en Genetics Genetics پژوهشي Orginal research papers A Gram-negative, rod-shaped, motile and halophilic bacterium identified as Vibrio harveyi was isolated from hatchery-reared larval of Iran Shrimp Research Centerfollowing mass mortality . Seven isolates of Vibrio spp.were collected from nauplii of Litopenaeus vannamei and then were evaluated for characteristics including morphology, physiology and biochemistry. The results indicated that the isolates belonged to a single species that grew on Thiosulfate citrate- Bile Sucrose agar and in 1.5 to 6% NaCl, positive lysine and ornithine decarboxylation and susceptible to O/129 disk. Identification of Vibrio harveyi strainIS01 (1 of 7 isolates) was confirmed by Polymerase Chain Reaction assay for Vibrio harveyi (expected amplicon 1493 bp). The 16S ribosomal DNA sequence (National Center for Biotechnology Information, GenBank accession number GU974342.1) gave 99% sequence identity to V. harveyi ATCC: 35084 (GenBank accession number EU130475.1). Vibriosis, shrimp diseases, Litopenaeus vannamei, 16S rDNA sequencing 384 393 http://jifro.ir/browse.php?a_code=A-10-1272-88&slc_lang=en&sid=1 M Mirbakhsh 100319475328460010139 100319475328460010139 Yes A Akhavan sepahy 100319475328460010140 100319475328460010140 No M Afsharnasab 100319475328460010141 100319475328460010141 No A Khanafari 100319475328460010142 100319475328460010142 No M.R Razavi 100319475328460010143 100319475328460010143 No