SALIVARY-GLAND APYRASE IN BLACK FLIES (SIMULIUM-VITTATUM)

Apyrase enzyme activity was demonstrated in the salivary glands of a c olonized strain of Simulium vittatum. Activity was maximum (8.5 +/- 0. 7 mU/pair of gland equivalents) at pH 8.0, with ADP as substrate and C a2+ as the divalent cation. Activity was minimal in newly emerged fema les (1.6 +/- 0.5 mU/pair of gland equivalents) but increased by 48 h. Activity in male salivary glands was marginally detectable (0.7 +/- 0. 8 mU/pair of gland equivalents), even 72 h after emergence. When newly emerged females were maintained at 4-degrees-C, salivary apyrase acti vity accumulated at a slow rate. Transferring females to warmer temper atures increased the rate of apyrase accumulation, but 27-degrees-C di d not yield greater activity than 20-degrees-C. Apyrase activity was d ecreased when females engorged on whole bovine blood or on a simulated blood meal. Activity remained low 6 h after feeding, but increased to prefeeding levels by 48 h. During the second, anautogenous gonotrophi c cycle, apyrase activity was not greater than during the first, autog enous gonotrophic cycle. Apyrase activity was not related to long term colonization as total salivary gland apyrase activity and pH profile in wild S. vittatum was not different from colonized S. vittatum.