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

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

A Global Population Genetic Study of Pantala flavescens

Among terrestrial arthropods, the dragonfly species Pantala flavescens is remarkable due to their nearly global distribution and extensive migratory ranges; the largest of any known insect. Capable of migrating across oceans, the potential for high rates of gene flow among geographically distant populations is significant. It has been hypothesized that P. flavescens may be a global panmictic population but no sufficient genetic evidence has been collected thus far. Through a population genetic analysis of P. flavescens samples from North America, South America, and Asia, the current study aimed to examine the extent at which gene flow is occurring on a global scale and discusses the implications of the genetic patterns we uncovered on population structure and genetic diversity of the species. This was accomplished using PCR-amplified cytochrome oxidase one (CO1) mitochondrial DNA data to reconstruct phylogenetic trees, a haplotype network, and perform molecular variance analyses. Our results suggested high rates of gene flow are occurring among all included geographic regions; providing the first significant evidence that Pantala flavescens should be considered a global panmictic population. © 2016 Troast et al

Effects of short-term, sublethal fipronil and its metabolite on dragonfly feeding activity - Fig 4

<p><b>Effect of (a) imidacloprid, (b) fipronil and (c) fipronil sulfone on feeding activity of <i>S</i>. <i>frequens</i> larvae after 48-h exposure.</b> Asterisks indicate a significant difference compared to control; **<i>p</i> < 0.01, ***<i>p</i> < 0.001. Time to capture in fipronil (100 and 1000 μg/L) and fipronil sulfone (10, 100 and 1000 μg/L) treatments exceeded the 5-min time limit, and Dunnett's test could not be applied to these treatments because the variance was zero due to setting the time to 5 min. Values for these treatment groups were interpreted as being significantly higher than in the control based on the 5-min time limit being much higher than the highest time to capture in the 10 μg/L (fipronil) and 1 μg/L (fipronil sulfone) treatments, which were significantly higher than the respective controls. The large variation observed particularly in the imidacloprid treatment and in the control is probably due to individual differences in locomotor activity.</p

Draft guidelines regarding appropriate use of 131I-MIBG radiotherapy for neuroendocrine tumors

Since the 1980s when clinical therapeutic trials were initiated, 131I-MIBG radiotherapy has been used in foreign countries for unresectable neuroendocrine tumors including malignant pheochromocytomas and neuroblastomas. In Japan, 131I-MIBG radiotherapy has not been approved by the Ministry of Health, Labour and Welfare; however, personally imported 131I-MIBG is now available for therapeutic purposes in a limited number of institutions. These updated draft guidelines aim to provide useful information concerning 131I-MIBG radiotherapy, to prevent side effects, and to protect physicians, nurses, other health care professionals, patients and their families from radiation exposure. The committee has also provided appendices on topics such as practical guidance for attending physicians, patient management, and referring physicians

Effects of short-term, sublethal fipronil and its metabolite on dragonfly feeding activity - Fig 3

<p><b>Mortality in 48-h acute toxicity test, FI after 48-h exposure and mortality to instar 3 for <i>S</i>. <i>infuscatum</i> larvae exposed to (a) imidacloprid, (b) fipronil and (c) fipronil sulfone.</b> Each treatment was conducted in quadruplicate and each replicate contained six larvae. To confirm that delayed toxicity after 48-h exposure consequently causes mortality to instar 3 via feeding inhibition, we compared mortality at 48 h to that at instar 3. Asterisks indicate significant differences; *<i>p</i> < 0.05, **<i>p</i> < 0.01, ***<i>p</i> < 0.001.</p

Mortality (48-h LC₅₀ and To instar 3 LC₅₀) and feeding inhibition (FI EC₅₀) endpoints of imidacloprid, fipronil and fipronil sulfoneto <i>S</i>. <i>infuscatum</i> and <i>S</i>. <i>frequens</i>.

<p>Mortality (48-h LC₅₀ and To instar 3 LC₅₀) and feeding inhibition (FI EC₅₀) endpoints of imidacloprid, fipronil and fipronil sulfoneto <i>S</i>. <i>infuscatum</i> and <i>S</i>. <i>frequens</i>.</p

Time to reach instar 3 after 48-h exposure.

<p>Time to reach instar 3 after 48-h exposure.</p

Maximum water and soil concentrations of imidacloprid, fipronil and fipronil sulfone in rice paddy fields sampled in previous studies with mesocosm and microcosm paddy experiments.

<p>These data are for concentrations following application at 10,000 g/ha as a commercial formulation.</p

Feeding behavior experimental design.

<p>(a) Experiment to score the number of brine shrimp consumed by <i>S</i>. <i>infuscatum</i> larvae. (b) Experiment to score the time to capture a brine shrimp by <i>S</i>. <i>frequens</i> larvae.</p

Minimum Spanning Haplotype Network.

<p>All haplotypes are based on the CO1 gene except for “India 4” which is “CO1-like”. Numbers in parentheses indicate the number of changes between haplotypes.</p