Department of Biology, University of Maryland, College Park, Maryland.
J Exp Zool B Mol Dev Evol. 2013 Dec;320(8):471-88. doi: 10.1002/jez.b.22523. Epub 2013 Aug 2.
Animals capable of multiple forms of post-embryonic development, such as growth, regeneration, and asexual reproduction, must make choices about which processes to invest in. What strategies guide post-embryonic resource allocation investments? We investigated this question in the annelid Pristina leidyi, which can grow continuously, regenerates well, and reproduces asexually by fission. We found that in this species growth is concentrated in three zones: a subterminal posterior zone (forming new segments), a mid-body zone (forming fission zones), and a previously undescribed subterminal anterior zone at the base of the prostomium (which we suggest continually builds the prostomium through a "conveyor-belt" like process). Body-wide counts of proliferating cells are greater under high food than low food conditions but proliferation patterns themselves are independent of feeding level. Proliferation patterns are strongly affected by amputation, however, with proliferation rapidly shutting-down throughout the body, except at the wound site, following injury. Relative investment to fission and regeneration is highly context-dependent, being sensitive to the position of the cut and the stage of fission. Outcomes range from fission acceleration and regeneration stalling (high fission:regeneration investment) to resorption of fission zones and progression of regeneration (low fission:regeneration investment). Our findings reveal strong interactions between growth, regeneration, and fission and demonstrate a particularly important effect of injury on resource allocation patterns. Patterns of resource investment in P. leidyi show similarities to those described in two other groups that evolved fission independently (naidine annelids and catenulid flatworms), suggesting that similar developmental and physiological contexts may drive convergent evolution of resource allocation strategies.
能够进行多种形式的胚胎后发育的动物，如生长、再生和无性繁殖，必须在投资于哪些过程中做出选择。哪些策略指导胚胎后资源分配投资？我们在环节动物 Pristina leidyi 中研究了这个问题，它可以持续生长，再生良好，并且可以通过分裂进行无性繁殖。我们发现，在这个物种中，生长集中在三个区域：一个末端后区（形成新的节段）、一个中体区（形成分裂区）和一个以前未描述的末端前区，位于 Prostomium 的基部（我们建议 Prostomium 通过类似于“输送带”的过程不断构建）。在高食物条件下，全身增殖细胞的计数高于低食物条件，但增殖模式本身与喂养水平无关。然而，增殖模式受到截肢的强烈影响，随着损伤，增殖迅速在全身停止，除了在伤口部位。相对于分裂和再生的投资高度依赖于上下文，对切口的位置和分裂的阶段敏感。结果从加速分裂和再生停滞（高分裂：再生投资）到分裂区的吸收和再生的进展（低分裂：再生投资）不等。我们的发现揭示了生长、再生和分裂之间的强烈相互作用，并证明了损伤对资源分配模式的特别重要影响。P. leidyi 中的资源投资模式与另外两个独立进化出分裂的群体（naidine 环节动物和 catenulid 扁形动物）中描述的模式相似，这表明类似的发育和生理背景可能导致资源分配策略的趋同进化。
