Estimation of the growth patterns of Oestrus ovis L. larvae hosted by goats in Baja California Sur, Mexico.

To estimate parameters for the variation in larval weight and dimension in Oestrus ovis L. and to describe the approximate pattern of growth, 2041 larvae were collected from 431 slaughtered goats and classified on a scale of 12 identified physiological ages, according to spiracular and integumental pigmentation. Larval live weight and measures of length, width, and thickness at the seventh segment were obtained. Weight increased from 0.23 mg in L1 larvae to 49 mg in late L2 larvae; however, the highest increases in weight were found to occur after the L2-L3 molt, especially during the early L3 period, when larvae acquired about 45% of the average mature weight (518 mg). Average larval length increased almost linearly from about 2 mm in L1 larvae to reach full length (21.3 mm) just before initiating integumental pigmentation, then it tended to stabilize until full maturation. Except for higher increases during the early L3 period, larval width and thickness increased linearly to reach mean maximum values (6.0 and 5.0 mm, respectively) at full maturity. Weight and measurement data were fitted by monophasic, s-shaped growth functions. The y = 0.25 [1 + tanh[0.504 (12-6.65)]] function (R2 = 0.99) indicated that L3 larvae began to have a decrease in weight gain rates before the beginning of integumental pigmentation. The patterns of growth of O. ovis described from individual measurements in larvae may be suitable for descriptive purposes.