Identification of Gut Microbiota in Blue Swimming Crabs Collected from the Eastern Coast of the Gulf of Thailand Containing Gill Net Debris

Abstract

The aim of this study was to investigate the gut microbiota of blue swimming crabs (Portunus pelagicus) in which a piece of gill net debris was found. Next-generation sequencing was performed to analyse the V1–V3 sequences of the 16S rRNA gene for bacteria and the internal transcribed spacer sequences for fungi. Samples of stomach crabs were collected from the coastal wetlands of eastern Thailand. Four fragments of gill nets were found (a single piece per gut sample), with lengths of 5.2–12.5 mm. Stomachs without gill net fragments from a total of four samples comprised Group A, whereas stomachs containing gill net fragments in the four samples comprised Group B. Groups A and B shared 131 OTUs (Operational Taxonomic Units), while they contained 51 and 26 OTUs, respectively. Photobacterium was the predominant Vibrionaceae present in both groups, but Marinobacter of Alteromonadaceae was present at high levels in Group A. Interestingly, a single sample in Group B was dominated by Vibrio. For fungi, 276 and 195 OTUs were included in Groups A and B, respectively, whereas 224 OTUs were shared by Groups A and B. Malassezia was predominant in both groups. Moesziomyces, Ustilago, Erythrobasidium and Schizophyllum were more common in Group B than in Group A. In contrast, Cladosporium, Ramicandelaber, Claroideoglomus and Stachybotrys were more common in Group B than in Group A. These results provide the first evidence of the microbiota in blue swimming crabs that have gill nets in their stomachs.