Metabolic rate does not scale with body size or activity in some tick species

Authors: EARLS, KAYLA - Washington State University; Oyen, Kennan

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2024
Publication Date: 9/17/2024
Citation: Earls, K.N., Oyen, K.J. 2024. Metabolic rate does not scale with body size or activity in some tick species. Experimental and Applied Acarology. https://doi.org/10.1007/s10493-024-00958-9.
DOI: https://doi.org/10.1007/s10493-024-00958-9

Interpretive Summary: Ticks are a significant vector of numerous livestock diseases. Understanding how ticks will respond to environmental change will help target control efforts. Ticks can only persist in areas where their eggs will survive, but almost nothing is known about how temperatures affect eggs. We measured the impact of stressful temperature exposure on 5 species of tick eggs and compared their hatching success. We found that tick eggs are particularly vulnerable to stressful temperature exposure early in development and this was common to all species. We also found that tick eggs are generally less hardy than other life stages so eggs might be a good target for tick control efforts.

Technical Abstract: Respiration in ticks is highly efficient and exceptionally low. Ticks can survive years between bloodmeals by having low activity and respiration to conserve energetic resources. Our objective was to compare metabolic (VCO2) and activity rates across 6 tick species. We predicted that VCO2 would be different among species and scale linearly with activity and body mass. Activity and CO2 production were measured for 32 hours in 6 tick species: Dermacentor andersoni, D. variabilis, Haemaphysalis longicornis, Rhipicephalus appendiculatus, R. microplus, and R. sanguineus. Individual ticks were measured for 30 minutes three times to ensure breathing occurred. Absolute and mass-specific VCO2, total activity, body mass, and ventilation patterns were compared among species. As expected, ticks did not always breathe during the 30-minute measurements, especially R. sanguineus. Ventilation patterns differed among species with R. microplus having primarily cyclic patterns and R. appendiculatus having discontinuous gas exchange. VCO2 did not scale with body mass in most species. Haemaphysalis longicornis and R. sanguineus had the lowest VCO2; however, H. longicornis was the second most active species. Life history, including questing behavior and range expansion, could be contributing to differences between species. For instance, H. longicornis had exceptionally low metabolic rates despite above average activity levels, suggesting an energetic advantage which may underlie recently documented range expansions in North America. Our results demonstrate how ticks utilize energetic resources to maximize longevity. Future research describing questing behavior and distribution modeling may help explain differences in metabolic rates and activity and impacts on life history traits.