Blue biliprotein as an effective factor for cryptic colouration in Rhodinia fugax larvae

Area of Science:

• Zoology
• Biochemistry
• Ecology

Background:

• The silkworm larva, Rhodinia fugax, exhibits cryptic coloration, closely resembling its host plant, Quercus serrata.
• Larval integument spectral reflectance matches that of Q. serrata leaves, suggesting adaptive camouflage.
• Differential distribution of blue biliproteins (BPs) on dorsal and ventral surfaces is observed.

Purpose of the Study:

• To investigate the role of light intensity in modulating larval coloration in Rhodinia fugax.
• To determine the biochemical basis of light-induced color changes, focusing on biliproteins and their chromophores.
• To elucidate the contribution of BPs to the cryptic coloration of R. fugax larvae.

Main Methods:

• Comparative analysis of larval coloration under different light intensities (1000 lux vs. 10 lux).
• Spectrophotometric analysis of larval integument and host plant leaves.
• Quantification of biliprotein (BP-I, BP-II) and chromophore content in larval tissues (haemolymph, cuticle, epidermis).

Main Results:

• Larvae exposed to light (1000 lux) are green, while those in darkness (10 lux) turn yellow.
• Light intensity significantly affects the accumulation of BP-I and its blue chromophore in haemolymph and cuticle.
• BP-II and yellow chromophore levels in the epidermis remain largely unaffected by light intensity.

Conclusions:

• Biliproteins and their chromophores are key determinants of Rhodinia fugax larval coloration.
• Light actively stimulates the accumulation of BP-I, enhancing cryptic coloration.
• These findings highlight the adaptive significance of biochemical regulation in insect camouflage.