Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR

The possibility of measuring the proton electromagnetic form factors in the time-like region at FAIR with the \PANDA detector is discussed. Detailed simulations on signal efficiency for the annihilation of $\bar p +p$ into a lepton pair as well as for the most important background channels have been performed. It is shown that precision measurements of the differential cross section of the reaction $\bar p +p \to e^++ e^-$ can be obtained in a wide angular and kinematical range. The individual determination of the moduli of the electric and magnetic proton form factors will be possible up to a value of momentum transfer squared of $q^2\simeq 14$ (GeV/c)$^2$. The total $\bar p +p\to e^++e^-$ cross section will be measured up to $q^2\simeq 28$ (GeV/c)$^2$. The results obtained from simulated events are compared to the existing data. Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations, 4 tables, 9 figure

Host adaptation and unexpected symbiont partners enable reef-building corals to tolerate extreme temperatures

© 2016 John Wiley & Sons Ltd. Understanding the potential for coral adaptation to warming seas is complicated by interactions between symbiotic partners that define stress responses and the difficulties of tracking selection in natural populations. To overcome these challenges, we characterized the contribution of both animal host and symbiotic algae to thermal tolerance in corals that have already experienced considerable warming on par with end-of-century projections for most coral reefs. Thermal responses in Platygyra daedalea corals from the hot Persian Gulf where summer temperatures reach 36°C were compared with conspecifics from the milder Sea of Oman. Persian Gulf corals had higher rates of survival at elevated temperatures (33 and 36°C) in both the nonsymbiotic larval stage (32-49% higher) and the symbiotic adult life stage (51% higher). Additionally, Persian Gulf hosts had fixed greater potential to mitigate oxidative stress (31-49% higher) and their Symbiodinium partners had better retention of photosynthetic performance under elevated temperature (up to 161% higher). Superior thermal tolerance of Persian Gulf vs. Sea of Oman corals was maintained after 6-month acclimatization to a common ambient environment and was underpinned by genetic divergence in both the coral host and symbiotic algae. In P. daedalea host samples, genomewide SNP variation clustered into two discrete groups corresponding with Persian Gulf and Sea of Oman sites. Symbiodinium within host tissues predominantly belonged to ITS2 rDNA type C3 in the Persian Gulf and type D1a in the Sea of Oman contradicting patterns of Symbiodinium thermal tolerance from other regions. Our findings provide evidence that genetic adaptation of both host and Symbiodinium has enabled corals to cope with extreme temperatures in the Persian Gulf. Thus, the persistence of coral populations under continued warming will likely be determined by evolutionary rates in both, rather than single, symbiotic partners

Genetic Traces of Recent Long-Distance Dispersal in a Predominantly Self-Recruiting Coral

Understanding of the magnitude and direction of the exchange of individuals among geographically separated subpopulations that comprise a metapopulation (connectivity) can lead to an improved ability to forecast how fast coral reef organisms are likely to recover from disturbance events that cause extensive mortality. Reef corals that brood their larvae internally and release mature larvae are believed to show little exchange of larvae over ecological times scales and are therefore expected to recover extremely slowly from large-scale perturbations.Using analysis of ten DNA microsatellite loci, we show that although Great Barrier Reef (GBR) populations of the brooding coral, Seriatopora hystrix, are mostly self-seeded and some populations are highly isolated, a considerable amount of sexual larvae (up to approximately 4%) has been exchanged among several reefs 10 s to 100 s km apart over the past few generations. Our results further indicate that S. hystrix is capable of producing asexual propagules with similar long-distance dispersal abilities (approximately 1.4% of the sampled colonies had a multilocus genotype that also occurred at another sampling location), which may aid in recovery from environmental disturbances.Patterns of connectivity in this and probably other GBR corals are complex and need to be resolved in greater detail through genetic characterisation of different cohorts and linkage of genetic data with fine-scale hydrodynamic models

Seasonal and sex-specific variations in levels of photo-protecting mycosporine-like amino acids (MAAs) in soft corals

This study focusses on the nature and extent of variation in mycosporine-like amino acids (MAAs) in relation to annual cycles in solar radiation, seawater temperature, and reproduction in reef-flat populations of two soft coral species. The results show MAA tissue concentrations in shallow water colonies of Lobophytum compactum and Sinularia flexibilis to be significantly correlated to annual cycles in solar radiation (P<0.0006 and P<0.0005, respectively) and seawater temperature (P<0.0006 and P<0.0004, respectively). Evidence of seasonal cycles in MAA levels in the tissues of shallow-reef invertebrates positively correlating with annual cycles in solar radiation and temperature suggests that they are an integral component of the soft corals' biochemical defence system against high irradiance and/or temperature stress and thus bleaching. This is further corroborated by the higher production of MAAs in females than males prior to spawning (up to 67% and 56% for L. compactum and S. flexibilis, respectively), presumably to provide a high level of protection against irradiance stress for progeny

The chemical ecology of the soft coral-zooxanthellae association and its signficance to the bleaching process

