Influence du pH du milieu au cours de la fécondation sur la survie embryonnaire de la carpe commune (Cyprinus carpio)

The effects of environmental pH during fertilization in carp eggs were studied by measuring the percentage of prehatching embryonic survival. These effects, which may be delayed beyond epiboly, were the same when the treatments lasted 15 and 30 min after insemination, and they were not modified either by the addition of a physiological salt solution to the medium or by exposure of the eggs for 10 s before insemination. Among the six types of buffer used, phosphate buffers were particularly toxic which may indicate the role played by calcium during fertilization. Normal fertilization requires that the osmolarity of the medium be lower than or equal to 200 mosmol/kg. Beyond the limits of favorable pH values (7.2 and 9.6), egg tolerance decreased less rapidly in a weakly buffered medium than in a strongly buffered one. In such a medium, there was no resistance at pH 6.2 or 9.9