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 lar vae 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 thickne ss at the seventh segment were obtained. Weight increased from 0.23 mg in L -1 larvae to 49 mg in late L-2 larvae however, the highest increases in wei ght were found to occur after the L-2-L-3 molt, especially during the early L-3 period, when larvae acquired about 45% of the average mature weight (5 18 mg). Average larval length increased almost linearly from about 2 mm in L-1 larvae to reach full length (21.3 mm) just before initiating integument al pigmentation, then it tended to stabilize until full maturation. Except for higher increases during the early L-3 period, larval width and thicknes s increased linearly to reach mean maximum values (6.0 and 5.0 mm, respecti vely) at full maturity. Weight and measurement data were fitted by monophas ic, s-shaped growth functions. The gamma = 0.25 [1 + tanh{0.504 (12-6.65)}] function (R-2 =0.99) indicated that L-3 larvae began to have a decrease in weight gain rates before the beginning of integumental pigmentation. The p atterns of growth of O. ovis described from individual measurements in larv ae may be suitable for descriptive purposes. (C) 1999 Elsevier Science B.V. All rights reserved.