92
ENRICO URBANI
water, and the latter in the soil. Our research was chiefly centred on
enzymatic activities and on the amounts of proteins, carbohydrates
and lipids utilized for energy and growth. Concerning the metamorphosis of insects and its possible analogies with the metamorphosis of the
amphibians, we shall confine ourselves to the results of our own studies
on Musca domestica L. The literature provides such a wealth of data on
the biochemistry of embryonic and larval development as well as on the
metamorphosis of insects, that we are unable to devote adequate space
to the subject, and therefore refer the reader to the recent paper by
Russo-Caia (1960a) for a general review of the problem.
A. Artemia salina Leach
The phyllopod crustacean Artemia salina Leach is a collective species
which includes several biotypes with amphigonic or parthenogenetic
reproduction, also characterized by polyploidy (Artom, 1906; Barigozzi,
1942; Geitler, 1953; Petrunkewitsch, 1902).
The eggs are spheroidal and protected by a thick shell: actually the
term 'egg' is not correct in this case. In fact these embryos stop developing at the gastrula stage and enter a more or less protracted period of
latent life (Fautrez-Firlefyn, 1951, 1957). The encysted embryos can
remain in these anabiotic conditions for several years, living through
the most adverse environmental conditions. Oxygen uptake is not
detectable during latent life, but can be observed 2-3 hours after the
encysted embryos are placed in water (Muramatsu, 1960; Urbani, 1946).
It is interesting to note that many enzymes like AG dipeptidases, acid
proteinase, phosphatases and amylases are preserved in the encysted
embryo, and are capable of hydrolysing their respective substrates
from the beginning of hydration. (Urbani and De Cesaris Coromaldi,
1953; Urbani and Urbani Mistruzzi, 1953; Urbani et al., 1952; Urbani
etai. y 1953.)
In sea water, at 25° C , the eggs swell; after about 50 hours the shell
breaks down and the nauplius swims out after about 90 hours. The
swimming nauplius still has some yolk material, and therefore is still in
'closed box' conditions, which continue for a short time, then the metanauplius begins to feed: in our experiments this occurred at about 120
hours.
Development is of course retarded at lower temperatures. For instance, the hatching rate and the enzyme activity of the diploid amphigonic embryo found in California are different from those of the tetraploid form found in the Great Salt Lake in Utah (De Cesaris Coromaldi
and Urbani, 1959, 1960). Changes in the activities of dipeptidases, acid
proteinases, lipases, and amylases in the Calif ornian Artemia salina
from the beginning of hydration to the metanauplius stage are shown in
ENRICO URBANI
water, and the latter in the soil. Our research was chiefly centred on
enzymatic activities and on the amounts of proteins, carbohydrates
and lipids utilized for energy and growth. Concerning the metamorphosis of insects and its possible analogies with the metamorphosis of the
amphibians, we shall confine ourselves to the results of our own studies
on Musca domestica L. The literature provides such a wealth of data on
the biochemistry of embryonic and larval development as well as on the
metamorphosis of insects, that we are unable to devote adequate space
to the subject, and therefore refer the reader to the recent paper by
Russo-Caia (1960a) for a general review of the problem.
A. Artemia salina Leach
The phyllopod crustacean Artemia salina Leach is a collective species
which includes several biotypes with amphigonic or parthenogenetic
reproduction, also characterized by polyploidy (Artom, 1906; Barigozzi,
1942; Geitler, 1953; Petrunkewitsch, 1902).
The eggs are spheroidal and protected by a thick shell: actually the
term 'egg' is not correct in this case. In fact these embryos stop developing at the gastrula stage and enter a more or less protracted period of
latent life (Fautrez-Firlefyn, 1951, 1957). The encysted embryos can
remain in these anabiotic conditions for several years, living through
the most adverse environmental conditions. Oxygen uptake is not
detectable during latent life, but can be observed 2-3 hours after the
encysted embryos are placed in water (Muramatsu, 1960; Urbani, 1946).
It is interesting to note that many enzymes like AG dipeptidases, acid
proteinase, phosphatases and amylases are preserved in the encysted
embryo, and are capable of hydrolysing their respective substrates
from the beginning of hydration. (Urbani and De Cesaris Coromaldi,
1953; Urbani and Urbani Mistruzzi, 1953; Urbani et al., 1952; Urbani
etai. y 1953.)
In sea water, at 25° C , the eggs swell; after about 50 hours the shell
breaks down and the nauplius swims out after about 90 hours. The
swimming nauplius still has some yolk material, and therefore is still in
'closed box' conditions, which continue for a short time, then the metanauplius begins to feed: in our experiments this occurred at about 120
hours.
Development is of course retarded at lower temperatures. For instance, the hatching rate and the enzyme activity of the diploid amphigonic embryo found in California are different from those of the tetraploid form found in the Great Salt Lake in Utah (De Cesaris Coromaldi
and Urbani, 1959, 1960). Changes in the activities of dipeptidases, acid
proteinases, lipases, and amylases in the Calif ornian Artemia salina
from the beginning of hydration to the metanauplius stage are shown in