Evolutionary ecology of opsin gene sequence, expression and repertoire.

Linking molecular evolution to biological function is a long-standing challenge in evolutionary biology. Some of the best examples of this involve opsins, the genes that encode the molecular basis of light reception. In this issue of Molecular Ecology, three studies examine opsin gene sequence, expression and repertoire to determine how natural selection has shaped the visual system. First, Escobar-Camacho et al. () use opsin repertoire and expression in three Amazonian cichlid species to show that a shift in sensitivity towards longer wavelengths is coincident with the long-wavelength-dominated Amazon basin. Second, Stieb et al. () explore opsin sequence and expression in reef-dwelling damselfish and find that UV- and long-wavelength vision are both important, but likely for different ecological functions. Lastly, Suvorov et al. () study an expansive opsin repertoire in the insect order Odonata and find evidence that copy number expansion is consistent with the permanent heterozygote model of gene duplication. Together these studies emphasize the utility of opsin genes for studying both the local adaptation of sensory systems and, more generally, gene family evolution

Pacific Herring, Clupea pallasi, spawning population assessment for San Francisco Bay, 1992-93

We conducted hydroacoustic surveys, spawn surveys, and sampled schools and fishery landings from 8 November 1992 through 18 March 1993 to assess the status of San Francisco Bay's Pacific herring spawning population. Our spawning biomass estimate of 21,186 tons is the lowest since 1978 when subtidal spawns were included in estimates; it also represents a third consecutive season of decline. The principal reason for this very low estimate is a lack of two-, three-, and four-year-old herring in the spawning population from the 1991,1990, and 1989 year-classes. Although four-year-olds were the most abundant cohort, their actual number was very low. Five-year-olds from the highly successful 1988 year-class were the second most abundant cohort. Warm-water conditions and poor upwelling associated with the 1991-92 El Nino are likely causes of the low spawning biomass, although adverse impacts on the condition and growth of spawners were not apparent. Warm water may have displaced herring to the north of San Francisco Bay. We also continued to collect data for a herring young-of-the-year abundance index during April, May, and June of 1993. The index was low for the 1990 and 1991 year-classes, but high for the 1989 year-class. The 1989 and 1990 year-classes appear poor; however, the success of the 1991 year-class will not be known until next season when it fully recruits to the spawning population.The index for the 1992 year-class is relatively low as is the index for 1993. The season's 5,555-ton quota (based on the previous season's biomass estimate) exceeded our harvest goal of no more than 20% of spawning biomass for the first time since the 1970s. The number of three-year-old fish in gill net catches increased substantially this season, possibly indicating the use of smaller mesh. Because of the extremely low spawning biomass and uncertainty about future recruitment, our recommendation to the Fish and Game Commission was to close the herring roe fishery in San Francisco Bay until the season following a spawning biomass estimate of 26,000 tons. (30pp.

The ForwardDiffSig scheme for multicast authentication

This paper describes ForwardDiffSig, an efficient scheme for multicast authentication with forward security. This scheme provides source authentication, data integrity, and non-repudiation since it is based on the use of asymmetric cryptography. At the same time, it offers also protection against key exposure as it exploits OptiSum, our optimized implementation of the ISum forward-secure signature scheme. A tradeoff exists in the used keys: Short keys provide speed at the signer, whereas long keys are preferable for long-term non-repudiation. Performance has been evaluated with a custom packet simulator and shows that, by grouping the packets, ForwardDiffSig is efficient in terms of speed even for long keys at the price of a significant signature overhead. Therefore, ForwardDiffSig is fast, exhibits low delay, and provides non-repudiation and protection against key exposure, but has a nonnegligible impact in applications with strict energy or bandwidth constraint

Differential elastic scattering cross sections for 54.9eV positrons incident on helium

Absolute differential elastic scattering cross sections measured with the 3-m, high resolution, time-of-flight spectrometer are presented for 54.9eV positrons incident on He. Five point moving average differential cross sections are plotted against average scattering angles which range from 14 to 36 deg. Also the averages of five differential cross sections which have adjacent values of scattering angle are plotted versus the corresponding averages of the scattering angles. The curve fitted to these data is shaped like the theoretical curve but has its minimum and its maximum at scattering angles that are about 4 deg higher and 15 deg lower respectively than predicted by theory

On Black Hole Thermodynamics of 2-D Type 0A

We present a detailed analysis of the thermodynamics of two dimensional black hole solutions to type 0A with q units of electric and magnetic flux. We compute the free energy and derived quantities such as entropy and mass for an arbitrary non-extremal black hole. The free energy is non-vanishing, in contrast to the case of dilatonic 2-d black holes without electric and magnetic fluxes. The entropy of the extremal black holes is obtained, and we find it to be proportional to q^2, the square of the RR flux. We compare these thermodynamics quantities with those from candidate matrix model duals.Comment: 20pp, v2: references adde