This study aimed to develop original laboratory culture and sediment toxicity testing protocols for the freshwater gastropod Bellamya aeruginosa (Reeve), a new potential species for sediment toxicity testing. B. aeruginosa was successfully cultured with an effective culture system under proposed laboratory conditions. Optimal ad libitum feeding levels for larvae, juveniles, and adults were 2.0, 6.0, and 16.0 mg fish food/(snail·day), respectively. Mean survival rates of juveniles were higher than 90%. The snails could be sexed at 9 weeks of age, and their generation time is approximately 4 months. Reproduction continued all year around; the mean fecundity was 0.55 newborn/(female·day). The utility of this species for bioassays was evaluated in both 10-day and 28-day case studies with artificial sediments. The 10-day LC 50 of Cu for larvae was 480 μg/g dry weight (dw), and the lowest observed effects concentration of Cu for survival and growth of larvae was 195 μg/g dw. Survival and growth are reliable indicators of acute toxicity. Larvae accumulated more Cu than adults. B. aeruginosa exhibited a higher sensitivity to Cu exposure than standard test species (Hyalella azteca and Chironomus tentans). The 28-day test of sediment toxicity with adults showed that fecundity was a robust endpoint indicator of reproductive toxicity, and the biochemical endpoints of superoxide dismutase, catalase, and glutathione could be used as sensitive biomarkers for Cu-induced oxidative damage. B. aeruginosa can be therefore recommended as a candidate for the standardization of the freshwater sediment toxicity test protocol.

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Morphological and biochemical indices, including hepatosomatic index, gonadosomatic index, and vitellogenin (VTG) induction, were compared between two teleostean species to determine their relative sensitivity of exposure to 17-alpha -ethinylestradiol (EE2). Chinese rare minnow (Gobiocypris rarus) and Japanese medaka (Oryzias latipes) were exposed to aqueous concentrations of EE2 ranging from 0.2 to 100 ng/L for 21 days. A stronger liver response to EE2 in Chinese rare minnow was observed than that in Japanese medaka. In Japanese medaka, significantly increased male GSI could be observed at 50 and 100 ngEE2/L. The semi-quantitative estimation by integrated optic density following electrophoresis showed that exposure of male Chinese rare minnow and Japanese medaka to EE2 resulted in significant (P<0.05) induction of VTG at 0.2 and 2 ngEE2/l, respectively. It indicated that the sensitivity of Chinese rare minnow to the stress of EE2 is about 10-fold greater than that of Japanese medaka.

The environmental factors are expected to affect the ecotoxicity of heavy metals in the presence of engineered nanoparticles (NPs) in aquatic ecosystems. However, in sediment scenario, little is known regarding their impacts on the ecotoxicity of co-exposure of sediment-associated heavy metals and NPs. This study evaluated the impacts of different levels of organic matter (OM) (4.8-11.6%) and pH (6-9) on the ecotoxicological effects of co-exposure of sediment-associated titanium dioxide nanoparticles (TiO-NPs) and cadmium (Cd) to a freshwater gastropod Bellamya aeruginosa. The burdens of Ti and Cd and biomarkers of DNA damage, Na/K-ATPase, lipid peroxidation (LPO), and protein carbonylation (PC) in the hepatopancreas were determined following 21 days of exposure. At background level of OM (4.8%) in sediments, TiO-NPs significantly promoted Cd accumulation in low-Cd treatments (5 mg/kg) but did not promote Cd accumulation in high-Cd treatments (25 mg/kg). At the relatively higher OM levels (7.1 and 11.6%), TiO-NPs significantly enhanced Cd accumulation and toxicity as evidenced by aggravated DNA damage, decreased Na/K-ATPase activities, and increased LPO and PC levels. Moreover, Cd burdens in both low-Cd and high-Cd treatment were positively correlated with corresponding Ti burdens, indicating TiO-NPs partially acted as carrier of Cd. At all pH levels, in low-Cd treatments, TiO-NPs did not affect Cd accumulation, LPO, and PC levels but significantly enhanced DNA damage and slightly facilitated the inhibition of Na/K-ATPase activities. In high-Cd treatments, only at pH 9, TiO-NPs significantly enhanced Cd accumulation and toxicity. Our results implied that interaction between TiO-NPs and OM or pH significantly affected the accumulation and toxicity of Cd in B. aeruginosa, but the underlying mechanisms need further investigation. Additionally, it should be noted that the potential ecological risk of co-exposure of NPs and coexisting pollutants might be closely species-specific and related to environmental media.

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