Project description:Stomach-less fishes comprise a diverse phylogenetic group within the teleosts indicating that the organ has been lost several times during evolution. In the present project we have combined Illumina short read platform with the PacBio long read platform to sequence the ballan wrasse (Labrus bergylta) genome and its intestinal transcriptome. The genome was applied to investigate the elimination and conservation of genes related to stomach function and appetite regulation in wrasse in relation to the loss of stomach in this species. We have sequenced the transcriptome of four intestinal segments from six ballan wrasse (Labrus bergylta) for the purpose of identifying possible functional organization along the wrasse intestine. The transcriptomic reads were mapped against the newly assembled genome. The analysis revealed a transcriptional gradient showing genes involved in nutrient digestion and uptake being highly expressed in the anterior intestine and declining towards the end of the intestine. The last segment, hind-gut, had the most distinct expression between the four segments with increased expression of genes coding for proteins involved in lysosomal activity, antigen presenting and vitamin b12 uptake. Overall, our results suggests that the wrasse entire digestive system is comparable to the small intestine of mammals with regards to gene expression missing both a stomach and colon. Gene expression related to colon in humans such as MS4A12 were found in the last segment. The genome analysis also confirmed the lack of genes coding for gastric proteins such as gastric lipase, pepsin, gastrin and ghrelin. Although ghrelin is not only related to stomach, ghrelin was missing in all stomach-less fish species with the exception of cyprinid. Ghrelin is currently the only known orexigenic hormone.
Project description:This paper presents data from a 5-week feeding trial in which Ballan wrasse was fed either a reference diet, or the identical diet supplemented with i) the antinutrient soya saponin (0.7%) ii) a commercial prebiotic (Aquate™ SG, 0.4%) or iii) a combination of soya saponin and prebiotics. Blood, tissue and gut content from four separate intestinal segments were sampled from 6 fish per duplicate tank. Gut health and digestive functions were evaluated by various endpoint measurements employing biochemical and histomorphological tools as well as global gene expression profiling. No significant differences in fish growth were seen between the four dietary groups. Saponin supplementation, both alone and in combination with prebiotics, increased weight indices of two mid gut segments (IN2 and IN3) and decreased blood plasma glucose, cholesterol and total protein. Dry matter of intestinal content and activity of digestive enzymes were not affected by diet. Histomorphological analyses revealed clear structural alterations in the gut of fish fed saponin, both alone and in combination with prebiotics. The results indicated a progressing inflammation with increased infiltration by immune cells particularly into the distal parts of the intestine. Gene expression profiles obtained by RNA sequencing and quantitative PCR mirrored the histological and biochemical changes induced by the saponin load. The work has provided novel basic knowledge on the anatomy, digestive and immune function of the Ballan wrasse intestine. Additionally, the study demonstrated that Ballan wrasse gut health and digestive function may be markedly affected by diet composition.
Project description:Ballan wrasse (Labrus bergylta) is used as a cleaner fish in Norwegian aquaculture to control sea lice. Thus, knowledge on the digestive physiology and nutrient requirements, as well as the ontogeny of the immune system is important. In this study, two different diets were tested; diet 1 was used as control diet consisting of artemia and rotifers cultivated and enriched in the in-house facility at IMR, Austevoll, Bergen (Norway). Diet 2 consists in plankton which has successfully been used before in cod larvae generating more robust individuals. Sampling was done according to the standard length of the larvae rather than age (dph). Sampling point 0 (BW0) (4 mm), sampling point 2 (BW2) (4,5 mm), sampling point 3 (BW3) (5,7 to 6 mm), sampling 4 (BW4) (7 to 7,5 mm), sampling point 5 (BW5) (10 to 10,5 mm), sampling point 6 (BW6) (16 to 16,5 mm), and sampling point 7 (BW7) (25 to 30 mm). Ontogeny of lymphoid organs and mucosal associated lymphoid tissues in ballan wrasse and the effect of different diets were investigated.
