scholarly journals Mass mortality of pearl oyster (Pinctada fucata (Gould)) in Japan in 2019 and 2020 is caused by an unidentified infectious agent

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12180
Author(s):  
Tomomasa Matsuyama ◽  
Satoshi Miwa ◽  
Tohru Mekata ◽  
Yuta Matsuura ◽  
Tomokazu Takano ◽  
...  

Mass mortality of 0-year-old pearl oysters, Pinctada fucata (Gould), and anomalies in adults were observed in Japan’s major pearl farming areas in the summer of 2019 and 2020. Although adult oyster mortality was low, both adult and juvenile oysters underwent atrophy of the soft body, detachment of the mantle from nacre (the shiny inner surface of the valves), deposition of brownish material on the nacre, and loss of nacre luster. Infection trials were conducted to verify the involvement of pathogens in this phenomenon. Healthy adult pearl oysters were obtained from areas where this disease had not occurred to use as the recipients. The sources of infection were either affected adult oysters with atrophied soft bodies or batches of juveniles in which mortality had reached conspicuous levels. Transmission of the disease to the healthy oysters were tested either by cohabitation with affected oysters or by injections of the hemolymph of affected animals. The injection infection test examined the effects of filtration and chloroform exposure on the pathogen. Occurrence of the disease was confirmed by the appearance of brown deposits on the nacre and loss of nacre luster. The abnormalities of nacre were clearly reproduced in recipient shells in three out of four cohabitation trials with affected oysters. The disease was also reproduced in six out of six injection trails either with hemolymph filtered through 100 nm filter or with hemolymph treated with chloroform. In a serial passage with hemolymph injections, the disease was successfully transmitted through eight passages. These results suggest that the etiology of the disease is a non-enveloped virus with a diameter ≤100 nm.

2011 ◽  
Vol 3 (2) ◽  
Author(s):  
M. S. Hamzah ◽  
Bisman Nababan ◽  
Bisman Nababan

The pearl oyster (Pinctada maxima) farming in the West Nusa Tenggara waters in particular and in other areas, complained to the mass mortality of pearl oysters saplings on shell width between 3-4 cm. The mass mortality, allegedly as a result of changing in environmental conditions and triggered by the shift in seasons. This research aimed to determine the effect of seasonal variations in water conditions at different depth levels on growth and survival of seedlings of pearl oysters conducted on March 23, 2008 to February 22, 2009. This research was very useful for pearl oyster farming in an effort to suppress the mass mortality rates based on the appropriate level of depth and seasons. Analysis of variance showed that the seasonal factors, the level of depth, and the interaction between both factors responded very significantly on pearl oyster seedling survival. The "significant difference test" showed that the interaction between season and level of 2 m depth provided the best result with 100% survival. The similar survival rate was also found at a depth of 8 m during the transition season I and the east season. For single factor (depth), the best result for growth and survival rate was found in 2 m deep during the transition season I.Keywords: Oyster sapling, Pinctada maxima, growth, mortality, season, depth, Kodek Bay


2002 ◽  
Vol 37 (3) ◽  
pp. 149-151 ◽  
Author(s):  
Tsuneo Morizane ◽  
Hirohumi Yamashita ◽  
Yoshiyuki Fujita ◽  
Hidemasa Kawakami ◽  
Osamu Ochi ◽  
...  

2021 ◽  
Vol 8 ◽  
Author(s):  
Zhe Zheng ◽  
Yongshan Liao ◽  
Jianming Ye ◽  
Chuangye Yang ◽  
Linda Adzigbli ◽  
...  

Environmental microbiota plays a vital role in the intestinal microbiota of aquatic organisms. However, data concerning the association between the intestinal microbiota of pearl oyster Pinctada fucata martensii and the surrounding seawater are limited. The existing bacterial communities in pearl oyster intestine and surrounding water from two sites (D and H, within Liusha Bay in Guangdong, China) were investigated using 16S rRNA-based sequencing to explore the relationship among the two. D located in the inner bay, and H located in the open sea area outside bay. Results revealed the richness and diversity of pearl oyster intestinal microbiota to be less than those of the surrounding water, with 38 phyla and 272 genera observed as a result of the classifiable sequence. The microbiota compositions in the intestine and the surrounding water were diversified at the phylum and genus levels, with the sequencing data being statistically significant. However, the functional prediction of microbiota emphasized the overall similarity in the functional profile of the surrounding seawater and intestinal microbiomes. This profile was associated with metabolism of cofactors and vitamin, carbohydrates metabolism, amino acids metabolism, metabolism of terpenoids, and polyketides, metabolism of other amino acids, lipids metabolism, and energy metabolism. Seven common operational taxonomic units (OTUs), which belonged to phyla Tenericutes, Cyanobacteria, and Planctomycetes, were noted in the intestines of pearl oysters from two different sites. These OTUs may be affiliates to the core microbiome of pearl oyster. Significantly different bacterial taxa in the intestines of pearl oysters from two different sites were found at the phylum and genus levels. This finding suggested that the bacterial communities in pearl oyster intestines may exhibit some plasticity to adapt to changes in the surrounding water-cultured environment. This study generally offers constructive discoveries associated with pearl oyster intestinal microbiota and provides guidance for sustainable aquaculture.


