Mass Mortalities of Japanese Pearl Oyster in Uwa Sea, Ehime in 1997-1999.

Morizane, Tsuneo; Takimoto, Shin-ichi; Nishikawa, Satoru; Matsuyama, Norihiko; Tyohno, Kazunori; Uemura, Sakujiroh; Fujita, Yoshiyuki; Yamashita, Hirofumi; Kawakami, Hidemasa; Koizumi, Yoshitsugu; Uchimura, Yuhshi; Ichikawa, Mamoru

doi:10.3147/jsfp.36.207

Cited by 26 publications

(8 citation statements)

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“…Adductor muscles were excised, and the degree of reddish-brown tincture was measured using a Chroma Meter CR-300 (Konica Minolta, Tokyo, Japan) and assigned an a-value on a Hunter color difference scale [ 19 ]. Abnormal reddish-brown tincture was clearly recognizable by eye when the a-value was over 3.0 [ 5 ], and an a-value above 4.0 was judged to be AOD [ 12 ].…”

Section: Methodsmentioning

confidence: 99%

“…A mass mortality event in 1994 greatly reduced the quantity and quality of Akoya pearl [ 2 ], and in 1996 and 1997, the annual mortality of Akoya oysters was more than 50% of the oysters in production [ 3 ] with localized losses of about 80% [ 4 ]. In 1999, mother pearl oyster production in Japan was reduced to 15.6% of the 1989 levels [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

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A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis

et al. 2017

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Mass mortality that is acompanied by reddish browning of the soft tissues has been occurring in cultured pearl oyster, Pinctada fucata martensii. The disease is called Akoya oyster disease (AOD). Although spreading pattern of the disease and transmission experiments suggest that the disease is infectious, the causative agent has not yet been identified. We used shotgun and 16S rRNA-based metagenomic analysis to identify genes that are present specifically in affected oysters. The genes found only in diseased oysters were mostly bacterial origin, suggesting that the causative agent was a bacterial pathogen. This hypothesis was supported by the inhibition of AOD development in naïve oysters injected with the hemolymph of diseased animals followed immediately with penicillin bath-administration. Further analyses of the hemolymph and mantle specifically and universally detected genes of bacteria that belong to phylum Spirochaetes in diseased pearl oysters but not in healthy oysters. By in situ hybridization or immunostaining, a Brachyspira-like bacterium was observed in the smears of hemolymph from affected oysters, but not from healthy oysters. Phylogenetic analysis using 16S rRNA sequences showed that the presumptive causative bacterium was outside of but most closely related to family Brachyspiraceae. We propose ‘Candidatus Maribrachyspira akoyae’ gen. nov, sp nov., for this bacterium.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis

et al. 2017

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“…The Japanese pearl oyster Pinctada fucata martensii is used for pearl production. Recently, there has been a drastic decrease in the Japanese population of the pearl oyster due to mass mortalities during summer 1,2 . Therefore, many culturists have introduced the exotic pearl oyster and cross‐bred them with Japanese populations.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, there has been a drastic decrease in the Japanese population of the pearl oyster due to mass mortalities during summer. 1,2 Therefore, many culturists have introduced the exotic pearl oyster and cross-bred them with Japanese populations. Consequently, it is very difficult to obtain pure Japanese lineages.…”

Section: Introductionmentioning

confidence: 99%

Effects of cryopreservation on sperm structure in Japanese pearl oysterPinctada fucata martensii

et al. 2008

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To clarify factors reducing the motility and fertility of cryopreserved spermatozoa of the Japanese pearl oyster Pinctada fucata martensii, the structure of spermatozoa before and after cryopreservation was observed by scanning electron microscopy. Testicular spermatozoa were diluted with cryopreservation diluent (10% methanol + 18% fetal bovine serum + 72% sea water), and dispensed into 0.25-mL straws. The straws were cooled at a rate of approximately -20°C/min to -50°C, and subsequently immersed in liquid nitrogen. Percentage motility of spermatozoa before cryopreservation was 69.9 Ϯ 4.2%, and that of cryopreserved spermatozoa was 24.0 Ϯ 1.8%, respectively. In cryopreserved spermatozoa, the percentage that lacked or had a deformed flagellum was 56.6 Ϯ 3.9%, while in fresh spermatozoa this was 8.7 Ϯ 2.0%. In cryopreserved spermatozoa, the percentage of deformed acrosomes was 76.6 Ϯ 5.2%, while in fresh spermatozoa this was only 0.9 Ϯ 0.3%. Cryopreserved spermatozoa with a normal acrosome and flagellum were only 15.4 Ϯ 3.5% of those in fresh spermatozoa. These results indicate that lesion of the flagellum and deformation of the acrosome occurred through the cryopreservation procedure, and both types of damage lead to loss of the motility and fertility in thawed spermatozoa.

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“…Ehime Prefecture ranked first nationwide in pearl production and income from 1974 until 1996, when a virus decimated the akoya oysters (Morizane et al, 2001). The Uwa-sea region was unable to escape the effect of the outbreak, resulting in a drastic decrease in akoya production to a mere 20% of the previous high.…”

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confidence: 99%

DNA Techniques Applied to the Identification of Pinctada Fucata Pearls from Uwajima, Ehime Prefecture, Japan

Saruwatari¹,

Suzuki²,

Zhou³

et al. 2018

G&G

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odern pearl identification-including the type of pearl and any treatment applied-is performed by applying almost exclusively nondestructive methods. These include macro to microscopic observations, spectroscopy, chemical analysis, fluorescence, and various forms of X-ray imaging (Scarratt, 2011). Surface inspection differentiates nacreous from non-nacreous pearls, while chemical analyses using X-ray fluorescence and luminescence can distinguish between saltwater and freshwater pearls (e.g., Hänni, 2000; Hänni et al., 2005;Kessrapong et al., 2017). Internal inspection using X-radiography, which was introduced to gemology in the 1930s (Dirlam and Weldon, 2013), has evolved into high-tech X-ray computed microtomography (μ-CT). This technology enables more consistent separation of natural, non-bead-cultured, and bead-cultured pearls (e.g., Sturman, 2009;Karampelas et al., 2010).One of the ongoing challenges is to identify the saltwater mollusk species producing white, cream, or silver nacreous pearls, since these can form in all Pinctada species as well as some other species, and can have similar appearances. As pearls are formed by mollusks, a direct identification method would be to find biological evidence such as DNA indicators. (For boldfaced terms, please refer to the glossary on pp. 48-49.) DNA studies emerged in the biological sciences (e.g., Toro, 1998;Masaoka and Kobayashi, 2004; Freier et al., 2008) after the development during the 1980s of the polymerase chain reaction (PCR) method of duplicating gene fragments (see figure 1A). A number of studies on pearl oysters of the Pinctada species (e.g., Masaoka and Kobayashi, 2006;Tëmkin, 2010;Masaoka et al., 2016) have investigated their nuclear and mitochondrial ribosomal ribonucleic acid (rRNA) and the internal

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Mass Mortalities of Japanese Pearl Oyster in Uwa Sea, Ehime in 1997-1999.

Cited by 26 publications

References 1 publication

A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis

A Spirochaete is suggested as the causative agent of Akoya oyster disease by metagenomic analysis

Effects of cryopreservation on sperm structure in Japanese pearl oysterPinctada fucata martensii

DNA Techniques Applied to the Identification of Pinctada Fucata Pearls from Uwajima, Ehime Prefecture, Japan

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