Physiological and proteomic traits underlying differential growth in the freshwater crayfish Cherax quadricarinatus

Differential growth, defined as intraspecific variability in growth rates among conspecifics, is commonly observed in aquatic animals, although its physiological mechanisms remain poorly understood. This study evaluated biochemical and molecular traits associated with differential growth in juveniles of the freshwater crayfish Cherax quadricarinatus by integrating digestive enzyme activities, energy reserves, and proteomic profiles. Recently independent juveniles (∼21 mg) hatched from 10 females were used (75 juveniles per female). Each progeny was maintained in an aquarium during 60 days. At the end of the experiment, juveniles were classified into slow- (SG), intermediate- (IG), and fast-growing (FG) categories based on final body weight. Slow-growing juveniles showed approximately threefold higher limb loss than FG juveniles, suggesting a greater impact of social interactions and associated physiological costs. Compared with FG juveniles, SG juveniles showed a higher hepatopancreatic lipid content, digestive enzyme activities, muscle glycogen levels, and hepatosomatic index values. These results may indicate differences in energy allocation and nutrient utilization between growth phenotypes. IG juveniles showed biochemical traits intermediate between SG and FG juveniles, evidencing the existence of a continuous growth gradient. Proteomic analyses revealed marked differences among growth phenotypes. In hepatopancreas, SG juveniles up-regulated proteins related to carbon metabolism, proteolysis, and cytoskeleton organization, while, down-regulated proteins associated with lipid-related processes. In muscle, FG juveniles showed up-regulated proteins related to cytoskeleton organization, protein folding, and oxidoreductase activity. These findings suggest that differential growth in C. quadricarinatus is associated with different patterns of energy storage and nutrient utilization during early juvenile development.