2021 ◽  
Author(s):  
Akihiro SAKATOKU ◽  
Kaito Hatano ◽  
Shoki Tanaka ◽  
Tadashi Isshiki

Abstract In the summers of 2019 and 2020, a previously undescribed disease occurred in both juvenile and adult shellfish, causing mass mortalities in cultured pearl production, characterized by the major symptom of extreme atrophy of the soft tissues, including the mantle. However, the causative organism was uncertain. We isolated Vibrio sp. strain MA3 from the mantles of diseased pearl oysters Pinctada fucata. Analyses of 16S rRNA gene and DNA gyrase sequence homologies and its biochemical and morphological characteristics suggested that strain MA3 is a new strain of Vibrio alginolyticus. In addition, a hemolysin gene (Vhe1) of strain MA3 was detected as one of the virulence factors, and the complete sequence was determined. BLAST searches showed that Vhe1 shares 99.8% nucleotide sequence identity with Vibrio alginolyticus strain A056 lecithin-dependent hemolysin (ldh) gene, complete cds. Experimental infection of healthy oysters via injection with strain MA3 indicated it could cause high mortalities of the typically affected oysters from which the strain was isolated. These results suggest that the newly isolated Vibrio sp. strain MA3 is a putative causal agent of the recent disease outbreaks in Akoya pearl oysters.


2014 ◽  
Vol 6 (1) ◽  
Author(s):  
M S Hamzah

<p>The pearl oyster (<span style="text-decoration: underline;">P</span>. <span style="text-decoration: underline;">maxima</span>) farming particularly in the Kapontori Bay, Buton Island waters and in other areas had complained for the mass mortality of pearl oysters saplings on the shell width between 3-4 cm. The mass mortality, was allegedly as a result of changing in environmental conditions and triggered by the shift in seasons. This research aimed to determine the effect of seasonal variations in water conditions at different depth levels on growth and survival of seedlings of pearl oysters conducted on March 27, 2007 to February 28, 2008. This research was very useful for pearl oyster farming in an effort to suppress the mass mortality rates based on the appropriate level of depth and seasons. The variance analyses showed that depth levels affected the survival rates of the pearl oyster seeds significantly (P&lt;0.01). Based on honest significantly difference test, it also showed that the percentage number of survival rate was found higher within the depth of 2m (93.33%). Based on the relationship analyses between length and weight of shell body in all depths indicated a similar growth pattern of  minor allometric (b&lt;3). The growth, survival rate, and environmental conditions based on depth levels on pearl oyster saplings were discussed in this paper.</p> <p>Keywords: Seasonal variation, survival rate, growth, pearl shell (<span style="text-decoration: underline;">P</span>. <span style="text-decoration: underline;">maxima</span>), depth level</p>


2001 ◽  
Vol 36 (4) ◽  
pp. 225-230 ◽  
Author(s):  
Yukio Maeno ◽  
Takafumi Ito ◽  
Takashi Kamaishi ◽  
Tsuneo Morizane ◽  
Kazuhiro Nakajima

2021 ◽  
Vol 12 ◽  
Author(s):  
Yanfei Cao ◽  
Yu Jiao ◽  
Shuzhi Zhan ◽  
Xueru Liang ◽  
Zhixin Li ◽  
...  

The polyamine putrescine (Put) is a ubiquitous small cationic amine. It plays an essential role in controlling the innate immune response. However, little is known about its function in mollusks. In this study, the Put content was observed to increase in the serum of pearl oyster Pinctada fucata martensii after 6 and 24 h of lipopolysaccharide (LPS) stimulation. Activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) increased, and nitric oxide synthase was downregulated in the Put group (i.e., combined treatment with Put and LPS) compared with that in the LPS group (i.e., combined treatment with phosphate-buffered saline and LPS). Furthermore, activities of alkaline phosphatase and acid phosphatase were inhibited after 6 h of LPS stimulation. The expression levels of the nuclear factor kappa B, IκB kinase, Janus kinase, and signal transducer and activator of transcription proteins genes were all significantly suppressed at 12 and 24 h in the Put group. Pseudomonas aeruginosa and Bacillus subtilis grew better after being incubated with the serum from the Put group than that from the LPS group. Additionally, the Put treatment remarkably inhibited the autophagy of hemocytes mediated by the AMP-activated protein kinase-mammalian target of rapamycin-Beclin-1 pathway. This study demonstrated that Put can effectively inhibit the inflammatory response induced by LPS in pearl oysters. These results provide useful information for further exploration of the immunoregulatory functions of polyamines in bivalves and contribute to the development of immunosuppressive agents.


2021 ◽  
Vol 8 ◽  
Author(s):  
Xingzhi Zhang ◽  
Bingcong Ye ◽  
Zhifeng Gu ◽  
Meng Li ◽  
Shouguo Yang ◽  
...  

Pearl oyster (Pinctada fucata martensii) is the main species cultured for marine pearls in the world. A breeding program was carried out for desirable production traits, including high growth rate, and a fast-growing selective strain of pearl oysters was established. In the current study, we compared the growth characteristics between a selective strain and a cultured population of P. f. martensii in Beihai, Guangxi Province, China. Large size (SL) and small size (SS) individuals of the selective strain were selected, and the differences of physiological and metabolic indexes, such as feeding, respiration, excretion, and enzyme activities between SL and SS and cultured population (CL), were also compared. The results showed that at the age of 6 months, pearl oysters of the selective strain were 14.61% larger than CL, and the proportion of SL (30–40 mm) was 59%, which was two times higher than CL (28%). SL with a rapid growth rate had a high clearance rate (CR), and the CR of SL was about 1.8 times higher than that of CL and 5 times higher than that of SS. In addition, the activities of digestive enzymes (amylase, pepsin, and lipase) and growth-related carbonic anhydrase enzymes in SL were higher than those in the other two groups (p &lt; 0.05). SS with a slow growth rate had higher oxygen consumption (OCR) and ammonia excretion (AER) rates than SL and CL (p &lt; 0.05). Our results suggest that the rapid growth of the selective strain P. f. martensii can be attributed to increased energy intake and reduced energy consumption.


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