Intestinal Histomorphometric Responses of Yellowtail Lambari (Astyanax bimaculatus) Fed Diets Containing Tenebrio molitor Larval Meal

The use of insect meals in aquafeeds has emerged as a sustainable strategy to reduce dependence on conventional protein sources. However, the effects of these ingredients on intestinal morphology remain poorly understood in Neotropical fish species. This study evaluated the intestinal histomorphometric responses of yellowtail lambari (Astyanax bimaculatus) fed diets containing increasing levels of Tenebrio molitor larval meal (TMLM). A total of 400 fish (2.53 ± 0.13 g) were distributed in a completely randomized design with five dietary treatments (0, 30, 60, 90, and 120 g kg⁻¹ TMLM) and four replicates for 56 days. Diets were formulated to be isonitrogenous (320 g kg⁻¹ crude protein) and isoenergetic (3,200 kcal kg⁻¹). Intestinal samples were processed using standard histological techniques, and morphometric analyses included mucosal thickness, villus height, villus width, and goblet cell volumetric and numerical densities. Data were subjected to one-way ANOVA and regression analysis at a significance level of P < 0.05. Dietary TMLM significantly affected most intestinal histomorphometric variables (P < 0.05). Mucosal thickness decreased linearly from 1,980 to 1,668 µm as TMLM inclusion increased. Villus height was not affected by dietary treatments (P > 0.05), remaining between 31.78 and 34.50 µm. Villus width showed a significant quadratic response, with lower values observed at intermediate and high inclusion levels. Goblet cell volumetric density decreased from 9.26 to 6.01%, while numerical density declined from 1.84 to 1.13 µm⁻³ with increasing TMLM inclusion. The maintenance of villus height, associated with reduced mucosal thickness and lower goblet cell densities, suggests adaptive intestinal remodeling without impairment of absorptive capacity. These findings indicate that TMLM promotes beneficial morphofunctional adjustments in the intestine of A. bimaculatus and supports its use as a sustainable functional ingredient in aquaculture feeds.

Acknowledgments: The authors thank the Minas Gerais Research Foundation (FAPEMIG) for financial support. The project was approved by the Institutional Animal Care and Use Committee (CEUA) under protocol number 010/21.