Valve morphogenesis in Diploneis smithii (Bacillariophyta)

Abstract

Diploneis species have perhaps the most complex valve structure among pennate diatoms. The development of this structure was studied in Diploneis smithii and begins with the formation of a primary band, which then develops secondary arms at both poles and the center, as in the classic Chiappino-Volcani model of raphid diatom ontogeny. Spine-like projections grow out from the primary band and secondary arms to establish the transapical ribs (virgae) of the mature valve and themselves develop spines, which are spaced first oppositely and then alternately and fuse with each other to delimit the stria pores. Subsequently, new pattern and structures develop both externally (formation of bifurcating projections that fuse to delimit the outer, sieve-like layer of the valve) and internally (growth and fusion of flanges from the first-formed ribs to create the longitudinal canals and deposition of a hymenate strip over the internal face of each stria). Comparisons are made with morphogenesis in other diatoms. Diploneis smithii ontogeny suggests how very slight developmental changes might have created the very variable external morphology of Diploneis species. It also indicates that the longitudinal canals of Diploneis and Fallacia have different origins, since the porous external wall is not formed as a unilaterally attached flap in Diploneis and the canal is internal to the first-formed rib-stria system in Diploneis, but external to it in Fallacia.

Auxospore wall structure and postsexual valve morphology in Rhabdonema minutum Kützing

“…This hypothesis clearly links them to the valves (not perizonial bands) of the diatom group that has rimoportulae. However, the ontogeny of the raphid valve in Diploneis smithii (Idei et al 2018) demonstrates first a single elongated structure which is then folded back on itself to expand towards the valve midsection, similar to what is observed in the primary longitudinal perizonial band in our diatom, not rimoportulae. More consideration of the possible reason(s) behind such a similarity is clearly warranted, following Round et al (1990, p. 42), who, further down on the same page cited above, noted this: "Clearly, however, there are other possible interpretations of the raphe-sternum and how it might have arisen.…”

An intimate view into the silica deposition vesicles of diatoms

“…Access to the developing biosilica structures inside the intracellular SDVs was achieved by two methods. The first method involved cell lysis using strong acids or detergent, which also removed all or most organic material, and allowed for imaging of the immature biosilica by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and AFM [35][36][37][38]. As a result, images of the entire volumes of developing biosilica structure, primarily from valves, were obtained.…”

An intimate view into the silica deposition vesicles of diatoms

“…Access to the developing biosilica structures inside the intracellular SDVs was achieved by two methods. The rst method involved cell lysis using strong acids or detergent, which also removed all or most organic material, and allowed for imaging of the immature biosilica by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and AFM (35)(36)(37)(38). As a result, images of the entire volumes of developing biosilica structure, primarily from valves, were obtained.…”