. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 100 H. FUJISAWA 10 15 20 25 30 Temperature (°C) Figure 1. Relationship between temperature and the relative devel- opmental velocity of Hemicentrotus pulcherrimus embryos. The results are based on the data shown in Table II. Each solid circle and bar represents the mean and standard error respectivelv. of the rela- tive velocities for development into the first, second, third, and fourth cleavages, mesenchyme ingression, and gastrula stage. Each open circle and bar indicates respectively the mean and standard error
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 100 H. FUJISAWA 10 15 20 25 30 Temperature (°C) Figure 1. Relationship between temperature and the relative devel- opmental velocity of Hemicentrotus pulcherrimus embryos. The results are based on the data shown in Table II. Each solid circle and bar represents the mean and standard error respectivelv. of the rela- tive velocities for development into the first, second, third, and fourth cleavages, mesenchyme ingression, and gastrula stage. Each open circle and bar indicates respectively the mean and standard error of the rela- tive velocity for development into the hatching stage at a given temper- ature. The dotted line is an extrapolation of the curve, assuming it to be a straight line. exocytosis of hatching enzyme and its hydrolytic action on the fertilization membrane. The factors determining the temperature tolerance or dependence of embryos have not yet been elucidated. Belehradek (1930) proposed that in general biological processes including development protoplasmic viscosity is the main factor determining the effect of temperature. Stephens (1972b) has tried to explain the temperature tolerance of embryos in terms of Inoue's mitotic dy- namic theory. Cellular activities in early embryogenesis, such as cleavage and cell adhesion (Fujisawa and Amemiya, 1988) are significantly affected by tempera- ture, and these processes are mainly dependent upon cy- toskeletal activities. However, cytoskeletal elements do not seem to be a candidate for a factor, since actin, as well as tubulin, is reported to be evolutionarily stable (Loewy, 1952; Hatano and Oosawa, 1966; Adelman and Taylor, 1969; Luduena and Woodward, 1973; Krauhs el a/.. 1981; Hall et ai, 1983; Sullivan and Cleveland. 1984). Temperature sensitivities of enzymes of DNA synthesis may also be another important factor since mitosis is closely connected with DNA synthesis. It is noteworthy that the temperature optimum of DNA polym
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