Genetic structure of the South European toothcarp Aphanius fasciatus (Actinopterygii: Cyprinodontidae) populations in the Mediterranean basin with a focus on the Venice lagoon

The genetic structure of Aphanius fasciatus populations has been analysed using two mitochondrial DNA (mtDNA) markers (16S rRNA and D-loop) obtained from specimens collected in nine sites from the Venice lagoon, Comacchio saltworks and Corsica. Available GenBank sequences were also included, in order to extend the results on a Mediterranean scale. Genetic polymorphism within the Venice lagoon was very low, with most of the specimens analysed (66% for 16S rRNA and 83% for D-loop) sharing the same haplotype for either of the two markers. The genetic homogeneity found within the Venice lagoon may be the consequence of the northward migration of southern Adriatic populations after the Last Glacial Maximum: mismatch analysis showed indeed clear signs of a rapid demographic and spatial expansion. To explain this genetic homogeneity other hypotheses were also suggested, such as adaptation to the high variability of brackish water habitats, and artificial introductions. On a Mediterranean scale, phylogenetic analyses showed the presence of five distinct geographical lineages: Aegean Sea, Greek coast of the Ionian Sea, Adriatic Sea, Tyrrhenian Sea and Southern Sicily. Analysis of molecular variance revealed a genetic partitioning mainly due to differences between groups presumably due to late Miocene geological events, while less polymorphism was present within groups and populations

A Voltage-Gated H+ Channel Underlying pH Homeostasis in Calcifying Coccolithophores

Marine coccolithophorid phytoplankton are major producers of biogenic calcite, playing a significant role in the global carbon cycle. Predicting the impacts of ocean acidification on coccolithophore calcification has received much recent attention and requires improved knowledge of cellular calcification mechanisms. Uniquely amongst calcifying organisms, coccolithophores produce calcified scales (coccoliths) in an intracellular compartment and secrete them to the cell surface, requiring large transcellular ionic fluxes to support calcification. In particular, intracellular calcite precipitation using HCO3− as the substrate generates equimolar quantities of H+ that must be rapidly removed to prevent cytoplasmic acidification. We have used electrophysiological approaches to identify a plasma membrane voltage-gated H+ conductance in Coccolithus pelagicus ssp braarudii with remarkably similar biophysical and functional properties to those found in metazoans. We show that both C. pelagicus and Emiliania huxleyi possess homologues of metazoan Hv1 H+ channels, which function as voltage-gated H+ channels when expressed in heterologous systems. Homologues of the coccolithophore H+ channels were also identified in a diversity of eukaryotes, suggesting a wide range of cellular roles for the Hv1 class of proteins. Using single cell imaging, we demonstrate that the coccolithophore H+ conductance mediates rapid H+ efflux and plays an important role in pH homeostasis in calcifying cells. The results demonstrate a novel cellular role for voltage gated H+ channels and provide mechanistic insight into biomineralisation by establishing a direct link between pH homeostasis and calcification. As the coccolithophore H+ conductance is dependent on the trans-membrane H+ electrochemical gradient, this mechanism will be directly impacted by, and may underlie adaptation to, ocean acidification. The presence of this H+ efflux pathway suggests that there is no obligate use of H+ derived from calcification for intracellular CO2 generation. Furthermore, the presence of Hv1 class ion channels in a wide range of extant eukaryote groups indicates they evolved in an early common ancestor

Differences in life-history traits in two clonal strains of the self-fertilizing fish, Rivulus marmoratus

We compared life-history traits such as fecundity, sex ratio, reproductive cycle, age at sexual maturity, embryonic period, egg size, early growth and morphology in two clonal strains (PAN-RS and DAN) of the mangrove killifish, Rivulus marmoratus, under constant rearing conditions. We found a positive relationship between growth and reproductive effort. Fecundity was significantly higher in the PAN-RS strain than in the DAN strain. The sex ratio was significantly different, with DAN producing more primary males than PAN-RS. Spawning and ovulation cycle did not clearly differ between the strains. PAN-RS showed a significantly higher growth rate than DAN from 0 to 100 days after hatching, however, age at sexual maturity, embryonic period, egg size, and morphometric and meristic characteristics (vertebral and fin-ray counts) did not differ between the two strains. The high fecundity of PAN-RS may provide an increased chance of offspring survival, while the attainment of sexual maturity at a smaller size in DAN may allow them to invest earlier in reproduction to increase breeding success. Variations in the life-history traits of PAN-RS and DAN may be adaptive strategies for life in their natural habitat, which consists of mangrove estuaries with a highly variable environment

