Effect of Some Pesticides on Reproduction of Rotifer Brachionus plicatilis Müller

Abstract

Pesticides have been major contributors to environmental pollution and they are now widely distributed in aquatic environments. Zooplankters are frequently used as test animals to detect aquatic contaminants because of their sensitivity and ecological importance. We investigated the effect of a 7-day exposure to four commonly used pesticides (diazinon, fenitrothion, methoprene and isoprothiolane) on reproduction of the rotifer Brachionus plicatilis. Pesticide concentrations of 3-7 times lower than the 24-h 50% lethal concentration (24-h LC 50 ) were tested to determine the 'no observed effectÕ concentration (NOEC), 'lowest observed effectÕ concentration (LOEC), and the '50% effectiveÕ concentration (EC 50 ) on specific growth rate (r), sexual reproduction, fertilization, resting egg production, and hatchability of resting eggs. Results showed that the lowest EC 50 value of r, mixis, fertilization, and resting egg production of 1.4 lM for diazinon was 63 times lower than its 24-h LC 50 of 88.4 lM, while for fenitrothion it was 66 times (3.5 and 229.8 lM, respectively). For isoprothiolane, the lowest EC 50 value of r, mixis, fertilization, and resting egg production of 8.9 lM was 25 times lower than its 24-h LC 50 of 220.7 lM, while for methoprene was 37 times (2.7 and 100.8 lM, respectively). In all pesticides, hatching rate of resting eggs consistently gave the lowest EC 50 values which is about 2-40 times lower than the lowest EC 50 of r, mixis, fertilization, and resting egg production. Hatchability of resting eggs therefore is the most sensitive parameter in detecting effects of pesticides exposure in rotifer B. plicatilis.

Diapause as escape strategy to exposure to toxicants: response of Brachionus calyciforus to arsenic

“…Regardless of the mechanisms driving this trend, our results suggest that significant toxicological effects may be observed in parameters related to the production and quality of diapausing eggs, although gross endpoints, such as population growth rate, are insensitive to toxicants. In rotifers there is broad evidence that the sexual phase can be more sensitive to environmental conditions, specifically exposure to toxicants, than the asexual phase (Snell and Carmona 1995;Snell et al 1999;Preston and Snell 2001;Marcial et al 2005). Our results are in agreement with those antecedents, but in addition this study provides interesting information about the adaptive value of the diapause strategy against adverse conditions.…”

“…Nevertheless, because only the asexual portion of the life cycle is commonly investigated in toxicity studies, the true vulnerability of zooplankton to toxicants is often underestimated (Preston and Snell 2001;Navis et al 2015). Several studies assessed the effects of pesticides, heavy metals, and endocrine-disrupting chemicals on sexual reproductive parameters of rotifers (Snell and Carmona 1995;Preston et al 2000;Yoshinaga et al 2000;Preston and Snell 2001;Radix et al 2002;Marcial et al 2005;Ríos-Arana et al 2007) and cladocerans (Tatarazako and Oda 2007;Navis et al 2013Navis et al , 2015. Their results showed that, depending on the species and contaminants tested, reproductive parameters such as mixis ratio (i.e., proportion of sexual females relative to all females, sexual and asexual) and fertilization, and diapause parameters such as resting egg production and resting egg hatchability are among the most sensitive endpoints to assess toxicity in zooplankton species.…”

Responses in the population growth and reproduction of freshwater rotiferBrachionus calyciflorusto four organochlorine pesticides

“…The general hypothesis that repression of sexual reproduction was a general response to environmental stresses of many types (Lubzens et al, 1985;Snell, 1986;Snell and Boyer, 1988;Snell and Carmona, 1995;Preston et al, 2000;Xi and Feng, 2004;Marcial et al, 2005;Xi et al, 2007). Similar results were obtained in the present study for dieldrin, chlordecone and b-HCH.…”

“…In the present study, dieldrin and b-HCH at higher concentrations decreased significantly the FR, which was similar to the result of DDT , but aldrin and chlordecone had no significant effect on it, which was similar to the results of pentachlorophenol, cadmium and naphthol (Snell and Carmona, 1995), dicofol, lindane and endosulfan , chlorpyrifos, flutamide, testosterone, nonylphenol, diazinon, fenitrothion, methoprene and isoprothiolane (Preston et al, 2000;Marcial et al, 2005), and cypermethrin and deltamethrin (Huang et al, 2011). It is possible that lower production of males is one of the reasons which decreased the FR of rotifers.…”

“…Discussion Halbach (1984) was among the first person to use population growth as a tool for evaluating the effects of toxicants. Several workers later have used this approach for many species of rotifers such as B. plicatilis, B. calyciflorus and B. patulus to quantify the effects of pesticides (i.e., DDT, lindane, thiophanate-methyl, glyphosate, diazinon, fenitrothion, methoprene, isoprothiolane, cypermethrin, deltamethin, dicofol, endosulfan, atrazine and carbaryl) Sarma, 1986, 1990;Janssen et al, 1994;Xi and Feng, 2004;Chu et al, 2005;Marcial et al, 2005;Xi et al, 2007;Huang et al, 2011;Lu et al, 2012) and other pollutants (i.e., growth hormone, human chorionic gonadotropin, 17b-estradiol, triiodothyronine, 20-hydroxyecdysone, 5-hydroxytryptamine, c-aminobutyric acid, juvenile hormone, ethinylestradiol, nonylphenol, testosterone, phthalate acid esters and melamine) (Gallardo et al, 1997;Radix et al, 2002;Zhao et al, 2007;Wen et al, 2011).…”