An in-depth characterisation of European seabass intestinal segments for assessing the impact of an algae-based functional diet on intestinal health

Abstract

Sustainable farming of fish species depends on emerging new feed ingredients, which can alter the features of the digestive tract and influence animals’ overall health. Recent research has shown that functional feeds hold great potential for enhancing fish robustness by evoking appropriate responses at the intestine level. However, there is a lack of extensive and accurate descriptions of the morphology of the gastrointestinal tract of most farmed fish. We have characterised the intestine of European seabass thoroughly, by targeting four segments − anterior, mid, posterior and rectum. Results indicated that the anterior segment is mostly associated with absorption-related features; this segment has the largest absorptive area, the longest villi, and the highest number of neutral goblet cells (GC). The posterior segment and rectum have distinct histomorphometric features, but both seem to be important for immunity, displaying the highest count of acid GC and the highest expression of immune-related genes. The strongest proliferating cell nuclear antigen (PCNA) signal was observed in the anterior intestine and rectum, with PCNA+ cells appearing at the base of the villi and the corresponding villi branches. We have also evaluated the impact of a novel feed supplemented with a macro- and microalgae blend and found that there were no differences in terms of growth. However, the alterations observed in the mid intestine of fish fed the blend, such as thickening of the submucosa and lamina propria, an increased number of leucocytes, and higher expression of immune- and oxidative stress-related genes, suggest that algae may have an immunomodulatory effect. In the current article, we have described the morphology and expression patterns of the intestine segments of European seabass in detail and have presented a comprehensive report of the indices and methods used for the semi-quantitative and quantitative histomorphometric assessments, thereby providing useful information for future studies that aim to maintain intestinal health through dietary interventions.

Exploring the Antioxidant and Genoprotective Potential of Salicornia ramosissima Incorporation in the Diet of the European Seabass (Dicentrarchus labrax)

“…Medicinal plants such as Yucca schidigera improved hematological parameters and immunological responses [ 33 ], while the introduction of prebiotics acted as immunostimulants through the increase of phagocytic activity [ 34 ]. It was also suggested that dietary supplementation with a macro- and microalgae blend may improve the intestinal health of D. labrax [ 35 ]. Recently, a study investigated the use of alternative feed resources from insects, crustacea, or microalgae biomass as functional supplements in a diet for juvenile D. labrax totally deprived of fish meal [ 36 ].…”

Use of Algae in Aquaculture: A Review

“…According to Gilbert [153], rotifers are subdivided into four categories as defined by types of food ingested: (1) nanoplankton, (2) microplankton, (3) 5-50 µm algae, and (4) 5-Fishes 2024, 9, 63 13 of 21 250 µm algae. Larval rearing of marine fish, for example, turbot (Scophthalmus maximus) and Atlantic halibut (Hippoglossus hippoglossus), can result in a bottleneck, and at this early life stage, it is important to transfer essential nutrients from algae to live food [154]. The reference to Yan et al [155] likely provides valuable insights into the specific methodologies, experimental setups, and findings related to using rotifers for toxicity testing of harmful algae.…”