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Asexual Reproduction

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Maria Jose Carmona – One of the best experts on this subject based on the ideXlab platform.

  • comparative toxicant sensitivity of sexual and Asexual Reproduction in the rotifer brachionus calyciflorus
    Environmental Toxicology and Chemistry, 1995
    Co-Authors: Terry W. Snell, Maria Jose Carmona

    Abstract:

    Cyclically parthenogenetic zooplankters like rotifers are important tools for assessing toxicity in aquatic environments. Sexual Reproduction is an essential component of rotifer life cycles, but current toxicity tests utilize only Asexual Reproduction. The authors compared the effects of four toxicants on Asexual and sexual Reproduction of the rotifer Brachionus calyciflorus. Toxicants had a differential effect on sexual and Asexual Reproduction, with sexual Reproduction consistently the most sensitive. Concentrations of 0.2 {mu}g/ml PCP (sodium pentachlorophenate) had no effect on the Asexual reproductive rate, but significantly reduced sexual Reproduction. Likewise, chlorpyrifos concentrations of 0.3 {mu}g/ml had no significant effect on Asexual Reproduction, but sexual Reproduction was significantly reduced. There was no difference in NOECs, LOECs, and chronic values for Asexual and sexual Reproduction for cadmium and naphthol tests. However, comparison of toxicant effect levels revealed that sexual Reproduction was more strongly reduced at each toxicant concentration. The four toxicants tested inhibited sexual Reproduction 2 to 68 times more than Asexual Reproduction at the lowest observed effect concentrations. Toxicants inhibited sexual Reproduction in its initial step: sexual female production. Because sexual Reproduction is more sensitive, toxicity tests based exclusively on Asexual Reproduction may not be protective of rotifer life cycles.

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Allen J Moore – One of the best experts on this subject based on the ideXlab platform.

  • genetic variation and Asexual Reproduction in the facultatively parthenogenetic cockroach nauphoeta cinerea implications for the evolution of sex
    Journal of Evolutionary Biology, 2001
    Co-Authors: L S Corley, Jill R Blankenship, Allen J Moore

    Abstract:

    Asexual Reproduction could offer up to a two-fold fitness advantage over sexual Reproduction, yet higher organisms usually reproduce sexually. Even in facultatively parthenogenetic species, where both sexual and Asexual repro- duction is sometimes possible, Asexual Reproduction is rare. Thus, the debate over the evolution of sex has focused on ecological and mutation-elimination advantages of sex. An alternative explanation for the predominance of sex is that it is difficult for an organism to accomplish Asexual Reproduction once sexual Reproduction has evolved. Difficulty in returning to Asexuality could reflect developmental or genetic constraints. Here, we investigate the role of genetic factors in limiting Asexual Reproduction in Nauphoeta cinerea ,a n African cockroach with facultative parthenogenesis that nearly always reproduces sexually. We show that when N. cinerea females do reproduce Asexually, offspring are genetically identical to their mothers. However, Asexual Reproduction is limited to a nonrandom subset of the genotypes in the population. Only females that have a high level of heterozygosity are capable of parthenogenetic Reproduction and there is a strong familial influence on the ability to reproduce parthenogenetically. Although the mechanism by which genetic variation facilitates Asexual Reproduction is unknown, we suggest that heterosis may facilitate the switch from producing haploid meiotic eggs to diploid, essentially mitotic, eggs.

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Terry W. Snell – One of the best experts on this subject based on the ideXlab platform.

  • comparative toxicant sensitivity of sexual and Asexual Reproduction in the rotifer brachionus calyciflorus
    Environmental Toxicology and Chemistry, 1995
    Co-Authors: Terry W. Snell, Maria Jose Carmona

    Abstract:

    Cyclically parthenogenetic zooplankters like rotifers are important tools for assessing toxicity in aquatic environments. Sexual Reproduction is an essential component of rotifer life cycles, but current toxicity tests utilize only Asexual Reproduction. The authors compared the effects of four toxicants on Asexual and sexual Reproduction of the rotifer Brachionus calyciflorus. Toxicants had a differential effect on sexual and Asexual Reproduction, with sexual Reproduction consistently the most sensitive. Concentrations of 0.2 {mu}g/ml PCP (sodium pentachlorophenate) had no effect on the Asexual reproductive rate, but significantly reduced sexual Reproduction. Likewise, chlorpyrifos concentrations of 0.3 {mu}g/ml had no significant effect on Asexual Reproduction, but sexual Reproduction was significantly reduced. There was no difference in NOECs, LOECs, and chronic values for Asexual and sexual Reproduction for cadmium and naphthol tests. However, comparison of toxicant effect levels revealed that sexual Reproduction was more strongly reduced at each toxicant concentration. The four toxicants tested inhibited sexual Reproduction 2 to 68 times more than Asexual Reproduction at the lowest observed effect concentrations. Toxicants inhibited sexual Reproduction in its initial step: sexual female production. Because sexual Reproduction is more sensitive, toxicity tests based exclusively on Asexual Reproduction may not be protective of rotifer life cycles.

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