Bacterial Flora in the Gill Tissues and Intestinal Tracts of Male and Female Chinese Mitten Crabs (Eriocheir sinensis) with Different Diets in a Mud Pond

Sex-bias of core intestinal microbiota in different stocks of Chinese mitten crabs (Eriocheir sinensis)

The differences in intestinal microbiota composition are synergistically shaped by internal and external factors of the host. The core microbiota plays a vital role in maintaining intestinal homeostasis. In this study, we conducted 16S rRNA sequencing analysis to investigate the stability of intestinal microbiota and sex-bias of six stocks of Chinese mitten crabs (105 females; and 110 males). The dominant phyla in all six stocks were Proteobacteria, Tenericutes, Bacteroidetes and Firmicutes; however, their relative abundance differed significantly. Twenty-seven core operational taxonomic units (OTUs), corresponding to 18 genera, were screened. Correlation analysis revealed that OTUs of four stocks in the Yangtze River system play important roles in maintaining the stability of intestinal microbiota. Additionally, the core intestinal microbiota was significantly sex-biased, and the top three genera in terms of relative abundance (Acinetobacter, Vibrio, and Candidatus_Hepatoplasma) were significantly dominant in female crabs. Network structure analysis also confirmed gender differences in the association pattern of intestinal microbiota. The intestinal microbiota of male crabs has a higher degree of functional enrichment. This study provided a theoretical basis for further investigating exploring the shaping effect of gender and geographical factors on the intestinal microbiota of Chinese mitten crabs.

Comparison of the gut microbiota and metabolism in different regions of Red Swamp Crayfish (Procambarus clarkii)

Background

The gut microbiota is very important for maintaining the homeostasis and health of crustaceans. Many factors affect the gut microbiota of crustaceans, one of which is temperature. However, it is currently unclear how temperature affects the gut microbiota and metabolites of Procambarus clarkii.

Methods

Using metagenomic sequencing and gas chromatography-mass spectrometry (GC-MS) techniques, the gut microbiota and metabolites of P. clarkii from Hubei (HB), Jiangsu (JS), Shandong (SD), and Zhejiang (ZJ) in China were investigated.

Results

Under the impact of temperature, the gut microbiota and metabolites of P. clarkii exhibit a specific trend of change. The primary pathogenic bacteria affecting P. clarkii are Citrobacter, Enterobacterium, and Aeromonas, which are affected by temperature. Two metabolites, namely, sugars and amino acids, are regulated by temperature.

Implication

This study demonstrated that the gut microbiota and gut metabolites of P. clarkii were considerably affected by temperature. It provides a theoretical basis for the systematic study of P. clarkii and provides a basis for a healthy culture of P. clarkii.

The shared microbiome in mud crab (Scylla paramamosain) of Sanmen Bay, China: core gut microbiome

Introduction

The mud crab, Scylla paramamosain, holds great commercial significance as a marine crustacean widely cultivated in the Indo-Pacific region. Understanding the core gut microbiota of aquatic animals is crucial for their overall health and growth, yet the core gut microbiota of mud crab remains poorly characterized.

Methods

In this study, we gathered gut samples from mud crabs across five locations within Sanmen Bay, China. Through the utilization of high-throughput sequencing, we delved into the composition of the gut microbial community and identified the core gut microbiome of mud crab.

Results

Our results demonstrate that the gut microbial diversity of mud crab did not exhibit significant variation among the five sampling sites, although there were some differences in community richness. At the phylum level, we identified 35 representative phyla, with Firmicutes, Proteobacteria, Bacteroidota, and Campilobacterota as the dominant phyla. Among the 815 representative genera, we discovered 19 core genera, which accounted for 65.45% of the total sequences. These core genera were distributed across 6 phyla, and among them, Photobacterium exhibited the highest average relative abundance.

Discussion

Photobacterium has probiotic activity and may play a crucial role in enhancing the immune response of the host and maintaining the diversity of the gut microbiota. Moreover, we observed a positive correlation between the relative abundance of core genera and the stability of the gut microbial community. Furthermore, our findings revealed distinct differences in gut microbial composition and specific taxa between the sexes of mud crab. These differences subsequently influenced the functionality of the gut microbial community. Overall, our investigation sheds light on the core gut microbiota of mud crab, emphasizing the importance of core gut microbial communities in maintaining the health and growth of these commercially significant marine crustaceans.

Occurrence of the protozoan parasites Toxoplasma gondii and Cyclospora cayetanensis in the invasive Atlantic blue crab Callinectes sapidus from the Lesina Lagoon (SE Italy)

The occurrence of the protozoan parasites Toxoplasma gondii and Cyclospora cayetanensis was molecularly investigated in the hemolymph, gills, stomach, hepatopancreas and gonads of the eleven invasive Atlantic blue crab Callinectes sapidus from the Lesina Lagoon (Mediterranean Sea). Out of 11 blue crabs, 6 (54.5%) and 4 (36.4%) were found positive to T. gondii and C. cayetanenis, respectively; parasites were found only in the six females analysed, while the remaining five males resulted negative. Moreover, out of 55 tissues samples, 7 (12.7%) and 8 (14.5%) were positive to T. gondii and C. cayetanensis, respectively with hemolymph and gills being the most infected tissues. This is the first report of the presence of protozoan pathogens in wild crab species collected from a Mediterranean lagoon. The present results may provide a baseline reference on microbial infection in the species for invaded Mediterranean waters, and on the potential health risks related with its consumption if eaten raw.

A high abundance of Firmicutes in the intestine of chinese mitten crabs (Eriocheir sinensis) cultured in an alkaline region

The Chinese mitten crab (Eriocheir sinensis) is a popular aquaculture product in East Asia, especially in China. In the last decade, rice-crab co-culture has rapidly expanded in China. Under this model, crabs are raised in rice fields instead of in traditional aquaculture ponds. In this study, we cultured two varieties of Chinese mitten crabs (Changjiang and Liaohe) in an alkaline region in northwest China and used Illumina MiSeq sequencing to compare the intestinal bacterial alpha diversity and community structure between traditional and co-culture aquaculture models, between two crab varieties, and between female and male crabs. Significant variations in intestinal bacterial communities were found between crab varieties and between female and male crabs but not between aquaculture models. These results show that rice-crab co-culture operations did not obviously impact the crab intestinal bacterial community compared with traditional pond aquaculture. Firmicutes was the most abundant bacterial phylum in the crab intestines (78%, relative abundance). Three dominant operational taxonomic units (OTUs) represented 73.2% of Firmicutes sequences and 56.8% of all sequences. A dominant OTU assigned as Firmicutes that was negatively correlated with crab body length, width, and weight was found in the source water for the experimental area. The results of this study suggest that the aquaculture of Chinese mitten crabs in alkaline regions requires more study to improve cultivation techniques.