The demographic traits of the solitary azooxanthellate scleractinian Leptopsammia pruvoti were determined in six populations on a sea surface temperature (SST) gradient along the western Italian coasts. This is the first investigation of the growth and demography characteristics of an azooxanthellate scleractinian along a natural SST gradient. Growth rate was homogeneous across all populations, which spanned 7 degrees of latitude. Population age structures differed between populations, but none of the considered demographic parameters correlated with SST, indicating possible effects of local environmental conditions. Compared to another Mediterranean solitary scleractinian, Balanophyllia europaea, zooxanthellate and whose growth, demography and calcification have been studied in the same sites, L. pruvoti seems more tolerant to temperature increase. The higher tolerance of L. pruvoti, relative to B. europaea, may rely on the absence of symbionts, and thus the lack of an inhibition of host physiological processes by the heat-stressed zooxanthellae. However, the comparison between the two species must be taken cautiously, due to the likely temperature differences between the two sampling depths. Increasing research effort on determining the effects of temperature on the poorly studied azooxanthellate scleractinians may shed light on the possible species assemblage shifts that are likely to occur during the current century as a consequence of global climatic change

The Biodiversity of the Mediterranean Sea: Estimates, Patterns, and Threats

The Mediterranean Sea is a marine biodiversity hot spot. Here we combined an extensive literature analysis with expert opinions to update publicly available estimates of major taxa in this marine ecosystem and to revise and update several species lists. We also assessed overall spatial and temporal patterns of species diversity and identified major changes and threats. Our results listed approximately 17,000 marine species occurring in the Mediterranean Sea. However, our estimates of marine diversity are still incomplete as yet—undescribed species will be added in the future. Diversity for microbes is substantially underestimated, and the deep-sea areas and portions of the southern and eastern region are still poorly known. In addition, the invasion of alien species is a crucial factor that will continue to change the biodiversity of the Mediterranean, mainly in its eastern basin that can spread rapidly northwards and westwards due to the warming of the Mediterranean Sea. Spatial patterns showed a general decrease in biodiversity from northwestern to southeastern regions following a gradient of production, with some exceptions and caution due to gaps in our knowledge of the biota along the southern and eastern rims. Biodiversity was also generally higher in coastal areas and continental shelves, and decreases with depth. Temporal trends indicated that overexploitation and habitat loss have been the main human drivers of historical changes in biodiversity. At present, habitat loss and degradation, followed by fishing impacts, pollution, climate change, eutrophication, and the establishment of alien species are the most important threats and affect the greatest number of taxonomic groups. All these impacts are expected to grow in importance in the future, especially climate change and habitat degradation. The spatial identification of hot spots highlighted the ecological importance of most of the western Mediterranean shelves (and in particular, the Strait of Gibraltar and the adjacent Alboran Sea), western African coast, the Adriatic, and the Aegean Sea, which show high concentrations of endangered, threatened, or vulnerable species. The Levantine Basin, severely impacted by the invasion of species, is endangered as well