Identification of Organs Inside Hard Tick Body Using Spectral-domain Optical Coherence Tomography

Abstract Ixodidae tick, also known as a hard tick, is one of the major vectors of various tick-borne diseases. Studying its anatomy is the fundamental approach for diverse acarological studies and the key to understanding tick morphology. However, the conventional methods of observing internal organs rely primarily on dissection, which damages specimens irrecoverably. In this study, we developed an optical coherence tomography (OCT) system to non-invasively investigate the morphological characteristics of the hard tick. Herein, OCT imaging was conducted by the developed spectral-domain OCT (SD-OCT) system with two different objective lenses. The developed system provides an axial resolution (in the air) of 6.2 µm and a maximum lateral resolution of 2.46 µm as an objective lens with a high numerical aperture (NA) and 10x magnification was employed. Using the developed SD-OCT system, internal organs of tick specimens, such as salivary glands, midgut, genital orifice, and ovary, were identified without inflicting damage. The study suggests the feasibility of the optical coherence imaging for the acarological study of the fundamental morphological inspection and for possible future studies, such as verifying the potential morphological differences among virus transmitted hard tick specimens.