Instituto de Fomento Pesquero (IFOP), Enrique Abello 0552, Casilla 101, Punta Arenas, Chile; Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Vigo, Subida a Radio Faro 50, 36390, Vigo, Spain.
Instituto Español de Oceanografía (IEO), Centro Oceanográfico de Vigo, Subida a Radio Faro 50, 36390, Vigo, Spain.
Harmful Algae. 2017 Sep;68:67-81. doi: 10.1016/j.hal.2017.07.008. Epub 2017 Aug 1.
Asexual and sexual life cycle events were studied in cultures of the toxic marine dinoflagellate Protoceratium reticulatum. Asexual division by desmoschisis was characterized morphologically and changes in DNA content were analyzed by flow cytometry. The results indicated that haploid cells with a C DNA content occurred only during the light period whereas a shift from a C to a 2C DNA content (indicative of S phase) took place only during darkness. The sexual life cycle was documented by examining the mating type as well as the morphology of the sexual stages and nuclei. Gamete fusion resulted in a planozygote with two longitudinal flagella, but longitudinally biflagellated cells arising from planozygote division were also observed, so one of the daughter cells retained two longitudinal flagella while the other daughter cell lacked them. Presumed planozygotes (identified by their longitudinally biflagellated form) followed two life-cycle routes: division and encystment (resting cyst formation). Both the division of longitudinally biflagellated cells and resting cyst formation are morphologically described herein. Resting cyst formation through sexual reproduction was observed in 6.1% of crosses and followed a complex heterothallic pattern. Clonal strains underwent sexuality (homothallism for planozygote formation and division) but without the production of resting cysts. Ornamental processes of resting cysts formed from the cyst wall under an outer balloon-shaped membrane and were fully developed in <1h. Obligatory dormancy period was of ∼4 months. Excystment resulted in a large, rounded, pigmented, longitudinally biflagellated but motionless, thecate germling that divided by desmoschisis. Like the planozygote, the first division of the germling yielded one longitudinally biflagellated daughter cell and another without longitudinal flagella. The longitudinal biflagellation state of both sexual stages and of the first division products of these cells is discussed.
研究了有毒海洋甲藻原甲藻(Porcratium reticulatum)培养物中的无性和有性生命周期事件。通过桥粒分裂进行无性分裂在形态上进行了描述，并通过流式细胞术分析了 DNA 含量的变化。结果表明，具有 C DNA 含量的单倍体细胞仅在光照期出现，而从 C 到 2C DNA 含量的转变（指示 S 期）仅在黑暗期发生。通过检查交配型以及性阶段和核的形态来记录有性生殖周期。配子融合导致具有两个纵向鞭毛的平面合子，但也观察到从平面合子分裂产生的纵向双鞭毛细胞，因此一个子细胞保留两个纵向鞭毛，而另一个子细胞则没有。假定的平面合子（通过其纵向双鞭毛形式识别）遵循两种生命周期途径：分裂和包囊（休眠囊形成）。本文描述了纵向双鞭毛细胞的分裂和休眠囊的形成。通过有性生殖形成休眠囊的过程在 6.1%的杂交中观察到，并遵循复杂的异宗配合模式。克隆株经历了有性生殖（同源配合形成平面合子和分裂），但没有形成休眠囊。休眠囊从囊壁下的外部气球状膜形成的装饰过程在<1 小时内完全发育。强制性休眠期约为 4 个月。出囊导致一个大的、圆形的、有色素的、纵向双鞭毛但不动的、有壳的原叶体，通过桥粒分裂进行分裂。像平面合子一样，原叶体的第一次分裂产生一个纵向双鞭毛的子细胞和另一个没有纵向鞭毛的子细胞。讨论了两个性阶段和这些细胞的第一次分裂产物的纵向双鞭毛状态。
