Effects of dietary threonine on growth and immune response of oriental river prawn (Macrobrachium nipponense)

A 70-day feeding trial was conducted to ascertain the effects of threonine on immune response of juvenile oriental river prawn (Macrobrachium nipponense). Six isonitrogen and isolipidic feeds were formulated according to levels of dietary threonine (0.35%, 0.79%, 1.18%, 1.67%, 2.08% and 2.48% respectively). The juvenile prawns were divided into six groups with four replicates, and stocked into 24 tanks with 50 prawns per tank (initial weight 0.20 ± 0.02 g). The results showed a significant increasing trend of final body weight, specific growth rate, protein efficiency ratio, and weight gain rate when threonine levels increased to 1.67% (P < 0.05). However, feed intake, feed conversion ratio, and whole-body lipid composition significantly decreased as threonine levels in the feed increased up to 1.67% (P < 0.05). Moreover, haemolymph N-urea content was significantly lowest at 1.67% threonine level (P < 0.05), whereas glucose was highest at 0.79% followed by 1.67% of threonine levels in the feeds. Aspartate aminotransferase (AST) enzyme activities were significantly decreased by an imbalance (except 1.67%) of threonine in the feed (P < 0.05). Activities of Alanine aminotransferase (ALT) and albumen (ALB) were not significantly affected by threonine in the feed (P > 0.05). Excessive dietary threonine level (2.48%) significantly activated haemolymph catalase (CAT) activity (P < 0.05), whereas malondialdehyde (MDA) content was significantly affected by deficient (0.35% and 0.79%) dietary threonine levels (P < 0.05). Inducible nitric oxide synthase (iNOS) activity and haemolymph complement component 4 (C4) content were significantly decreased by deficient levels of threonine in the feed (P < 0.05). Excess threonine concentration significantly down-regulated Toll, Dorsal, Relish, and heat shock protein 60 (Hsp60) gene expressions in the hepatopancreas of M. nipponense (P < 0.05), while all genes were significantly up-regulated by the optimal (1.67%) threonine level (P < 0.05). The threonine level at which maximum specific growth rate of M. nipponense occurred was estimated by second degree polynomial regression analysis as 1.65% of threonine level, equivalent to 4.44% dry weight bases of protein in the feed.

Comparative Analysis of the Intermolt and Postmolt Hepatopancreas Transcriptomes Provides Insight into the Mechanisms of Procambarus clarkii Molting Process

In the present study, we used RNA-Seq to investigate the expression changes in the transcriptomes of two molting stages (postmolt (M) and intermolt (NM)) of the red swamp crayfish and identified differentially expressed genes. The transcriptomes of the two molting stages were de novo assembled into 139,100 unigenes with a mean length of 675.59 bp. The results were searched against the NCBI, NR, KEGG, Swissprot, and KOG databases, to annotate gene descriptions, associate them with gene ontology terms, and assign them to pathways. Furthermore, using the DESeq R package, differentially expressed genes were evaluated. The analysis revealed that 2347 genes were significantly (p > 0.05) differentially expressed in the two molting stages. Several genes and other factors involved in several molecular events critical for the molting process, such as energy requirements, hormonal regulation, immune response, and exoskeleton formation were identified and evaluated by correlation and KEGG analysis. The expression profiles of transcripts detected via RNA-Seq were validated by real-time PCR assay of eight genes. The information presented here provides a transient view of the hepatopancreas transcripts available in the postmolt and intermolt stage of crayfish, hormonal regulation, immune response, and skeletal-related activities during the postmolt stage and the intermolt stage.

Dynamic changes in microbial community structure in farming pond water and their effect on the intestinal microbial community profile in juvenile common carp (Cyprinus carpio L.)

Water quality parameter dynamics, gut, sediment and water bacteria communities were studied to understand the environmental influence on the gut microbial community of a new strain of Huanghe common carp. A total of 3,384,078 raw tags and 5105 OTUs were obtained for the gut, water and sediment bacteria. The water quality had a stronger influence on the water bacteria community than gut and sediment bacteria communities. The ambient water quality parameters also significantly influenced the water and sediment bacteria communities. Comparing the gut, sediment, and water microbial communities, a relationship was found among them. However, gut bacteria were more closely related to sediment bacterial communities than to water bacteria communities. The results showed that the top three bacterial taxa were identical in gut and sediment samples in the early days of rearing. Interestingly, bacterial communities in the carp gut, water, and sediment had different adaptabilities to variations in environmental factors.

Relationship Between the Fatty Acid Profiles and Gut Bacterial Communities of the Chinese Mitten Crab (Eriocheir sinensis) From Ecologically Different Habitats

The gut microbiota plays an important role in a variety of physiological functions such as intestinal digestion, metabolic homeostasis, immune response, and responses to disease treatment. Whether there is a relationship between gut microbial communities and fatty acid (FA) profiles of Chinese mitten crab is unclear. Hence, we analyzed the relationship between FA profiles and the gut bacterial communities of six Chinese mitten crab (Eriocheir sinensis) populations from different lakes. The crabs were sampled from six different lakes in Jiangsu Province, China. The FA profiles of these crab populations were compared and clustered, and then used to determine the relationship between geographic location and FA composition. We also characterized the gut microbial communities of these crabs using 16S rRNA high-throughput gene sequencing. The FA profiles varied significantly (P < 0.05) between crabs from different geographical locations. A similar trend was also observed in the gut microbial communities, which also varied significantly based on their geographical origin (P < 0.05). Furthermore, alpha diversity, cluster analysis, and matching bacterial community structures with specific locations revealed patterns that significantly linked FA profiles to the gut microbiota. Further analysis of FA profiles and gut microbial community generated patterns that linked the two parameters. Hence, it was observed that the gut microbial community seems to contribute significantly to the FA composition of the Chinese mitten crab. However, further studies need to be conducted to investigate the interactions between gut microbial communities and the biochemical composition of the Chinese mitten crab, which will ultimately unravel the complexity of microbial ecosystems for potential applications in aquaculture and species conservation.