Characterization of the Chaetae Autofluorescence in the Earthworm Eisenia foetida and their Role in Locomotion

Abstract

Earthworms are the most abundant invertebrates in terrestrial ecosystems and play a vital role in maintaining soil structure and fertility, they interact constantly with soil particles and microorganisms, improving macroporosity, water dynamics, aeration, and organic matter decomposition. Their bodies are composed of segments known as rings or metameres, from which small bristle-like structures called chaetae protrude. These chaetae assist in burrowing and locomotion through the soil. Despite their functional importance, the detailed composition and optical properties of chaetae remain poorly understood. In this study, chaetae from Eisenia foetida were isolated and analyzed using fluorescence microscopy, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDX) and infrared spectroscopy (FTIR). Fluorescence analysis revealed strong intrinsic blue autofluorescence, with an excitation peak at 320 nm and an emission peak at 410 nm, matching the DAPI filter set. SEM-EDX showed a composition dominated by carbon and oxygen, along with trace elements such as chlorine, potassium, sodium, and copper, while FTIR confirmed the presence of β-chitin as the primary structural component. These findings expand our understanding of the molecular and optical properties of annelid chaetae. The discovery of intrinsic autofluorescence linked to β-chitin opens new possibilities for non-invasive imaging, species identification, and the potential use of annelid-derived chitin in biomaterials research.

Keywords: Annelida; Chitin; Earthworms; Movement; SEM–EDX; Spectroscopy IR-FT; Ultraviolet.