Play media The beating heart of Daphnia under the microscope The body of Daphnia is usually 1—5 millimetres 0. In most species, the rest of the body is covered by a carapace , with a ventral gap in which the five or six pairs of legs lie. Daphnia, like many animals, are prone to alcohol intoxication, and make excellent subjects for studying the effects of the depressant on the nervous system due to the translucent exoskeleton and the visibly altered heart rate. They are tolerant of being observed live under a cover slip and appear to suffer no harm when returned to open water. Each subgenus has been further divided into a number of species complexes. The understanding of species boundaries has been hindered by phenotypic plasticity, hybridization, intercontinental introductions and poor taxonomic descriptions.
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Abstract As one of the most frequently detected pharmaceutical compounds in aquatic environments, carbamazepine CBZ has recently been shown to cause acute and chronic toxicity in a variety of non-target aquatic organisms. However, little is known about the ecotoxicological effects it has on the molting and reproduction of crustaceans. The aim of the present work was to evaluate the acute and chronic toxic responses to CBZ in the crustacean Daphnia similis. After acute exposure 4 days , CBZ did not cause lethal toxicity at the tested concentrations.
However, CBZ did inhibit the molting and release of chitobiase at concentrations higher than 6. The results of chronic exposure showed that the mean number of molts, size of the first brood, mean number of offspring per brood, mean number of broods per female, and total offspring per female decreased significantly with increasing CBZ concentrations. Significant effects of CBZ on the molting or fecundity in D. In conclusion, CBZ can cause inhibition of molting, delayed reproduction, and reduced fecundity in D.
CBZ toxicity to D. Moreover, our results indicated that CBZ would act as an endocrine disrupter in D. Keywords: carbamazepine, molting, Daphnia similis, chitobiase, chronic toxicity, reproduction 1. Introduction In recent years, with advances in environmental analysis technology, a new class of environmental pollutants pharmaceuticals and personal care products PPCPs has begun to receive widespread attention [ 1 , 2 ].
Most PPCPs in the environment have low concentrations, complex structures, and difficult degradation and accumulation characteristics [ 3 ]. Although the concentrations are low in the environment, long-term pollution of PPCPs may cause endocrine disruption or reproductive toxicity to aquatic organisms, induce changes in biochemical functions of aquatic habitats, and do great harm to the environment [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ].
Carbamazepine CBZ , a heavily used pharmaceutical, is mainly employed for the treatment of epilepsy, arrhythmia, depression, and other diseases [ 6 ]. CBZ is discharged into the environment in a variety of ways, and can be residual in the environment, resulting in its persistence in water bodies and adverse effects on ecosystems [ 9 ].
Liu et al. Due to its high concentrations in aquatic environments, CBZ has received growing attention as an emerging contaminant based on its potential threat to non-target species [ 15 , 16 , 17 , 18 ]. For example, Malarvizhi et al. In addition, exposure to environmentally relevant concentrations of CBZ altered the siphoning behavior, biomarkers, hsp mRNA levels, and protein levels in the gills and digestive gland of the Asian clam Corbicula fluminea.
The changes in the biomarkers suggest that the effect of CBZ is related to oxidative stress [ 6 ]. Therefore, research into the toxic effects of CBZ on aquatic organisms should not be neglected.
Concerning crustaceans, the existing knowledge about the toxic effects of CBZ is limited to the model species e. Kovacevic et al. Molting is a natural biological process in arthropods, including crustaceans. During molting, the animal generates a new exoskeleton and sheds the old one to grow and develop [ 21 ].
In terms of endocrine-disrupting effects, molting is used as an effective biomarker to assess the toxicity of contaminants in crustaceans. Previous studies have reported that various xenobiotics such as polychlorinated biphenyls, perfluorooctane sulfonate, pesticides, and heavy metals can affect molting in crustaceans by disrupting molting hormone signaling, including chitinolytic enzyme, hydroxyecdysone, and molting hormone signaling genes [ 22 , 23 , 24 , 25 , 26 ]; however, as a neuro-active pharmaceutical, and a potential endocrine disruptor in fish [ 10 ], neither the effects of CBZ on molting in crustaceans nor the underlying mechanisms are well studied or understood.
Thus, the aim of the current study was to determine the acute and chronic effect of CBZ on the molting, growth, and reproduction of Daphnia similis, which is a main crustacean species in Lake Taihu, China. In the present study, newborn D.
After the acute exposure, the survival, number of molts, and chitobiase activity were measured. Chitobiase, a major chitinolytic enzyme in the molting fluid, is required for complete degradation of the old exoskeleton [ 21 ].
Based on the toxicological findings, we discuss the possible mechanism of CBZ action on molting and reproduction in this crustacean species. Materials and Methods 2. CBZ stock solution was made anew every week.
Revision of the Old World Daphnia (Ctenodaphnia) similis group Cladocera: Daphniidae).
Daphnia similis Claus, 1876