The Introduced Green Alga Caulerpa Taxifolia Continues to Spread in the Mediterranean

The tropical green alga Caulerpa taxifolia in the Mediterranean has spread steadily since its introduction in 1984. At the end of 2000, approximately 131km² of benthos had been colonized in 103 independent areas along 191km of coastline in six countries (Spain, France, Monaco, Italy, Croatia and Tunisia). Large regions neighboring the invaded areas appear favorable to further colonization, and there is thus no reason to believe that spreading will slow down in the years to come.     

Distribution and trophic ecology of chaetognaths in the western Mediterranean in relation to an inshore-offshore gradient

This study examines the distribution patterns and feeding ecologyof chaetognaths in the Catalan Sea in relation to mesoscalefeatures along an inshore–offshore gradient. The studywas conducted during two different periods of the year: latespring of 1995 and late summer of 1996. The two periods differedin hydrographic conditions and mesoscale processes, which affectedthe distribution patterns of the different species of chaetognathsfound. The diet of the chaetognaths was mainly composed of copepodsand differed between species. Prey size was not always stronglyrelated to chaetognath size and for certain species, there wasan overlap in prey size spectrum. Trophic niche breadth (ona ratio scale) appeared to be constant with growth. Ingestionrates and predation pressure by chaetognaths did not followa clear trend related to the mesoscale features in the area,such as the presence of a density front. The impact of chaetognathson copepod standing stock appeared to be extremely low (<1%),but it became more relevant when the species and prey size specificityof the chaetognaths was taken into account.     

Morphological and Molecular Characterization of Dietary-Induced Pseudo-Albinism during Post-Embryonic Development of Solea senegalensis (Kaup, 1858)

The appearance of the pseudo-albino phenotype was investigated in developing Senegalese sole (Solea senegalensis, Kaup 1858) larvae at morphological and molecular levels. In order to induce the development of pseudo-albinos, Senegalese sole larvae were fed Artemia enriched with high levels of arachidonic acid (ARA). The development of their skin pigmentation was compared to that of a control group fed Artemia enriched with a reference commercial product. The relative amount of skin melanophores, xanthophores and iridophores revealed that larval pigmentation developed similarly in both groups. However, results from different relative proportions, allocation patterns, shapes and sizes of skin chromatophores revealed changes in the pigmentation pattern between ARA and control groups from 33 days post hatching onwards. The new populations of chromatophores that should appear at post-metamorphosis were not formed in the ARA group. Further, spatial patterns of distribution between the already present larval xanthophores and melanophores were suggestive of short-range interaction that seemed to be implicated in the degradation of these chromatophores, leading to the appearance of the pseudo-albino phenotype. The expression profile of several key pigmentation-related genes revealed that melanophore development was promoted in pseudo-albinos without a sufficient degree of terminal differentiation, thus preventing melanogenesis. Present results suggest the potential roles of asip1 and slc24a5 genes on the down-regulation of trp1 expression, leading to defects in melanin production. Moreover, gene expression data supports the involvement of pax3, mitf and asip1 genes in the developmental disruption of the new post-metamorphic populations of melanophores, xanthophores and iridophores.     

Rapid biodiversity assessment and monitoring method for highly diverse benthic communities: a case study of mediterranean coralligenous outcrops

Increasing anthropogenic pressures urge enhanced knowledge and understanding of the current state of marine biodiversity. This baseline information is pivotal to explore present trends, detect future modifications and propose adequate management actions for marine ecosystems. Coralligenous outcrops are a highly diverse and structurally complex deep-water habitat faced with major threats in the Mediterranean Sea. Despite its ecological, aesthetic and economic value, coralligenous biodiversity patterns are still poorly understood. There is currently no single sampling method that has been demonstrated to be sufficiently representative to ensure adequate community assessment and monitoring in this habitat. Therefore, we propose a rapid non-destructive protocol for biodiversity assessment and monitoring of coralligenous outcrops providing good estimates of its structure and species composition, based on photographic sampling and the determination of presence/absence of macrobenthic species. We used an extensive photographic survey, covering several spatial scales (100s of m to 100s of km) within the NW Mediterranean and including 2 different coralligenous assemblages: Paramuricea clavata (PCA) and Corallium rubrum assemblage (CRA). This approach allowed us to determine the minimal sampling area for each assemblage (5000 cm(2) for PCA and 2500 cm(2) for CRA). In addition, we conclude that 3 replicates provide an optimal sampling effort in order to maximize the species number and to assess the main biodiversity patterns of studied assemblages in variability studies requiring replicates. We contend that the proposed sampling approach provides a valuable tool for management and conservation planning, monitoring and research programs focused on coralligenous outcrops, potentially also applicable in other benthic ecosystems.     

