Molecular identification of marine crustacean-pathogenic peronosporomycetes using DNA sequences of ITS1 and their pathogenicity for nauplii of brine shrimps

Abstract

We isolated 27 strains of marine crustacean-pathogenic Peronosporomycetes from various infected marine crustaceans collected in Japan, Thailand, Vietnam and the Philippines, and identified them morphologically. The internal transcribed spacer (ITS) l region of the nuclear rRNA gene of the 27 strains and 12 reference strains of six peronosporomycete species isolated from marine crustaceans were sequenced. The phylogenic relationship inferred from the sequences corresponded well to the morphological identification, indicating that sequencing of the ITS1 region is a useful tool for identification of marine crustacean-pathogenic Peronosporomycetes. Nauplii of brine shrimp Artemia salina were experimentally challenged by bathing in zoospore suspensions (1 × 104 zoospores/mL, 25°C) with 18 strains belonging to nine species in four genera. The 48-h mortalities varied from 1.1% to 99.4% among the species, though all the strains were isolated from diseased animals. © 2012 The Japanese Society of Fish Pathology.