A new tiny species of Minidiscus, M. vodyanitskiyi, was found in the water column collected from the central part of the Sea of Azov. Its morphology was examined by scanning electron microscopy, described and illustrated. This centric diatom is characterized by: 1) small valve diameter of less than 10 µm; 2) one central fultoportula surrounded by two satellite pores located opposite each other; 3) one rimoportula located one areola away from the central fultoportula which internally appears similar to a slit surrounded by a plan elliptic rim oriented radially or slightly tangentially; 4) 4–6 (10) marginal fultoportulae that are equally spaced on a border between the valve surface and valve mantle; 5) three satellite pores that surround every marginal fultoportula, where a central satellite pore is directed towards the valve margin; 6) hexa- or heptagonal pattern of valve areolae; and 7) a hyaline conical flange connects the cingulum with the valve. The new species is compared with similar ones. A new term ‘polygonal areolae pattern’ is proposed instead of ‘eccentric pattern’. The term emphasizes that the pattern comprises concentric polygons formed by tangential areolae rows. Its qualitative characteristic, ‘polygonality’, has been described which allows more precise differentiation of the geometry of the valve pattern and describing areolae size variability.
We construct the 3D models of phytoplankton. In presented article we solve the problem about deformation of the created models: How to deform the model so that its shape should conform to the shape of the natural microorganism? We use the Free Form Deformation (FFD) for the solving of this problem. In the first case, when the dimensions of the microorganism are given, the distances between control points of the FFD are equated to these dimensions. In the second case, when a scientist has the image of the microorganism, he should deform the model, displacing the control points, so that the image edge and the model's outer border has coincided. The control points location is used in the studying morphological changes of microorganisms and describing their shapes.
Morphology of the horseshoe spot (HHS) with the cavity has been investigated in details in several species of Planothidium Round et Bukht. that carry out an attached mode of life. On the base of photomicrographs obtained with light and scanning electron microscopy, the model of the HSS longitudinal section was designed and light rays tracing through it has been implemented. It has been shown that HHS is an optical system that may diffuse or focus light, depending on the refractive index of the matter inside the cavity. For the first time HHS functions are revealed in a living diatom organism: diffusion of light over the chloroplast side turned to the substrate. The vertical part of inner convexity generates on the attached valve the heating arc that provides a diatom cell with additional heating energy. Thus, a new mechanism of light utilization was detected in the diatom species widely distributed in benthic ecosystems. A new term, lensoid, and terminology for its morphological description are proposed.
The diatoms interact with the environment through the siliceous frustule. The total area of frustule perforations determines the ability of diatom to exchange nutrients, gases and other matters. The aim of the present study was to estimate the area of perforations on the valve surface of a centric diatom. In the paper we describe a method for the estimation of the area of perforations on a diatom valve using SEM images. The method is tested on valves of centric diatom Minidiscus vodyanitskiyi Lyakh et Bedoshvili. The results show that the total area of cribral pores is less than 5% of the total valve area. This value is consistent with the relative perforation of land plants leaves, which is less than 3%. We hypothesize that such small valve area occupied by perforations is usual for many other centric diatom species. To verify this hypothesis additional researches are necessary.
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