Variaciones morfológicas de Tetranychus Urticae Koch (Acari: Tetranychidae) originadas por Solanum muricatum y Passiflora tripartita

Abstract

The Tetranychidae includes more than 1,250 species commonly known as spider mites, many of them can become agricultural importance species due to damage to different crops. Morphological identification of Tetranychidae species is difficult due to the limited number of morphological characters that serve in the diagnosis and in addition many of the key characteristics frequently show a wide phenotypic plasticity. In the present study, the effect of the host plant on morphological variations (disposition and length of idiosomal setae (chaetotaxy) in females of T. urticae populations collected in natural plantations of taxo (Passiflora tripartita) and sweet cucumber (Solanum muricatum) was evaluated. In the laboratory, samples were examined under a stereoscopic microscope for morphotype separation. Morphotypes were mounted on slides for microscopic observation using a phase contrast optical microscope for species confirmation, using taxonomic keys. Once the species was confirmed, 20 slides were prepared for the examination of the following morphological characters length of the dorsal (ve, sci, sce, c1, c2, d1, d2, e1, e2, f1, f2, h1, IC1, c3, c4) and ventral (pg, g, h2, h3) setae as well as the distance between them. Additionally, values of length and width of the idiosoma, length of the gnatosoma, morphology of the female genital shield and length and shape of the aedeagus in the male were determined. The morphological analysis of the different populations of T. urticae collected in sweet cucumber and taxo in three localities showed the effect of the host plant on the length and width of the idiosome was found, but there was no effect of the locality. The morphology analysis showed that there are differences in the size of the mite due to the effect of the host plant, the females being significantly larger when feeding on cucumber plants, which could suggest that this species of plant offers better conditions for mite development. The host plant caused differences in the length of the idiosomal setae (sc1, e1, f1, h1 and h2) and in the distance between their bases (sc2, c1, c2, e1, e2, f1, h2) in T urticae females, being greater in specimens collected in sweet cucumber plants, which corresponds to the largest size of the idiosoma, except when the length of h1 and h2 was considered. Based on the results of the morphological analysis, it is recommended to carry out molecular biology studies using specific molecular markers for this species, in order to correlate the findings with studies at the genetic level.