Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni

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Abstract
1. An in vitro method is described for stimulating the salivary gland of Dermacentor andersoni to secrete fluid. In vitro glands require the presence of a catecholamine for salivation to occur. Natural haemolymph from salivating ticks does not trigger secretion suggesting that the tick does not produce a ‘salivation hormone’ analogous to the diuretic hormones of certain insects. 2. Piocarpine, glutamate and malate did not stimulate secretion in vitro. Isoproterenol and 5-hydroxytryptamine were relatively weak stimulants (threshold concentrations of approximately 10-5 M and greater than 10-4 M respectively). Adrenaline, noradrenaline and dopamine were highly effective stimulants, the threshold concentrations being no more than 10-5 M. Adrenaline could also elicit a copious secretion in vivo at a final haemocoele concentration of about 2 x 10-5 M. 3. We postulate that salivation occurs by means of a secretory rather than a filtration-resorption mechanism. Control of fluid secretion is probably neural rather than hormonal, the transmitter substance being a catecholaminergic substance.