A Vibrio anguillarum-related (VAR) strain, isolated in pure culture from an epizootic in a commercial hatchery producing Argopecten purpuratus, was characterized, and its potential pathogenicity to veliger larvae of A. purpuratus determined. Experimental challenges indicated that the bacterium affects larval survival at concentrations of 104 to 108 cells ml-l The effect of water quality and temperature on pathogenicity was also evaluated. Larval survival in seawater filtered through 5 pm pore-size membranes was 45.6%, whereas using seawater passed through 1 and 0.2 pm filters, larval survival increased to 66.4 and 80.4 % respectively. Temperature also affected pathogenicity as larval survival at 15OC for 24 h was 69.3 % but decreased to 30 and 26.9 % at 20 and 25°C respectively. Toxic activity was found in cell-free supernatant of bacterial culture. Larval survival was reduced to 68.9 and 36.4% after 20 and 40% (v/v) of supernatant, respectively, was added to the rearing water. These results suggest that exotoxins produced by the VAR strain play an in~portant role in its pathogenicity for scallop larvae.

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SUMMARY Microalgae are an important source of unsaturated fatty acids, phospholipids, glycolipids, and carotenes, which are useful compounds for the food and pharmaceutical industries. The Atacama Desert of northern Chile is one of the driest deserts on Earth and, as such, it is a great natural laboratory in which to study new microorganisms adapted to extreme environments. A microalgal strain, referred to here as CH03, was isolated from a microbial mat in salt flat water in Salar de Atacama. Genetic analysis of the 18S ribosomal RNA gene showed that the strain had homology with other known sequences of the species Chlorella sorokiniana. Our results revealed the adaptability of this microalga to freshwater medium under laboratory conditions, despite coming from an extremely high‐salinity environment. The fatty acid profile of CH03(A) newly isolated in Bold's basal medium differed from that of CH03(B) cultured in vitro in modified F/2 medium and from another five strains of C. sorokiniana and three strains of Chlorella vulgaris in that it had a high stearic acid content and had no polyunsaturated fatty acids. The major biochemical components observed in this strain were proteins (64.3–73.6%) and lipids (26.6–32.6%). This study suggests that the strain CH03 could be a protein source and that this oleaginous microalga is easy to grow in vitro as a biological model for future studies.