Byzantine Fault Tolerant Symmetric-Persistent Circle Evacuation

We consider (n, f)-evacuation on a circle, an evacuation problem of a hidden exit on the perimeter of a unit radius circle for n> 1 robots, f of which are faulty. All the robots start at the center of the circle and move with maximum speed 1. Robots must first find the exit and then move there to evacuate in minimum time. The problem is considered complete when all the honest robots know the correct position of the exit and the last honest robot has evacuated through the exit. During the search, robots can communicate wirelessly. We focus on symmetric-persistent algorithms, that is, algorithms in which all robots move directly to the circumference, start searching the circle moving in the same direction (cw or ccw), and do not stop moving around the circle before receiving information about the exit. We study the case of (n, 1) and (n, 2) evacuation. We first prove a lower bound of 1+4πn+2sin(π2-πn) for one faulty robot, even a crash-faulty one. We also observe an almost matching upper bound obtained by means of an earlier search algorithm. We finally study the case with two Byzantine robots and we provide an algorithm that achieves evacuation in time at most 3+6πn, for n≥ 9, or at most 3+6πn+δ(n), for n< 9, where δ(n)≤2sin(3π2n)+2-4sin(3π2n)+4sin2(3π2n)-2. © 2021, Springer Nature Switzerland AG

The DPSIR Approach for an Integrated River Management Framework. A Preliminary Application on a Mediterranean Site (Kalamas River -NW Greece)

The European Water Policy introduced the necessity to apply new methodological approaches for the sustainable management of water resources. In the present paper the Driving-Pressure-State-Impact-Response (DPSIR) framework was developed as a methodological tool for the case study of Kalamas River basin (NW Greece). According to the DPSIR approach, it was revealed that the main driving forces, leading to pressures, were the agriculture, the livestock and the numerous point-pollution sources located at the catchment area. Elevated nutrients concentrations (NO3-N:0.1-2.6 mg/L, NH4-N:0.01-1.29 mg/L, SRP: 0.03-5.76 mg/L) along with high chlorophyll-a values (0.54-6.14 mg/m(3)) highlight river eutrophication. Response actions include elimination of diffuse pollution as well as reduction of the organic load through the optimization of the existed treatment plants. Since several parts of Kalamas River are designated as protected areas, specific measures for protecting biodiversity should be undertaken

Linking habitat structure to life history strategy: insights from a Mediterranean killifish

Modern theories of life history evolution deal with finding links between environmental factors, demographic structure of animal populations and the optimal life history strategy. Small-sized teleost fish, occurring in fragmented populations under contrasting environments, have been widely used as study models to investigate these issues. In the present study, the Mediterranean killifish Aphanius fasciatus was used to investigate the relationships between some habitat features and life history strategy. We selected four sites in the Venice lagoon inhabited by this species, exhibiting different combinations of two factors: overall adult mortality, related to intertidal water coverage and a consequent higher level of predator exposure, and the level of sediment organic matter, as indicator of habitat trophic richness. Results showed that these were the two most important factors influencing demography and life history traits in the four sites. Fish from salt marshes with high predator pressure were smaller and produced a higher number of eggs, whereas bigger fish and a lower reproductive investment were found in the two closed, not tidally influenced habitats. Habitat richness was positively related with population density, but negatively related with growth rate. In particular the synergy between high resources and low predation level was found to be important in shaping peculiar life history traits. Results were discussed in the light of the interactions between selective demographic forces acting differentially on age/size classes, such as predation, and habitat trophic richness that may represent an important energetic constraint on life history traits. The importance to link habitat productivity and morphology to demographic factors for a better understanding of the evolution of life history strategy under contrasting environments was finally suggested. (C) 2013 Elsevier B.V. All rights reserved