Structural and elemental characterization of α-chitin isolated from Eupelops torulosus torulosus and Achipteria (A.) acuta (Acari, Oribatida), in related to soil geochemistry

Chitin, a linear polysaccharide composed of N-acetyl-D-glucosamine units, is a fundamental structural component in the exoskeletons of invertebrates, including members of the phyla Arthropoda, Mollusca, Annelida, and others, as well as in fungal and bacterial cell walls. In the present study, chitin was isolated from two oribatid mite species, Eupelops torulosus torulosus (Koch, 1839) and Achipteria (A.) acuta Berlese, 1908, which were extracted from soil and litter samples using Berlese funnel systems. The structural, morphological, and thermal characteristics of the chitin were analyzed using Fourier-transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), and thermogravimetric–differential thermal analysis (TG-DTA). FT-IR spectral data confirmed successful chitin extraction and revealed that both samples contained chitin in the α-crystalline form, consistent with arthropod-derived chitin. FE-SEM imaging further revealed a fibrous, layered surface morphology typical of well-structured exoskeleton chitin. To complement structural characterization, elemental composition of both the mite tissues and their corresponding soil microhabitats was analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The results indicated the presence of trace and macroelements such as calcium (Ca), magnesium (Mg), iron (Fe), and zinc (Zn), with significant interspecific and site-based variations. Elemental accumulation patterns suggested potential ecological interactions between soil geochemistry and mite physiology, highlighting the role of environmental factors in shaping elemental uptake and bioaccumulation in microarthropods. These findings provide a comprehensive understanding of the chitin composition in oribatid mites and offer new perspectives on their ecological interactions with soil chemistry. The integration of structural and elemental analyses enhances our knowledge of invertebrate biomaterials and their potential role in environmental monitoring.