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The analysis of water samples collected during the MD218 CROTALE expedition (February-March, 2019), and the 4th Indian Southern Ocean Expedition (SOE) (January-February, 2010) (re-visited samples) resulted in the occurrence of a new coccolithophore species belonging to the genus Alisphaera, and is named Alisphaera crostae sp. nov. This new species appears monomorphic and shows distinctive morphological differences in terms of its coccolith size, flange structure, and nodules, compared to other known Alisphaera species. In this study, morphological differences between A. crostae and other Alisphaera species are illustrated and compared. We suggest that the genus Alisphaera may have a higher diversity and may possess a wider distribution than previously evidenced, which requires more careful observation [ABSTRACT FROM AUTHOR]

The families Calciosoleniaceae, Syracosphaeraceae and Rhabdosphaeraceae belong to the order Syracosphaerales and constitute a significant component of extant coccolithophore species, sharing similar ultrastructural bauplans. The literature on Calciosoleniaceae is reviewed and combined light- and scanning electron microscope studies of four extant species including Calciosolenia subtropicus sp. nov. described herein, reveal the unique interpretative V/R structure of the Calciosoleniaceae. Calciosolenia subtropicus sp. nov. is primarily distinguished from previously well documented extant species, Calciosolenia murrayi, Calciosolenia brasiliensis and Calciosolenia corsellii, by the consistent presence of prominent clockwise imbricated wedge shaped R-elements at the inner margin and in distal view of both ordinary and apical scapholiths, distinctly tapering in size towards the major axis of the scapholiths, as observed under the scanning electron microscope. Prompted by the contrasting birefringence displayed by the rim, central area, apical and ordinary coccoliths under crossed-polarized illumination in earlier publications, the Energy Dispersive Spectrometry of Calciosolenia subtropicus sp. nov. reveals the presence of (a) calcite + high silica in the ordinary coccoliths showing dark appearance and (b) high calcite + negligible silica in the apical coccoliths showing bright appearance; besides the c-axis orientation of calcite, the different elemental composition of coccoliths seems to control birefringence. Molecular genetic studies are necessary to provide insight on the relationship between the Calciosoleniaceae and other coccolithophore families including reasons for its successful invasion in contrasting ecological regimes. [ABSTRACT FROM AUTHOR]

Here we propose a new species of genus Trigonium namely Trigonium curvatus from the surface sediments of coastal Antarctica. Acomparative study was done between Trigonium curvatus and Trigonium arcticum to find out the differentialmorphological characters. Trigonium curvatus is differentiated from the earlier described Trigonium arcticum on the basis of valvemorphology such as the presence of clustered rimoportulae at centre of the valve, concave sides of the valve, smaller areolae, constricted structure of areolae and fewer pores surrounding areolae. On the contrary, in Trigonium arcticum rimoportulae are absent or inconspicuous, sides of the frustules are convex/straight and it has larger areolaewhich appear to be flattenedwith more pores encircling it. Both species show basic resemblance to genus Trigonium such as triangular valve structure, centrally radiating areolae and valve apices comprised of pseudocelli. Hence, it is proposed that Trigonium curvatus is different from the originally described Trigonium arcticum and is a new species of genus Trigonium. [ABSTRACT FROM AUTHOR]

Sea surface and sub-surface (0-110m) water samples were collected from the Southern Indian Ocean between 39°S and 65°S (along ~48°E and 57.3°E) during the austral summer of 2010 which yielded Petasaria heterolepis. Out of the two known P. heterolepis forms, the scales with brim are observed with a size range (short and long axes length) of 1.68×1.80μm-2.17×2.27μm. The occurrence of minute pores on the scales is documented except on the brim which remains poreless. The elemental analysis of the scales revealed silica (Si) as the major constituent with the occurrence of a small peak of calcium (Ca). In spite of the presence of Ca in the scales, P. heterolepis showed lack of birefringence in the light microscopic observation. P. heterolepis is neither recognizable in the fossil record nor in the bottom sediments and shows affinity towards the extant Prymnesium neolepis recorded from off the Japan coast and Southern Indian Ocean. The present study highlights the occurrence of P. heterolepis in the open ocean regions of the Southern Indian Ocean stressing its ability to grow under diverse oceanographic conditions. The phylogenetic-molecular aspects need to be carried out which could reveal better understanding of rare Si and Ca accumulation among such haptophyte algae. [ABSTRACT FROM AUTHOR]