Geotropic, hydrokinetic and random walking differ between sympatric tick species: the deer tick Ixodes scapularis and the lone star tick Ambylomma americanum

Authors: OTALORA-LUNA, FERNANDO - University Of Richmond; DICKENS, JOSEPH - Collaborator; BRINKERHOFF, JORY - University Of Richmond; Li, Andrew

Submitted to: JOURNAL OF ETHOLOGY
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2021
Publication Date: 1/25/2022
Citation: Otalora-Luna, F., Dickens, J.C., Brinkerhoff, J., Li, A.Y. 2022. Geotropic, hydrokinetic and random walking differ between sympatric tick species: the deer tick Ixodes scapularis and the lone star tick Ambylomma americanum. Journal of Ethology. https://doi.org/10.1007/s10164-021-00741-y.
DOI: https://doi.org/10.1007/s10164-021-00741-y

Interpretive Summary: The deer tick and lone star tick are among major tick species of medical and veterinary importance in the United States. They are vectors of pathogens that cause serious diseases, including Lyme disease, babesiosis, ehrlichiosiss, Rocky Mountain spotted fever, and Red Meat Allergy. Tick control involves use of synthetic pesticides that target free-living ticks in environment or ticks feeding vertebrate hosts. Chemical repellents, such as DEET, are used to prevent ticks from biting humans. Variations in biology and behavior of the tick species are contributing factors that affect tick control efficacy and effectiveness of personal protection measures people take. USDA-ARS scientists joined force with university researchers in a study to investigate behavioral differences between two common tick species in the northeastern United States. Study results revealed for the first time that the lone star tick demonstrated a positive geotropism while the deer tick showed strong negative geotropism. Understanding the behavioral differences between these two major tick species will facilitate design of new tick behavior-modifying compounds or devices for tick surveillance and/or tick bite prevention. Results obtained from this study are of interest to tick behavior researchers, ecologists, and evolutionary biologists, and likely also to pest control professionals who work in the field of repellent development and vector control.

Technical Abstract: The deer tick Ixodes scapularis and the lone star tick Ambylomma americanum are sympatric species whose distributions overlap both geographically and ecologically. Each species vectors a number of pathogens including the agents responsible for Lyme disease and ehrlichiosis. We performed ethological observations of both species in five behavioral arenas focusing on geotropism and hydrokinesis. A. americanum adults showed positive geotropism by: a) walking down a precipice, b) descending a wire, and c) refusing to climb up a wall at the first encounter. In contrast, I. scapularis adults and most nymphs of both species showed negative geotropism in the same tests. Adults of both species and nymphs of A. americanum walked into water while clinging to a cork, and even walked a distance beneath the surface of the water. On a servosphere, adults of A. americanum walked faster than I. scapularis adults, but I. scapularis spent more time walking. We discuss the importance of these attributes from behavioral ecology perspectives including previously reported notions of aggressiveness of the species. The assessment of behavioral distinctness between these sympatric species will facilitate design of experiments aimed at evaluations of attractants and repellents, and contribute to biorational control and surveillance strategies.