The Institute of Marine Ecology-Kristineberg, University of Gothenburg, Kristineberg, Fiskebäckskil, Sweden.
J Exp Zool B Mol Dev Evol. 2011 Jun 15;316(4):276-83. doi: 10.1002/jez.b.21399. Epub 2011 Jan 11.
In organisms that propagate by agametic cloning, the parental body is the reproductive unit and fitness increases with clonal size, so that colonial metazoans, despite lack of experimental data, have been considered potentially immortal. Using asexual propagation rate as a measure of somatic performance, and telomerase activity and relative telomere length as molecular markers of senescence, old (7-12 years) asexual strains of a colonial ascidian, Diplosoma listerianum, were compared with their recent sexually produced progeny. We report for the first time evidence for long-term molecular senescence in asexual lineages of a metazoan, and that only passage between sexual generations provides total rejuvenation permitting indefinite propagation and growth. Thus, this colonial ascidian has not fully escaped ageing. The possibility of somatic replicative senescence also potentially helps to explain why metazoans, with the capacity for asexual propagation through agametic cloning, commonly undergo cycles of sexual reproduction in the wild.
在通过无性克隆进行繁殖的生物中，亲本体是繁殖单位，并且随着克隆大小的增加适应性也会增加，因此尽管缺乏实验数据，多细胞后生动物被认为具有潜在的永生性。我们使用无性繁殖速度作为体细胞表现的衡量标准，使用端粒酶活性和相对端粒长度作为衰老的分子标记，比较了 7-12 岁的无性殖民地海鞘 Diplosoma listerianum 与其最近的有性繁殖后代。我们首次报告了在后生动物的无性谱系中存在长期分子衰老的证据，而且只有在有性世代之间的传递才能提供完全的年轻化，从而允许无限期的繁殖和生长。因此，这种殖民地海鞘并没有完全逃脱衰老。体细胞复制衰老的可能性也有助于解释为什么具有通过无性克隆进行无性繁殖能力的后生动物通常在野外经历有性繁殖的循环。
