Tenebrio molitor larvae meal inclusion affects hepatic proteome and apoptosis and/or autophagy of three farmed fish species

Herein, the effect of dietary inclusion of insect (Tenebrio molitor) meal on hepatic pathways of apoptosis and autophagy in three farmed fish species, gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax) and rainbow trout (Oncorhynchus mykiss), fed diets at 25%, 50% and 60% insect meal inclusion levels respectively, was investigated. Hepatic proteome was examined by liver protein profiles from the three fish species, obtained by two-dimensional gel electrophoresis. Although cellular stress was evident in the three teleost species following insect meal, inclusion by T. molitor, D. labrax and O. mykiss suppressed apoptosis through induction of hepatic autophagy, while in S. aurata both cellular procedures were activated. Protein abundance showed that a total of 30, 81 and 74 spots were altered significantly in seabream, European seabass and rainbow trout, respectively. Insect meal inclusion resulted in individual protein abundance changes, with less number of proteins altered in gilthead seabream compared to European seabass and rainbow trout. This is the first study demonstrating that insect meal in fish diets is causing changes in liver protein abundances. However, a species-specific response both in the above mentioned bioindicators, indicates the need to strategically manage fish meal replacement in fish diets per species.

Biochemical and immune response in red tilapia (Oreochromis mossambicus × O. niloticus) with dietary chitosan supplementation

The use of biostimulants in fish diets is a promising strategy to reduce the use of antibiotics, enhance the biochemical and immune response, which contributes to improving productive yields and reducing economic losses. The biochemical and immune response was evaluated in juvenile red tilapia (Oreochromis mossambicus × O. niloticus), with different levels: 0 (control), 1, 2, 3, 4 and 5% chitosan in diet. 270 animals (7.53 ± 0.50 g of initial weight), distributed in a completely randomized design of 6 treatments with 3 replicates and 45 tilapia.treatment-1, were sown in 18 tanks with 90 L of water in a closed system. The juveniles were fed for 55 days with the experimental diets and at the end of the bioassay the tissue and blood plasma samples were taken. Differences were found (p<0.05) in the variables evaluated responses, where the content of lipids, triglycerides, cholesterol, carbohydrates and glucose showed higher levels (p<0.05) at lower chitosan concentrations. However, for protein content, a better response (p<0.05) was found at higher levels of chitosan in the diet. Regarding dry matter and ash, no differences were found (p˃0.05). While superoxide dismutase and leukocytes were found in higher concentration (p<0.05) when supplemented with chitosan by 3 and 4%. It was concluded that the juvenile biochemical and immune response of red tilapia was favored with dietary chitosan supplementation.

Contribution to the special issue on Reptile cognition: Chemically mediated self-recognition in sibling juvenile common gartersnakes (Thamnophis sirtalis) reared on same or different diets: evidence for a chemical mirror?

Although self-recognition or self-awareness has been studied with the visually-based mirror test, passed by several species, primarily apes, the possibility of a chemically-based analogue is controversial. Prior studies suggested that chemical self-recognition may occur in some squamate reptiles. To evaluate this possibility, we studied 24 individually housed gartersnakes, Thamnophis sirtalis, raised from birth on either earthworm or fish diets and tested 12 male and 12 female snakes with cage liners that were either clean, their own, or from same-sex siblings fed their own or the opposite diet. Tongue flicking and activity were recorded in 30-minute video-recorded trials in a balanced design. After initial habituation to the stimuli, male, but not female, snakes discriminated between their own stimuli and those from littermates fed the same diet. Combined with other data and studies, the possibility that a chemical ‘mirror’ form of self-recognition exists in squamate reptiles is supported.

