Bonamia exitiosus n.sp. (Haplosporidia) infecting flat oysters Ostrea chilensis in New Zealand

Abstract

Bonamia sp. is a pathogenic parasite that occurs in the haemocytes of dredge oysters Ostrea chilensis Philippi in New Zealand. Ultrastructurally it resembles other haplosporidians in the possession of haplosporosomes, haplosporogenesis, persistence of mitotic microtubules during interphase and of the nuclear envelope during mitosis, and occurrence of a diplokaryotic or multi-nucleate plasmodial stage. Another stage containing a large vacuole derived from enlargement of 1 or more mitochondria has not previously been described from other haplosporidians. It most closely resembles B. ostreae Pichot et al., 1979, which parasitises and is pathogenic in haemocytes of European flat oysters, O. edulis. However, B. ostreae is smaller and denser, and has fewer lipoid bodies and haplosporosomes. We have nearly completely sequenced the small ribosomal gene of the organism from O. chilensis. Initial comparisons of these sequences with those of other protozoans showed similarities to B. ostreae. Polymorphism within Bonamia sp. was confirmed by restriction fragment length polymorphism analysis. On the basis of ultrastructural and molecular considerations it is proposed that this organism be named Bonamia exitiosus sp. nov. KEY WORDS: Bonamia exitiosus · Ostrea chilensis · Ultrastructure · 18S rDNA · New Zealand Resale or republication not permitted without written consent of the publisherDis Aquat Org 47: [63][64][65][66][67][68][69][70][71][72] 2001 MATERIALS AND METHODS Ultrastructural studies. Infected Ostrea chilensis (n = 237) from Foveaux Strait were opened one at a time, the heart was removed and cut in two, imprints were made with one half, and the other half was fixed for ultrastructural studies. Imprints were stained with Hemacolor™ (Merck) and microscopically examined, and heavily infected oysters were selected for further study. Hearts were fixed in 2.5% glutaraldehyde in 0.22 µm filtered seawater for 1 to 2 h, washed twice in filtered seawater, post-fixed in 1% OsO 4 for 1 h, stained en bloc with 5% uranyl acetate in 0.1 M sodium acetate buffer for 45 min, dehydrated in ascending (50 to 100%) ethyl alcohol, embedded in Araldite, sectioned, stained with 5% uranyl acetate for 10 min and in 5% lead citrate for 5 to 6 min, and examined on a Philips 420ST TEM.To compare Bonamia sp. with B. ostreae, quantitative data were taken from published studies on the ultrastructure of B. ostreae (Pichot et al. 1979, Brehélin et al. 1982, Balouet et al. 1983, Grizel 1985, Hervio et al. 1991 and from archived material held at the IFREMER laboratory at Ronce-les-Bains, La Tremblade, France. Samples were compared directly under the TEM from blocks of B. ostreae infected Ostrea edulis kindly lent by Steve Feist of the MAFF Fish Diseases Laboratory, Weymouth, England.Base sequence studies. DNA extraction: Genomic DNA was extracted from Bonamia sp. infected Ostrea chilensis using the following procedure. Ethanol fixed tissues were suspended in 1 ml of extraction buffer (NaCl 100 mM, EDTA 25 mM, pH 8, SDS 0.5%) with proteina...

Detection of Bonamia ostreae and B. exitiosa (Haplosporidia) in Ostrea edulis from the Adriatic Sea (Italy)

“…Dis Aquat Org 89: [79][80][81][82][83][84][85] 2010 Bonamia exitiosa infects Ostrea chilensis in New Zealand (Hine et al 2001) and O. angasi in Australia (Corbeil et al 2006) and has been recently reported in O. edulis in Spain (Abollo et al 2008). B. roughleyi, previously called Mikrocytos roughleyi, infects Saccostrea glomerata in southeast Australia (Farley et al 1988).…”

“…B. ostreae (Pichot et al 1980) occurs naturally in O. edulis L. (Grizel et al 1983). Bonamia exitiosa infects Ostrea chilensis in New Zealand (Hine et al 2001) and O. angasi in Australia (Corbeil et al 2006) (Farley et al 1988). B. perspora is a newly described protozoan species found in Ostreola equestris (North Carolina, USA) and represents the first Bonamia species producing a typical haplosporidian spore (Carnegie et al 2006).…”

“…The presence of haplosporosomes (Pichot et al 1980, Hine et al 2001) and the molecular analysis of the small subunit rRNA (SSU rRNA) gene (Carnegie et al 2000, Cochennec et al 2000, Cochennec-Laureau et al 2003, Carnegie & Cochennec-Laureau 2004, Reece et al 2004 placed, phylogenetically, the genus Bonamia in the phylum Haplosporidia. Four characterized species are included in this genus: B. ostreae, B. exitiosa, B. roughleyi (OIE 2006), and B. perspora.…”

A comparative appraisal of the resilience of marine social-ecological systems to mass mortalities of bivalves

“…Technical measures that have had some success include: (1) introduction of new or resistant species and varying the sources of spat to maintain the same level of economic activity (Grizel 1983, Grizel and Héral 1991, Ewart and Ford 1993, McKindsey et al 2007, Padilla 2010, Castinel et al 2015; (2) chemical or physical solutions such as water treatment, animal purification, immunostimulants, penicillin, active clay, hydrogen peroxide, and coagulants to prevent or limit disease (Di Salvo et al 1978, Matsuyama 1999, Mydlarz et al 2006; and (3) prevention measures such as monitoring and surveillance systems, quarantine and prevention of oyster movements to contain the disease, awareness and reporting by the industry, and risk assessment (Matsuyama 1999, Hine et al 2001, Murray et al 2012, Paul-Pont et al 2014, Castinel et al 2015. Organizational responses (e.g., state aid, mutual funds, diversification strategies, private insurance, inventories, and savings) occur at both individual and collective levels (Grizel 1983, Le Bihan et al 2013, Lupo et al 2014.…”

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

“…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.…”