Lead toxicity on growth and biochemical constituents in postlarvae of Penaeus indicus

Estuaries and backwaters, the potential breeding grounds of penaeid shrimps, are subject to heavy metal pollution through industrial effluents and domestic sewage. In this investigation, laboratory experiments were conducted to study the effects of lead on growth and biochemical constituents of postlarvae (PL) of Penaeus indicus. The PL were exposed to a sublethal concentration of lead (1.44 ppm) for 30 days. Parallel controls were maintained without exposure to the toxicant. The growth of PL was determined by measuring length and weight. The major biochemical constituents, including total carbohydrates, proteins, lipids, and ninhydrin-positive substances (TNPS), were estimated using standard methods. Lead exposure resulted in retardation of growth with a significant decrease in length and weight occurring at day 10 and onwards. There was a gradual and significant decrease in all of the biochemical constituents except TNPS which increased upon exposure to lead. Of all the biochemical constituents, total proteins showed the maximum decrease (79.3%), followed by total lipids (68.1%), and then by total carbohydrates (51.4%) in lead-exposed PL. The data suggest lead exposure causes reduced growth and the depletion of biochemical constituents. This may be due to metal interactions and inhibition of metabolic pathways responsible for synthesis of biochemical constituents or to greater utilization of these constituents under metal stress conditions.