Acute effects of UVB radiation on the survival, growth, development, and reproduction of Daphniopsis tibetana Sars (Crustacea: Cladocera)

Application of Moina mongolica and Daphniopsis tibetana in marine ecotoxicology studies in China: A review

Moina mongolica and Daphniopsis tibetana are typical saline Cladocera in China that are characterized by a wide salinity range, rapid reproduction, and high-density culture. In this paper, the characteristics and life history of M. mongolica and D. tibetana are reviewed. The application of these two species of Cladocera to ecotoxicology in recent years is also summarized from the aspects of environmental factors and environmental pollutants, including ultraviolet B radiation, temperature, salinity, alkalinity, pH, heavy metals, harmful red tide, pesticides, and persistent organic pollutants. Additionally, the toxicity sensitivity of saline Cladocera in different reproductive statuses and inter-generational embryos is discussed. Finally, the need to enhance knowledge of the molecular genomics, population dynamics, and strategies for protection of saline Cladocera, along with the need for establishment of estuarine and marine environmental monitoring standards are discussed. Overall, this review highlights the potential for using these Cladocera species as indicator organisms for estuarine and marine ecotoxicology studies.

Physiological response and molecular mechanisms against UV-B radiation in Brachionus asplanchnoidis (Rotifera)

Ultraviolet B (UV-B, 280-320 nm) radiation is a major environmental stressor for aquatic organisms on Earth's surface. Its effects on biological systems are well known, but the mechanisms by which organisms respond and adapt to UV-B radiation are still being explored. In this study, we investigated the effects of UV-B radiation on the monogonont rotifer Brachionus asplanchnoidis, focusing on physiological parameters, antioxidant systems, DNA damage, and DNA repair-related molecular mechanism. Our results showed that the LD50 was at 28.53 kJ/m2, indicating strong tolerance to UV-B. However, UV-B radiation caused adverse effects on growth and reproduction, with shortened reproductive period and longevity, decreased fecundity and hatchability, and inhibition of population growth. Biochemical analyses revealed severe oxidative damage and lipid peroxidation, with increased ROS and MDA levels. Activities of antioxidant enzymes were highly induced at low doses but decreased at high doses. DNA damage also occurred in UV-B-exposed rotifers. Furthermore, selected DNA repair-related genes were up-regulated in a dose-dependent manner. These findings provide a comprehensive understanding of the effects of UV-B radiation on rotifers and highlight the importance of considering both ecological and molecular responses in assessing the impact of UV-B radiation on aquatic organisms.