CHANGES IN MICROBIAL INTESTINE FLORA OF BROWN TROUT (SALMO TRUTTA FARIO) FED WITH PREBIOTIC ADDED FEEDS

In this research, Brown trout (Salmo trutta fario L., 1758) with 100±15 g from the fish production center of Aquaculture department of Fisheries Faculty at Ataturk university was used. The effects of addition of prebiotic (0 % prebiotic as control and 0.1 % prebiotic) to the fish diets was determined from a-90 days of feeding trial (Experiment 1) with 4 replications (2x4=8 tanks). Fish were distributed randomly to each group of tanks including 40 fish each. Fish were fed with experimental diets twice a day at 10±1°C water temperature. In the experiment treatment vs time interaction was investigated by taking samples from intestine for determination of intestinal bacterial flora and body proximate composition at 0, 30, 60 and 90. days. Feeding fish with prebiotic showed that there were significant changes in the number of all bacteria counted from intestinal flora and percentages of chemical composition from fish fillets (p<0.05).

Production Performance, Nutrient Digestibility, Serum Biochemistry, Fillet Composition, Intestinal Microbiota and Environmental Impacts of European Perch (Perca Fluviatilis) Fed Defatted Mealworm (Tenebrio Molitor)

Background: Yellow mealworm (Tenebrio molitor) larvae meal (TM), one of seven approved insect species used in aquafeeds, is a frequently investigated candidate for fish diets. Results: This study aimed to investigate the effects of dietary defatted TM on production performance, serum biochemistry, nutrient digestibility, fillet traits, intestinal microbiota, and environmental impacts of perch (Perca fluviatilis). Four experimental diets, characterized by defatted TM inclusion levels of 0, 6.8, 13.5 and 20.3%, respectively, or 0, 25, 50, and 75% at the expense of fishmeal (TM0, TM25, TM50, and TM75, respectively) were fed to juvenile perch (bodyweight 20.81 ± 3.36 g, total length 117.7 ± 7.2 mm) (quadruplicated per diet) for 105 days. Inclusion levels of 6.8% or 25% fishmeal replacement by defatted TM did not show a significant effect on specific growth rate and feed conversion ratio (P > 0.05), while further levels of 13.5 and 20.3%, or 50 and 75% fishmeal replacement with defatted TM, respectively, displayed a significant delay in these indices compared to the control diet (P < 0.001). The aspartate aminotransferase activities in perch’s serum increased with increasing dietary TM (P = 0.044). Nutrient digestibility of perch exhibited TM-dose dependent (P < 0.05). Dietary defatted TM did not lead to any significant changes in the fillet composition of perch (P > 0.05). Defatted TM did not modify diversity of fish gut microbiota (Chao1 index, P = 0.742; Shannon index, P = 0.557; and observed species, P = 0.522), but significantly reduced abundance of Lactobacillus (P = 0.018) and Streptococcus (P = 0.013) while fed TM75 relative to TM0. TM-containing diets generated a comparable amount of total solid waste and solid phosphorus waste with TM0, except TM25, whereas solid nitrogen waste significantly increased with elevated TM levels (P < 0.001). Perch fed TM25 was comparable with TM0 for global warming potential, acidification, and land use (P > 0.05), whereas TM50 and TM75 exerted heavier burdens on energy use, eutrophication, and water use than TM0 (P < 0.001). Fishmeal replacement by TM significantly reduced economic fish-in fish-out (P < 0.001).Conclusion: The inclusion of 6.8% or 25% fishmeal replacement by defatted insect meal (T. molitor) in European perch diets resulted in comparable production performance but entailed heavier burdens associated with solid outputs waste and environmental impacts. The present study underlined the major bottleneck of a substantial inclusion of defatted insect meal (T. molitor) in fish diets associated with solid nitrogen waste and environmental consequences associated with one unit of farmed perch produced. Our multidisciplinary study suggested important aspects while formulating diets for fish, using insect meals regarding production performance and environmental issues.

