Effect of temperature on size and shape of silica scales in Synura petersenii and Mallomonas tonsurata (Stramenopiles)

Abstract

Synurophytes are planktonic protists whose cells are covered with silica scales. According to the temperature-size rule, protists decrease in size with increasing temperature. Here, we showed that inorganic silica scales responded to increasing temperature in the same way as the cells did. Two species, Mallomonas tonsurata and Synura petersenii, were cultivated at five temperature levels (5, 10, 15, 20 and 25°C) and the methods of geometric morphometrics were applied for scale size and shape data analyses. We observed that the shape of the scales was significantly affected by the cultivation temperature. The overall shape change from rounded, circular scales to oval or more elongated scales seemed to be a general feature in synurophytes and may be considered a consequence of rising temperature. Moreover, the difference in shape remained significant even if the effect of size (allometric effect) was separated. Finally, we compared the level of the scales' morphological variation among all temperature treatments. The results indicated that the cultivation temperature of 25°C negatively affected cellular processes involved in scale biogenesis. The use of the scale shape data has potential in palaeoecological research.

Morphological delineation and distribution patterns of four newly described species within theSynura peterseniispecies complex (Chrysophyceae, Stramenopiles)

“…This species has been subjected to various ecophysiological experiments (e.g. Saxby-Rouen et al, 1997;Kim et al, 2008;Pichrtová & Němcová, 2011).…”

Shape dynamics of silica scales (Chrysophyceae, Stramenopiles) associated with pH.

“…After the silica scales mature, silicify and are exocytosed to the cell surface their shape is fixed and invariable (Leadbeater & barker 1995), consequently the allometric effect is weaker (Pichrtová & Němcová 2011; this study). Size accounted for 5.3% and 12.2% of total scale shape variation in S. petersenii and M. tonsurata, respectively (Pichrtová & Němcová 2011). Allometry in synurophyte scales is not related to growth of scales but may reflect their position within the scale case .…”

“…Relative position of landmarks among various objects may be used for multivariate analysis of shape. Extent of plasticity (the variety of shapes) may be quantified using a morphological disparity measure (ZeLditch et al 2004 (Pichrtová & Němcová 2011), to characterize the patterns of scale shape variation in S. echinulata Korshikov in combined gradients of light and temperature , to describe scale shape variation in relation to their position within the scale-case , and to emphasize the shape differences between scales belonging to the two distinct varieties -Mallomonas striata var. striata Asmund and M. striata var.…”

Mallomonas alpestrina sp. nov. (Synurales, Chrysophyceae, Stramenopiles) and its spineless relatives—Mallomonas alata group

“…A scale is formed endogenously within a silicon deposition vesicle (SDV); its shape cannot be changed after silicification and extrusion to the cell surface (Leadbeater 1990). However, slight changes in scale shape and proportions during scale biogenesis inside the SDV are inducible by shifts in environmental conditions such as temperature , Pichrtová & Němcová 2011) and pH (Němcová & Pichrtová 2012). Insufficiently silicified scales are often reported in dense cultures where a deficiency of diluted SiO 2 may occur .…”