64
ENRICO URBANI
mg
30
25
20
15
10
5
50
100
150 200
250
300
350 400 hours
FIG. 1. Changes in fresh, dry and reduced weight during embryonic development.
B : blastula; T B : tail bud; L: larva (Urbani, 1957).
1-82 to 1-40 mg. The sudden drop in fresh weight observed at about 80
hours from the beginning of development, and specifically at neuralization, is due to the collapse of the archenteron walls and outflow of liquid
from the blastopore (Brown, 1941), and represents a critical stage of
the development mechanisms which is common to both anura and
urodeles.
Proof that metabolic activity gradually increases during embryonic
development is given by the respiratory rate which, from the tail bud
stage on, compares quite well with the growth curve (Atlas, 1938;
Brächet, 1944, 1960a; Lovtrup, 1953a, b ; Needham, 1931, 1942;
Stefanelli, 1938; Urbani and Urbani Mistruzzi, 1946; ten Cate, 1946;
Wills, 1936). Actually, oxygen consumption provides us with a clue
both to utilization of the reserves and to metabolic activity of the multiplying and differentiating cells (Barth, 1946; Hultin, 1953; Levy, 1952).
The work of Stefanelli (1938) further revealed a relationship between
respiratory activity and the surface area of the embryo, whose development reflects on the growing need for oxygen.
For lack of space, we must omit the results of research on oxygen
uptake at different temperatures during development (see L0vtrup,
1953b; Needham, 1942). It is the opinion often Cate (1952, 1953) that
oxygen consumption reflects two basic activities of the embryo,
maintenance and development: the amount of energy required to
attain a given stage does not vary, but when development is slowed
down because of low temperature, there is an increase in the proportion
of energy required for maintenance.
In this connection, it should be recalled that respiratory activity during
-
Reduced weight + {y)
Wet weight ® (mg)
Dry weight ° (mg)
B
,
JB
,
Bufb vulgar is
L,
ir
+
1
1
J
'.
P^+
-
1
1500
1250
1000
750
500
250
ENRICO URBANI
mg
30
25
20
15
10
5
50
100
150 200
250
300
350 400 hours
FIG. 1. Changes in fresh, dry and reduced weight during embryonic development.
B : blastula; T B : tail bud; L: larva (Urbani, 1957).
1-82 to 1-40 mg. The sudden drop in fresh weight observed at about 80
hours from the beginning of development, and specifically at neuralization, is due to the collapse of the archenteron walls and outflow of liquid
from the blastopore (Brown, 1941), and represents a critical stage of
the development mechanisms which is common to both anura and
urodeles.
Proof that metabolic activity gradually increases during embryonic
development is given by the respiratory rate which, from the tail bud
stage on, compares quite well with the growth curve (Atlas, 1938;
Brächet, 1944, 1960a; Lovtrup, 1953a, b ; Needham, 1931, 1942;
Stefanelli, 1938; Urbani and Urbani Mistruzzi, 1946; ten Cate, 1946;
Wills, 1936). Actually, oxygen consumption provides us with a clue
both to utilization of the reserves and to metabolic activity of the multiplying and differentiating cells (Barth, 1946; Hultin, 1953; Levy, 1952).
The work of Stefanelli (1938) further revealed a relationship between
respiratory activity and the surface area of the embryo, whose development reflects on the growing need for oxygen.
For lack of space, we must omit the results of research on oxygen
uptake at different temperatures during development (see L0vtrup,
1953b; Needham, 1942). It is the opinion often Cate (1952, 1953) that
oxygen consumption reflects two basic activities of the embryo,
maintenance and development: the amount of energy required to
attain a given stage does not vary, but when development is slowed
down because of low temperature, there is an increase in the proportion
of energy required for maintenance.
In this connection, it should be recalled that respiratory activity during
-
Reduced weight + {y)
Wet weight ® (mg)
Dry weight ° (mg)
B
,
JB
,
Bufb vulgar is
L,
ir
+
1
1
J
'.
P^+
-
1
1500
1250
1000
750
500
250