Salivary apyrase in New World blackflies (Diptera: Simuliidae) and its relationship to onchocerciasis vector status.
Salivary gland apyrase is believed to be critical to blood-feeding in arthropod vectors. This enzyme was measured in six New World blackflies representing three taxonomic pairs of non-vectors and vectors of Onchocerca volvulus. In Simulium (Psilopelmia) ochraceum, a highly anthropophilic vector in Mexico and Guatemala, apyrase exhibited maximum activity between pH 8.0 and 9.0, mean 39.8 +/- 4.7 milliUnits/pair of gland equivalents (mU), and was enhanced when ATP was used as a substrate. In the zoophilic non-vector Simulium (Psilopelmia) bivittatum maximum activity was significantly less (5.1 +/- 0.7 mU) under all conditions examined. Preference for ADP or ATP as substrate was a function of the pH of the reaction for this species. Apyrase activity in Simulium (Simulium) metallicum Bellardi (29.5 +/- 11.5 mU), a zoophilic secondary vector in Mexico and Guatemala, resembled that of S. (Ps.) ochraceum (24.8 +/- 13.7 mU at pH 8.5) with ADP as substrate, but showed reduced activity with ATP. Both these Central American vectors had higher apyrase activity than found in Simulium (Notolepria) exiguum, a vector of O. volvulus in Ecuador and Colombia. However, maximum apyrase activity, measured at pH 8.0 with ADP as substrate, was greater in S. (N.) exiguum (10.9 +/- 0.6 mU) than in Simulium (Notolepria) gonzalezi (5.9 +/- 1.9 mU), a non-vector species widespread in Central America. Therefore, for the consubgeneric species pairs examined, a positive association was detected between higher concentrations of apyrase activity and their vector status for O.volvulus.
Cupp
M S
MS
Department of Veterinary Science, University of Arizona, Tucson 85721, USA.
Cupp
E W
EW
Ochoa-A
J O
JO
Moulton
J K
JK
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001081:Apyrase / Q000378:metabolism*; D002118:Calcium; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007303:Insect Vectors / Q000201:enzymology / Q000469:parasitology; D008274:Magnesium; D017181:Onchocerca volvulus / Q000502:physiology*; D009855:Onchocerciasis / Q000635:transmission; D012469:Salivary Glands / Q000201:enzymology*; D012843:Simuliidae / Q000201:enzymology* / Q000469:parasitology*; D013379:Substrate Specificity
D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D001081:Apyrase; D008274:Magnesium; D002118:Calcium