C Y T O G E N E T I C M E C H A N I S M S I N S I L K W O R M S
221
1953) and emphasizing its significance for the selection and genetics of
the silkworm (Jucci, 1941a,b, 1951), there are also communications
concerning the applicability of thermoactivation to other races and
species of the silkworm.
Chowdhury (1953, 1963) in India demonstrated the use of thermal
activation on the Indian polyvoltine Nistari and Mysore local races
of the silkworm, which greatly differ from the mono- and bivoltine ones.
He succeeded also (1964) in inducing thermal parthenogenesis in Mugaworm, a wild Saturniid silkworm of Assam, Antheraea assama Westwood.
In France, Hook (quoted by Rostand, 1950), induced parthenogenesis
in the giant wild silkworm of India Antheraea mylitta by a modified
method of heat activation. J. Rostand himself succeeded in inducing
parthenogenesis in unfertilized eggs of Saturnia pyri by the heat activation method. In all the experiments of Lepidoptera eggs, effective temperatures are very close to those used in B. mori. In large-scale experiments performed on Antheraea pernyi (1948), and especially on B.
mandarina eggs very similar temperature relationships, values of temperature characteristics, and effective thermal doses were obtained.
More than that, not only heat parthenogenesis, but heat elimination
of the embryonic diapause can also be achieved in B. mori and other
species of moths, such as Lymantria dispar, Orgyia antiqua, and Malacosoma neustria (Astaurov, 1943). As far as some detailed inquiry shows,
the general regularities of heat elimination of diapause seem to have all
the peculiar features of heat activation of unfertilized eggs.
It is important that there exists a far-reaching similarity between heat
parthenogenesis in the silkworm and many other cases of a stimulating
effect which a sublethal heating exerts on such blocked biological systems
as unfertilized eggs and diapausing embryos of animals, dormant spores,
seeds, and buds of plants (Astaurov, 1940, 1943, 1956a, 1957, 1958a).
The above evidence would hardly be comprehensible if we discard
the suggestion that general features of all these processes of heat activation are associated with some general properties of the universal life
substrate, the living protein, as manifested in its heat denaturation.
Trying to understand the intimate nature of heat activation, we must
bear in mind that heat death and heat denaturation of proteins also
undergo similar changes as a function of temperature and these changes
are characterized by very high temperature coefficients (Q 10 ).
Additional indirect evidence to this effect is provided by the fact that
an insignificant increase of the thermal doses causing activation (parthenogenesis or nondiapause development) results in heat death. This may
be attributed to a further irreversible phase of the denaturation process
and subsequently to coagulation of protoplasmic proteins.
There are hardly many examples where the two extreme poles, death
221
1953) and emphasizing its significance for the selection and genetics of
the silkworm (Jucci, 1941a,b, 1951), there are also communications
concerning the applicability of thermoactivation to other races and
species of the silkworm.
Chowdhury (1953, 1963) in India demonstrated the use of thermal
activation on the Indian polyvoltine Nistari and Mysore local races
of the silkworm, which greatly differ from the mono- and bivoltine ones.
He succeeded also (1964) in inducing thermal parthenogenesis in Mugaworm, a wild Saturniid silkworm of Assam, Antheraea assama Westwood.
In France, Hook (quoted by Rostand, 1950), induced parthenogenesis
in the giant wild silkworm of India Antheraea mylitta by a modified
method of heat activation. J. Rostand himself succeeded in inducing
parthenogenesis in unfertilized eggs of Saturnia pyri by the heat activation method. In all the experiments of Lepidoptera eggs, effective temperatures are very close to those used in B. mori. In large-scale experiments performed on Antheraea pernyi (1948), and especially on B.
mandarina eggs very similar temperature relationships, values of temperature characteristics, and effective thermal doses were obtained.
More than that, not only heat parthenogenesis, but heat elimination
of the embryonic diapause can also be achieved in B. mori and other
species of moths, such as Lymantria dispar, Orgyia antiqua, and Malacosoma neustria (Astaurov, 1943). As far as some detailed inquiry shows,
the general regularities of heat elimination of diapause seem to have all
the peculiar features of heat activation of unfertilized eggs.
It is important that there exists a far-reaching similarity between heat
parthenogenesis in the silkworm and many other cases of a stimulating
effect which a sublethal heating exerts on such blocked biological systems
as unfertilized eggs and diapausing embryos of animals, dormant spores,
seeds, and buds of plants (Astaurov, 1940, 1943, 1956a, 1957, 1958a).
The above evidence would hardly be comprehensible if we discard
the suggestion that general features of all these processes of heat activation are associated with some general properties of the universal life
substrate, the living protein, as manifested in its heat denaturation.
Trying to understand the intimate nature of heat activation, we must
bear in mind that heat death and heat denaturation of proteins also
undergo similar changes as a function of temperature and these changes
are characterized by very high temperature coefficients (Q 10 ).
Additional indirect evidence to this effect is provided by the fact that
an insignificant increase of the thermal doses causing activation (parthenogenesis or nondiapause development) results in heat death. This may
be attributed to a further irreversible phase of the denaturation process
and subsequently to coagulation of protoplasmic proteins.
There are hardly many examples where the two extreme poles, death