Fine-structure of the vegetative frustule, perizonium and initial valve ofAchnanthes yaquinensis(Bacillariophyta)

Abstract

This study clarifies the fine structure of the vegetative and initial valves of Achnanthes yaquinensis and briefly compares them to other Achnanthes species. It also elucidates the structure of the perizonium, based on auxospore development in short-term cultures. The araphid valve has marginal ridges and terminal spines that allow connecting valves to form a chain. The terminal spines develop from the rapheless sternum. The complete cingulum consists of 3-5 split bands with two rows of areolae. These features can be used to discriminate species within the genus. Sexual reproduction is isogamous with two mother cells producing two auxospores, which are enclosed in mucilage. The perizonium develops on one side of an auxospore only, comprising one large central longitudinal band and four closed bands. There are no transverse perizonial bands. The raphid valve of the initial cell forms first, underneath the longitudinal perizonium, followed by the araphid valve, which is not covered by any perizonial bands. The araphid valve of the initial cells lacks a marginal spine, and the rapheless sternum lies more centrally than in the vegetative cell. The relationship of the genus Achnanthes to other monoraphid diatoms is discussed briefly.

Pseudostriatella(Bacillariophyta): a description of a new araphid diatom genus based on observations of frustule and auxospore structure and 18S rDNA phylogeny

“…We believe, however, that some of the LP bands were hidden by folding of the auxospore, which seems likely because all of the longitudinal perizonia reported so far in pennate diatoms are structurally symmetrical (e.g. von Stosch 1962Stosch , 1982Mann 1982b;Toyoda et al 2005), even in Amphora (Nagumo 2003). There would therefore be five longitudinal bands in P. oceanica (Fig.…”

“…The TP bands combine to form a cigar-shaped perizonium with a narrow ventral suture, beneath which there is often a set of LP bands, again differentiated into a central primary band and two short flanking series of secondary bands (e.g. Mann 1982b;Mann & Stickle 1993;Nagumo 2003;Sato et al 2004;Toyoda et al 2005). The function of the perizonium appears to be to support and constrain anisometric expansion of the auxospore (Mann 1994).…”

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

“…Williams & Round (1986: 324) (Sato et al 2008a), and in the biraphid diatoms, S. marvanii, D. papula, C. linearis and F. tenera (this study). In monoraphid diatoms Achnanthes crenulata Grunow in Cleve & Grunow (1880: 20) (Toyoda et al 2005) and Achnanthes yaquinensis McIntire & Reimer (1974: 174) (Toyoda et al 2006), however, scales were not present. Also, the transverse perizonial bands were not present in the two monoraphid species.…”

“…The ultrastructure of a perizonium in pennate diatoms has been reported in many species covering araphid (Sato et al 2004, Sato et al 2008a and raphid diatoms (Mann 1982, Toyoda et al 2005, Poulíčková & Mann 2006, Toyoda et al 2006, Kaczmarska et al 2007, Poulíčková et al 2007, Mann & Poulíčková 2009, Mann et al 2011. It also has been suggested that the ultrastructure of the perizonium has phylogenetic significance at higher taxonomic levels (Medlin & Kaczmarska 2004).…”

Capsules of the diatom Achnanthidium minutissimum arise from fibrillar precursors and foster attachment of bacteria

“…While diatom capsules have mostly been characterised biochemically, electron microscopical analyses was so far focussed on the morphology of diatom frustules (Toyoda et al, 2005(Toyoda et al, , 2006Morin, Coste & Hamilton, 2008) and the development of its morphological variations as environmental markers (Potapova & Hamilton, 2007;Hlúbiková, Ector & Hoffmann, 2011;Cantonati et al, 2014). In the present study, scanning electron microscopy (SEM), as well as energy-dispersive X-ray (EDX) spectroscopy were employed to analyse the microstructure and development stages of Achnanthidium minutissimum capsules in order to further develop this species as a model system for diatom-bacteria interactions, and to elucidate one aspect of the complex interactions of diatoms and other micro-organisms.…”