Mortality in immatures of the floodwater mosquito <i>Ochlerotatus albifasciatus</i> (Diptera: Culicidae) and effects of parasitism by <i>Strelkovimermis spiculatus</i> (Nematoda: Mermithidae) in Buenos Aires Province, Argentina

Abstract

Life tables were constructed for six cohorts of immature stages of the floodwater mosquito <i>Ochlerotatus albifasciatus</i> (Macquart) in a park in Buenos Aires, highlighting the mortality attributable to the parasitic nematode, <i>Strelkovimermis spiculatus</i> Poinar & Camino. Two cohorts were selected to compare parasite incidence in all mosquito stages when low and high parasitism occurred. Development time of <i>Oc. albifasciatus</i> from first instar to adult was 7.7-10 days in the spring, 6 days in the summer, and 10.9-21.9 days in the fall. Survival was estimated as 0-1.4% in the spring, 2% in the summer and 0.2-4.4% in the fall. The highest "K" value (Killing power) occurred during a fall cohort when prevalence of the parasite was 86.9%, and the lowest in a spring cohort. Parasitism occurred during all seasons, but <i>S. spiculatus</i> persisted to adult only in the summer and fall, when adult mosquitoes developed from parasitized third and fourth instars larvae. The abundance of <i>S. spiculatus</i> differed between old and young larvae only when parasite prevalence was the highest. Although pupae and adults of <i>Oc. albifasciatus</i> were parasitized, no pupal mortality attributable to parasitism was recorded. The proportion of parasitized adults ranged from 14.2% and 5.7% in the two cohorts compared. Pupal wet weight and adult wing lengths did not differ between parasitized and unparasitized individuals.