The 2005 ESA Annual Meeting and Exhibition
December 15-18, 2005
Ft. Lauderdale, FL

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Friday, December 16, 2005

Plastron respiration in ticks (Acari: Ixodidae)

Susan M. Villarreal,, Truman State University, tick group, Science Division, 100 East Normal, Kirksville, MO and Bach Q. Ha, Truman State University, Math & Computer Science Division, 100 East Normal, Kirksville, MO.

Ticks are blood-feeding arthropods that are well known for their survivability. Although ticks are terrestrial organisms, they can survive extended periods of submergence under water as for example after heavy rainfall or flooding. A plastron is a physical gill consisting of a thin layer of air trapped by hydrophobic hairs or other cuticular projections. Hence a plastron is an alternate respiration system that can absorb oxygen from water. The complex spiracular plates of ticks have been postulated to serve as plastrons but until now, this has not been verified. In this study, we confirm the existence of plastron respiration in the dog tick Dermacentor variabilis. Adult dog ticks can survive submergence in water for over two weeks. Wetting the spiracular plate with alcohol, thereby debilitating any potential plastron function lowered survival to less than three days. Biomathematical studies currently in progress are modeling the efficiency of the spiracular plate as a plastron. We have developed a mathematical model to predict survivability of submerged ticks under water. This model requires determination of a suite of physical and biological parameters including volume of the air film contained within the spiracular plate, the plastron air/water interface area and the oxygen consumption and biomass of the submerged tick. It is hoped that this model can be successfully used in the future to predict underwater survivability of other species of ticks which show both interspecific and intergeneric morphological variation in spiracular plate structure. This study provides the first example of plastron respiration in the Ixodidae.

Species 1: Acari Ixodidae Dermacentor variabilis (Dog tick)
Keywords: Plastron, Respiration