An insect-like mushroom body in a crustacean brain.
An insect-like mushroom body in a crustacean brain.
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DOI：
10.7554/elife.29889
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发表时间：
2017-09-26
期刊：
影响因子：
7.7
通讯作者：
Strausfeld NJ
中科院分区：
文献类型：
--
作者：
Wolff GH;Thoen HH;Marshall J;Sayre ME;Strausfeld NJ
蘑菇体是昆虫标志性的学习和记忆中心。尽管被称为半椭球体的甲壳类动物中心在感觉整合中起作用，被认为在进化上与蘑菇体趋同，但以前没有描述过具有严格形态学标准定义的蘑菇体的甲壳类动物。在这里，使用关键标识符来表征神经排列，我们展示了口足类甲壳类动物（螳螂虾）的昆虫状蘑菇体。螳螂虾在捕食、空间记忆和视觉识别方面表现出与昆虫相当的复杂行为，比任何其他甲壳类动物都要多。然而，基于神经解剖学的分支学表明昆虫和口足甲壳类动物在系统发育上的接近性与六足类动物与简单甲壳类动物雷足类动物密切相关的基因组证据相冲突。我们讨论这里描述的相应解剖表型是否反映了panrustaceae共同祖先的大脑形态或趋同进化的非凡例子。节肢动物有400多万种，是地球上最大、最多样化的动物群体，包括甲壳类动物、昆虫和蜘蛛。它们的特点是身体分节，外骨骼坚硬，四肢关节。所有节肢动物都有一个共同的祖先，生活在5.5亿多年前。这种古老的节肢动物究竟是如何产生出今天存在的无数物种的尚不清楚，但我们知道，在某个时刻，节肢动物家族树分裂成分支，其中一个分支后来成为甲壳类动物。然后甲壳类分支再次分裂，产生了一系列的后代，这些后代将成为昆虫。但是，尽管昆虫是从甲壳类动物进化而来，昆虫的大脑却拥有甲壳类动物所没有的结构。这些结构被称为蘑菇体，有助于形成和储存记忆。因此，它们在甲壳类动物中的缺失一直是一个谜。Wolff等人现在通过展示一种现代甲壳类动物——螳螂虾——实际上确实拥有蘑菇体来解开这个谜团。Wolff等人通过观察螳螂虾以及一些密切相关的物种大脑内的细胞和通路，表明只有这些虾拥有真正的蘑菇体。然而，螳螂虾的一些近亲拥有这些结构的一些特征。这表明，蘑菇体在进化上是一种古老的结构，在昆虫和甲壳类动物的共同祖先中出现，然后在大多数甲壳类动物中消失或彻底改变。那么为什么会发生这种情况呢？螳螂虾是顶级捕食者，具有出色的视力，可以在相当远的距离内捕猎，这要求它们评估和记忆环境的复杂特征。这些认知需求可能与其他甲壳类动物不同，这可能导致螳螂虾保留了它们的蘑菇体。对螳螂虾的大脑和行为的进一步研究可能会为蘑菇体如何构建复杂感官世界的记忆提供见解。
Mushroom bodies are the iconic learning and memory centers of insects. No previously described crustacean possesses a mushroom body as defined by strict morphological criteria although crustacean centers called hemiellipsoid bodies, which serve functions in sensory integration, have been viewed as evolutionarily convergent with mushroom bodies. Here, using key identifiers to characterize neural arrangements, we demonstrate insect-like mushroom bodies in stomatopod crustaceans (mantis shrimps). More than any other crustacean taxon, mantis shrimps display sophisticated behaviors relating to predation, spatial memory, and visual recognition comparable to those of insects. However, neuroanatomy-based cladistics suggesting close phylogenetic proximity of insects and stomatopod crustaceans conflicts with genomic evidence showing hexapods closely related to simple crustaceans called remipedes. We discuss whether corresponding anatomical phenotypes described here reflect the cerebral morphology of a common ancestor of Pancrustacea or an extraordinary example of convergent evolution. With more than four million species, arthropods are the largest and most diverse group of animals on the planet and include, for example, crustaceans, insects and spiders. They are defined by their segmented bodies, hard outer skeletons and jointed limbs. All arthropods share a common ancestor that lived more than 550 million years ago. Exactly how this ancestral arthropod gave rise to the myriad species that exist today is unclear but we know that at some point the arthropod family tree split into branches, one of which went on to become the crustaceans. The crustacean branch then split again, giving rise to a line of descendants that would become the insects. But although insects evolved from crustaceans, the brains of insects possess structures that those of crustaceans do not. Known as mushroom bodies, these structures help to form and store memories. Their absence in crustaceans has therefore been an enduring mystery. Wolff et al. now add a piece to the puzzle by showing that one group of modern-day crustaceans, the mantis shrimps, does in fact possess mushroom bodies. By visualizing cells and pathways within the brains of mantis shrimps, and also a number of closely related species, Wolff et al. show that only these shrimps possess true mushroom bodies. However, some of the mantis shrimp’s close relatives possess a few attributes of these structures. This suggests that mushroom bodies are evolutionarily ancient structures that arose in a common ancestor of insects and crustaceans, before being lost or radically modified in most of the crustaceans. So why did this happen? Mantis shrimps are top predators with excellent vision that hunt over considerable distances, requiring them to evaluate and memorize complex features of their environment. These cognitive demands, which might not be shared by other crustaceans, may have led to the mantis shrimps retaining their mushroom bodies. Further research into the brains and behavior of the mantis shrimp may provide insights into how mushroom bodies construct memories of a complex sensory world.