Gonadal State of the Oyster Crassostrea Angulata Cultivated in Taiwan

Sun

et al. 2018

Appl Environ Microbiol

Symbiotic microorganisms have been found in the hemolymph (blood) of many aquatic invertebrates, such as crabs, shrimps and oysters. Hemolymph is a critical site in host immune response. Currently, studies on hemolymph microorganisms are mostly performed with culture-dependent strategies using selective media (e.g., TCBS, 2216E, and LB) for enumerating and isolating microbial cells. However, doubts remain about the "true" representation of the microbial abundance and diversity of symbiotic microorganisms in hemolymph, particularly for uncultivable microorganisms which are believed to be more abundant than the cultured. To explore this, we developed a culture-independent cell extraction method for separating microbial cells from the hemolymph of three aquatic invertebrates (, , and) involving filtration through a 5-μm mesh filter membrane (the Filtration Method). A combination of the Filtration Method with fluorescence microscopy and high-throughput sequencing technique provides insight into the abundances and diversity of the total microbiota in the hemolymph of these three invertebrates. More than 2.6 × 10 cells/mL of microbial cells dominated by and, and, and and, were detected in the hemolymph of ,, and , respectively. A parallel study for investigating the hemolymph microbiome by comparing the Filtration Method and a culture-dependent method (the Plate Count Method), showed significantly higher microbial abundances (between 26 and 369-folds difference; P<0.05) and less biased community structures of the Filtration Method than those of the Plate Count Method. Furthermore, hemolymph of the three invertebrates harbored many potential pathogens, including ,, and Finally, the Filtration Method provides a solution that improves understanding of the metabolic functions of uncultivable hemolymph microorganisms (e.g., metagenomics) devoid of host hemocytes contamination. Microorganisms are found in invertebrates' hemolymph, a critical site in host immune response. Currently, studies on hemolymph microorganisms are mostly performed with culture-dependent strategies. However, doubts remain about the "true" representation of hemolymph microbiome. This study developed a culture-independent cell extraction method that could separate microbial cells from the hemolymph of three aquatic invertebrates (, , and) based on filtration through a 5-μm mesh filter membrane (the Filtration Method). A combination of the Filtration Method with fluorescence microscopy and high-throughput sequencing technique provides insight into the abundances and diversity of the total microbiota in the hemolymph of these three invertebrates. Our results demonstrate that the hemolymph of aquatic invertebrates harbors a much higher microbial abundance and distinct microbial community composition than previously estimated. Furthermore, this work provides a less biased solution for studying the metabolic functions of uncultivable hemolymph microbiota devoid of host hemocytes contamination.

Section: Resultssupporting

confidence: 87%

Hemolymph Microbiomes of Three Aquatic Invertebrates as Revealed by a New Cell Extraction Method

Sun

et al. 2018

Appl Environ Microbiol

“…This constant reproductive pattern has also been found in other Crassostrea spp., in subtropical and tropical areas, showing significant differences to the pattern of oysters in temperate regions. (Baqueiro‐Cárdenas et al, ; Castilho‐Westphal et al, ; Lenz & Boehs, ; Vaschenko, Hsieh, & Radashevsky, ). The reproductive period of mollusks living in temperate and cold climates is seasonal, the frequency of reproductive activity increases as latitude decreases (Baqueiro, ).…”

Section: Discussionmentioning

confidence: 99%

Influence of gonadal development on metal accumulation in the Portuguese oyster,Crassostrea angulata,in subtropical areas

Shi

Zhou

et al. 2019

Aquac Res

Metal enrichment makes oyster considered to be an appropriate food source for trace elements, but excessive accumulation can threaten human health. Reproduction is an important biotic factor that affects the metal accumulation in oysters. However, the influence of continuous gonad development model on metal accumulation in some subtropical oysters is still unclear. The present study addresses the concentrations of trace metals and glycogen associated with the gonadal and somatic tissues throughout the reproductive cycle of diploid and triploid Crassostrea angulata cultured in Fujian, China. Cu, Zn and Pb contents of gonads were negatively correlated (p < 0.05) with gonadosomatic index (GSI). The correlation between Cd content and GSI was not significant. There was a positive correlation (p < 0.05) between GSI and Mn content in female gonads while the correlation was negative (p < 0.05) in males, indicating Mn plays an important role in gametogenesis of females. The effects of gonadal maturity and gender on metal accumulation in somatic tissue were not significant (p > 0.05). The concentrations of all metals in sterile triploids were not significantly different from those of the somatic tissue of diploids. Gonadal glycogen content showed a negative correlation with the GSI. However, somatic glycogen content was not affected by gonadal development, indicating that the energy consumed during gametogenesis comes mainly from recently ingested food rather than from energy stored in somatic tissue. The effects of the gonadal development on the metal accumulation in oysters varied according to the metal and tissue type.

“…In several aquatic species, chemical pollution has already been shown to impair gametogenesis. In the oyster, Crassostrea angulata, from different locations in Taiwan, low gonad maturity index and pathological alterations (e.g., atresia, hemocytic infiltration of gonadal tissue) were associated to chemical pollution, in particular to the presence of elevated heavy metal concentrations (Vaschenko et al 2013). Recently, in vitro exposure of zebra fish ovary tissue to the herbicide glyphosate (15 days, 65 mg/L) resulted in a significant increase in both oocyte diameter and in the presence of unusual concentric membranes associated with the external membranes of mitochondria and yolk granules (Armiliato et al 2014).…”

Section: Diuron Affected the Expression Of Genes Belonging To Functions Known To Play A Major Role During Oyster Gametogenesis And Modulamentioning

confidence: 99%

Effects of an environmentally relevant concentration of diuron on oyster genitors during gametogenesis: responses of early molecular and cellular markers and physiological impacts

Akcha

Barranger

Bachère

et al. 2016

Environ Sci Pollut Res

Genitors of the Pacific oyster Crassostrea gigas were submitted during gametogenesis to a short pulse exposure to the herbicide diuron at a realistic environmental concentration. Histological analysis showed no effect of diuron on gametogenesis course, sex ratio and reproductive effort. A non-significant increase in testosterone and progesterone levels was observed in genitors exposed to the herbicide. At cell level, diuron exposure was shown to modulate the phagocytic activity of circulating hemocytes. The results of a transcriptional analysis showed that diuron affected the expression of genes belonging to functions known to play a major role during oyster gametogenesis such as gene transcription regulation, DNA replication and repair, DNA methylation and cytokinesis. Taking into account the results we previously obtained on the same genitors, this study showed a negative effect of diuron on oyster reproduction by inducing both structural and functional modifications of the DNA.