Acute and chronic effects of exposure to the juvenile hormone analog fenoxycarb during sexual reproduction in Daphnia magna

Abstract

Recent studies have demonstrated that insect growth regulating insecticides are able to affect reproductive endpoints in zooplankton species at very low levels. For the cyclic parthenogenetic water flea Daphnia, most of this research has focused on the asexual part of the life cycle and induction of male offspring. Even though Daphnia and many other aquatic invertebrates rely on sexual reproduction and subsequent production of dormant eggs to recover from environmentally harsh conditions, much less is known about the effects of toxicants on the sexual reproductive phase. Using fenoxycarb as a model pesticide, we exposed male and female neonate Daphnia magna, under conditions inducing a switch to sexual reproduction, and tested for effects on dormant egg (ephippia) production and sex ratio of parthenogenetic offspring. Subsequently, we assessed whether fenoxycarb exposure affected the quality of the produced dormant eggs and viability of the hatchlings. Our results showed that exposure to sub-lethal concentrations of fenoxycarb caused a sharp decrease in parthenogenetic reproduction, while inducing male offspring. Dormant egg production was marginally negatively affected, but survival and fitness of the hatched individuals were not significantly affected. This indicates that under pesticide stress, surviving adult females invested in sexual reproduction at the expense of parthenogenetic reproduction. Exposure to toxicants during the sexual reproductive phase, could affect the active aquatic phase as well as the dormant phase in natural zooplankton populations. This indicates the need for further ecotoxicological research and development of test protocols taking into account the full life cycle of zooplankton species.

Transgenerational effects of methyl farnesoate on Daphnia pulex clones: Male and ephippia production and expression of genes involved in sex determination

“…Recently, Navis et al. (2018) found evidence of marginal influence of fenoxycarb (an insecticide analogue of MF) on ephippia formation in D. magna . From a physiological point of view, male offspring and ephippia productions are regarded as two independent events allowing females to delay ephippia production in favour of parthenogenetic reproduction (De Meester & Vanoverbeke, 1999).…”

Speciation in Daphnia

“…In daphniids, sex determination and sexual reproduction depend on environmental factors (Deng, 1996;Alekseev & Lampert, 2001;Slusarczyk, Ochocka, & Cichocka, 2012; see Glossary). Induction of sexual reproduction of females and production of males under laboratory conditions is influenced primarily by photoperiod (Stross & Hill, 1965;Kleiven, Larsson, & Hobaek, 1992), and at times by a second stimulus such as population density (Stross & Hill, 1965;Hobaek & Larsson, 1990), temperature (Stross, 1969;Korpelainen, 1986;Camp, Haeba, & LeBlanc, 2019), chemical cues (Slusarczyk, 1995;Pijanowska & Stolpe, 1996;Navis, Waterkeyn, De Meester, & Brendonck, 2018), or a combination of these factors (Kleiven et al, 1992). Current research progress into the genetic and molecular basis of sexual reproduction revealed candidate genes that are likely to facilitate the switch from parthenogenetic reproduction to sexual reproduction (Kato et al, 2008;Liu et al, 2014;Guo et al, 2015;Li et al, 2016), including the production of ephippial eggs and males (Kato, Kobayashi, Watanabe, & Iguchi, 2011;Xu et al, 2014;Guo et al, 2015).…”

Determination of 12 insect growth regulator residues in foods of different matrixes by modified QuEChERS and UPLC-MS/MS

“…10,11 With the wide application of IGRs as insecticides, it has been found that RH-5849 is a moderately toxic insecticide, with a certain degree of damage to the genetic material of human peripheral blood lymphocytes; 12 excessive use of fenoxycarb will produce a certain reproductive toxicity to animals and lead to anemia in mammals. 13,14 To ensure food safety and human health, many countries and regions have set the maximum residue limit (MRL) standards for IGRs in food. The United States, EU, and Japan have published thousands of maximum residue limits (MRLs) for pesticides.…”