Effect of temperature on the ovipositional biology and egg viability of the cattle tickBoophilus annulatus (Acari: Ixodidae)

Abstract

The effect of temperature on the ovipositional biology ofBoophilus annulatus (Say) was determined under laboratory conditions. Engorged females subjected to constant temperatures of 12 and 45°C died without ovipositing, while females held at 15 and 40°C laid eggs which did not hatch. The preoviposition period at 25–40°C was 2–3 days; however, significant increases occurred at 20°C (5.2 days) and at 15°C (16.3 days). The number of eggs laid per female was ca. 2700 at temperatures of 25–35°C, but decreased significantly at 20°C (ca. 2300 eggs/female), 15°C (ca. 1800 eggs/female), and at 40°C (ca. 300 eggs/female). No differences were observed in the Conversion Efficiency Index (CEI) values at temperatures of 20–30°C (ca. 50%), while temperatures of 15 and 40°C produced the lowest CEI values at 35.6 and 4.9%, respectively. Hatch-ability of eggs was ca. 80% at temperatures of 20–35°C. Incubation period of eggs ranged from 52.2 days at 20°C to 16.2 days at 35°C. The thermal threshold for egg development determined by linear regression was 12.9°C. Females subjected to four fluctuating temperature regimes produced no differences in number of eggs/female (ca. 2400), CEI (ca. 50%), or hatchability of eggs (ca. 75%). Preoviposition period and incubation were significantly affected by a change in the thermoperiod, becoming longer in duration as the temperatures were decreased. From studying females exposed for various intervals from 0 to 105 days at 12°C, indications were that the longer the exposure period the more adverse the effects were on oviposition and egg-hatch. Correspondingly, exposure of eggs to a temperature of 15°C for up to 105 days gave indications that the longer the eggs remained at 15°C, the lower the hatch would be after transfer back to a temperature of 25°C.