Azadirachta indica A. Juss (neem) induced morphological changes on oocytes of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) tick females

Abstract

Many studies have been conducted with plants whose extracts have the potential to be used for pest control. One of these plants is Azadirachta indica (neem), whose main active ingredient is azadirachtin, a compound shown to have acaricide and insecticide activity. Rhipicephalus sanguineus (brown dog tick) is currently considered to be an "urban pest," because of its high levels of infestation and its ability to attack humans. In the present study partially and fully engorged R. sanguineus females were exposed to aqueous extracts of neem at concentrations of 10% and 20%, and to a control treatment. The results showed that differently from what was observed in the control, the pedicel cells of females exposed to neem at both concentrations lost their original shape. In the latter cases, the cytoplasm of the cells became fully vacuolated, especially near the germinal vesicle (oocyte nuclei) and in the oocyte pole, which is in contact with the cells of the pedicel. Oocytes in early stages of development (I and II) of ticks treated with both concentrations had irregular germinal vesicle, including the presence of two nucleoli as well as fragments of these. Oocytes in stages IV and V of exposed individuals showed full granular cytoplasm with bigger yolk granules when compared to the early stages. Chorion of mature oocytes was also altered, showing folds and deformations along their entire extension. The observed changes in cells of the reproductive system of R. sanguineus, especially in the oocytes, indicated the potential of neem as a new alternative method to control these ectoparasites.

Ultrastructural changes in the ovary cells of engorged Rhipicephalus sanguineus female ticks treated with esters of ricinoleic acid from castor oil (Ricinus communis)

“…Moreover, the presence of vacuoles full of electron-dense bodies in the interdigitations indicated the possible establishment of a defense mechanism for removing damaged or toxic materials (e.g., organelles, membrane residues, and the chemical compound itself) that should not remain or reach the interior of the oocyte. Our results corroborate those obtained in studies conducted by Denardi et al (2010) when he treated female R. sanguineus ticks with the aqueous extract of ''Neem'' leaves.…”

“…Juss.) (Denardi et al, 2010), as well as extracts from other plants of the Asteraceae family (Ribeiro et al, 2008). More recent studies have shown that derivatives of castor oil (Ricinus communis), especially an ricinoleic acid ester of this oil, when incorporated into animal feed, can drastically interfere in the physiology of the salivary glands and ovaries of R. sanguineus ticks that feed on these animals, offering an effective contribution to the reduction of tick populations in the environment (Arnosti et al, 2011a,b).…”

Morphological effects of neem (Azadirachta indica A. Juss) seed oil with known azadirachtin concentrations on the oocytes of semi-engorged Rhipicephalus sanguineus ticks (Acari: Ixodidae)

“…In ticks, the use of neem products showed relevant effects for the control of Amblyomma variegatum (Ndumu et al 1999), Hyalomma dromedarii (Al-Rajhy et al 2003), Hyalomma anatolicum excavatum (Abdel-Shafy and Zayed, 2002), Rhipicephalus decoloratus (Choudhury 2009), Rhipicephalus (Boophilus) microplus (Srivastava et al 2008;Broglio-Micheletti et al 2010) and R. sanguineus (Denardi et al 2010(Denardi et al , 2011(Denardi et al , 2012, affecting reproductive processes or even causing mortality.…”

Effect of aqueous extract of Azadirachta indica A. Juss (neem) leaf on oocyte maturation, oviposition, reproductive potentials and embryonic development of a freshwater fish ectoparasite Argulus bengalensis Ramakrishna, 1951 (Crustacea: Branchiura)

“…It is also a known disruptor of larval development of insects (Schmutterer 1990;Singh 2003;Rharrabe et al 2008). However, the reports are scarce about the efficacy of it on oogenesis (Sayah et al 1996;Denardi et al 2010) and reproductive potential of parasites. Moreover, no such information is available on the crustacean reproductive biology.…”