AMPHIBIAN AND INVERTEBRATE DEVELOPMENT 87
100
75
50
25
B 50
TB
150
200
250
L
350 hours
FIG. 13. Total nitrogen (TN), total carbohydrates (TC) and total lipids (TL) in the
embryonic development of Bufo vulgaris. Initial content of compounds: 100; B : blastula;
T B : tail bud; L: larva (Urbani, 1957).
The results were very precise and showed that both compounds are
released in small quantities during segmentation, the amounts increasing gradually thereafter, though in different proportions (Fig. 14). In
Y
3.0
2.5
2.0
1.5
1.0
0.5
B 50
TB 150 200 250 hours
L
I
ΠΪ IV V
yy%*,
FIG. 14. Elimination of urea and ammonia during embryonic development, larval
growth and metamorphosis of Bufo vulgaris. Notations and symbols as in Fig. 3 (Urbani
and De Cesaris Coromaldi, 1957).
the initial developmental stages the amount of urea eliminated exceed
that of ammonia; from the tail bud to the tail fin stage (i.e. at hatching),
the situation is reversed; in the swimming embryo the amount of ammonia eliminated greatly exceeds that of urea and the larva is almost
_
s
N, N#
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1
1
1
Bufo vulgaris
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TC
TL
1
L_
Bufo vulgaris
Embryonic development
3 U Ammonia
» I Urea
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Metamorphosis
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