Active floating with buoyancy of pseudopodia versus passive floating by hydrodynamic drag force: A case study of the flat-shaped spumellarian radiolarian Dictyocoryne
Active floating with buoyancy of pseudopodia versus passive floating by hydrodynamic drag force: A case study of the flat-shaped spumellarian radiolarian Dictyocoryne
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DOI：
10.2517/2018pr023
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发表时间：
2019-10-01
影响因子：
0.9
通讯作者：
Kishimoto, Naoko
中科院分区：
文献类型：
--
作者：
Ichinohe, Ryo;Shiino, Yuta;Kishimoto, Naoko
有人建议，伪足的放射虫发挥作用，在控制浮力的浮动行为。为了了解伪足在营养能力方面的功能，我们对扁平形放射虫Dictyocoryne进行了培养实验。利用玻璃池、体视显微镜和X-Y-Z载物台从侧面观察了Dictyocoryne的行为。在静态条件下，固着于玻璃细胞底部的网伞子从平皿表面的两侧伸出伪足。随后，这些个体略微上升，其长度等于延长的伪足的长度，但仍然附着在底部。这些结果表明，Dictyocoryne缺乏通过伪足的出现获得浮力而浮出水面的能力。在对流条件下，只有当伪足完全伸展时，Dictyocoryne才向下游方向移动。当对流向上移动时，个体随着流动移动到表面之下。此外，对流改变了一个长而厚的伪足的方向，称为轴鞭毛，与流动平行。因此，轴鞭毛总是朝向下游侧，是盘面在轴鞭毛侧上翻。由于扁形的泡状藻细胞内有共生藻类，其独特的光合作用能力导致藻类光合作用的稳定效率。
It has been suggested that the pseudopodia of radiolarians play a role in controlling buoyancy for floating behaviour. To understand the function of pseudopodia in terms of planktonic capability, we performed culture experiments on the flat-shaped radiolarian Dictyocoryne. A glass cell, a stereomicroscope and an X-Y-Z stage were used to observe the behaviour of Dictyocoryne from a lateral view. Under static conditions, Dictyocoryne grounded on the bottom of the glass cell extended pseudopodia from both sides of the flat disc surface. Subsequently, these individuals rose slightly by a length equal to that of the extended pseudopodia but remained attached to the bottom. These results suggest that Dictyocoryne lacks the ability to surface by obtaining buoyancy through the emergence of pseudopodia. Under conditions of convection flow, Dictyocoryne moved in the downstream direction only when pseudopodia were completely extended. When the convection flow moved upward, the individuals moved with the flow to just under the surface. In addition, convection flow changed the direction of a long, thick pseudopodium, called the axoflagellum, to be parallel with the flow. Consequently, the axoflagellum was always oriented towards the downstream side, being the disc face in the axollagellum side on the upturn. Given that the flat-shaped spumellarians has c symbiotic algae inside their cells, their unique planktonic capability leads to the stable efficiency of the algal photosynthesis.