31Vertebrate vision is accomplished through a set of light-sensitive photopigments, which 32 are located in the photoreceptors of the retina and consist of a visual opsin protein bound 33 to a chromophore. In dim-light, vertebrates generally rely upon a single rod opsin (RH1) 34 for obtaining visual information. By inspecting 101 fish genomes, we found that three 35 deep-sea teleost lineages have independently expanded their RH1 gene repertoires. 36 Amongst these, the silver spinyfin (Diretmus argenteus Johnson 1863) stands out as having 37 the highest number of visual opsins known for animals to date (2 cone and 38 rod opsins). 38 Spinyfins simultaneously express up to 14 RH1s encoding for photopigments with 39 different peak spectral sensitivities (λmax=448-513 nm) that cover the range of the residual 40 daylight, as well as the bioluminescence spectrum present in the deep-sea. Our findings 41 present novel molecular and functional evidence for the recurrent evolution of multiple 42 rod opsin-based vision in vertebrates. 43 44 SHORT ABSTRACT: Contrary to the single rod opsin used by most vertebrates, some fishes 45 use multiple rod opsins for vision in the dimly lit deep-sea. 46 Animals use vision for a variety of fundamental tasks including navigation, food acquisition, 47

Coral reefs belong to the most diverse ecosystems on our planet. The diversity in coloration and lifestyles of coral reef fishes makes them a particularly promising system to study the role of visual communication and adaptation. Here, we investigated the evolution of visual pigment genes (opsins) in damselfish (Pomacentridae) and examined whether structural and expression variation of opsins can be linked to ecology. Using DNA sequence data of a phylogenetically representative set of 31 damselfish species, we show that all but one visual opsin are evolving under positive selection. In addition, selection on opsin tuning sites, including cases of divergent, parallel, convergent and reversed evolution, has been strong throughout the radiation of damselfish, emphasizing the importance of visual tuning for this group. The highest functional variation in opsin protein sequences was observed in the short- followed by the long-wavelength end of the visual spectrum. Comparative gene expression analyses of a subset of the same species revealed that with SWS1, RH2B and RH2A always being expressed, damselfish use an overall short-wavelength shifted expression profile. Interestingly, not only did all species express SWS1 - a UV-sensitive opsin - and possess UV-transmitting lenses, most species also feature UV-reflective body parts. This suggests that damsels might benefit from a close-range UV-based 'private' communication channel, which is likely to be hidden from 'UV-blind' predators. Finally, we found that LWS expression is highly correlated to feeding strategy in damsels with herbivorous feeders having an increased LWS expression, possibly enhancing the detection of benthic algae.

Visual sensitivity can be tuned by differential expression of opsin genes. Among African cichlid fishes, seven cone opsin genes are expressed in different combinations to produce diverse visual sensitivities. To determine the genetic architecture controlling these adaptive differences, we analysed genetic crosses between species expressing different complements of opsin genes. Quantitative genetic analyses suggest that expression is controlled by only a few loci with correlations among some genes. Genetic mapping identifies clear evidence of trans‐acting factors in two chromosomal regions that contribute to differences in opsin expression as well as one cis‐regulatory region. Therefore, both cis and trans regulation are important. The simple genetic architecture suggested by these results may explain why opsin gene expression is evolutionarily labile, and why similar patterns of expression have evolved repeatedly in different lineages.

BackgroundCichlid fishes, particularly tilapias, are an important source of animal protein in tropical countries around the world. To support selective breeding of these species we are constructing genetic and physical maps of the tilapia genome. Physical maps linking collections of BAC clones are a critical resource for both positional cloning and assembly of whole genome sequences.ResultsWe constructed a genome-wide physical map of the tilapia genome by restriction fingerprinting 35,245 bacterial artificial chromosome (BAC) clones using high-resolution capillary polyacrylamide gel electrophoresis. The map consists of 3,621 contigs and is estimated to span 1.752 Gb in physical length. An independent analysis of the marker content of four contigs demonstrates the reliability of the assembly.ConclusionThis physical map is a powerful tool for accelerating genomic studies in cichlid fishes, including comparative mapping among fish species, long-range assembly of genomic shotgun sequences, and the positional cloning of genes underlying important phenotypic traits. The tilapia BAC fingerprint database is freely available at .

Three-body rate coefficients for reactions of H + 0 2 + M where M = Nz and HzO have been measured in a high-temperature flow reactor as a function of temperature up to 750 K. Room-temperature rate coefficients for M = Ar have also been quantified. The rate coefficients are measured by the flash photolysis method where atomic hydrogen is produced by excimer laser photolysis of precursor molecules (HzS or HzO) and then probed by either laser-induced fluorescence or resonance absorption. The rate coefficient measurements for nitrogen (298-580 K) can be described by the Arrhenius expression exp[(825 f 130)/T] cm6 molecuk2 s-l. Rate coefficients measured for water are k~~o ( S 7 5 ) = (1.2 f 0.3) X k~,o(650) = (1.0 f 0.3) X 10-31, and k~~o ( 7 5 0 ) = (1.22;) X cm6 molecule-2 s-'. Room-temperature measurements for Ar gave a rate coefficient of kk(298) = (2.1 f 0.2) X 10-32.= (2.9 f 0.8) X