Color-specific porosity in double pigmented natural 3d-nanoarchitectures of blue crab shell

Fran Nekvapil,Lucian Barbu–Tudoran,Maria Suciu,Vasile Chiș,Tudor Tamaș,Branko Glamuzina,Simona Cintă Pinzaru

doi:10.1038/s41598-020-60031-4

Abstract

3D-engineered nano-architectures with various functionalities are still difficult to obtain and translate for real-world applications. However, such nanomaterials are naturally abundant and yet wasted, but could trigger huge interest for blue bioeconomy, provided that our understanding of their ultrastructure-function is achieved. To date, the Bouligand pattern in crustaceans shell structure is believed to be unique. Here we demonstrated that in blue crab Callinectes sapidus, the 3D-nanoarchitecture is color-specific, while the blue and red-orange pigments interplay in different nano-sized channels and pores. Thinnest pores of about 20 nm are found in blue shell. Additionally, the blue pigment co-existence in specific Bouligand structure is proved for the green crab Carcinus aestuarii, although the crab does not appear blue. The pigments interplay, simultaneously detected by Raman spectroscopy in color-specific native cuticles, overturns our understanding in crustaceans coloration and may trigger the selective use of particular colored natural nanoarchitectures for broaden area of applications.

Highlights

Nikola Tesla would have been surprised to find out that thinking “in terms of energy, frequency, and vibration”, the secrets of the blue crab colors could be elucidated
Relying on combinatory multi-laser resonance Raman (RR) micro-spectroscopy and imaging, assisted by electron microscopy, X-ray diffraction and computational chemistry, we show that two interplayed pigments and their distribution in the 3D-nanoarchitecture of the plywood path is color-specific and the blue shell of C. sapidus is not exclusively determined by the presence blue pigment, astaxanthin bounded in crustacyanin
We combined the unique ability of the multi-laser Raman spectroscopic techniques to localize the chemical and structural information, with the morphology from the high resolution scanning electron microscopy (HR-SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD) of native blue, red and white shell counterparts of C. sapidus, and the green C. aestuarii crab

Summary

Introduction

Nikola Tesla would have been surprised to find out that thinking “in terms of energy, frequency, and vibration”, the secrets of the blue crab colors could be elucidated. The “universal” nature of the 3Dhierarchical calcite arrays which follows a twisting plywood path (Bouligand-type pattern) in crustacean exoskeleton has been suggested, based on studies on several species of crabs[8,28,29,30,31,32], but lacking any connection with the pigments populating the morphological pattern. Katsikini[33] detected ATX only in C. sapidus blue crab cuticle, due to the use of a single laser line (488 nm), which fulfilled the RR conditions for the respective carotenoid only, but suggested that Br and Sr are involved in two different mechanisms contributing to the blue color. Comprehensive understanding of chemical structure-morphology relationship in blue crab shell is absent, of high interest for transforming such aquatic porous by-product into added-value material within the blue bioeconomy goal

Methods

Results

Conclusion