Study of the effect of cypermethrin on the spider Polybetes phytagoricus in different energy states

Highlights

• The LD₅₀ of cypermethrin on young, males and females of spider Polybetes pythagoricus was studied.

• The activity of antioxidant enzymes and acetylcholinesterase was analyzed.

• The LD₅₀ was significantly lower in young in relation to the three models of adults.

• Sublethal doses of cypermethrin did not generate alterations in any of the enzymes analyzed in juveniles

• The enzymatic activity CAT, GR, and GST was sex-dependent.

Abstract

Spiders are found among the most important predators of plague insects of numerous agricultural systems. They are the most numerous representatives of the Class Arachnid and are widely distributed in numerous ecosystems. Due to multiple variables, living beings are exposed to quantitative transitions of their energetic reserves, which affect their sensitivity before the different xenobiotics. In the present study we evaluate the effect of cypermethrin (pyrethroid) on different metabolic/energetic stages of the spider Polybetes pythagoricus (Sparassidae). We firstly studied LD₅₀ of cypermethrin on young, males and, pre-vitellogenic and post-vitellogenic females. The activity of superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione-S-transferase (GST) and acetylcholinesterase (AChE) was analyzed. Results indicate that young have a higher caloric content compared to adults, females have a higher caloric content than males and vitellogenesis generates a great calory decrease in females. The LD₅₀ was significantly lower in young (10%) (103 ng/g weight) in relation to the three models of adults (969–1108 ng/g weight). Vitellogenesis causes an increase of free radicals as a result of the different metabolic processes which manifest as an increase in the lipid peroxidation. Doses at the LD₃₀ and LD₄₀ levels of cypermethrin did not generate alterations in any of the enzymes analyzed in young, this fact may probably provoke an increase of lipid peroxidation (evaluated as a great MDA increase). The activity of the enzymes linked to oxidative stress was altered by this doses in the three adult models, the enzymatic activity CAT, GR, and GST was sex-dependent. Post-vitellogenic females showed a greater activity of CAT, SOD, GST and GR before the xenobiotics than pre-vitellogenic ones, probably as a consequence of metabolic stress generated during vitellogenesis.

Introduction

At present the use of pyrethroids is worldwide justified, since these xenobiotics have many desirable properties that include high toxicity for target insects, low toxicity for mammals, high biodegradability, photostability and effect on minimum doses (Baatrup and Bayley, 1993; Stenersen, 2007).

Pyrethroid insecticides are neurotoxic compounds that affect not only the peripheral nervous system but also the central one of insects. They act on the voltage-gate sodium channels placed in nervous cell membranes. When the opening of these channels is prolonged, pyrethroids stimulate nervous cells to produce repetitive discharges thus provoking paralysis and death of insects (Ray and Fry, 2006; García et al., 2011; Clark and Symington, 2012; Kaisarevic et al., 2019).

Cypermethrin (IUPAC name: [cyano-(3-phenoxyphenyl)methyl] 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate) is an insecticide of the pyrethroid class type II, synthetic, fast action (Santos et al., 2007), used extensively to control both a wide range of agricultural and horticultural insects. It has a broad action range against external parasites of animals and humans. Also, pyrethroids are commonly used in urban environments to control undesirable pests such as spiders and termites (Fernandez et al., 2012; Weston and Lydy, 2012; Weston et al., 2015; Maruya et al., 2016).

Most of the studied related to this topic analyses the undesirable ecotoxicological effects of the use of pesticides on vertebrates, but there is a great proportion of non-target invertebrate organisms that are affected, for instance, arthropods and particularly arachnids. The ecotoxicology of spiders has received rather limited attention (Babczyńska et al., 2006; Pekár, 2012).

