Exploiting the Freshwater Shrimp Neocaridina denticulata as Aquatic Invertebrate Model to Evaluate Nontargeted Pesticide Induced Toxicity by Investigating Physiologic and Biochemical Parameters

As a nicotinoid neurotoxic insecticide, imidacloprid (IMI) works by disrupting nerve transmission via nicotinic acetylcholine receptor (nAChR). Although IMI is specifically targeting insects, nontarget animals such as the freshwater shrimp, Neocaridina denticulata, could also be affected, thus causing adverse effects on the aquatic environment. To investigate IMI toxicity on nontarget organisms like N. denticulata, their physiology (locomotor activity, heartbeat, and gill ventilation) and biochemical factors (oxidative stress, energy metabolism) after IMI exposure were examined. IMI exposure at various concentrations (0.03125, 0.0625, 0.125, 0.25, 0.5, and 1 ppm) to shrimp after 24, 48, 72 h led to dramatic reduction of locomotor activity even at low concentrations. Meanwhile, IMI exposure after 92 h caused reduced heartbeat and gill ventilation at high concentrations. Biochemical assays were performed to investigate oxidative stress and energy metabolism. Interestingly, locomotion immobilization and cardiac activity were rescued after acetylcholine administration. Through molecular docking, IMI demonstrated high binding affinity to nAChR. Thus, locomotor activity and heartbeat in shrimp after IMI exposure may be caused by nAChR blockade and not alterations caused by oxidative stress and energy metabolism. To summarize, N. denticulata serves as an excellent and sensitive aquatic invertebrate model to conduct pesticide toxicity assays that encompass physiologic and biochemical examinations.

Short Communication: The lifecycle of Neocaridina denticulata and N. palmata in aquariums

Mahmoud HHA, Sastranegara MH, Kusmintarsih ES. 2020. Short Communication: The lifecycle of Neocaridina denticulata and N. palmata in aquariums. Biodiversitas 21: 2396-2402. The study on the life cycle of Neocaridina spp. is important because it plays a major role in the economy and trade between countries. However, there is a lack of sufficient studies on this particular topic. One of the factors that influence Neocaridina spp. life production is its life cycle and the associated water parameters. The objectives of this study were to conduct, observe, and record the life cycle of Neocaridina denticulata and N. palmata and the associated with water parameters (temperature, pH, ammonia, nitrite, and oxygen) in the aquarium. The results showed that there was no difference in the life cycle stages between the two shrimp species. Both species reached the first sexual maturity stage of the life cycle at 75 days, with the maximum body length of the mature shrimp ranging from 2.30-3.00 cm. The eggs became larvae in 15 days, larvae reached the juvenile stage after 60 days, and the juvenile became mature in 15 days. The number of eggs was influenced by the body size of the female shrimps; smaller females produced fewer eggs. Optimal water quality varies by species and must be monitored to ensure growth and survival. The temperature range in this study was 25-28°C and the pH was 6.5-8.0. The ammonia level was in the range between 1.21 and1.72 mg/L, the nitrate was between 0.06 and 7.91 mg/L, and the oxygen was around 5.5-7.9 mg/L. All of the water quality parameters in this study are within the acceptable range for Neocardina cultivation.

Omnivorous shrimp Neocaridina denticulata sinensis enhances the growth of submerged macrophyte Vallisneria denseserrulata

Lake eutrophication often causes declines and even losses of submerged macrophytes through the shading effects of increased periphyton and phytoplankton. The Chinese swamp shrimp Neocaridina denticulata sinensis Kemp (Decapoda, Atyidae) is a common omnivore in Chinese lakes, where its presence may impact both periphyton and phytoplankton, with previously unstudied consequences for submerged macrophytes. Here, using a mesocosm experiment, we studied the effect of N. d. sinensis on periphyton, phytoplankton and the submerged macrophyte Vallisneria denseserrulata. Results showed that in the presence of N. d. sinensis, the biomass of periphyton on the leaves of V. denseserrulata was significantly reduced, and that growth rate of V. denseserrulata increased. The presence of N. d. sinensis also significantly increased the total phosphorus concentrations in the water column and phytoplankton biomass (chlorophyll-a). The enhanced growth of V. denseserrulata is likely to be linked to improved light harvesting due to the reduced periphyton attached to their leaf surface. The results suggest that stocking with Chinese swamp shrimps may enhance the development of macrophytes in eutrophic shallow lakes.