Effects of a Dietary Multienzyme Extract on Isotope Biokinetics in Red Claw Crayfish Cherax quadricarinatus Juveniles

Abstract

Understanding the nutritional and metabolic physiology of aquatic organisms is essential for optimizing aquaculture practices andinforming ecological models. We investigated the influence of dietary composition, specifically the incorporation of multienzymeextract derived from Pleoticus muelleri waste, on the growth and metabolic processes of juvenile Cherax quadricarinatus. Weinvestigated how these dietary changes influence dietary assimilation and tissue turnover using stable isotope δ13C and δ15Ndynamics, in both the pleon muscle and hepatopancreas. Juvenile crayfish were subjected to two isocaloric diets for a 90-dayperiod: a control diet (diet C) and a diet supplemented with a multienzyme extract (diet E) from red shrimp waste. Despitecomparable growth rates, isotopic analysis (δ13C and δ15N) of the pleon muscle and hepatopancreas revealed distinct metabolicpatterns between both dietary treatments. The hepatopancreas exhibited accelerated isotopic turnover relative to muscle tissue,irrespective of diet, suggesting a more dynamic metabolic role. Diet E further accelerated turnover rates in both tissues, indicativeof enhanced nutrient assimilation and utilization. Consistent isotopic disparities between the hepatopancreas and muscle tissueshighlighted tissue-specific metabolic functions, with the hepatopancreas serving as a metabolic hub. Molting-induced shifts inisotopic patterns underscored the dynamic interplay between metabolic processes and nutrient mobilization. Isotopic equilibriumwas reached earlier for δ13C than δ15N, with lower discrimination factors in the hepatopancreas. While δ13C primarily supportedmetabolic processes, δ15N contributed substantially to growth, especially in muscle. These findings illuminate the complexinterplay of dietary composition, isotopic fractionation, and physiological regulation in C. quadricarinatus. The metabolicenhancements induced by the diet supplemented with the extract warrant further investigation to optimize nutrient utilizationand growth performance in aquaculture settings.