Differentiations of chitin content and surface morphologies of chitins extracted from male and female grasshopper species

Abstract

In this study, we used Fourier transform infrared spectroscopy (FT-IR), elemental analysis (EA), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), and scanning electron microscopy (SEM) to investigate chitin structure isolated from both sexes of four grasshopper species. FT-IR, EA, XRD, and TGA showed that the chitin was in the alpha form. With respect to gender, two main differences were observed. First, we observed that the quantity of chitin was greater in males than in females and the dry weight of chitin between species ranged from 4.71% to 11.84%. Second, using SEM, we observed that the male chitin surface structure contained 25-90 nm wide nanofibers and 90-250 nm nanopores, while no pores or nanofibers were observed in the chitin surface structure of the majority of females (nanofibers were observed only in M. desertus females). In contrast, the elemental analysis, thermal properties, and crystalline index values for chitin were similar in males and females. Also, we carried out enzymatic digestion of the isolated chitins using commercial chitinase from Streptomyces griseus. We observed that there were no big differences in digestion rate of the chitins from both sexes and commercial chitin. The digestion rates were for grasshoppers' chitins; 88.45-95.48% and for commercial chitin; 94.95%.

Figure 1. FT-IR spectra of the α-chitin isolated from female and male of five grasshopper species.

a) Celes varabilis female, b) C. varabilis male, c) Dectius verrucivorus female, d) D. verrucivorus male, e) Melanogryllus desertus female, f) M. desertus male, g) Paracyptera labiata female, h) P. labiata male.

Figure 2. TGA curves of α-chitin extracted from female and male grasshoppers.

a) Celes varabilis female, b) C. varabilis male, c) Dectius verrucivorus female, d) D. verrucivorus male, e) Melanogryllus desertus female, f) M. desertus male, g) Paracyptera labiata female, h) P. labiata male.

Figure 3. XRD of chitin extracted from female and male grasshoppers.

a) Celes varabilis female, b) C. varabilis male, c) Dectius verrucivorus male, d) Melanogryllus desertus female, e) M. desertus male, f) Paracyptera labiata female, g) P. labiata male.

Figure 4. SEM of four grasshoppers spiecies: a) Celes variabilis female, b) C. variabilis male, c) Decticus verrucivorus female, d) D. verrucivorus male, e) Melanogryllus desertus female, f) M. desertus male, g) Paracyptera labiate female, h) P. labiate male.