## 4 Discussion
Concentration-dependent increase in DNA damage in the present study was directly proportional to the increased frequency of apoptotic and necrotic cells during exposure as well as in the recovery period. TCS promotes the production of reactive oxygen species which break the crosslinks between DNA histones and DNA strands and cause DNA damage [19]. It has also been observed to alter DNA methylation and transcription of histone methyltransferases in the early life stages of zebra fish [48], which could be the possible reasons behind the dose-dependent increase in DNA damage in our study. The genotoxic potential of TCS has been reported in _Driessena polymorpha_[15], _Tetrahymena thermophila_[49], _Eisenia fetida_[50; 51], _Carassius auratus_[46], _Danio rerio_[17], _Pangasianodon hypophthalmus_[18; 19] and _L. rolita_[13]. Our results are supported by Hemalatha et al. [9] and Gyimah et al. [20], who reported significant DNA damage in _L. rolita_ after exposure to 0.039 and 0.078 mg/L TCS for 7, 14, 21, 28 and 35 days and in the liver of zebrafish after exposure of 50, 100 and 150 \(\upmu\)g/L TCS for 30 days, respectively. Glucose monitoring is highly preferred in ecotoxicological studies because it indicates the physiological health of an organism. The significant decline in glucose content after exposure and recovery period might be attributed to an enhanced rate of glycolysis in the hatchlings under the stress of TCS. Rapid utilization of glucose to compensate for high energy demand during oxidative stress might be the possible reason behind the decrease in glucose level [52]. Similarly, Hemalatha et al. [9] observed a significant decline in glucose levels of _L. rohita_ after 35 days of exposure to 39 and 78 ug/L TCS. Hypoglycemia has also been reported in _C. punctatus_ under the stress of monocrotophos [21] and malathion [53]. Chol and TG are essential components of the cell membrane and important energy sources. These are also involved in cell signaling and molecular recognition pathways [54]. The probable cause of reduced Chol and TG levels in the present study seems to be malnutrition, low absorption and improper biosynthesis, as suggested by Hatami et al. [55]. Not only during exposure, but even during the recovery period, the TCS-exposed hatchlings at much less, and their weight was also lower compared with the control hatchlings. TCS impairs lipid metabolism [56], which could be the possible reason for decrease in TG and Chol levels in exposed hatchings. Agrahari et al. [21] suggested that the accumulation of pesticides in fish tissues may inhibit the synthesis of Chol. The decline in TG content could also be corelated with its mobilization to meet the constant energy demand and utilization in membrane biogenesis under stress [54; 57]. The increased concentration of TG after recovery may be attributed to nephritis syndrome and metabolic disorders [58; 59]. Similar results were reported in _C. punctatus_ after 21 days of exposure to 200 and 400 ug/L paraquat [60] and 25 and 50 ug/L chlorpyrrifos [55]. Proteins are the important biomolecules that play a critical role in almost all the structures and functions of living organisms [61]. The depleted protein content in the present study may be due to proteolysis as a result of elevated energy demand for maintaining homeostasis, tissue repair and detoxification reactions during stress. Previous reports also showed that TCS significantly decreased the protein content in _C. punctatus_[27], _Orechromis niloticus_[16] and _Orechromis mossambicus_[62]. Alb is the most dominant plasma protein having storage and transport functions [63]. A decline in Alb after exposure may be attributed to cellular destruction, liver necrosis and the impairment of protein synthesis machinery [18]. Our finding is corroborated by Bera et al. [64], who reported a decrease in serum Alb in _P. hypophthalmus_ on exposure to TCS. However, an increase in Alb is suggested due to liver damage [65], and this could be the underlying cause for the observed increase in Alb after the recovery period.