Environmental Science and Pollution Research https://doi.org/10.1007/s11356-019-06013-0 RESEARCH ARTICLE Biological and physiological responses of Perionyx excavatus to abamectin Beewah Ng1 & Ratmanee Chanabun2 & Somsak Panha1 Received: 31 January 2019 /Accepted: 22 July 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Biological and behavioral responses of the tropical earthworm Perionyx excavatus towards different concentrations of abamectin were evaluated. Abamectin significantly reduced the biomass and reproduction (cocoon production) of P. excavatus as well as inducing histopathological alterations in the cuticle. Biomass loss was recorded in P. excavatus exposed to abamectin at a concentration as low as 0.1 mg active ingredient (a.i.) kg−1, while atrophy, another physiological response, was observed at an abamectin concentration of 0.21 μgcm−2 in a filter paper test. Cocoon production was significantly reduced in the presence of abamectin, and no cocoons were produced at doses of 20 mg a.i. kg−1 or higher, while abamectin at 50 mg a.i. kg−1 induced extreme pathology, characterized by the loss of the integrity of the whole body wall and intestine of P. excavatus. Histopathological alterations can be used as a biomarker to evaluate the toxicological impact of exposure to abamectin. Keywords Abamectin . Perionyx excavatus . Physiological morphology . Cocoon production . Histopathology Introduction tomato russet mite (Aculops lycopersici), armyworms (Spodoptera sp.), and tomato pinworms (Keiferia Agriculture remains an important sector of Malaysia’secono- lycopersicella). The first record of P. xylostella in Malaysia my, contributing 12% to the national gross domestic product was reported in 1925 and it became a serious pest of crucifers (GDP) and providing employment for 16% of the population. in this region after the mid-1940s (Corbett and Pagden 1941). In 2016, about 4.06 million ha of land was used for agricul- In order to intensify agriculture practices, typically as mono- ture, of which vegetable plantations accounted for about cultures, and overcome the subsequent pest invasions, differ- 44,000 ha (1.08%). In terms of the land area used for cultiva- ent pesticides have been applied to control the outbreaks, in- tion, the top five vegetable crops and fruit plants were leaf cluding chlorpyrifos, organophosphates, pyrethroid, and mustard, round cabbage, chili, long bean, and tomatoes abamectin (also known as avermectin). Among all the pesti- (MAMPU open data 2016). cides used, abamectin has been the most effective pesticide at However, during growth, these top five vegetable crops controlling these pest outbreaks (Dybas 1989). and fruit plants are easily damaged by many insects and dis- Abamectin is a mixture of 80% avermectin B1a and less eases, such as the diamondback moth (Plutella xylostella), than 20% avermectin B1b that is produced by the soil bacte- various leafminers (mostly Agromyzidae flies and rium Streptomyces avermitilis. Research has shown that Lepidoptera), two-spotted spider mite (Tetranychus urticae), abamectin and avermectin have very similar biological and toxicological properties (Campbell 1989;Halleyetal.1993). Responsible editor: Chris Lowe Prior to use as a pesticide in agriculture farms, abamectin was used for the treatment and control of gastrointestinal nema- * Somsak Panha todes as well as to control endo- and ecto-parasite infections in [email protected] small ruminants (McKeller 1997; Chandrawathani and Nurul Aini 2012; Epe and Kaminsky 2013). Currently, abamectin is 1 Animal Systematics Research Unit, Department of Biology, Faculty registered (RI. 01010119921065) for use on vegetable crops at of Science, Chulalongkorn University, 254 Phayathai Road, a recommended application dose of 5–27 g ha−1 as a foliar Pathumwan, Bangkok 10330, Thailand 2 spray (Lasota and Dybas 1990). However, most farmers ex- Program in Animal Science, Faculty of Agriculture Technology, ceed the recommended dosage and/or spray more frequently Sakon Nakhon Rajabhat University, Sakon Nakhon 47000, Thailand Environ Sci Pollut Res (typically as calendar spraying without prior scouting) in an the Sakorn Nakhon Rajabhat University, Thailand. The earth- attempt to ensure its effectiveness. In the calendar spraying worms were acclimatized in stock soil (see below) for at least method, farmers will apply pesticides at set interval days to a week and then a day in a wet paper towel without soil to void control the pest outbreak, and without prior scouting means their guts before conducting the experiment. even though there is no sign of any pest damage, farmers still followed the scheduled plan to apply the pesticide in order to Test soil and substance avoid any perceived possibility of lowering the product’sprice due to pest damage (Amoako et al. 2012;Halimatunsadiah Stock soils were prepared from 10% (w/w)fermented et al. 2016). These actions have indirectly caused potential Terminalia catappa leaves, 3% (w/w) fermented cow dung harm to soil organisms, and predominantly to the earthworms, (fermented for at least 2 weeks), 2% (w/w) peat moss, and resulting in a loss of biodiversity (Hole et al. 2005). 