SPERMATOGENESIS AND AUXOSPORE STRUCTURE IN THE MULTIPOLAR CENTRIC DIATOM HYDROSERA
SPERMATOGENESIS AND AUXOSPORE STRUCTURE IN THE MULTIPOLAR CENTRIC DIATOM HYDROSERA
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DOI：
10.1111/jpy.12261
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发表时间：
2015-02-01
影响因子：
2.9
通讯作者：
Mann, David G.
中科院分区：
文献类型：
--
作者：
Idei, Masahiko;Sato, Shinya;Mann, David G.
研究了淡水中心硅藻Hydrosera triquetra的精子发生和孢子发育。精子发生是不寻常的，缺乏脱泡细胞分裂的精原细胞内。相反，一系列的有丝分裂发生在一个未分裂的细胞内，产生一个多核的原生质体与周围的核，然后进行减数分裂。32或64个精子从原质团中出芽，留下一个含有所有叶绿体的大的残留细胞。类似的发展显然发生在侧链藻属、凹盘藻属和Guinardia属中，它们的亲缘关系如此之远，以致原质团精子发生的独立进化似乎是可能的。假定受精后，水螅卵细胞向远端扩展，形成三角形的末端部分。然而，与其他三角形硅藻（Lithodesmium，Triceratium）不同的是，三辐射对称的发展并不受perizonium的“规范”方法的控制，这种方法限制了膨胀到辅助孢子壁的小终端区域。相反，孢子壁缺乏周层，只有鳞片和一层密集的薄的、明显缠绕的二氧化硅条带。没有这样的结构已被报道从任何其他中心硅藻，最接近的类似物，而不是一些针硅藻（菱形藻和羽纹藻）的incuncubalstrips。这些二氧化硅结构是否通过正常方法（二氧化硅沉积囊泡内的细胞内沉积）形成尚不清楚。除了比营养细胞更圆外，原始细胞的结构也是异常的，因为它具有该物种特有的“三联”孔的极化分布。
Spermatogenesis and auxospore development were studied in the freshwater centric diatom Hydrosera triquetra. Spermatogenesis was unusual, lacking depauperating cell divisions within the spermatogonangium. Instead, a series of mitoses occurred within an undivided cell to produce a multinucleate plasmodium with peripheral nuclei, which then underwent meiosis. 32 or 64 sperm budded off from the plasmodium leaving a large residual cell containing all the chloroplasts. Similar development apparently occurs in Pleurosira, Aulacodiscus, and Guinardia, these being so distantly related that independent evolution of plasmodial spermatogenesis seems likely. After presumed fertilization, the Hydrosera egg cell expanded distally to form a triangular end part. However, unlike in other triangular diatoms (Lithodesmium, Triceratium), the development of triradiate symmetry was not controlled by the "canonical" method of a perizonium that constrains expansion to small terminal areas of the auxospore wall. Instead, the auxospore wall lacked a perizonium and possessed only scales and a dense mat of thin, apparently entangled strips of imperforate silica. No such structures have been reported from any other centric diatoms, the closest analogs being instead the incunabular strips of some raphid diatoms (Nitzschia and Pinnularia). Whether these silica structures are formed by the normal method (intracellular deposition within a silica deposition vesicle) is unknown. As well as being more rounded than vegetative cells, the initial cell is aberrant in its structure, since it has a less polarized distribution of the "triptych" pores characteristic of the species.