Impact of larval high density on the performance of Anastrepha ludens: competition or feeding facilitation?

A critical point in diet management is maximizing density as a strategy for reducing costs. Artificial diets elaborated with large particle sizes have increased volume, possess high porosity and aeration capacity, are more penetrable and facilitate the movement of larvae, and increase the bioavailability of nutrients. The present experiment consisted in demonstrating that the bulking agent facilitates feeding and could have more capacity to support a high density of larvae with a minimal effect of competition on the life-history traits of Anastrepha ludens. The results indicate that density affected larval and pupal weight, but not pupation at 24 h, adult emergence, and flier percentage, which remained unchanged. However, there was an increase in yield and bioconversion. Larvae in high density conditions aggregated to increase the effect of regurgitation of amylases and proteases as a strategy to metabolize the food prior to ingestion through enzymes secreted in the saliva, contributing thus to feeding facilitation and the uptake of ingested food, which decreased the negative impact of competition in high density conditions. High density leads to an increase in food consumption and a consequent increase in digestive enzyme activity, contributing to the bioavailability of macronutrients ─ proteins, carbohydrates, and lipids ─ in the diet.

Identifying the properties of bulking agents and other ingredients and their interaction under high-density conditions is essential to develop novel artificial diets and improve the mass-rearing strategies for the SIT.