Auxosporulation, morphology of vegetative cells and perizonium of Fallacia tenera (Hust.) D.G. Mann (Bacillariophyceae)

Abstract

Specimens of Fallacia tenera were collected from the surface sediment at in a river estuary in Japan. Auxosporulation occurred in a rough culture. Morphological structures of vegetative cells and auxospores were observed in detail. The vegetative cells have one H-shaped chloroplast. The striae were interrupted by two depressed lateral sterna internally and partly covered by a finely porous conopeum on the external surface. The lateral sterna and porous conopea formed two more or less curved longitudinal canals connecting with the exterior via opening pores on both sides of a terminal fissure. This combination of characteristics is unique to the genus Fallacia. The cingulum was composed of three bands, such as an open valvocupula and two comparatively thin pleurae. The two pleurae could be distinguished by the shape of their ligulae. The second band had a triangular ligula, whereas the ligula of the third band is arc-shaped. The auxosporulation was type IA1a in Geitler's classification. Two paired gametangia formed two anisogametes in each of them. Two auxospores formed in the thecae of the gametangia after a trans physiological anisogamy. The perizonium of the auxospore consisted of a set of transverse bands and five longitudinal bands. The primary transverse band was about twice wider than the secondary ones. The circular incunabular scales were present on the two terminals of the auxospore and on the surface of the primary transverse band. The primary longitudinal band had an acute terminal and was flanked by secondary longitudinal bands. Each side had two secondary longitudinal bands. All longitudinal bands were immediately beneath the transverse bands. Morphological comparison between Fallacia and Pseudofallaica, and the taxonomic position of F. tenera is also discussed.

Valve morphogenesis in Diploneis smithii (Bacillariophyta)

“…, Li et al. ). It would not be surprising, therefore, if Diploneis and Fallacia were found to be phylogenetically close, and the limited molecular data available are consistent with a close relationship between Diploneis and a clade containing Fallacia , Pinnularia , and Caloneis although the nodal support for this is low (e.g., Theriot et al.…”

“…Both of these genera possess longitudinal canals in the valve face and in both the canals are covered externally by a porous layer and internally by a wholly or largely plain wall. Furthermore, both genera commonly occur together in marine and freshwater epipelon; many species of Diploneis and most of Fallacia have an elliptical or linear-elliptical outline; species of both genera have an unusual cytological characteristic (though it is not unique to them), in that the chloroplasts are often invaginated by channels of cytoplasm; and the type of sexual reproduction is similar in some species of both genera , Li et al 2014). It would not be surprising, therefore, if Diploneis and Fallacia were found to be phylogenetically close, and the limited molecular data available are consistent with a close relationship between Diploneis and a clade containing Fallacia, Pinnularia, and Caloneis although the nodal support for this is low (e.g., Theriot et al 2015).…”

Morphology, molecular phylogeny and systematics of the diatom genus Fallacia (Sellaphoraceae), with descriptions of three new species1

“…They transferred four Fallacia species from the F. tenera group to this genus. However, the transfer of F. tenera to Pseudofallacia may be inappropriate, since the depressions in F. tenera are nonporous (Li et al 2014b). Rossia also has lateral longitudinal canals and a conopeum like Fallacia.…”

“…tenera to Pseudofallacia may be inappropriate, since the depressions in F. tenera are nonporous (Li et al. 2014b). Rossia also has lateral longitudinal canals and a conopeum like Fallacia .…”

Fallacia californica sp. nov. (Bacillariophyta), a new freshwater diatom species from streams in California, USA

“…The current understanding about the morphological variation of F. tenera is unclear (Li et al 2014), since Schoeman & Archibald (1979) lumped freshwater Navicula tenera (syn. N. uniseriata Hust.)…”