Crustacean biodiversity as an important factor for mosquito larval control

Abstract

Newly established ponds, which are highly dynamic systems with changing levels of biological interactions among species, are common larval mosquito habitats. We investigated the impact of crustacean abundance and taxa diversity on mosquito oviposition and larval development. The effects of the biological larvicide Bacillus thuringiensis israelensis (Bti) on mosquito larvae were monitored according to fluctuations in crustacean communities. Populations of the mosquito Culex pipiens colonized artificial ponds that contained crustacean communities at different time points of colonization by crustaceans: 1) 'no colonization' (no crustaceans), 2) 'simultaneous colonization' by crustaceans and mosquitoes, and 3) 'head-start colonization' by crustaceans (preceding colonization by mosquitoes). All types of ponds were treated with three concentrations of Bti (10, 100, or 1,000 µg/liter). Colonization of all ponds by Cx. pipiens (in terms of oviposition, larval abundance, and larval development) decreased significantly with increasing diversity of crustacean taxa. The total abundance of crustaceans had a minor effect on colonization by Cx. pipiens. The presence of crustaceans increased the sensitivity of Cx. pipiens larvae to Bti treatment by a factor of 10 and delayed the time of recolonization. This effect of Bti was relevant in the short term. In the long term, the presence of Cx. pipiens was determined by crustacean biodiversity.

Microbial communities and nutrient dynamics in experimental microcosms are altered after the application of a high dose of Bti

“…Kroeger, Duquesne & Liess () demonstrated the reduction of chlorophyll in microcosms treated with Bti (Vectobac 12 AS) in the absence of microcrustacean colonization. Filter‐feeder microcrustaceans (e.g.…”

Effects of a larval mosquito biopesticide and Culex larvae on a freshwater nanophytoplankton (Selenastrum capricornatum ) under axenic conditions

“…The fact that temephos, which has a different mode of action than Bti, affected water quality supports a trophic cascade effect, more likely due to the removal of mosquito larvae from water column independent of the activities of larvicides (Mulla et al 2004). While antimicrobial properties of Bacillusbased biopesticides against prokaryotes have been reported in laboratory studies (Yudina et al 2003, Revina et al 2005, the suppression of eukaryotic and other prokaryotic autotrophs including Cyanobacteria reported in the previous studies (Su and Mulla 1999, Mulla et al 2004, Kroeger et al 2013, Duguma et al 2015 may have been caused by microbial trophic cascade effects resulting from larval removal from the water column using Bti. Application of other Bacillus-based probiotic bacteria to promote the growth and health of aquatic invertebrates such as shrimp and oysters have been shown to enhance primary production essential for the survival of these aquatic organisms while suppressing members of toxic bacteria such as Cyanobacteria (Lukwambe et al 2015).…”

“…Kroeger and colleagues (2013) reported a significant reduction of chlorophyll biomass following the application of Bti that concurrently reduced Culex mosquitoes in the absence of controphic microcrustacean filterfeeders. The findings of these studies (Su and Mulla 1999, Mulla et al 2004, Kroeger et al 2013, Duguma et al 2015 contradicted the top-down population regulation hypothesis: microbial organisms including small primary producers proliferate following removal of the top predator (mosquito larvae).…”

“…Previous field studies reported the suppression of phytoplankton species following application of biopesticide formulations based on Bti and Lysinibacillu s (formerly Bacillus ) sphaericus ( Ls ) (Su and Mulla , Mulla et al , Kroeger et al , Duguma et al ). Application of both Bti and water dispersible granular Ls significantly reduced the biomass of two eukaryotic algae: Closterium sp.…”

“…Similarly, a significant suppression of photoautotrophic algal communities accompanied by increased diversity of heterotrophic bacterial community was observed in mesocosms treated with high doses of Bti (Duguma et al ). Kroeger and colleagues () reported a significant reduction of chlorophyll biomass following the application of Bti that concurrently reduced Culex mosquitoes in the absence of controphic microcrustacean filter‐feeders. The findings of these studies (Su and Mulla , Mulla et al , Kroeger et al , Duguma et al ) contradicted the top‐down population regulation hypothesis: microbial organisms including small primary producers proliferate following removal of the top predator (mosquito larvae).…”