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Valve Face (valve + face)
Selected AbstractsINTER- AND INTRASPECIFIC VARIATION OF THE PSEUDO-NITZSCHIA DELICATISSIMA COMPLEX (BACILLARIOPHYCEAE) ILLUSTRATED BY RRNA PROBES, MORPHOLOGICAL DATA AND PHYLOGENETIC ANALYSES,JOURNAL OF PHYCOLOGY, Issue 2 2006Nina Lundholm A study of 25 cultures tentatively identified as Pseudo-nitzschia delicatissima (Cleve) Heiden, and originating from geographically widely distributed locations, showed both morphological and genetic variation among strains. Use of rRNA-targeted DNA probes on 17 different strains showed large variation in the hybridization patterns. Detailed morphological studies placed the isolates into three groups. The sample on which the neotype of P. delicatissima is based was also examined, and used to establish the morphological identity of P. delicatissima. Phylogenetic analyses of 16 strains, based on sequences of internal transcriber spacer 1 (ITS1), 5.8S and ITS2 of the nuclear-encoded rDNA, supported the morphological observations and the hybridization studies, and revealed large genetic variation among strains. A combination of the morphological and molecular findings resulted in the description of two new species, P. decipiens sp. nov. and P. dolorosa sp. nov. P. dolorosa has a mixture of one or two rows of poroids in the striae whereas P. delicatissima always has two rows. In addition, P. dolorosa has wider valves and a lower density of poroids. P. decipiens differs from P. delicatissima by a higher density of striae on the valve face as well as a higher density of poroids on the girdle bands. Among the strains referred to P. delicatissima, an epitype was selected. Large genetic variation was found among the P. delicatissima strains and a subdivision into two major clades represent cryptic species. [source] Pelagodictyon Clarke, a newly recorded nanodiatom genus for ChinaJOURNAL OF SYSTEMATICS EVOLUTION, Issue 2 2009Yang LI Abstract Marine nanoplanktonic diatoms have been frequently either underestimated or overlooked in phyto-plankton investigations due to their small size (2,20 ,m), which allows most of them to pass through a regular phytoplankton net of 70-,m pore size. For nanoplanktonic diatom classification, water samples (each 2000 mL) were collected from several representative sea areas of Chinese coast from May 2002 to May 2006. Pelagodictyon Clarke was identified as a newly recorded nanodiatom genus for China under transmission electron microscope (TEM). This genus is characterized by the delicate structure of the valve face. The striae are seen to be formed by ribs with cross-ribs (frets) and the intervening spaces are occupied by polygonal cribra situated much close to the exterior face of the valve. Just one species was found, i.e., P. tenue Clarke. Detailed description of the taxonomic characteristics with TEM photographs of this species and its ecological habitat and distribution are given in this paper. Morphological characteristics comparisons among several resembling genera were discussed. [source] New species of the diatom genus Fryxelliella (Bacillariophyta), Fryxelliella pacifica sp. nov., from the tropical Mexican PacificPHYCOLOGICAL RESEARCH, Issue 3 2008David U. Hernández-Becerril SUMMARY During phytoplankton monitoring of coasts off Salina Cruz, Oaxaca, in the tropical Mexican Pacific, a new species, Fryxelliella pacifica sp. nov., was found and is described in this paper. The species is solitary, with cells of medium size, discoid with three relatively large ocelli on the valve face, located close to the margins (3,5 areolae from the margins) and placed symmetrically. Significantly, it possesses the morphological characters that distinguish the genus Fryxelliella from related genera: the presence of the ,circumferential marginal tube' (siphon marginalis), the external subcircular or subtriangular apertures at the valve margins, and the ,juxtaposed rectangular plates' in the valve mantle. The species that appears to be the most closely related is Fryxelliella floridana Prasad, an extant species and the type of the genus. However Fryxelliella pacifica differs from it (i) the size and shape of the cell; (ii) the size, location and structure of the ocelli (which additionally are not elevated); (iii) the shape and density of the subcircular to subtriangular marginal apertures; (iv) the external morphology of the rimoportulae (short process, two concentric tubes with the outer tube tip as a crown); and (v) it is marine rather than brackish. Externally the rimoportulae have a rather complex structure of two concentric tubes: the exterior tube has a tip divided like a crown. In spite of the fact this species was found in plankton samples, it is considered to inhabit sandy sediments (epipsammic) or as tychoplanktonic. [source] Thalassiocyclus pankensis sp. nov., a new diatom from the Panke Swamp, northern Japan (Bacillariophyta)PHYCOLOGICAL RESEARCH, Issue 2 2008Hiroyuki Tanaka SUMMARY Thalassiocyclus pankensis sp. nov. is described from Panke Swamp (Panke-numa) located in Horonobe Town, Hokkaido, northern Japan. The species is characterized by a strong transversely undulate central area of the valve face with one to three fultoportulae on the elevated part and one fultoportula on the depressed part. The external valve face has costate radial interfascicles and very wide fascicles on the marginal area. Thickened openings of mantle fultoportulae are located at the end of interfascicles with roofed board spines. The cingulum consists of five bands. The new species is compared to the only other species belonging to genus Thalassiocyclus, T. lucens (Hustedt) Håkansson & Mahood. Thalassiocyclus pankensis is the second species in the genus Thalassiocyclus and also the first report of a Thalassiocyclus species in Japan. [source] | ||||||||||