Water mites as experimental organisms: taxon-dependent starvation resistance under cold conditions

Widening the range of organisms available as experimental models contributes to a more comprehensive understanding of the functional and evolutionary diversity of the living world. Water mites (Acari, Hydrachnidia) are globally distributed and highly accessible for experimental work, yet their long-term laboratory maintenance has traditionally been considered challenging. Here, we report that specific water mite taxa can be successfully maintained ex situ for extended periods under cold conditions with minimal logistical requirements. A set of water mite cohorts was sampled from an unpolluted stream in the Spanish Pyrenees. Individuals were kept separately in hermetically sealed microtubes containing native stream water and monitored weekly for 29 weeks. Survival dynamics under absolute fasting, with neither diurnal light cycles nor atmospheric gas exchange, were analyzed using Kaplan–Meier estimators. The results revealed a highly significant divergence in physiological resilience among the studied taxa: individuals of the genus Atractides exhibited a marked sensitivity to starvation (median survival: 7 weeks), whereas the most resilient genera ( Torrenticola , Lebertia , and Protzia ) showed exceptional endurance, maintaining >95% survival throughout the entire 29-week study. Specific water mite genera are therefore proposed as highly suitable alternative experimental organisms due to their ease of collection, minimal maintenance needs (requiring no feeding, artificial aeration, or specialized flow configurations), and robust performance in longitudinal bioassays.