Selective breeding for photoperiodically induced developmental diapause in laboratory strains of Amblyomma americanum (Acari: Ixodidae).
Offspring of Amblyomma americanum (L.) reared for four generations in a 12:12 (L:D) photoperiod in the laboratory were held in 10:14 (L:D) conditions and bred to select for developmental diapause (DIA) or nondiapause (NON) characteristics for two additional generations. Sequential generations of fed DIA nymphs had mean molting times (days from detachment to ecdysis) that were 8.0% (DIA1) and 35.7% (DIA2) greater than parental ticks, and maximal development time was extended by 20% in DIA2 ticks over that of parentals. Selection in NON strains resulted in a significant decrease of detachment to ecdysis times in NON1 ticks, but the detachment to ecdysis times in NON2 ticks increased and was not different from parental ticks. Breeding for DIA and NON extremes did not affect the ability of either strain to develop rapidly if held in long-light (14:10 [L:D]) conditions. Selection for DIA resulted in extension of the period from detachment of fed nymphs to preapolysial posturing rather than from posturing to ecdysis of adults.
Knipling-Bushland U.S. Livestock Insects Research Laboratory, USDA-ARS, Kerrville, Texas 78029-0232.
J M
JM
Pound
J E
JE
George
D000818:Animals; D001947:Breeding; D008027:Light; D010507:Periodicity; D013987:Ticks / Q000235:genetics / Q000502:physiology*