Effects of Natural and Artificial Seawater on Digestive Gland and Gill Microorganisms of the Manila Clam (Ruditapes philippinarum) during Temporary Rearing without Feeding

Abstract

The bacteria of shellfish bioaccumulate mainly in the gill and digestive gland tissues, which can affect shellfish health status and disease susceptibility under stressful conditions or environmental effects. Ruditapes philippinarum is a filter-feeding shellfish with both ecological and economic significance, and it is classified as a Mollusca (phylum), Bivalvia (class), Veneridae (family), and Ruditapes (genus). In this study, 16S high-throughput sequencing was used to explore the microbiomics of digestive glands and gills of R. philippinarum under temporary rearing without feeding (including the purification process) in different water environments (natural vs. artificial seawater) from 0–7 days. The results revealed that the digestive glands and gills of R. philippinarum had their own unique bacterial community structures. Tissue microorganisms under the overlap of different water environments and starvation factors showed different dynamic effects within 0–7 days. The sand spitting and purification steps (posttransport rehydration stage of 24 hours) effectively reduced microorganism abundance. There were different biomarkers in the prerearing and postrearing periods, and R. philippinarum may be more susceptible to the enrichment of opportunistic pathogenic bacteria during the postrearing period in artificial seawater.

Tracking the hologenome dynamics in aquatic invertebrates by the holo-2bRAD approach

“…We evaluated and optimized the use of two kinds of noninvasive materials (gill swabs and feces), and applied a sampling method for the detection of pathogenic bacteria associated with the mortality of scallop larvae. The gill is a vital respiratory and filter-feeding organ of aquatic organisms, in which pathogens in seawater can be filter-fed and enriched 33 . Meanwhile, feces, containing the DNA of both the host and microorganisms from the intestine, can provide useful information about gastrointestinal health 34 and was also demonstrated to be an extremely valuable source of samples in hologenomic analysis 35 .…”