Influence of Dietary Spermidine on Larval Growth and Development in Bombyx mori L.

Abstract

The silkworm, Bombyx mori, is a key organism in sericulture, where the quality and nutritional composition of its exclusive host plant, Morus alba, critically influence larval growth and silk yield. Polyamines such as spermidine have emerged as important dietary supplements due to their role in cellular metabolism and protein synthesis, yet their stage-specific effects during silkworm development remain inadequately explored. The present study examined the impact of spermidine (Spd) supplementation on the larval growth performance of the silkworm, Bombyx mori. Larval length and weight were assessed during the 4th and 5th instars under varying concentrations of spermidine (Spd 25, Spd 50, Spd 75, and Spd 100) along with a control treatment. During the 4th instar, no significant differences in larval length and weight were observed on the first day; however, significant variations became evident from the third day onward. By the fifth day, the highest larval length and weight were recorded in Spd 25 (4.06 cm, 1.00 g) and Spd 50 (4.09 cm, 0.97 g), whereas comparatively lower values were observed in the control group (3.94 cm, 0.83 g). A comparable trend was noted during the 5th instar, where treatments with Spd 25 and Spd 50 resulted in the greatest larval length and weight on the seventh day (7.27 cm, 4.75 g and 7.27 cm, 4.57 g, respectively), while the control group showed the lowest measurements. Furthermore, analysis of overall growth rate (OGR) and compound periodical growth rate (CPGR) demonstrated a significant enhancement in larval length and weight under spermidine supplementation. Overall, the results indicate that moderate levels of spermidine, particularly Spd 25 and Spd 50, effectively stimulate larval growth, suggesting its potential application as a growth-promoting dietary additive in silkworm rearing systems.