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At least 199 records · Page 11Linked to original sources
PubMed2006

Automictic and apomictic parthenogenesis in psocids (Insecta: Psocoptera).

Karyotypes and meiosis patterns in three obligatory thelytokous Psocoptera species have been studied for the first time. Females of Aaroniella badonneli (Danks) display 9 chiasmatic bivalents in oocyte metaphase I (2n = 18), hence meiosis is of the automictic type. Females of Ectopsocus meridionalis Ribaga and Valenzuela sp. display 3n = 27, and 27 univalent chromosomes are present in oocyte metaphase I. Thus, meiosis in these species is of the apomictic type.

Animals↗
PubMedDate not supplied

[Phenomenon of obligate parthenogenesis in rotifer (Rotifera, Bdelloida)].

A comparative analysis of biological and morphological organization of obligate parthenogenous bdelloids and heterogonic monogononts clarifies the specificity of bdelloids' environmental adaptation and variability. It is shown that phenotypic polymorphism of bdelloids differs from that of monogononts. The heterogonic Monogononta are characterized by tremendous phenotypic diversity in body structure adapted to different biotopes in continental waters. This diversity is reflected also in structure of corona and mastax used as major criteria for definition of high range taxa (classes, orders). The polymorphism of bdelloids manifests itself in variability of tiny morphological structures connected with living in restricted volumes of water, mainly in terrestrial biotopes. Being isolated from other Rotifera at the first stages of evolution, bdelloids have been specialized for living under extremely unstable terrestrial conditions that led to the development of anhydrobiosis and loss of amphimixis. Variability of bdelloids is not connected with characters of high taxonomic ranks and has principally different nature in comparison with monogononts. Tempo of specialization seems to be slower in obligate parthenogenous rotifers than in heterogonic ones.

Adaptation, Physiological↗
PubMed1975

[Variability of the eggs of the local silkworm (Bombyx mori 1.) according to the capacity for thermal parthenogenesis and heat resistance. Report 3. Causes and characteristics of the variability of egg batches according to heat resistance].

The variability of eggs from different batches was studied by the resistance against the sublethal temperature (48 degrees) at the early stages of embryogenesis. The variability of heat resistance at three developmental stages markedly differing by the organization of the embryo was shown to be, to a great extent, conditioned hereditarily and depend as well on the environmental conditions. On the basis of positive correlation between the heat resistance of eggs from the same parents but at different developmental stages, a conclusion is drawn that the variability of heat resistance of the egg cellular proteins is one of the main causes of the variability of egg batches by heat resistance.

Animals↗
PubMedDate not supplied

[Genomic imprinting and problem of parthenogenesis in mammals].

Genomic imprinting belongs by its nature to problems of epigenetics, which studies hereditary changes in gene expression not related to defective sequences of DNA nucleotides. Epigenetic mechanisms of control, including genomic imprinting, are involved in many processes of normal and pathological development of humans and animals. Disturbances of genomic imprinting may lead to various consequences, such as formation of developmental anomalies and syndromes in humans, appearance of the large offspring syndrome and increased mortality upon cloning of mammals, and death of parthenogenetic embryos soon after implantation and beginning of organogenesis. The death of diploid parthenogenetic or androgenetic mammalian embryos is determined by the absence of expression of the genes of imprinted loci of the maternal or paternal genome, which leads to significant defects in development of tissues and organs. A review is provided of the studies aimed at search of possible normalization of misbalanced gene activity and modulation of genomic imprinting effects during parthenogenetic development in mammals.

Animals↗