In vitro acaricidal activity of green synthesized nickel oxide nanoparticles against the camel tick, Hyalomma dromedarii (Ixodidae), and its toxicity on Swiss albino mice

The green synthesized nanoparticles have been determined as a novel pesticide against arthropod pests. This study was designed to evaluate the in vitro acaricidal activity of green synthesized nickel oxide nanoparticles (NiO NPs) using aqueous extract of Melia azedarach ripened fruits against different developmental stages of the camel tick Hyalomma dromedarii in addition to their toxic effect on laboratory animals. The synthesized NiO NPs were characterized by UV-visible (UV-Vis) spectroscopy, Fourier transforms infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). The UV-Vis spectra of the NiO NPs showed an absorption peak at 307 nm. FTIR analysis showed the possible functional groups used for capping and stabilization of NiO NPs with strong bands at 3416.2 and 1626.6 cm^-1. The SEM images of the NiO NPs exhibited a size ranging from 21 to 35 nm. The immersion test was used for the in vitro application of the synthesized NiO NPs on the various tick stages (egg, nymph, larva, and adult). Mortality percentages and LC₅₀ values of each tick stage were calculated. The oviposition and hatchability of the engorged females were monitored for the survived tick after treatment. The LC₅₀ values for NiO NPs on embryonated eggs, larvae, and engorged nymphs were 5.00, 7.15, and 1.90 mg/mL, respectively. The egg productive index (EPI), egg number, and hatchability (%) were lower in females treated with the NiO NPs than in control ticks. The toxicity of the NiO NPs on laboratory animals was also investigated using Swiss albino mice by oral dose of 500 mg/kg/day administration for five consecutive days. The hematological, biochemical, and histopathological changes were evaluated. The hematological analysis showed significant increase in the level of white blood cells (WBC) and hemoglobin (Hb). Biochemical analysis showed non-significant decrease in alkaline phosphatase (ALP) and alanine amino transferase (ALT). We concluded that NiO NPs have a significant acaricidal activity as demonstrated on eggs, larvae, engorged nymphs, and fully fed females of H. dromedarii. From a toxicological point of view further in vivo investigations are needed to determine the mechanism of toxic effect of NiO NPs.

Additional morphometric and phylogenetic studies on Mothocya melanosticta (Isopoda: Cymothoidae) parasitizing the Red Sea Nemipterus randalli fish in Egypt

Cymothoidae, Leach, 1818 (Crustacea: Isopoda) are ectoparasites of marine, brackish and freshwater fishes that are reported to induce deleterious tissue impacts on the infested fish hosts. The present study aimed for the first-time screening of Mothocya melanosticta collected from the red sea fish Nemipterus randalli in Egypt. Surveillance study was conducted for isopod infestation among the Red Sea fish N. randalli revealing a total infestation rate of 40.96% with the species identified as M. melanosticta. The parasite species was isolated from the branchial cavity and gills. Morphometric description was estimated using dissecting stereo-microscope, and scanning electron microscope (SEM) provided new additional features for the isolated species including the microtrich sensillum in the body cuticle and the fine structure of the mouth parts and body appendages. Mitochondrial COI gene of M. melanosticta female isolated in the present study from N. randalli was detected for the first time in Egypt and recorded in the GenBank (MK168807). The study showed that the detected isopod species represents one monophyletic group closely affiliated to the genospecies of M. melanosticta, and can be distinguished clearly from other isopods genospecies. Based on the genetic distance values, lower level of genetic divergence was indicated within the genospecies of the present M. melanosticta isolated from Egypt and the same species isolated from India. The present investigation recorded N. randalli fish as a new host for the isopod M. melanosticta in Egypt and provided additional morphological features through SEM as well as molecular characterization of this isopod species for the first time.