Wyniki wyszukiwania - BazTech

1

Discovery of plywood structure in Sphenothallus from Gurovo Formation (Mississippian), Central Russia

Vinn Olev, Mironenko Aleksandr A.

Annales Societatis Geologorum Poloniae

|

2021

|

Vol. 91, No. 1

67--74

EN

Sphenothallus specimens are reported for the first time from the Mississippian of Central Russia. All Sphenothallus specimens have a phosphatic composition and a characteristic laminar structure, which is best observable in the thickened lateral parts of a tube. Most of the lamellae in the tube wall are straight, but some have a wavy morphology and a few are so wrinkled that they form hollow “ribs”. The wrinkled lamellae presumably had an originally higher organic content than the straight lamellae. There are borings on the surfaces of some lamel-lae that are similar in morphology to the bioerosional traces in various hard, biomineral substrates. Lamellae in the inner parts of the tube wall are composed of fibres. The fibres are parallel to the surface of the tube wall and in successive laminae they differ in orientation by irregularly varying angles. It is possible that the plywood micro-structure in Sphenothallus was originally organic and was later phosphatized during fossilization. An alternative, but less likely explanation is that the plywood structure was originally mineralized and therefore is comparable to the phosphatic lamello-fibrillar structures of vertebrates.

2

Cocconeis subantarctica sp. nov. from Kerguelen Archipelago (Austral Ocean) and comparison with Cocconeis stauroneiformis (W.Smith) Okuno

Riaux-Gobin C., Witkowski A.

Oceanological and Hydrobiological Studies

|

2017

|

Vol. 46, No. 3

350--362

EN

Cocconeis subantarctica sp. nov., a small monoraphid marine diatom, previously described as C. scutellum cf. var. parva Grunow, is reported from the Kerguelen Archipelago. Based on the careful re-examination of the material using SEM (scanning electron microscopy), both valves and the cingulum were described, which enabled a better classification of this small Subantarctic taxon. The shape of the frustule is widely rounded to subdiscoid, with uniseriate and radiate striae on both valves. The SV (sternum valve) areolae have rota-like hymenate pore occlusions, with larger marginal areolae separated by a hyaline rim. The RV (raphe valve) areolae are more complex than those of the SV, with several reniform concentric hymenate occlusions. This taxon has no real stauros, only one virga, which is larger on one side of each valve. The species is not a member of the Cocconeis scutellum ‘complex’, but is closely related to C. stauroneiformis despite several morphological differences.

3

Ulva flexuosa subsp. pilifera (Chlorophyta, Ulvophyceae) from the Wielkopolska region (West Poland) : a new observation on the ultrastructure of vegetative cells [commun.]

Messyasz B., Czerwik-Marcinkowska J., Uher B., Rybak A., Szendzina L., Pikosz M.

Oceanological and Hydrobiological Studies

|

2013

|

Vol. 42, No. 2

209-215

EN

Ulva flexuosa subsp. pilifera previously known from northern Poland, from the channel near Szczecin and ponds near Łódź, has recently been found in the Malta Reservoir in the Wielkopolska (West Poland) region. Specimens collected in the Wielkopolska region were examined in detail, also under a transmission electron microscope (TEM). The morphometric analysis of Ulva thalli (both young and mature specimens) was performed in order to study the differences in the ultrastructure of vegetative cells. Rectangular cells in young thalli measured from 32.21 - 55.81 μm to 20.24 – 35.12 μm, and they formed clear longitudinal rows, while cells in the mature specimens ranged from 25.09 – 47.66 μm to 18.90 – 31.56 μm. This study indicates that vegetative cells of the mature thalli show tendency towards distortions of both the longitudinal and transverse cells arrangement. This distortion is determined by the development of possible carbonate calcium crystals on the thalli surface. The ultrastructural analysis (TEM) confirmed that the structure and placement of thylakoids is genus/species specific.