A New Approach in Investigation the Chemotaxis Response of Mammalian Parasitic Nematode: In Vitro Study

Chemotaxis is the biologically intrinsic navigation towards or away from chemical stimuli. It is a crucial behavioral response for animals when interacting with their environment and a tool for locating sustenance, hosts, and other vital environmental signals. Prior research has predominantly concentrated on the chemotactic behaviors of free-living and entomopathogenic nematodes in response to volatile soil constituents. The present work conducts for the first time the chemotaxis assay of Syphacia obvelata (Nematoda: Oxyuridae) parasitizing the vertebrate cecum as an experimental model for detecting this behavior in parasitic nematodes. We tested two mouse biological samples, namely urine, and serum, as odorants to study the in vitro chemotactic behavior of S. obvelata. The experiments were conducted in triplicate groups of twenty-two worms for gradient dilutions between 10^-0, 10^-1, 10^-3, and 10^-5ml, using a semi-solid formula of agar (Brenner 1974; Stiernagle. 2006) as a nutrient surface medium for cultivation. The chemotaxis chamber and photography system were applied according to Hirotsu et al. 2015 with some modification to be convenient with the current experiment. The chemotaxis index is computed along with the cultivated worms' mean number attracted toward or repulsed away from the odorants. The control groups included ten worms with an ablated olfactory sense organ (amphid) that was targeted using a 785 nm picosecond pulsed laser with a power of 10 mW and a confocal Raman microscope. dose-dependent chemotactic response to both urine and serum, with diluted concentrations (10⁻⁵) acting as attractants and undiluted forms acting as repellents. There is also a time-dependent enhancement of chemotaxis, with stronger positive responses at 60 min for both stimuli. Unexpectedly, the high concentration of anal gland secretion consistently repels worms, with stronger repulsion over time. This study advances our knowledge of the sensory mechanisms of Oxyuridae, life cycle navigation, and parameters that promote retro-infection. It also provides the first insight into the chemotactic behavior of these creatures. It also highlights the potential of laser microsurgery as a precise tool for investigating complex sensory systems in minute organisms.