Susceptibility of the floodwater mosquito Aedes albifasciatus from eggs of different dormancy times to the nematode parasite Strelkovimermis spiculatus

Abstract

This study aimed to evaluate the effects of egg dormancy times on susceptibility of larvae of the floodwater mosquito Aedes albifasciatus (Diptera: Culicidae) to parasitism by their natural enemy Strelkovimermis spiculatus (Nematoda: Mermithidae) and on their life history traits. Aedes albifasciatus eggs stored for 2, 4, 6, 8 and 10 months were hatched, and the larvae either exposed to S. spiculatus (treatment group) or not exposed (control group). Egg dormancy time had a negative effect on the retention of parasites, but no effect on the prevalence and intensity of parasitism or the melanization of nematodes. The survival to adulthood of control individuals decreased as dormancy time increased, whereas that of exposed individuals that remained uninfected was constant and low. A trend towards increasing development times with longer dormancy times was detected in the control group, but not in the exposed noninfected group. The results suggest nonconsumptive effects of parasites in exposed but not infected larvae from eggs with short dormancy times. In contrast, the relatively low fitness of larvae from eggs with long dormancy times regardless of their contact with the nematodes may be the result of the nutritional deprivation during the egg stage.

Behavior of Aedes albifasciatus (Diptera: Culicidae) larvae from eggs with different dormancy times and its relationship with parasitism by Strelkovimermis spiculatus (Nematoda: Mermithidae)

“…In Ae. albifasciatus, no behavioral studies have taken these aspects into account, but it is known that prolonged egg dormancy periods negatively affect larvae, decreasing survival and increasing larval development time (Di Battista et al 2020). The results of the present study showed no behavioral changes reflecting this negative effect.…”

“…It is relevant to mention that, in the Ae. albifasciatus-S. spiculatus system, the intensity of parasitism showed no effect on the timing of mosquito larval mortality (Di Battista et al 2020) but affected the parasite's mortality within the host (Di Battista et al 2015). Despite the variability here observed in behavior, the decrease in the number of behaviors performed by parasitized larvae reflects an alteration in the overall activity of the individuals.…”

“…At the laboratory, they were fed with guinea pig blood and then placed in individual containers with moist substrate to promote egg laying. The eggs obtained were placed on Petri dishes with a damp cloth and absorbent paper at the bottom to maintain humidity during storage time (Di Battista et al 2020).…”

“…albifasciatus larvae, which came from eggs that had remained dormant for 2, 4, or 6 months. The choice of dormancy time was based on observations of the performance of larvae from eggs with similar dormancy, carried out in a previous study (Di Battista et al 2020). Observations were made using larvae from 2 to 6 h post-molting to the fourth instar.…”

“…During periods of drought, pharate larvae remain in a dormant state inside the egg, consuming the energy reserves until conditions are favorable for hatching (Vinogradova 2007;Denlinger Section Editor: Helge Kampen We are deeply saddened by the passing of Raúl E. Campos (Oct 21th 2021) and Armbruster 2014). The prolongation of the egg dormancy period negatively affects larvae, increasing their development time and reducing their survival (Di Battista et al 2020), probably related to the reduction of the energy reserves of pharate larvae during the dormancy period (Perez and Noriega 2012). It is expected that larvae from long-dormant eggs would compensate for the reduction in reserves with an increase in feeding time compared to larvae from short-dormant eggs.…”