AMPHIBIAN AND INVERTEBRATE DEVELOPMENT 71
where morphogenesis and differentiation processes are most active
(Fig. 4).
The presence of an animal-vegetal dipeptidase gradient in the gastrula
of amphibians has been proved by Barth and Sze (1953) and by Gregg
and Lovtrup (1950).
Enzymatic activity shows a marked decline in the young unfed larva,
due to the fact that synthesis and growth processes are slowed down in
Bufo vulgaris
§ Acid proteinase
FIG. 4. Enzyme activity, oxygen uptake and RNA content in the cephalic, central and
caudal portions at the tail bud stage of Bufo vulgaris (Urbani, 1957).
individuals that have used up their yolk reserves and have not started
feeding.
The activity of these and other enzymes, which we will examine later
on, is definite biochemical proof of the humoral and metabolic changes
which Cotronei (1922, 1930, 1932) demonstrated to be instrumental in
the transition from the embryonic stage to the larval stage. Changes in
the activity of AG dipeptidase follow the same pattern in Rana esculenta,
Bufo viridis and Rana dalmatina, but the percentage increase in activity
from the tail bud stage to complete utilization of the yolk is different
for each species, indicating that in order to satisfy the metabolic requirements during embryonic development each Anura has a different
enzyme demand (De Cesaris Coromaldi, 1960; Urbani et ah, 1957).
One of the possible causes of this could be sought in the ecological
where morphogenesis and differentiation processes are most active
(Fig. 4).
The presence of an animal-vegetal dipeptidase gradient in the gastrula
of amphibians has been proved by Barth and Sze (1953) and by Gregg
and Lovtrup (1950).
Enzymatic activity shows a marked decline in the young unfed larva,
due to the fact that synthesis and growth processes are slowed down in
Bufo vulgaris
§ Acid proteinase
FIG. 4. Enzyme activity, oxygen uptake and RNA content in the cephalic, central and
caudal portions at the tail bud stage of Bufo vulgaris (Urbani, 1957).
individuals that have used up their yolk reserves and have not started
feeding.
The activity of these and other enzymes, which we will examine later
on, is definite biochemical proof of the humoral and metabolic changes
which Cotronei (1922, 1930, 1932) demonstrated to be instrumental in
the transition from the embryonic stage to the larval stage. Changes in
the activity of AG dipeptidase follow the same pattern in Rana esculenta,
Bufo viridis and Rana dalmatina, but the percentage increase in activity
from the tail bud stage to complete utilization of the yolk is different
for each species, indicating that in order to satisfy the metabolic requirements during embryonic development each Anura has a different
enzyme demand (De Cesaris Coromaldi, 1960; Urbani et ah, 1957).
One of the possible causes of this could be sought in the ecological