Thermal resistance and acclimation rate in young white and brown shrimp, Penaeus setiferus Linn, and Penaeus aztecus Ives.

Penaeus aztecus postlarvae acclimated at three temperatures (24, 29, and 34 C) were tested for thermal resistance at five lethal temperatures for each acclimation temperature (34-38 C; 35-39 C; and 36- 40 C). Penaeus setiferus postlarvae acclimated at two temperatures (29 and 34 C) were tested for thermal resistance at six lethal temperatures for each acclimation temperature (35-40 C; 36-41 C). The temperature which caused 50% mortality at 10,000 minutes was between 35 and 36 C for postlarvae acclimated at 24 C, and between 36 and 37 C for those acclimated at 29 and 34 C. Twenty-four hour LC [subscript 50]'s were 36.3, 37.5, and 38.3 C for Penaeus aztecus postlarvae acclimated at 24, 29, and 34 C, respectively, and 38.3 and 38.9 C for Penaeus setiferus postlarvae acclimated at 29 and 34 C, respectively. Postlarval Penaeus aztecus were more resistant at most lethal temperature than were 30 mm Penaeus aztecus. Postlarval and 30 mm Penaeus setiferus had similar resistance times, which were greater than those of 50 mm Penaeus setiferus.