Kutschera Ulrich, Weisblat David A
Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720-3200, USA.
Theory Biosci. 2015 Dec;134(3-4):93-104. doi: 10.1007/s12064-015-0216-4. Epub 2015 Nov 23.
Model organisms are important tools in modern biology and have been used elucidate mechanism underlying processes, such as development, heredity, neuronal signaling, and phototropism, to name but a few. In this context, the use of model organisms is predicated on uncovering evolutionarily conserved features of biological processes in the expectation that the findings will be applicable to organisms that are either inaccessible or intractable for direct experimentation. For the most part, particular species have been adapted as model organisms because they can be easily reared and manipulated in the laboratory. In contrast, a major goal in the field of evolutionary developmental biology (Evo-Devo) is to identify and elucidate the differences in developmental processes among species associated with the dramatic range of body plans among organisms, and how these differences have emerged over time in various branches of phylogeny. At first glance then, it would appear that the concept of model organisms for Evo-Devo is oxymoronic. In fact, however, laboratory-compatible, experimentally tractable species are of great use for Evo-Devo, subject to the condition that the ensemble of models investigated should reflect the range of taxonomic diversity, and for this purpose glossiphoniid leeches are useful. Four decades ago (1975), leeches of the species-rich genus Helobdella (Lophotrochozoa; Annelida; Clitellata; Hirudinida; Glossiphoniidae) were collected in Stow Lake, Golden Gate Park, San Francisco, CA (USA). These and other Helobdella species may be taken as Evo-Devo models of leeches, clitellate annelids, and the super-phylum Lophotrochozoa. Here we depict/discuss the biology/taxonomy of these Evo-Devo systems, and the challenges of identifying species within Helobdella. In addition, we document that H. austinensis has been established as a new model organism that can easily be cultivated in the laboratory. Finally, we provide an updated scheme illustrating the unique germ line/soma-differentiation during early development and speculate on the mechanisms of sympatric speciation in this group of aquatic annelids.
模式生物是现代生物学中的重要工具，已被用于阐明诸如发育、遗传、神经信号传导和向光性等过程背后的机制，这里仅列举几个例子。在此背景下，模式生物的使用基于揭示生物过程中进化上保守的特征，期望这些发现将适用于那些难以直接进行实验研究或难以处理的生物体。在很大程度上，特定物种被选作模式生物是因为它们可以在实验室中轻松饲养和操作。相比之下，进化发育生物学（Evo-Devo）领域的一个主要目标是识别和阐明与生物体之间身体结构的巨大差异相关的物种发育过程中的差异，以及这些差异如何在系统发育的各个分支中随时间出现。乍一看，Evo-Devo的模式生物概念似乎是矛盾的。然而，事实上，对于Evo-Devo来说，实验室兼容、易于实验操作的物种非常有用，但前提是所研究的模型集合应反映分类学多样性的范围，为此，舌蛭科水蛭是有用的。四十年前（1975年），在美国加利福尼亚州旧金山金门公园的斯托湖收集了物种丰富的扁蛭属（Lophotrochozoa；环节动物门；寡毛纲；蛭纲；舌蛭科）水蛭。这些以及其他扁蛭属物种可被视为水蛭、寡毛纲环节动物和冠轮动物总门的Evo-Devo模型。在这里，我们描述/讨论这些Evo-Devo系统的生物学/分类学，以及在扁蛭属中识别物种的挑战。此外，我们记录了奥斯汀扁蛭已被确立为一种可以在实验室中轻松培养的新的模式生物。最后，我们提供了一个更新的方案，说明早期发育过程中独特的生殖系/体细胞分化，并推测这组水生环节动物中同域物种形成的机制。
