Avoidance of Pentachlorophenol by Postlarval Brown Shrimp (Penaeus aztecus) (Decapoda, Penaeidae) in a Laminar-Flow Choice Chamber

Responses of postlarval brown shrimp (Penaeus aztecus) to pentachlorophenol (0–450 μg∙L−1) were measured in synthetic seawater and estuarine water using a laminar-flow choice chamber. This chamber provides individual postlarvae with equal exposure to two parallel olfactant streams separated by a steep concentration gradient. Shrimp detected and avoided pentachlorophenol concentrations above 91 μg∙L−1 in synthetic seawater. This detection threshold reflects limitations in statistical power, and with increased replication the physiological threshold could probably be resolved at a much lower concentration. Pentachlorophenol appeared to be more repellent when dissolved in estuarine water from Galveston Bay, Texas. The 96-h LC50 for pentachlorophenol was 317 μg∙L−1 which suggests that postlarvae are capable of avoiding acutely toxic concentrations of this pollutant. For postlarvae of this species, behavioral avoidance appears to provide a more sensitive indicator of pollutant responses than the conventional toxicity bioassay.