No abstract

We present the Wrst study of the eVects of ocean acidiWcation on settlement of benthic invertebrates and microfauna. ArtiWcial collectors were placed for 1 month along pH gradients at CO 2 vents oV Ischia (Tyrrhenian Sea, Italy). Seventy-nine taxa were identiWed from six main taxonomic groups (foraminiferans, nematodes, polychaetes, molluscs, crustaceans and chaetognaths). Calcareous foraminiferans, serpulid polychaetes, gastropods and bivalves showed highly signiWcant reductions in recruitment to the collectors as pCO 2 rose from normal (336-341 ppm, pH 8.09-8.15) to high levels (886-5,148 ppm) causing acidi-Wed conditions near the vents (pH 7.08-7.79). Only the syllid polychaete Syllis prolifera had higher abundances at the most acidiWed station, although a wide range of polychaetes and small crustaceans was able to settle and survive under these conditions. A few taxa (Amphiglena mediterranea, Leptochelia dubia, Caprella acanthifera) were particularly abundant at stations acidiWed by intermediate amounts of CO 2 (pH 7.41-7.99). These results show that increased levels of CO 2 can profoundly aVect the settlement of a wide range of benthic organisms. Communicated by F. Bulleri. M. Cigliano and M. C. Gambi contributed equally.

Optical tweezers, tools based on strongly focused light, enable optical trapping, manipulation, and characterisation of a wide range of microscopic and nanoscopic materials. In the limiting cases of spherical particles either much smaller or much larger than the trapping wavelength, the force in optical tweez

Nitric oxide (NO) is essential to many physiological functions and operates in several signaling pathways. It is not understood how and when the different isoforms of nitric oxide synthase (NOS), the enzyme responsible for NO production, evolved in metazoans. This study investigates the number and structure of metazoan NOS enzymes by genome data mining and direct cloning of Nos genes from the lamprey. In total, 181 NOS proteins are analyzed from 33 invertebrate and 63 vertebrate species. Comparisons among protein and gene structures, combined with phylogenetic and syntenic studies, provide novel insights into how NOS isoforms arose and diverged. Protein domains and gene organization--that is, intron positions and phases--of animal NOS are remarkably conserved across all lineages, even in fast-evolving species. Phylogenetic and syntenic analyses support the view that a proto-NOS isoform was recurrently duplicated in different lineages, acquiring new structural configurations through gains and losses of protein motifs. We propose that in vertebrates a first duplication took place after the agnathan-gnathostome split followed by a paralog loss. A second duplication occurred during early tetrapod evolution, giving rise to the three isoforms--I, II, and III--in current mammals. Overall, NOS family evolution was the result of multiple gene and genome duplication events together with changes in protein architecture.