The alpha-Gpdh polymorphism in the tick Ixodes ricinus: similar diurnal trends in genotypic composition in Irish and Swedish population samples.

Analysis of the alpha-Gpdh locus, coding for the enzyme alpha-glycerophosphate dehydrogenase (glycerol-3-phosphate dehydrogenase), was conducted using starch-gel electrophoresis on samples from one Irish and one Swedish population of the tick Ixodes ricinus. Morning ('AM') and late afternoon ('PM') samples of unfed adults were collected in each case. The results show a higher frequency of homozygotes in females in the AM than in the PM sub-samples in both populations. No such diurnal differentiation was found in the case of male ticks. The results are discussed in relation to previous studies on the polymorphism in Ireland and in the context of the known metabolic role of alpha-glycerophosphate dehydrogenase in insect muscle. The possible selective influence of climatological factors is considered.