The whole of experiments carried on from thermal constraints on the larval development of Palaemon serratus allows the following observations: -individual rearings obtain the best survival rates in the witness groups and neutralize by a dense food and the absence of intraspecific cannibalism, factors which can interfere with the results ascribed only to the experiments; - slight thermal increases (10 and 12 degree C) do not involve secondary effects on the post larvae when the development is realized at 20 degree C; - if the TL 50 is reaching 34 degree C, letal effects are observed, as soon as the final temperature; - whatever is the temperature increase, the relation = mortality/temperature reached is similar and this factor mortalities observed, that would accredit a very rapid answer from the organisms.