With fertilization, the paternal and maternal contributions to the zygote are not equal. The oocyte and spermatozoon are equipped with complementary arsenals of cellular structures and molecules necessary for the creation of a developmentally competent embryo. We show that the nucleolus is exclusively of maternal origin. The maternal nucleolus is not necessary for oocyte maturation; however, it...

Xenopus eggs are laid arrested at second metaphase of meiosis lacking a functional centrosome. Upon fertilization, the sperm provides the active centrosome that is required for cleavage to occur. The injection of purified centrosomes mimics fertilization and leads to tadpole formation (parthenogenesis). In this work we show that the parthenogenetic activity of centrosomes is inactivated by urea...

Ann. Entomol. Soc. Am. 76: 400-402 (1983) ABSTRACT No males were found among 559 specimens of Pityophthorus puberulus (LeConte) from several localities. No sperm was found in the spermatheca of 10 females taken from recently established galleries containing eggs and young larvae. This is the third record of thelytoky in a scolytid. The known distribution and environment of parthenogenetic popul...

Details of the life cycle of Aneugmenus merida Smith (Hymenoptera: Tenthredinidae) reared under laboratory conditions are reported. Females may produce parthenogenetic or non-parthenogenetic eggs. After eclosion, males of A. merida go through five larval instars, pre-pupa, pupa and imago. The complete life cycle lasts approximately 44 days. Larvae feed on bracken [Pteridium caudatum (L.) and Pt...

Parthenogenetically activated BCF1 and fertilized BALB/c embryos were aggregated to form chimaeras. The fate of the parthenogenetic component was followed in the conceptus during the second half of gestation. The results indicate an early strong selection against parthenogenetic cells in the extra-embryonal part, which is presumably complete by term, and a weaker selective process in the embryo...

In certain extraembryonic tissues of normal female mouse conceptuses, X-chromosome-dosage compensation is achieved by preferential inactivation of the paternally derived X. Diploid parthenogenones have two maternally derived X chromosomes, hence this mechanism cannot operate. To examine whether this contributes to the inviability of parthenogenones, XO and XX parthenogenetic eggs were construct...

Stimuli associated with copulatory behavior are often needed to maximize reproductive output in internally fertilized sexual taxa. Although non-pseudogamous parthenogenetic females have no need for sperm, parthenogens descended from sexual ancestors may still require copulatory stimuli to reach their full reproductive potential. Retention of physiological dependence on copulation in parthenogen...

Background: Studies of preimplantation stage embryos by classic cytogenetic techniques have limitations, starting with the need for good metaphase stage when only one third of all analyzed embryos may show good quality metaphases. The incidence of chromosome anomalies in embryos produced by in vitro procedures is generally higher than that of embryos formed in vivo. Pressure specifically affect...