Influence of Aquatain™, a monomolecular surface film on surface tension for controlling the filarial vector Culex pipiens (Diptera: Culicidae)

Abstract

Surface tension is a phenomenon in the liquid media and plays an important part in the development and survival of aquatic animals. Influence of Aquatain™ monomolecular film on surface tension was determined against mosquito larvae and pupae at different temperatures (10, 15, 20, 25, 30 and 35 °C) and Aquatain™ doses (0.5, 1.0 and 2.0 ml/m 2 ). In the laboratory, Aquatain™ showed larvicidal and pupicidal effects against the filarial vector Culex pipiens . Higher mortality was observed in late and more weighted instars/stages than young ones as well as in the pupal stage. The pupal mortality reached 76.2%, 86% and 93.3% after 12 h post-treatment at 0.5, 1.0 and 2.0 ml/m 2 , respectively, and it was completely eliminated (100%) within 24 h compared to 15.1%, 26.9% and 38.2% for 1 st larval instar, respectively. Also, results showed at 0.5 ml/m 2 with temperature range: 10, 15, 20, 25, 30 and 35 °C, the mortality reached 4.0, 6.7, 10.8, 17.3, 22.7, 29.3% and 32, 44, 54, 72, 84, 97.3% for 1 st and 4 th larval instar, respectively, where the surface tension (γ) was 65.6, 62.4, 58.0, 57.0, 54.2 and, 49.6 dyn/cm, while the Aquatain™ was more effective on mosquito larvae and pupae at high doses with the temperature range. On the other hand, without Aquatain™ dose, the mortality value ranged between 0.0 - 1.2%, and the surface tension (γ) was 74.5 dyne/cm, which is considered as an accidental death. Aquatain™ was effective against all aquatic phases of mosquitoes, especially against the last and weighted ones. Not only was the efficacy of Aquatain™ increased by increasing the dose, but it also increased with the increased temperature of the environment. This efficiency of Aquatain™ is due to its ability to reduce the surface tension of the water medium, preventing different stages of mosquitoes from reaching the surface for breathing thereby leading to suffocation and death. Therefore, we recommended Aquatain™ in programmes for mosquito control and other aquatic insects as a safe, cost-effective control agent.

Aquatain® Causes Anti-Oviposition, Egg Retention, Oocyte Melanization and Triggers Female Death in Ae. Aegypti

“…For instance, Mbare et al [50], dealing with Anopheles vectors, noted a 90% larval mortality and over 80% adult emergence inhibition with an AMF lm. Dawood et al [32], working with Culex pipiens, investigated the effects of AMF on different immature stages. They found signi cantly far greater mortality rates in rst-, second-and fourth-instar larvae and pupae in treated containers than untreated ones; they attributed these impacts to the ability of AMF to alter the water surface tension.…”

“…In particular, water surface tension has been shown as a critical factor in uencing oviposition [22]. Water tension typically occurs when oil is added to water; following addition, the layer of water molecules and that of oil molecules balance force between the two interfaces, causing the reduction of the surface tension at the water surface [35] and the apparition of a lm [32]. Ae.…”

“…During the 10-day oviposition period, the mortality rates of gravid females were high in arenas with the increased presence of AMF-treated oviposition containers, especially the "AMF-based no-choice treatment", compared to water-based no-choice treatment", thus denoting the presence of adulticidal factors of the AMF medium. AMF is a polydimethylsiloxane (PDMS, 80%)-based liquid that is not toxic [32] as indicated by its certi cation for use in drinking water [77, 78]; so, death due to toxic chemicals is unexpected. The observed differences in female mortality responses may have been due to at least two causes.…”

“…aegypti [27,28,29,30]. Surface tension is a property of water that plays an integral part in the development and survival of aquatic insects, including mosquitoes [31,32]. Surface tension can be generated when a water surface is covered with an oil lm [33,34]-putting oil over water results in an elastic behavior of the water, causing it to acquire a minor surface area possible [35].…”

Aquatain® causes anti-oviposition, egg retention and oocyte melanization and triggers female death in Aedes aegypti

“…Surface tension is a property of water that plays an integral part in the development and survival of aquatic insects, including mosquitoes [ 31 , 32 ]. Surface tension can be generated when a water surface is covered with an oil film [ 33 , 34 ]; in this situation, the oil film elicits an elastic behavior in the water, causing it to acquire as small a surface area as possible [ 35 ].…”