THE EFFECT OF TEMPERATURE ON THE RATE OF THE FERTILIZATION REACTION IN VARIOUS MARINE OVA

¹ From the Hopkins Marine Station, Stanford University, California

1. The activity of the spermatozoön is affected by extreme temperatures. At 2° C. the sperm of Dendrasler and Patiria are feebly active while the sperm of Strongylocentrotus and Urechis are very active. The activity of the sperm increases with rise in temperature and is retarded at high temperatures. At 25° C. sperm of all species were very active, but at 28.5° C.-30° C. Dendraster and Patiria sperm became inactive. Strongylocentrotus and Urechis sperm became inactive at 35° C.-40° C.

2. At 2° C. unfertilized eggs of Dendraster, Strongylocentrotus, and Urechis were apparently unaffected while eggs of Patiria were activated by cold at temperatures of 8° C. and below. High temperatures caused partial activation of the eggs, usually followed by cytolysis. These effects occurred at and above the following temperatures: Dendraster, 29° C.; Patiria, 30° C.; Strongylocentrotus, 32° C.; and Urechis, 35° C.

3. The rate of the cortical reactions leading to the development of the fertilization membrane in eggs of the four species was retarded at low temperatures and, in the case of eggs of Dendraster and Strongylocentrotus, increased with rise in temperature up to 22° C. but decreased above 22° C. up to the maximum fertilization temperatures. In eggs of Patiria and Urechis the rate of the reaction increased steadily up to the maximum fertilization temperatures.

4. The effect of temperature on the rate of the cortical reactions in the different kinds of eggs affords a functional basis for grouping the eggs in two general categories with respect to the underlying reactions, which agrees entirely with other types of evidence in regard to the mode of the development of the fertilization membranes.

5. The temperature coefficients (Q₁₀) of the rates of the cortical reactions leading to the development of the fertilization membrane in eggs of Dendraster, Strongylocentrotus, Urechis, and to a lesser extent of Patiria, are not constant over the range of fertilization, but shift progressively over a wide range. At colder temperatures the coefficients attain values of 6.0 to 12.0 except in Patiria, whose eggs were not fertilized at low temperatures. At mid-temperature ranges the coefficients are 1.3 to 1.5 in the four types of eggs.

6. The coefficients indicate (see Table II) that the rate of the cortical reaction is not limited by metabolic rate over most of the viable temperature range since over most of the range Q₁₀ is not of the order of magnitude of 2.

7. It is suggested that in the cortical reactions, as in such developmental phenomena as the division of egg cells, in addition to metabolic factors, other factors such as viscosity, diffusion, imbibition, etc., are involved; and that over most of the viable temperature range, it is such factors which limit the rate of reaction.