Spiders are important regulators of insect populations, due to their quantity (they constitute the most numerous and important order of the Class Arachnida) and their biodiversity (they are distributed virtually in all the terrestrial habitats), inhabiting even in strongly changed ecosystems (Nentwig, 1986; Majkus, 1988.; Nyffeler, 1999). They are capable of consuming until 50% of the insect biomass present in crops, with a prevailing role in the biological control of the species damaging crops of economic importance (Riechert and Lockley, 1984; Oraze and Grigarick, 1989; Tarabaev and Sheykin, 1990; Riechert, 1999; Birkhofer et al., 2008). And also, they are widely distributed in all kinds of crops (Riechert and Lockley, 1984).

Spiders as generalist predators which are exposed to elevated level of environmental insecticide (Pekár, 2012). Spiders were the most abundant beneficial arthropod (Loch, 2005). It has been recently estimated of 400 specimens of arthropods, the spiders have the most biomass consumption from bod length by dry weight (Straus and Aviles, 2018).

Undernourishment or malnutrition of spiders in croplands seems to be frequent, since insecticide application significantly reduces prey availability and places for web locations (Vickerman and Sunderland, 1977; Pedersen et al., 2002; Pekár, 2012). Studies on diverse insects have demonstrated a dependence between insecticide tolerance and food levels and diet composition (Kramer et al., 1990; Singh and Sarup, 1991; Kalushkov, 1999). In the spider Pardosa prativaga it has been observed that the effect of insecticides can vary in relation to the nutritional history of the animal (Pedersen et al., 2002).

The entry pathways of cypermethrin spiders in the field can be performed by contact or by food (insects mainly). The concern about the impact of pesticides on spiders surpasses the effect of insecticides, since it is extended to not only acaricides but also fungicides and herbicides. Also, it has been demonstrated that glyphosate herbicide affects spiders (Haughton et al., 1999; Haughton et al., 2001a; Haughton et al., 2001b; Benamú et al., 2010). In general, the scientific community is in accordance with the fact that biological control is a pathway to minimize the contamination generated by the indiscriminate use of pesticides. Among others it possesses the advantages of: having scarce or non-existent resistance of the plagues to the biological control, avoiding secondary pests, the lack of intoxication problems, the favourable condition of the cost-benefit relationship. Many efforts are being carried out to preserve the different natural enemies of pest insects, spiders being among them (Liao et al., 2016; Rathod et al., 2016; Rauch et al., 2017).

The concern about this topic is increasing since some reports have comparatively analyzed the toxicity of insecticides on pest insects and natural enemies (Croft and Whalon, 1982). In 2015 Li and collaborators observed that cypermethrin among other insecticides affected the natural enemy (wolf spider) in a greater extent than target insects (Li et al., 2015).

Pesticides can cause various metabolic effects, including increased endogenous production of reactive oxygen species (ROS) (Masoud et al., 2003; Wilczek et al., 2013). Tolerance to this metabolic imbalance is possible due to the antioxidant defense system that includes, among other enzymes, superoxide dismutase (SOD, EC1.15.1.1), catalase (CAT, EC1.11.1.6) glutathione-s-transferase (GST, EC2.5.1.18) and glutathione reductase (GR, EC1.8.1.7) (Nielsen et al., 1999; Wilczek et al., 2013).

Because the response to insecticides depends on the metabolic and nutritional state of the organism (Nielsen and Toft, 2000; Pedersen et al., 2002), and that this nutritional state may vary in relation to age, sex, or reproductive status (Romero et al., 2018, Romero et al., 2019), the aim of this study was to analyse the effect of the insecticide cypermethrin on the different physiological/metabolic stages on the spider.

We analyzed comparatively the enzymes related to the antioxidant defense system of the spider Polybetes pythagoricus (Sparassidae): superoxide dismutase, catalase, glutathione-s-transferase and glutathione reductase as well as MDA levels, and AChE inhibition. The choice of P. pythagoricus was based on the fact that there is a great deal of information with relation to its biochemistry (Cunningham et al., 2007; Laino et al., 2009, Laino et al., 2011) and that it is a large species and could be analyzed more easily. The purpose of the present study was to obtain essential data to support an overall understanding of the effects of cypermethrin on non-target organisms such as spiders and to provide useful information on the potential ecological risks of cypermethrin for agricultural ecosystems.