Molecular analysis of a haplosporidian parasite from cultured New Zealand abalone Haliotis iris

Abstract

In the Austral summer and autumn of 2000 and 2001, mortalities of black-footed abalone Haliotis iris (Martyn, 1784) occurred in a commercial facility in New Zealand. Histological analyses suggested that infection by a haplosporidian parasite was responsible. To confirm identification as a haplosporidian and to help determine if this parasite represented a new, undescribed species, DNA was extracted from infected host tissues scored as positive for infection by histological examination. Small-subunit rRNA (SSU rRNA) gene sequences from both the host abalone and a parasitic organism were amplified by PCR and characterized. Although the sequence for this parasite was novel, not matching any known SSU rRNA gene sequences, phylogenetic analyses strongly supported grouping this parasite with the haplosporidians. Parsimony analyses placed the parasite at the base of the phylum Haplosporidia, ancestral to Urosporidium crescens and the Haplosporidium, Bonamia, and Minchinia species. Sequencing of multiple parasite DNA clones revealed a single polymorphic site in the haplosporidian SSU rRNA gene sequence.KEY WORDS: Haplosporidian · Abalone · SSU rDNA · Parasite · Molecular phylogenetic Resale or republication not permitted without written consent of the publisherDis Aquat Org 53: [61][62][63][64][65][66] 2003 ease, is morphologically similar to H. nelsoni and has been responsible for mortalities of eastern oysters in seaside embayments of the US mid-Atlantic coast (Andrews et al. 1962). Bonamia ostreae, pathogenic in the European flat oyster Ostrea edulis, has devastated the flat oyster industry in Western Europe. Katkansky et al. (1969) reported a 'microcell' parasite that resembled B. ostreae in O. edulis from California. Elston et al. (1986) later traced B. ostreae in France to importation of oysters from California. More recently, this parasite was also found on the east coast of the United States (Friedman & Perkins 1994), presumably by introductions of infected O. edulis from the west coast. Bonamia exitiosus, morphologically similar to B. ostreae, is pathogenic to the dredge oyster Ostrea chilensis in New Zealand (Hine 1991, Hine et al. 2001. Both species of Bonamia were tentatively considered haplosporidians despite the apparent absence of sporulation during their life cycles (Pichot et al. 1980, Hine & Wesney 1992, Hine et al. 2001) and molecular evidence has recently confirmed their inclusion in the phylum Haplosporidia (Carnegie et al. 2000.Histological examination of cultured abalone from a New Zealand aquaculture facility experiencing mortalities suggested the presence of a haplosporidian parasite, although no spores were observed . Molecular genetic analysis was performed using SSU rDNA obtained from infected abalone to further characterize this organism. MATERIALS AND METHODSDNA isolation and PCR amplification. DNA was isolated from epipodium tissue of 5 infected Haliotis iris individuals (2 animals received in September 2000 and 3 animals received in February 2001) using the protocol for anim...

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