Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Optimizing laboratory production of Strelkovimermis spiculatus (Nematoda: Mermithidae) with a discussion of potential release strategies for mosquito biological control.

Abstract

We assessed Strelkovimermis spiculatus preparasite (J2) infectivity and postparasite (J4) production in rearing pans using a laboratory host, second-instar Aedes aegypti mosquitoes, and evaluated first the production efficiency by testing increasing J2 concentrations (preparasite:host ratios). At 10 000 host larvae/rearing pan, we obtained the maximum yield of J4s (3.50 g), number of J4s/larva (3.1), and parasitism frequency (94.9±9.5%) at a 10:1 J2/larva ratio. This 10:1 ratio, however, resulted in a significantly male-skewed sex ratio, whereas at ratios between 4:1 and 7:1 females predominated and parasite frequencies were still acceptable. Next, postparasite-inoculation methods were compared under culture conditions reflecting two categories of mosquito habitat (permanently flooded or desiccated cultures). The J4s were left to develop into adults, mate, and oviposit in the substrate. The flooded-culture J2s hatched at week 3 and after 30 weeks gave a total production of 6.2×104 per pan. Maximum J2 yield in desiccated cultures occurred at the first flooding (5 weeks), but emergence continued through drying flooding cycles for 10 weeks, giving a total J2 production of 4.5×105 per pan. The J2s infected mosquito larvae under both conditions. S. spiculatus preparasites or postparasites would serve as mosquito bioregulatory agents in temporary or permanent mosquito habitats. Relevant strategies are discussed.