Study of insect metamorphosis by means of Raman spectroscopy
Insect metamorphosis is a process of the internal and external restructuring of the body, in which two opposite phenomena occur - histolysis and histogenesis. We are studying Hymenoptera insects with complete metamorphosis, hence, histolysis occurs in the last instar larva, resulting in the destruction of larval organs. The goal of histogenesis is the construction of new organs from the liquid mass. The study of metamorphosis has many challenges. We first applied Raman spectroscopy to study the metamorphosis of Hymenoptera. The non-invasiveness of the method for insects allowed us to quantify the molecular content in the larva and pupa, to visualize the movement of molecules during the pupa formation. Raman spectra of insects were recorded using a Renishaw inVia Raman microspectrometer (UK) with a 532 nm laser. We obtained the following peaks characteristic of different molecular groups: 1005 (C-CH3), 1156 (C-C), and 1522 (C=C) in carotenoids, 1445 (CH2) in lipids, 1650 (amide I) in proteins, etc. We found that during metamorphosis, the amount of carotenoids increases, while the amount of proteins and lipids does not change. This allowed us to use proteins and lipids as a normalization parameter to calculate quantitative changes in carotenoids during metamorphosis. Using Raman mapping, we first demonstrated the concentration of carotenoids in the legs and wings of the Hymenoptera pupa. Our study leads to fundamental questions in insect molecular composition during metamorphosis. We consider the method of Raman spectroscopy to be promising in the non-invasive study of biological objects.
Matvey I. Nikelshparg
Saratov State University
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