AMPHIBIAN AND INVERTEBRATE DEVELOPMENT 89
Rana temporaria contained 135 y of glycogen, while the embryo at hatching contained only 79 γ, showing a 41-5% decrease. Needham (1927),
working on the same species over the same period of development,
showed that the decrease was very much smaller but later when he
studied the subject again (Brächet and Needham, 1935) the results, on
the whole, confirmed the findings of Faure-Fremiet and Dragoiu (1923).
A 30% decrease in carbohydrates, from gastrulation to hatching, was
observed in Ranafusca.
Savage (1938) also found a 28% decrease in carbohydrates in the first
developmental stage of Rana temporaria.
Gregg (1948) showed a 44% decrease in total carbohydrates in Rana
pipiens from the beginning of development to shortly after hatching.
Both Brächet and Needham (1935) and Gregg (1948) noted that during
segmentation, and practically until gastrulation the content of carbohydrates remains constant, indicating that carbohydrates are not used
as a source of energy in these early stages.
Lovtrup (1953a, b), found that at the end of embryonic development
of Ambystoma mexicanum the content of total carbohydrates is about
30%-40% below the initial value; in this case also, utilization of these
compounds is remarkably high. However, Lovtrup, on the basis of his
calculations on oxygen uptake and reduced weight at the different stages
of development, considers that carbohydrate consumption starts during
segmentation but this is merely hypothesis, and could only be confirmed through chemical analysis.
Studies on total carbohydrates (TC) during the embryonic development of Bufo vulgaris and Rana esculenta (Urbani, 1957) have shown that
the changes in content are similar in the two species. There is a measurable decrease in the carbohydrate content even during segmentation,
although this is not apparent, if only glycogen is measured. During
development until the beginning of swimming the TC content decreases
to approximately 45-50% of the initial value, and then—in both Bufo
vulgaris and Rana esculenta—a slight increase occurs for which no
explanation can be given at the moment (Fig. 13).
After this increase, the value remains constant, so that at the end of
the embryonic period it fluctuates around 56-61% of the initial TC
content. In the young non-feeding larvae of both species, no measurable
decrease in TC content occurs. It is evident that the sugars can no longer
be used as a source of energy.
This work not only shows an early and substantial utilization of
carbohydrates for the energy requirements of the embryo, but also
confirms the results obtained by other authors for different amphibian
species. Unlike proteins,
r a high proportion of carbohydrates is utilized
during embryonic development. During metamorphosis of Bufo vulgaris
Rana temporaria contained 135 y of glycogen, while the embryo at hatching contained only 79 γ, showing a 41-5% decrease. Needham (1927),
working on the same species over the same period of development,
showed that the decrease was very much smaller but later when he
studied the subject again (Brächet and Needham, 1935) the results, on
the whole, confirmed the findings of Faure-Fremiet and Dragoiu (1923).
A 30% decrease in carbohydrates, from gastrulation to hatching, was
observed in Ranafusca.
Savage (1938) also found a 28% decrease in carbohydrates in the first
developmental stage of Rana temporaria.
Gregg (1948) showed a 44% decrease in total carbohydrates in Rana
pipiens from the beginning of development to shortly after hatching.
Both Brächet and Needham (1935) and Gregg (1948) noted that during
segmentation, and practically until gastrulation the content of carbohydrates remains constant, indicating that carbohydrates are not used
as a source of energy in these early stages.
Lovtrup (1953a, b), found that at the end of embryonic development
of Ambystoma mexicanum the content of total carbohydrates is about
30%-40% below the initial value; in this case also, utilization of these
compounds is remarkably high. However, Lovtrup, on the basis of his
calculations on oxygen uptake and reduced weight at the different stages
of development, considers that carbohydrate consumption starts during
segmentation but this is merely hypothesis, and could only be confirmed through chemical analysis.
Studies on total carbohydrates (TC) during the embryonic development of Bufo vulgaris and Rana esculenta (Urbani, 1957) have shown that
the changes in content are similar in the two species. There is a measurable decrease in the carbohydrate content even during segmentation,
although this is not apparent, if only glycogen is measured. During
development until the beginning of swimming the TC content decreases
to approximately 45-50% of the initial value, and then—in both Bufo
vulgaris and Rana esculenta—a slight increase occurs for which no
explanation can be given at the moment (Fig. 13).
After this increase, the value remains constant, so that at the end of
the embryonic period it fluctuates around 56-61% of the initial TC
content. In the young non-feeding larvae of both species, no measurable
decrease in TC content occurs. It is evident that the sugars can no longer
be used as a source of energy.
This work not only shows an early and substantial utilization of
carbohydrates for the energy requirements of the embryo, but also
confirms the results obtained by other authors for different amphibian
species. Unlike proteins,
r a high proportion of carbohydrates is utilized
during embryonic development. During metamorphosis of Bufo vulgaris