Morphology and Wall Ultrastructure of the Devonian Spore Acinosporites macrospinosus Richardson 1965 and Its Bearing on the Origin of the Megaspore Apical Prominence
Morphology and Wall Ultrastructure of the Devonian Spore Acinosporites macrospinosus Richardson 1965 and Its Bearing on the Origin of the Megaspore Apical Prominence
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DOI：
10.1086/720388
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发表时间：
2022-04
影响因子：
2.3
通讯作者：
C. Wellman
中科院分区：
文献类型：
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作者：
C. Wellman
在苏格兰奥卡迪亚盆地中泥盆世(艾菲尔期)中古红砂岩沉积中发现的保存极为完好的分散孢子组合中，常见的孢子是大棘孢子菌1965。本文报道了这些孢子的光镜、扫描电子显微镜和透射电子显微镜的详细分析。孢子大而多刺，顶端突起与三柱体的记号有关。透射电子显微镜分析表明，墙体由四层组成，均由以白线为中心的片层发育成片层。孢子壁的超微结构与现存的和化石的石松属植物的孢子壁结构最为相似，并提出了与原植物的石松属植物的亲缘关系。在此基础上，提出了孢子壁发育的机制。其亲本石松属植物的性质和生态尚不清楚。然而，基于与较年轻的真正大孢子的相似性，我们认为大棘拟石杉可能是第一批采用异源孢子繁殖策略的石松属植物所产生的早期大孢子。这是关于石松孢子顶端突起的最早报告，这一特征后来成为许多石松大孢子的特征，导致了广泛的凹陷和块状孢子的发育。
The spore Acinosporites macrospinosus Richardson 1965 is common in exceptionally well-preserved dispersed spore assemblages recovered from the Middle Devonian (Eifelian) Middle Old Red Sandstone deposits in the Orcadian Basin, Scotland. This article reports on a detailed LM, SEM, and TEM analysis of these spores. The spores are large and spinose with an apical prominence associated with the trilete mark. TEM analysis reveals that the wall consists of four layers that were all formed by white-line-centered lamellae that develop into laminae. The spore wall ultrastructure is most similar to that of extant and fossil lycopsids, and a lycopsid affinity is proposed for the parent plant. On the basis of this interpretation, a mechanism for spore wall development is presented. The nature and ecology of the parent lycopsid plant are unclear. However, on the basis of similarities to younger bona fide megaspores, it is suggested that A. macrospinosus was probably an incipient megaspore produced by one of the first groups of lycopsids to have experimented with a heterosporous reproductive strategy. This is the earliest report of an apical prominence on a lycopsid spore, a feature that went on to characterize many later lycopsid megaspores, leading to the development of extensive gulas and massas.