RhoE deficiency produces postnatal lethality, profound motor deficits and neurodevelopmental delay in mice

Rnd proteins are a subfamily of Rho GTPases involved in the control of actin cytoskeleton dynamics and other cell functions such as motility, proliferation and survival. Unlike other members of the Rho family, Rnd proteins lack GTPase activity and therefore remain constitutively active. We have recently described that RhoE/Rnd3 is expressed in the Central Nervous System and that it has a role in promoting neurite formation. Despite their possible relevance during development, the role of Rnd proteins in vivo is not known. To get insight into the in vivo function of RhoE we have generated mice lacking RhoE expression by an exon trapping cassette. RhoE null mice (RhoE gt/gt) are smaller at birth, display growth retardation and early postnatal death since only half of RhoE gt/gt mice survive beyond postnatal day (PD) 15 and 100% are dead by PD 29. RhoE gt/gt mice show an abnormal body position with profound motor impairment and impaired performance in most neurobehavioral tests. Null mutant mice are hypoactive, show an immature locomotor pattern and display a significant delay in the appearance of the hindlimb mature responses. Moreover, they perform worse than the control littermates in the wire suspension, vertical climbing and clinging, righting reflex and negative geotaxis tests. Also, RhoE ablation results in a delay of neuromuscular maturation and in a reduction in the number of spinal motor neurons. Finally, RhoE gt/gt mice lack the common peroneal nerve and, consequently, show a complete atrophy of the target muscles. This is the first model to study the in vivo functions of a member of the Rnd subfamily of proteins, revealing the important role of Rnd3/RhoE in the normal development and suggesting the possible involvement of this protein in neurological disorders.     

Mechanisms Governing the Endosomal Membrane Recruitment of the Core Retromer in Arabidopsis

The retromer complex localizes to endosomal membranes and is involved in protein trafficking. In mammals, it is composed of a dimer of sorting nexins and of the core retromer consisting of vacuolar protein sorting (VPS)26, VPS29, and VPS35. Although homologs of these proteins have been identified in plants, how the plant retromer functions remains elusive. To better understand the role of VPS components in the assembly and function of the core retromer, we characterize here Arabidopsis vps26-null mutants. We show that impaired VPS26 function has a dramatic effect on VPS35 levels and causes severe phenotypic defects similar to those observed in vps29-null mutants. This implies that functions of plant VPS26, VPS29, and VPS35 are tightly linked. Then, by combining live-cell imaging with immunochemical and genetic approaches, we report that VPS35 alone is able to bind to endosomal membranes and plays an essential role in VPS26 and VPS29 membrane recruitment. We also show that the Arabidopsis Rab7 homolog RABG3f participates in the recruitment of the core retromer to the endosomal membrane by interacting with VPS35. Altogether our data provide original information on the molecular interactions that mediate assembly of the core retromer in plants.     

An integrative systematic approach to species diversity and distribution in the genus Mesophyllum (Corallinales,Rhodophyta) in Atlantic and Mediterranean Europe

For the first time, a comprehensive assessment of Mesophyllum species diversity and their distribution in Atlantic Europe and the Mediterranean Sea is presented based on molecular (COI-5P, psbA) and morphological data. The distribution ranges were redefined for the four species collected in this study: M. alternans, M. expansum, M. macroblastum and M. sphaericum. Mesophyllum sphaericum, which was previously known only from a single maerl bed in Galicia (NW Spain), is reported from the Mediterranean Sea. The known range of M. expansum (Mediterranean and Macaronesia) was extended to the Atlantic Iberian Peninsula. The occurrence of M. alternans was confirmed along the Atlantic French coast south to Algarve (southern Portugal). Mesophyllum lichenoides was only recorded from the Atlantic, whereas M. macroblastum appears to be restricted to the Mediterranean Sea. A positive correlation was observed between maximum Sea Surface Temperature (SSTmax) and the depth at which M. expansum was collected, suggesting that this species may compensate for higher SST by growing in deeper habitats where the temperature is lower. The latter indicates that geographic shifts in the distribution of coastal species as a result of global warming can possibly be mitigated by changes in the depth profile at which these species occur. Mesophyllum expansum, an important builder of Mediterranean coralligenous habitats, may be a good target species to assess its response to climate change.     

A2A adenosine receptor ligand binding and signalling is allosterically modulated by adenosine deaminase

A2ARs (adenosine A2A receptors) are highly enriched in the striatum, which is the main motor control CNS (central nervous system) area. BRET (bioluminescence resonance energy transfer) assays showed that A2AR homomers may act as cell-surface ADA (adenosine deaminase; EC 3.5.4.4)-binding proteins. ADA binding affected the quaternary structure of A2ARs present on the cell surface. ADA binding to adenosine A2ARs increased both agonist and antagonist affinity on ligand binding to striatal membranes where these proteins are co-expressed. ADA also increased receptor-mediated ERK1/2 (extracellular-signal-regulated kinase 1/2) phosphorylation. Collectively, the results of the present study show that ADA, apart from regulating the concentration of extracellular adenosine, may behave as an allosteric modulator that markedly enhances ligand affinity and receptor function. This powerful regulation may have implications for the physiology and pharmacology of neuronal A2ARs.