234 M
.H.S. Santos et al. J. Exp. Mar. Biol. Ecol. 247 2000 233 –242
1. Introduction
Industrial activity along coastal regions has significantly contributed to increases of natural levels of heavy metals in aquatic systems. In the Patos Lagoon estuary Southern
Brazil, areas in which copper and zinc concentrations exceed the estimated natural levels have been reported Baisch et al., 1988; Niencheski et al., 1994. However, this
region is a natural hatchery for the pink shrimp Farfantepenaeus paulensis, which is the most important fishing resource in Southern Brazil Valentini et al., 1991. The life cycle
includes both, marine and estuarine phases. They penetrate the Patos Lagoon estuary as postlarvae 6th substage at approximately 3 weeks of age Iwai, 1978, and develop
until a pre-adult stage 7–8 cm total length when they return to sea D’Incao, 1991. During their residence in the estuary, postlarvae are susceptible to all contaminants
available in the environment, and as mentioned below, the effects of excessive copper and zinc concentrations on postlarvae physiology must be considered.
Copper and zinc are essential metals to normal physiology of crustaceans. However, they become toxic if high environmental concentrations are attained. Some general
effects of heavy metals on crustacean physiology have been reported Thurberg et al., 1973; Spicer and Weber, 1991; Wong et al., 1993. These effects also include growth
and reproduction disturbances Nimmo and Hamaker, 1982. Some of these effects may be due to an energetic imbalance carried out by the action of heavy metals on enzymatic
systems, which in turn lead to metabolic changes. Considering food ingestion as the major input of energy in crustaceans, and oxygen consumption as a measure of
metabolism, the effects of sub-lethal copper and zinc concentrations on these parameters were analysed in F
. paulensis postlarvae. Their effects on feeding response were also considered. Chronic effects of sub-lethal concentrations of copper and zinc on PL
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growth was studied for 35 days. All studies were performed using copper and zinc singly, and in a mixture of equipotent concentrations.
2. Material and methods
