90
ENRICO URBANI
the TC content decreases steadily and at the end of it is about equal to
53% of the initial value (Fig. 13).
3. Total Lipids
Research by Bialaszewics and Mincovna (1921) on the changes in
chemical composition of amphibian embryos during development has
shown that a reduction in fatty acids cannot be detected in Rana fusca
and Rana temporaria before hatching; a 50% loss is noted in subsequent
stages. Parnas and Krasinska (1921) confirmed these results and did not
detect lipid breakdown before hatching. Barthelemy and Bonnet (1926)
observed that lipid utilization during embryonic development of the
same species is independent of temperature, and consequently of the
duration of the different stages.
We have already drawn attention to the effect of temperature on respiration during development, correlating this with biochemical development, development rate, and morphogenesis.
The data available on this subject are essentially consistent, with the
exception of those submitted by Faure-Fremiet and Dragoiu (1923) who
reported a substantial loss in lipids during early development. This is
odd, for whatever lipid utilization occurs in the initial developmental
stages, it must be very low; the decrease cannot be 25% of the initial
value, as stated by them.
Atlas (1938) claimed that the highest consumption of lipids occurs
from the tail bud stage to operculation of the gills. An increase in fatty
acids, by about 1 1 % , was observed by Görtner (1914) in the Urodeles
prior to hatching: this finding is accepted by Needham (1931), and is
not discussed here for lack of additional data on the subject. Lovtrup
(1953a) determined the reduced weight (RW) of Ambystoma mexicanum
during development; the increase in RW from the neurula-tail bud
stage onwards is attributed by this author to lipid utilization, which he
believes to begin at this stage.
In the majority of cases, the data found in the literature clearly confirm that lipids are used as a source of energy during development from
the tail bud stage. It should be pointed out that the complex chemical
techniques in use are of doubtful significance and not fully reliable when
applied to small quantities of biological material.
Observations on changes in phospholipid content are limited in
number and do not provide an adequate basis for discussion (FaureFremiet and Dragoiu, 1923; Parnas and Krasinska, 1921; Plimmer and
Kaya, 1909).
In our own studies on chloroform-methanol (2:1) extracts of embryos
of Bufo vulgaris and Rana esculenta we found that the lipid content of
the fertilized egg of Bufo vulgaris may vary from 430 to 600 y in the
ENRICO URBANI
the TC content decreases steadily and at the end of it is about equal to
53% of the initial value (Fig. 13).
3. Total Lipids
Research by Bialaszewics and Mincovna (1921) on the changes in
chemical composition of amphibian embryos during development has
shown that a reduction in fatty acids cannot be detected in Rana fusca
and Rana temporaria before hatching; a 50% loss is noted in subsequent
stages. Parnas and Krasinska (1921) confirmed these results and did not
detect lipid breakdown before hatching. Barthelemy and Bonnet (1926)
observed that lipid utilization during embryonic development of the
same species is independent of temperature, and consequently of the
duration of the different stages.
We have already drawn attention to the effect of temperature on respiration during development, correlating this with biochemical development, development rate, and morphogenesis.
The data available on this subject are essentially consistent, with the
exception of those submitted by Faure-Fremiet and Dragoiu (1923) who
reported a substantial loss in lipids during early development. This is
odd, for whatever lipid utilization occurs in the initial developmental
stages, it must be very low; the decrease cannot be 25% of the initial
value, as stated by them.
Atlas (1938) claimed that the highest consumption of lipids occurs
from the tail bud stage to operculation of the gills. An increase in fatty
acids, by about 1 1 % , was observed by Görtner (1914) in the Urodeles
prior to hatching: this finding is accepted by Needham (1931), and is
not discussed here for lack of additional data on the subject. Lovtrup
(1953a) determined the reduced weight (RW) of Ambystoma mexicanum
during development; the increase in RW from the neurula-tail bud
stage onwards is attributed by this author to lipid utilization, which he
believes to begin at this stage.
In the majority of cases, the data found in the literature clearly confirm that lipids are used as a source of energy during development from
the tail bud stage. It should be pointed out that the complex chemical
techniques in use are of doubtful significance and not fully reliable when
applied to small quantities of biological material.
Observations on changes in phospholipid content are limited in
number and do not provide an adequate basis for discussion (FaureFremiet and Dragoiu, 1923; Parnas and Krasinska, 1921; Plimmer and
Kaya, 1909).
In our own studies on chloroform-methanol (2:1) extracts of embryos
of Bufo vulgaris and Rana esculenta we found that the lipid content of
the fertilized egg of Bufo vulgaris may vary from 430 to 600 y in the