Allozyme polymorphism of Mdh and alpha-Gpdh in Ixodes ricinus populations: comparison of borreliae-infected and uninfected ticks.

Ixodes ricinus Linnaeus (Acari: Ixodidae) ticks are vectors of numerous infectious diseases in humans and animals. The allozyme variability of MDH and alpha-Gpdh was detected by native polyacrylamide gel electrophoresis in I. ricinus natural populations in three localities in Serbia. Four alleles of Mdh locus (MDH 1, MDH 2, MDH 3 and MDH X) and four alleles of alpha-Gpdh locus (VS, S, F and VF) were detected. Interpopulation differences in Mdh and alpha-Gpdh allele frequencies were statistically insignificant. Significant difference in alpha-Gpdh allele frequencies between males and females was recorded in the largest sample only. Differences in allele frequencies, detected between borreliae-infected and uninfected I. ricinus ticks, were close to the level of statistical significance, especially for alpha-Gpdh locus. Clear significant difference appeared in females when sexes were tested separatelly (P = 0.037). It is interesting that genotypes containing rarer alleles (MDH 1 and S) were infected in higher proportion in comparison to other genotypes. Our results point towards a possible role of Mdh and alpha-Gpdh loci in I. ricinus ticks in the determination of energy requirements for host seeking. Sex differences in alpha-Gpdh allele frequencies suggest that selective pressure, concerning efficiency of reserve materials utilisation, points to alpha-Gpdh rather than to Mdh locus.