Insect-Based Feed Ingredients for Aquaculture: A Case Study for Their Acceptance in Greece

Although the inclusion of insects in fish diets is officially allowed in the EU since 2017, insect-based aquafeeds have not been widely adopted by the European aquaculture sector. In order to investigate the perceptions related with adoption trends, it is critical to explore the beliefs of people associated with the aquaculture sector on the use of insects in farmed fish diets. A survey was conducted among 228 participants of an aquaculture conference to explore their perceptions on the inclusion of insect meal in fish diets. Additionally, we investigated the attitudes of nine companies operating in the aquaculture and aquafeed sector in Greece that attended the conference towards this direction. The findings of the conference survey provide evidence that there is a wide-range awareness and acceptance regarding the use of insect-based feeds in farmed fish diets among the respondents. This is mainly driven by the expectations for the decline in fishing pressure on wild fish stocks, the reduction of the ecological footprint and the enhancement of the sustainability of the aquaculture sector. The results of the stakeholder survey show that six out of the nine companies that participated in the survey are favorably disposed towards the use of insect-based feeds. Specifically, four of them stated that they would produce or use aquafeeds based on insects. However, the results highlight the need for further research on the implementation of the wider adoption of insect-based feeds in aquaculture. The present study provides some first insights into the use of insect-based aquafeeds in Greece, for which there are no data available.

Effects of a Bioprocessed Soybean Meal Ingredient on the Intestinal Microbiota of Hybrid Striped Bass, Morone chrysops x M. saxatilis

The hybrid striped bass (Morone chrysops x M. saxatilis) is a carnivorous species and a major product of US aquaculture. To reduce costs and improve resource sustainability, traditional ingredients used in fish diets are becoming more broadly replaced by plant-based products; however, plant meals can be problematic for carnivorous fish. Bioprocessing has improved nutritional quality and allowed higher inclusions in fish diets, but these could potentially affect other systems such as the gut microbiome. In this context, the effects of bioprocessed soybean meal on the intestinal bacterial composition in hybrid striped bass were investigated. Using high-throughput sequencing of amplicons targeting the V1–V3 region of the 16S rRNA gene, no significant difference in bacterial composition was observed between fish fed a control diet, and fish fed a diet with the base bioprocessed soybean meal. The prominent Operational Taxonomic Unit (OTU) in these samples was predicted to be a novel species affiliated to Peptostreptococcaceae. In contrast, the intestinal bacterial communities of fish fed bioprocessed soybean meal that had been further modified after fermentation exhibited lower alpha diversity (p < 0.05), as well as distinct and more varied composition patterns, with OTUs predicted to be strains of Lactococcus lactis, Plesiomonas shigelloides, or Ralstonia pickettii being the most dominant. Together, these results suggest that compounds in bioprocessed soybean meal can affect intestinal bacterial communities in hybrid striped bass.

Allocation of the diet of the Argentine Islands’ inshore ichthyofauna

Fish diets are important indicators of ecosystem change. This aspect of the ichthyofauna of the coast of the Argentine Islands has been insufficiently studied in comparison with other regions. This article presents the results of comparison of dietary and somatic parameters of the dominant species Notothenia coriiceps depending on the point, depth and season of catch. The sample was collected between February 2006 and February 2007. In the year of study, N. coriiceps, Trematomus bernacchii, Chaenocephalus aceratus (common species), Harpagifer antarcticus and Pagothenia borchgrevinki (rare species in this region) were caught. The average fish size in this region does not differ from other places in the Southern Ocean. In Cornice Channel and Stella Creek, N. coriiceps was smaller than at other points due to the narrowness and shallow depth of these places. In winter, large individuals apparently migrated from the coast. The diet of N. coriiceps consisted mainly of crustaceans and seaweeds, with a small number of mollusks (especially limpets), which are common. The number of fish in the diet of N. coriiceps is relatively low for this region. Access to food was relatively the same at different points and depths of the catch. The lowest amount of food was in the fall, the highest amount of food was in the spring and summer. The condition and hepatosomatic index also did not change depending on the point and depth of the catch, but they were low in spring and high in summer. Perhaps this is due to the low energy value of food, which is not compensated by the amount. It is necessary to conduct studies of the diet of N. coriiceps in other years to clarify the specificity of fish in the diet and phenological changes in somatic parameters. Similar studies are needed for other species in the region if catches are sufficient to collect a representative sample.