Morphometrical changes in eggs of Rhodnius prolixus ( Heteroptera : Reduviidae ) during development

CHAVES LF, RAMONI-PERAZZI P, LIZANO E, AÑEZ N. 2003. Morphometrical changes in eggs of Rhodnius prolixus (Heteroptera: Reduviidae) during development. Entomotropica 18(2):83-88. We explore morphometric changes during development in 124 eggs of Rhodnius prolixus, kept under laboratory conditions. Measurements were performed using a dissecting microscope coupled to a video camera connected to a monitor. Our results show that only maximal diameter varies significantly (t = 14.61, d.f. = 123, P < 1,19*10-18) changing from (0.88 ± 0.05) mm to (0.93 ± 0.04) mm. Such changes are correlated in a positive way according to a linear function (R2= 0.63; F= 206.29; d.f.= 1, 121; P<0.0001). The increase of this measurement is mainly explained by the intercept value (A= 0.186 ± 0.052; t= 3.57; d.f.= 120; P < 5*10-4), and this value could represent the maximun elasticity of eggs in this species. Additional key words: Development, eggs, Rhodnius prolixus, Triatominae. Resumen CHAVES LF, RAMONI-PERAZZI P, LIZANO E, AÑEZ N. 2003. Cambios morfométricos en huevos de Rhodnius prolixus (Heteroptera: Reduviidae) durante su desarrollo. Entomotropica 18(2):83-88. Exploramos los cambios morfométricos durante el desarrollo de 124 huevos de Rhodnius prolixus, mantenidos bajo condiciones de laboratorio. Las medidas fueron realizadas empleando un microscopio de disección acoplado a una cámara de video conectada a un monitor. Nuestros resultados indican que sólo el diámetro máximo aumenta de manera significativa (t= 14,61, d.f.= 123, P < 1,19*10-18) pasando de (0,88 ± 0,05) mm a (0,93 ± 0,04) mm. Tales cambios están correlacionados de una manera positiva de acuerdo a una función lineal (R2= 0,63; F= 206,29; d.f.= 1, 120; P<0,0001). El aumento en las medidas es explicado principalmente por el valor del intercepto (A= 0,186 ± 0,052; t= 3,57; d.f.= 120; P < 5*10-4), dicho valor podría representar la elasticidad máxima de los huevos de esta especie. Palabras clave adicionales: Desarrollo, huevos, Rhodnius prolixus, Triatominae. Introduction Rhodnius prolixus, Stål (1859), is in northern South America the main natural vector of Trypanosoma cruzi, Chagas (1909), which causes Chagas disease (Schofield & Dujardin 1997). In the World an estimation for a total eradication and control of vectorial transmission is for the year 2010 (Visschedijk & Siméant 1998). This proposition appears to be very optimistic considering recent reports on domiciliary invasions by Triatominae species, where they have been previously eradicated (Almeida et al. 2000). Such situation points out to the importance and relevance of further studies of the natural history of these insects, especially those poorly understood stages of their life cycle, as may be eggs (Barata 1998). Information on eggs measurements have been previously produced by researchers interested in the biology of R. prolixus. Brumpt (1913) indicates a length(L) of 2 mm; Uribe (1925) shows a L of 2.5 mm; Briceño-Iragorry (1934) recorded a L of 1.95 mm, a diameter(D) of 0.80 mm, and a caudal to neck length of 1.85 mm; Galliard (1935) reports a L among 1.7 and 1.8 mm and a D of 0.820 mm; Barata et al. (1980) reported a L of (1.782 ± 0.067)mm and a D of (0.880 ± 0.044)mm. None of these works were done