Effects of short-term, sublethal fipronil and its metabolite on dragonfly feeding activity

Abstract

Dragonflies, Sympetrum spp., are indispensable to agriculture and are a central element of culture in Japan. However, S. frequens populations in rice paddy fields have declined in recent decades. Dragonfly larvae are predatory aquatic insects that feed on other organisms found in habitats with slow-moving or standing water. The increasing use of fipronil and neonicotinoid insecticides in agriculture is also increasing exposure to Sympetrum spp. in larval stages through paddy soil and water. The role of fipronil insecticides in the decline of dragonflies is of concern, and we here examine the sublethal effects of this insecticide on the feeding behaviors of two Sympetrum spp. Based on the quantity of prey items consumed and the time to capture prey items, feeding inhibition was determined to be a potential mechanism of the decline of Sympetrum spp. following 48-h exposure to fipronil and fipronil sulfone. Prey consumption by S. infuscatum was significantly reduced for fipronil sulfone at all concentrations (0.01–1000 μg/L). S. frequens exposed to 1, 10, 100 and 1000 μg/L fipronil sulfone had significantly longer prey capture times. Fipronil sulfone was 2.8, 9.7 and 10.5 times more toxic to S. infuscatum than fipronil in terms of acute toxicity, feeding inhibition and delayed toxicity, respectively. In addition, fipronil sulfone was 6.6, 2.9 and 9.1 times more toxic, respectively, to S. frequens than fipronil. Our findings suggest that sublethal effects on feeding inhibition lead to severe mortality at realistic paddy soil and water concentrations. Our results provide the first demonstration that short-term exposure to fipronil and fipronil sulfone can consequently cause significant harm to dragonfly larvae survival due to feeding inhibition. These findings have implications for current pesticide risk assessment and dragonfly protection.

Sublethal Effects of the Milky Latex of Sodom Apple, Calotropis procera (Alton) on the Growth, development, and some Physiological Aspects of the Greater Wax Moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae)

“…Such delays in larval development due to feeding inhibition may result in impaired larval development and unsuccessful emergence of adults. The high value of FI percentage, calculated in this study proves that C. procera latex possess feeding inhibition properties as, generally, the higher the value of FI, the lower the rate of feeding (Szczepanik et al, 2016 andJinguji et al, 2018). The feeding inhibition of C. procera leave extract against another two lepidopteran larvae; Spodoptera littoralis and Spodoptera lithura has been reported by Abdel-Rahman and Al-Mozini (2007) and Bakavathiappan, et al (2012), respectively.…”

“…This experiment was continued until adult emergence from pupae in control group, then accumulated mortality, duration of larval stage, pupal weight and the consumed diet weights were calculated. The feeding inhibition percentage and feeding indices were estimated after 15 days of feeding using the following formulae (Waldbauer, 1968 andJinguji et al, 2018):…”

Heterogeneous expression of GABA receptor‐like subunits LCCH3 and GRD reveals functional diversity of GABA receptors in the honeybee Apis mellifera

“…During acute intoxication, structure–function studies and resistant insect strains have demonstrated that RDL is the main target (Ffrench‐Constant et al, 1993; Hosie, Baylis, Buckingham, & Sattelle, 1995). However, in the case of off‐target species, the mechanism underlying death from chronic sublethal exposure has been less investigated (Aliouane et al, 2009; Charreton et al, 2015; Decourtye et al, 2005; El Hassani, Dacher, Gauthier, & Armengaud, 2005; Jinguji, Ohtsu, Ueda, & Goka, 2018; Pisa et al, 2015). In particular, there is a lack of the comparative analysis of the different GABA receptor properties needed to identify all the molecular determinants that could be involved.…”

Effects of Sodium Chloride on Oviposition Behavior of Aedes albopictus

“…albopictus. The oviposition repellent effect of the NaCl concentration was estimated using an oviposition inhibition (OI) score, which was calculated using the following equation and in accordance with inhibition test methods for testing chemicals (Jinguji et al 2018):…”