The present study was conducted to assess the influence of dietary zinc nanoparticles (size 50 nm) on the growth, biochemical constituents, enzymatic antioxidant levels and the nonspecific immune response of the freshwater prawn, Macrobrachium rosenbergii post larvae (PL). The concentrations of dietary supplement zinc nanoparticles (ZnNPs) were 0, 10, 20, 40, 60 and 80 mg kg(-1) with the basal diet, and the level of Zn in ZnNP-supplemented diets were 0.71, 10.61, 20.73, 40.73, 60.61 and 80.60 mg kg(-1), respectively. ZnNP-incorporated diets were fed to M. rosenbergii PL (initial body weight, 0.18 ± 0.02 g) in a triplicate experimental setup for a period of 90 days. ZnNP supplemented feed fed PL up to 60 mg kg(-1) showed significantly (P < 0.05) improved performance in survival, growth and activities of digestive enzymes (protease, amylase and lipase). The concentrations of biochemical constituents (total protein, total amino acid, total carbohydrate and total lipid), total haemocyte count and differential haemocyte count were elevated in 10-60 mg kg(-1) ZnNP supplemented feed fed PL. However, the PL fed with 80 mg ZnNPs kg(-1) showed negative results. Activities of enzymatic antioxidants [superoxide dismutase (SOD) and catalase (CAT)], metabolic enzymes [glutamate-oxaloacetate transaminase (GOT) and glutamate-pyruvate transaminase (GPT)] and the process of lipid peroxidation (LPO) in the hepatopancreas and muscle showed no significant alterations in 10-60 mg kg(-1) ZnNP supplemented feed fed PL. Whereas, 80 mg ZnNPs kg(-1) supplemented feed fed PL showed significant elevations in SOD, CAT, LPO, GOT and GPT. Therefore, 80 mg ZnNPs kg(-1) was found to be toxic to M. rosenbergii PL. Thus, the study suggests that up to 60 mg ZnNPs kg(-1) can be supplemented for regulating survival, growth and immunity of M. rosenbergii.

Background: Zooplankton biodiversity serves as an ecological indicator of aquatic environment due to their rapid response according to environmental changes. At the present study, impact of seasonal changes on zooplankton biodiversity was conducted in the Ukkadam Lake (Lat 10°59′ N and Long 76°57′ E), at Coimbatore city, Tamil Nadu, India. Results: The biodiversity of zooplankton taxa were studied for a period from December 2011 to November 2012 on seasonal basis. During this time period, in total, 28 species of zooplankton were noticed, which includes 9 species of each Rotifera and Cladocera and 5 species of Copepoda and Ostracoda. In this present observation, total abundance of Rotifera was found to be predominant with 35%, followed by Cladocera 29%, Copepoda 29% and Ostracoda 7%. The population density of various group of zooplankton was observed, and it was found to be following order Rotifera > Copepoda > Cladocera > Ostracoda. The high and low population densities were recorded in summer and early monsoon season respectively. This higher zooplankton population density in summer might be due to the temperature acceleration in the Ukkadam Lake. Conclusions: The present study revealed that zooplankton productivity was found to be higher in the Ukkadam Lake when the temperature was increased in summer season. It indicates that the temperature has influence on the zooplankton diversity. Therefore, increased temperature due to global climate change might have influence on the zooplankton production. Assessment of zooplankton biodiversity will be useful to monitor the health (water quality) and wealth (fishery productivity) of this lake system in the near future.

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