Biological comparisons between a laboratory-maintained and a recently isolated field strain of Boophilus microplus

Biological differences between two strains of Boophilus microplus were examined. The A-strain of ticks had been maintained at the laboratory for many years and the N-strain was recently isolated, being a composite strain derived from ticks from different sources in the field. In three experiments, up to three times as many N-strain ticks grew to maturity than did A-strain ticks, although A-strain ticks matured earlier. N-strain ticks were 17 to 60% heavier, and laid 50 to 100% more eggs than A-strain ticks. N-strain eggs were significantly more fertile than A-strain eggs. Unfed, N-strain larvae survived much longer than A-strain larvae. The reduced vitality of the A-strain is attributed to its long history in the laboratory during which time it has become biologically disadvantaged through inbreeding. These results suggest that some laboratory-maintained strains of ticks may be unsuitable for ecological or acaricide studies.