Embryonic cuticle from artemia cyst shell displays amyloid-like characteristics and nontoxicity after oral consumption.

Artemia cysts are the essential food product for industrial larviculture of fishes. The cyst shell protects the artemia embryo from mechanical damage, ultraviolet light, excessive water loss, thermal variation and anoxia condition. However, the underlying mechanism of such environmental protection is largely unclear. The embryonic cuticle of cyst shell mainly constitutes chitin and proteins. Absence of cyst shell proteins compromises embryo survival. In literature, there are few examples of functional amyloids where proteins adapt amyloid-like structures and act as protective covering. We hypothesized that the proteins from the embryonic cuticle of artemia cyst shell may have amyloid-like properties. Using FTIR and CD analysis, we found that proteins in embryonic cuticle have high β-sheet secondary structures. Embryonic cuticles displayed high Congo red binding affinity and stained samples showed apple-green birefringence under polarized light, confirming the presence of amyloid-like structures. Amyloid structures have a tendency to propagate and cause amyloidosis. However, feeding of amyloid rich embryonic cuticles to zebrafish did not show any signs of discomfort or morbidity and amyloid deposition. Taken together, the study reveals that amyloid-like structures are present in embryonic cuticle of artemia cyst and their consumption does not induce amyloidosis in zebrafish.