Embryotoxicity of the alkylphenol degradation product 4-nonylphenol to the crustacean Daphnia magna.

Abstract

Laboratory studies have suggested that some alkylphenols and pesticides elicit developmental toxicity to crustaceans. The purpose of the present study was to evaluate the possibility that the alkylphenol degradation product 4-nonylphenol is embryotoxic to the crustacean Daphnia magna through its known ability to interfere with the metabolic elimination of testosterone. Direct exposure of maternal daphnids to testosterone caused developmental abnormalities in neonates that consisted of partial arrest of early embryonic development and abnormalities in shell spine and first antennae development. Exposure of maternal daphnids to concentrations of 4-nonylphenol also produced developmental abnormalities though the profile of abnormalities was distinct from that observed throughout the testosterone concentration-response curve. Thus, 4-nonylphenol is a developmental toxicant in daphnids, but its toxicity is not consistent with that elicited by elevated testosterone accumulation. Further experiments demonstrated that testosterone was directly toxic to developing embryos, and the maternal organism can serve as the vector for this toxicity. In contrast, neither direct embryo exposure nor early maternal exposure to 4-nonylphenol elicited embryotoxicity consistent with that observed during continuous maternal and gestational exposure. Thus, 4-nonylphenol is not directly embryotoxic at these exposure levels, but rather toxicity is mediated by maternal influences during gestation. The threshold concentration for the occurrence of developmental abnormalities ( approximately 44 microg/L) indicates that typical environmental concentrations of 4-nonylphenol pose no imminent hazard with respect to developmental toxicity. However, these effects do occur at sufficiently low levels to warrant evaluation of the relative susceptibility of other crustacean species to this previously uncharacterized mode of toxicity.

Patterns of Fluctuating Asymmetry and Shape Variation in Chironomus riparius (Diptera, Chironomidae) Exposed to Nonylphenol or Lead

“…In addition, Meregalli et al [38] observed mouthpart defects in Chironomus riparius larvae for exposure concentrations of 100 µg/l. Morphological abnormalities were also reported in other taxa, such as Daphnia magna (Crustacea) for concentrations of 44 µg/l [39]. Moreover, effects on growth and reproduction were observed in Caernorhabditis elegans (Nematoda) for concentration of 40 µg/l [40].…”

Effects of chlordecone on 20-hydroxyecdysone concentration and chitobiase activity in a decapod crustacean, Macrobrachium rosenbergii

“…Moreover, knowing that crustacean reproduction is linked to the molt cycle (Hyne, 2011), disruption in the molting process could also cause disturbances in reproduction as hypothesized by Gismondi and Thomé (2014) in the amphipod, G. pulex. Indeed, it was observed that the anti-ecdysteroidal activity of nonylphenol caused a reduction in fecundity of many insects (LeBlanc et al, 2000).…”

Validation of a two-generational reproduction test in Daphnia magna: An interlaboratory exercise

“…Indeed we found that PBO affected mostly embryo viability and hence cumulative fecundity (which in this study refers to alive offspring production) rather than juvenile or adult survival and age at first reproduction. Piperonyl butoxide (PBO) is a cytochrome P450 (CYP) inhibitor (Hardstone et al, 2015) that inhibits steroid hydroxylases in Daphnia (Baldwin and LeBlanc, 1994), and hence is likely to alter the biosynthesis and metabolism of ecdysteroids, which are crucial for embryo development (LeBlanc et al, 2000). This is in line with a previous study that found that effects of PBO on D. magna population growth rate was mostly related to PBO effects on embryo survival and hence on cumulative fecundity.…”

“…PBO is a well-known and widely used insecticide synergist, known to inhibit the activity of the insect cytochrome P450 detoxification system (Hardstone et al, 2015). This compound inhibits steroid hydroxylases in daphnids (Baldwin and LeBlanc, 1994), which are necessary for embryo development (LeBlanc et al, 2000). Furthermore, as a broad inhibitor of cytochrome P450 enzymes, this compound can alter metabolic pathways in exposed embryos.…”