85% (w/w) soil with the stock soil moisture content adjusted Earthworms are important soil organisms and are frequent- to about 50% of the maximum water holding capacity. The ly used as indicators of soil quality as well as contamination moisture content was measured using a moisture meter levels. Their biological changes (biomarker of effect) and (DM400, Guangdong, China). The soil preparations were physiological changes are relatively immediate responses mixed by hand and sieved following preparation before the when they are exposed to contaminant (Lam and Gray water was added (mesh size, 2 mm). Standard toxicity test 2003). These biological and physiological changes can be methods were only applied in the preparation of the test soil used as biomarkers of adverse conditions, and their use has but not the test soil composition, which was mainly due to the been reported as early warning tools for the measurement of relatively high costs of the standard test methods. Commercial biological effects. Lourenço et al. (2011) reported the biolog- grade abamectin [1.8% (w/v) EC] was purchased from ical changes (histological alterations in tissue) in the earth- Mitsomboon Chemical (Thailand) Co. Ltd.. Stock solutions worm Eisenia andrei after exposure to metals and radionu- of abamectin were diluted with distilled water to the required clides. Likewise the histopathology of Eisenia fetida changed nominal concentrations. after exposure to imidacloprid (Dittbrenner et al. 2011)asdid the tropical earthworm Eudrilus eugeniae when exposed to Laboratory exposure heavy metals (Fernando et al. 2015). Perionyx excavatus, a widely cultured compost earthworm in Filter paper test tropical regions, has been shown to be suitable as a test species for tropical soils (Maboeta et al. 1999;AnandLee2008;De Filter paper test (modified OECD Test 207) was conducted in Silva et al. 2010). It was recently reported that P. excavatus is a round, flat-bottomed (internal diameter 60 mm, height more sensitive than the temperate species (Eisenia species) to 30 mm, volume 65 mL) container lined with filter paper. three of the commonly used pesticides: chlorpyrifos, carbofuran, Two milliliters of the prepared test concentration (0.0 (con- and mancozeb (De Silva et al. 2010). Although a few reports trol), 0.3, 3, 30, 150, 300, 1500, and 3000 mg L−1)of have examined the toxicity of abamectin, they have focused on abamectin solution was added to the filter paper of each test temperate earthworm species (Diao et al. 2007;Jensenetal. unit to yield concentrations in the filter paper of 0 (control), 2007; Kolar et al. 2008). Keeping in view none of them reported 0.021, 0.21, 2.12, 10.6, 21.2, 106.1, and 212 μgcm−2,respec- the histopathology and physiological changes in P. excavatus tively. Each treatment was performed with ten replicates, each associated with exposure to abamectin. Here, we aim to study consisting of one worm per container and maintained at am- the effect of abamectin towards cellular responses by evaluating bient temperature (30 ± 2 °C). The morphology and behavior the changes in the histopathology, biomass, behaviour response, of P. excavatus were monitored over the first 10 min after and cocoon production in P. excavatus at different concentrations exposure to abamectin, and then, the test containers were and exposure times. With respect to the responses of P. excavatus maintained at ambient temperature in the dark for 48 h. to abamectin, the responses can be a tool in monitoring field populations where the assessment of conventional endpoints is Abamectin-treated soil test difficult to be applied. All earthworms were exposed for 2, 7, and 14 days to soil pretreated with abamectin at different concentrations. Materials and methods Rectangular plastic containers (internal diameter 90 mm, length 145 mm) were filled with 500 g of the corresponding Test organism artificially abamectin-contaminated soil (0.1, 1.0, 10, 50, 100, 500, and 1000 mg active ingredient, (a.i.) kg−1 soil). Ten earth- Adult P. excavatus of 150–300 mg (wet weight) with a well- worms were released into each container with four replicates developed clitellum were obtained from an in-house culture at of each treatment. The tests were conducted at ambient Environ Sci Pollut Res temperature (30 ± 2 °C) under a constant light intensity of Minitab 16 Statistical software and significance was accepted 400–800 lx and a 16/8 h light/dark cycle. at the P <0.05level. A similar working protocol was applied to the reproduction test, where the earthworms were exposed to abamectin at a concentration of 0.0 (control), 0.1, 1.0, 10, 20, 30, 40, and Results and discussion 50 mg a.i. kg−1 soil and control soil (without abamectin) for 28 days, except finely ground cow dung (30 g) was added Filter paper test: behavioral monitoring and body each week to each container as food. mass measurements Body mass measurements The morphology and behavior of P.