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In addition to pesticidal activity, the capacity of natural compounds to inhibit the reproduction of parasites emerge as an important alternative tick control method. In this context, Satureja spp. stand out due to their recognized pesticidal properties. Among parasites of veterinary importance, the cattle tick, Rhipicephalus microplus, is responsible for great economic losses in livestock and transmission of relevant pathogens. Thus, the aim of this study was to evaluate the effects of different concentrations of the essential oil of Satureja montana L. on the ovary morphology of R. microplus engorged females through histological and histochemical techniques. The most remarkable morphological changes found were: cytoplasmic vacuolation of germ cells, irregular and thicker chorion, irregular oocyte shape, ring-shaped nucleolus, decrease in protein and carbohydrate content in oocytes, in addition to cellular changes in the oviduct and pedicel. All morphological changes were assessed using a semiquantitative method already established in the literature. Ticks exposed to 5.0 μl/ml of essential oil showed the most significant changes when compared to control groups. Thus, the essential oil of S. montana L. damaged the reproductive system of R. microplus, which may impair ticks' offspring production and promote a long-term control of this species. HIGHLIGHTS: The essential oil of Satureja montana L. affects the ovary morphology of the cattle tick. The main morphological alterations found were cytoplasmic vacuolation, irregular and thicker chorion and irregular oocyte shape. These alterations may impair the development of eggs.

Made available in DSpace on 2020-12-12T01:36:15Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-01-01 Rhipicephalus sanguineus sensu lato (s.l.), also known as the brown dog tick, is among the main tick species involved in the transmission of pathogens to humans and other animals and, therefore, the target of numerous control methods. However, due to the disadvantages of synthetic acaricides, the use of alternative products such as plant derivatives has been encouraged. This study aimed to evaluate the acaricidal potential of acetylcarvacrol and to determine its efficacy at sublethal doses for the control of R. sanguineus s.l. female ticks. In addition, as acetylcarvacrol was applied topically, morphological alterations in the integument were assessed. Acetylation of carvacrol was performed by reaction with acetic anhydride in a sodium hydroxide solution, being confirmed by infrared spectroscopy. The lethal concentration for 50 and 90% (LC50 and LC90) of unfed ticks and the efficacy of acetylcarvacrol in engorged females were determined after the Adult Immersion Test (AIT). For the evaluation of effects of acetylcarvacrol in the integument, routine histological techniques were employed after the AIT. The LC50 and LC90 in unfed females were 2.8 and 7.2 μL/mL, respectively. Regarding reproductive performance, after treatment with 8.0 μL/mL acetylcarvacrol 90.9% control was achieved, as ticks showed the lowest egg production index (EPI), hatching rate (HR), and fecundity rate (FR). In the integument, considerable morphological alterations were observed both in cuticle and epithelium. Thus, acetylcarvacrol affected R. sanguineus s.l. external coating and reproduction when applied at sublethal concentrations, probably contributing to a long-term control. Department of Health Sciences Federal University of Lavras (UFLA), Av. Dr. Sylvio Menicucci 1001 Department of Veterinary Medicine Federal University of Lavras (UFLA) Department of Chemistry Federal University of Lavras (UFLA) Department of Biology São Paulo State University (UNESP) Department of Natural Sciences Federal University of Acre (UFAC) Department of Biology São Paulo State University (UNESP)

Rhipicephalus sanguineus sensu lato (s.l.), commonly known as brown dog tick, is a widely distributed tick species that is substantially important for human and veterinary medicine. Therefore, it is the target of different control methods. Carvacrol and its semisynthetic derivative, acetylcarvacrol, are promising chemical compounds for alternative tick control. Thus, this study aimed to compare the repellent activities of carvacrol and acetylcarvacrol at different concentrations and drying times. Additionally, morphological alterations found in salivary glands were evaluated through histological techniques after exposure to acetylcarvacrol. The impact of the morphological changes on the development and survival of acini/cells in salivary glands was measured by a semiquantitative analysis. The repellent action of both compounds did not differ when evaluated at different concentrations, although acetylcarvacrol increased its effects as the concentration raised. Regarding the different drying times, acetylcarvacrol maintained its effects after 3 hours of exposure, while the efficacy of carvacrol decreased during this time period. Salivary glands of unfed R. sanguineus s.l. females showed dose-dependent alterations in the size and shape of acini as well as cytoplasmic vacuolization. Loss of the acinar cell limit, rupture of secretory granules and nuclear changes in the cells were also observed in the treated groups. Thus, our results demonstrated the potential of acetylcarvacrol to act as repellent against R. sanguineus s.l. Additionally, the morphological alterations found in salivary glands may interfere with the feeding process of ticks, which contributes to mitigate infestation by this species.

Unstiffened cylindrically curved panels constitute a common subset of shell structures and therefore share the advantages and disadvantages of such structural solution. One of the bigger disadvantages of shells is their sensitivity to imperfections that lower significantly their ultimate strength. At the European level, in the scope of plate design by FEM, imperfections are treated in EN 1993-1-5 (Annex C) and in shell structures designed by global numerical analysis using GMNIA, recommendations are given in EN 1993-1-6 (clause 8.7.2). Since curved panels are neither flat nor full revolution cylinders, rules for estimating equivalent geometric imperfections remain unclear. In order to tackle this problem, this paper introduces a numerical parametric study on the imperfection sensitivity of cylindrically curved panels. The effect of the amplitude and shape of initial geometric imperfections (together with different values of curvature and aspect ratio) on the ultimate strength of unstiffened cylindrically curved steel panels is studied, results are presented and conclusions are drawn.

A numerical study on the post-buckling behaviour of simply supported short cylindrically curved panels, with longitudinal edges unconstrained and loaded edges constrained (internal element of a section), including the influence of curvature and loading type (pure compression and in-plane bending) is presented in this paper. Additional relevant parameters are identified and their influence on the ultimate strength of cylindrically curved panels is studied. Numerical results of the ultimate reduction factor from the parametric study are converted into geometry (width) reduction factors by an iterative routine. Subsequently, an extension of rules for internal plated members’ ultimate load calculation from EN 1993-1-5 is proposed based on the effective width concept. It is concluded that (except for stocky panels) the increase in the curvature parameter led to an increase on the cylindrically curved panel's resistance and that the upper limit proposed by EN 1993-1-5 to the value of the curvature parameter is reasonable. Finally, a statistical study is performed that concludes that the proposed approach provides an accurate estimate of the ultimate load.

A numerical study on the elastic buckling behaviour of simply supported cylindrically curved panels, with longitudinal edges unconstrained and loaded edges constrained, including the influence of curvature, aspect ratio and loading type (from pure compression to full in-plane bending) is presented in this paper. Subsequently, an extension of rules for internal plated members’ critical stress calculation from EN 1993-1-5 is proposed that takes into account the effect of curvature. The proposed approach, based on the numerical results, gives a safe but accurate estimate (lower bound) for the elastic critical stress.