Hierarchical clustering analysis based on metabolite levels in the hemolymph of different genetic strain of silkworms (Bombyx mori L., 1758) with regard to cocoon shell to cocoon weight ratio

Abstract Biochemical profile of silkworms can depict the profound body biomass conversion throughout the larval stages. In view of this, the determination of metabolite levels in the hemolymph of caterpillars ready to pupate may be interpreted in relation to the imminent silk filament synthesis. Due to different extents of silk production according to the genetic strain of silkworm, it was hypothesized that a potential effect of selection of desirable traits of economic importance could have conditioned levels of some biochemical parameters. To test this hypothesis, twenty silkworm strains from Iranian gene bank were used. Aspartate amino transferase (AST), Alanine amino transferase (ALT), Alkaline phosphatase (ALP), phosphorus (P) sodium (Na), potassium (K) and iron (Fe) were determined in the haemolymph of caterpillars ready to pupate (5th day of the 5th instar stage) of each genetic strain. Enzymes and electrolytes were selected in the light of acquaintances on the terminal larval metabolism and development, potentially involved in synthesizing and spinning fibroin and sericin filaments for cocoon creation. Biochemical profiles pointed to differences between strains that were used in the hierarchical clustering analysis. Results showed that the highest level of (AST) was found in strain 113-K (191.63 U/L) and the lowest in 31(94.81 U/L) reflecting the different activity of protein transamination, likely related to body protein conversion into fibroin and sericine. Significantly, Na+ (p = 0.032) and K+ (p = 0.022) displayed to vary in relation to cocoon shell weight categories among the genetic strains investigated. However, AST varied only closed to significance (p = 0.062). The canonical discriminant analysis (CANDISC) pointed to a good discrimination of high performance strains on the basis of the metabolic profile, from those with performance below the median value, but in a non significant way. Dendrograms of hierarchical clustering analyses pointed to 3 distinct groups with different apparent metabolic levels for silk synthesis.