Effect of temperature on toxicity of deltamethrin and oxygen consumption by Porcellio scaber Latr (Isopoda).

This study describes the toxicity of deltamethrin, in relation to its LD50 value, as well as variation in respiratory metabolism of the isopod species Porcellio scaber Latr kept at 3 temperature values (10, 22 and 30ºC). The low LD50 values obtained indicate that deltamethrin is a highly toxic pyrethroid for the crustacean tested, particularly at 10ºC. We also observed that, in all the 3 experimental temperatures, the deltamethrin toxicity was lower in females than in males. Particularly distinct differences between both sexes were visible at 10 and 30ºC, i.e. temperatures that are too low and too high for the species studied. Oxygen uptake measurement showed an increase in respiratory metabolism directly after intoxication. The most substantial increase, 64% in males and 80% in females, was observed at the temperature 10ºC, whereas at the other temperatures, it did not exceed 20%. During the successive experimental days, the respiratory consumption in P. scaber had a tendency to decrease, which was more visible at 10 and 30ºC, compared to the optimal temperature 22ºC.