Biochemical changes in soft corals (Lobophytum compactum and Sinularia flexibilis) affected by bleaching were investigated, with the ultimate aim of understanding how molecular changes are linked to biological responses observed in the wake of bleaching events. Annual variation in photo-protective mycosporine-like amino acids (MAAs) in soft coral populations provides the first evidence that MAA tissue concentrations are positively correlated with seasonal cycles in both solar irradiance and sea-surface temperatures. The timing of peak concentrations of MAAs in summer when exposure to solar irradiance and sea temperatures are greatest, and in female colonies prior to spawning, further corroborate their role as photo-protectants. In manipulative bleaching experiments elevated UVR and temperature were found to act synergistically in the bleaching process. However, chemical degradation of MAAs during exposure to elevated temperature is not, as previously assumed, the key to understanding the synergistic interaction. In fact, MAA levels increased in response to simultaneous exposure to high temperature and UVR, in both experimentally and naturally bleached colonies, suggesting increased resource allocation towards photo-protection in corals already experiencing thermal stress. Soft coral responded to bleaching by increasing the production of terpenoid secondary metabolites, which aid in the prevention of microbial and algal fouling. While changes in secondary metabolites were short-lived, a substantial increase of an anti-microbial agent in S. flexibilis may have contributed to the prevention of fouling by opportunistic bacteria. This suggests that soft corals may alter their secondary metabolite chemistry to prevent fouling by opportunistic bacteria following bleaching. These experimental results were validated through analysis of soft corals affected by the 1998 mass bleaching event, where bleached colonies with high levels of algaecides remained free of fouling, while conspecifics with substantially lower levels were found to be overgrown. This suggests that soft corals are capable of surviving short-term bleaching events and detrimental algal overgrowth that is often associated with bleaching, by regulating their secondary metabolite chemistry to counteract fouling. Understanding the role of symbiotic zooxanthellae in the production of terpenoid secondary metabolites is integral to evaluating the full impact of bleaching disturbances on the soft coral host. Zooxanthella cross-infection experiments with freshly metamorphosed polyps of Lobophytum compactum demonstrated that control over the production of secondary metabolite lies with the animal host. Moreover, the equivalence of secondary metabolite chemistry in apo-and symbiotic polyps clearly shows that the algal partner is not essential for biosynthesis. Despite no direct algal involvement in terpene production, a strong correlation between polyp growth and investment into terpenes suggests that, via their contribution to coral nutrition through primary metabolism, zooxanthellae have the capacity to indirectly influence secondary metabolism. The implications for bleached soft corals are that while the host, with or without energetic contributions from the algal symbiont controls the production of ecologically important terpenes, energy reserves may be insufficient to maintain the production of ecologically significant concentrations. Severe experimental bleaching was found to have long-term sub-lethal impacts on soft corals, reducing overall reproductive output of Lobophytum compactum for at least two spawning seasons. Polyp fecundity and mean egg diameters were inversely correlated with the degree of bleaching, with complete failure of fertilisation in heavily bleached colonies in the first year and significantly reduced fecundity in the second year after the bleaching event. Although bleached corals recovered their zooxanthellae within 4 months, protein, lipid, MAA and carotenoid concentrations were reduced for at least eight months in adult tissues. The reductions were amplified when they were passed on to gametes, with the greatest reductions occurring in lipid and protein concentrations. Although reductions in MAAs were relatively smaller when passed on to gametes, even minor proportional reductions have significant implications for larval survival, given that MAA levels are approximately three times higher in eggs than in maternal tissues. By the second spawning season (20 months after experimental bleaching) the biochemical compositions of both adult tissues and their gametes were indistinguishable from those of control (unbleached) corals

Impacts of bleaching on the soft coral Lobophytum compactum. II. Biochemical changes in adults and their eggs

Experimental bleaching reduces the levels of important biochemical parameters in adult tissues and eggs of the soft coral Lobophytum compactum. Protein, lipid, mycosporine-like amino acids (MAAs) and carotenoid concentrations remained lower in bleached adults than in controls for at least 8 months. Reductions in concentrations of all four parameters were greater in eggs than in maternal tissues, potentially jeopardizing egg and larval viability. In particular, reductions in lipids, proteins and carotenoids in tissues of heavily bleached soft corals were amplified approximately twofold in eggs. In comparison, amplification of maternal tissue reductions were not as great for MAAs, suggesting that MAAs are given higher priority in egg provisioning. Our finding that MAA levels are normally three times higher in eggs than in unbleached maternal tissues supports the importance of MAAs for larval survival. Twenty months after experimental bleaching the biochemical composition of both adult tissues and their eggs were indistinguishable from those of control (unbleached) soft corals

Impacts of bleaching on the soft coral Lobophytum compactum. I. Fecundity, fertilization and offspring viability

We document long-term effects of a simulated bleaching event on the reproductive output and offspring viability of the soft coral Lobophytum compactum. Corals were subjected to temperature and solar radiation treatments to produce both moderately (48–60%) and heavily (90–95%) bleached colonies. Although bleached colonies recovered their zooxanthellae within 10 to 18 weeks, impacts on reproductive output were significant for at least two annual spawning seasons. In the first year, both polyp fecundity and mean oocyte diameter were reduced and inversely correlated with the degree of bleaching, with complete failure of fertilization in the group of heavily bleached colonies. For moderately bleached soft corals, survival and growth of sexual offspring did not differ significantly from those of unbleached colonies. Although no further reductions in zooxanthellae densities in experimental soft corals were recorded throughout the subsequent second year, egg size and fecundity of the heavily bleached soft corals were still significantly reduced 20 months later. Severe bleaching clearly has long-term sub-lethal impacts, reducing overall reproductive output for at least two spawning seasons