Biological and physiological characterization of in vitro blood feeding in nymph and adult stages of Ornithodoros turicata (Acari: Argasidae)

Abstract

Biological and physiological aspects of blood feeding in nymph and adult Ornithodoros turicata were investigated using an in vitro technique combined with electrophysiological recordings and respirometry. The duration of blood feeding through a Parafilm® membrane was similar (19.2–22.6min) in both developmental stages. The mean (±SD) size of blood meal ingested by nymphs, females, and males was 44.2±17.9, 150.6±48.7, and 74.2±36.9mg, respectively, representing a 2.5-, 2.8- and 3.0-fold increase from their respective unfed weights. Electrophysiological recordings of the pharyngeal pump during blood feeding revealed that ticks ingested blood at a rate of 6.1–6.4 suctions per second. Mean blood volume ingested per suction was 0.013μl in females and 0.007μl in both males and nymphs. Blood meal size (mg) correlated with unfed body weight (mg) (r2=0.50, p<0.05) and with blood volume ingested per suction (r2=0.71, p<0.05). Unfed ticks exhibited a circadian ventilation rhythm with discontinuous gas exchange pattern during the daytime and continuous pattern during nighttime. Mean standard metabolic rates (SMR, V̇CO2) in unfed nymphs, females and males of 1.4, 3.0 and 0.9μlh−1 increased to 2.0, 5.7 and 2.4μlh−1, respectively, after a blood meal. SMR correlated positively with blood meal size (r2=0.89, p<0.05). Mean coxal fluid weight excreted after a blood meal in nymphs, females, and males was 8.7, 20.0, and 7.7mg, respectively, which represents 27.0%, 23.4% and 26.7% of their blood meal size. This study revealed biological and physiological characteristics of soft tick blood feeding and metabolism important to tick survival.