Chloroplast rotation and morphological plasticity of the unicellular alga Rhodosorus (Rhodophyta, Stylonematales)

Abstract

Time-lapse videomicroscopy was used to film chloroplast rotation in the 13 isolates of Rhodosorus marinus Geitler and one isolate of Rhodosorus magnei Fresnel & Billard maintained in culture. Cell diameter, rates of chloroplast rotation and the number of chloroplast lobes were measured in all isolates. Chloroplast rotation is a definitive characteristic of the genus Rhodosorus and should be included in its taxonomic description. Isolates of the type species, R. marinus, measure 4-7 µm in diameter in low light (2-4 µmol photons m -2 s -1 ) and 4.5-11.5 µm in diameter in bright light (15-20 µmol photons m -2 s -1 ), and have two to seven chloroplast lobes. Rhodosorus magnei is 9 µm in diameter and has seven to nine chloroplast lobes in bright light. However, these cells are much smaller (approx. 4 µm diam.) and have only two to three chloroplast lobes when maintained in low light. The species R. magnei was created based on its larger cell size and numerous chloroplast lobes compared with R. marinus, but since these characteristics were found to be quite variable and dependant on culture conditions, they cannot be used to differentiate these two species.

Flora of drift plastics: a new red algal genus, Tsunamia transpacifica (Stylonematophyceae) from Japanese tsunami debris in the northeast Pacific Ocean

“…rather than by oblique and longitudinal divisions, as in Tsunamia. Furthermore, in contrast to spores of other Stylonematophyceae observed in culture (Pickett-Heaps et al 2001, Wilson et al 2002, West et al 2005, 2007, neither gliding nor amoeboid motility was observed in Tsunamia spores.…”

Observations on Purpureofilum apyrenoidigerum gen. et sp. nov. from Australia and Bangiopsis subsimplex from India (Stylonematales, Bangiophyceae, Rhodophyta)

“…Spore movement has now been observed in Purpureofilum, Stylonema and Bangiopsis, but not in Chroodactylon (Pickett-Heaps et al 2001;the present study). In Rhodosorus, the only unicellular genus of the order Stylonematales, chloroplast rotation occurs within the cell, but whole cell movement does not occur (Wilson et al 2002).…”

“…The order was also shown to have a close affinity to the unicellular genus Rhodosorus by Müller et al (2001). Müller et al (2001) placed the genus Goniotrichopsis sublittoralis Smith (Smith & Hollenberg 1943) in the Stylonematales (as Porphyridiales 2) based on molecular evidence, but their analyses were done with an isolate (1689) from The University of Texas (UTEX) Culture Collection of Algae of Stylonema alsidii Zanardini (K. Drew) that had been misidentified as G. sublittoralis (Wilson et al 2002).…”

“…Stylonema and Chroodactylon are widely distributed in Australia (Womersley 1994;Pickett-Heaps et al 2001;Karsten et al 2003). In Australia, Rhodosorus marinus Geitler is known only from Sydney, New South Wales (NSW) (see Table 1, Wilson et al 2002). The genus Bangiopsis has not been reported in Australia.…”

LOW MOLECULAR WEIGHT CARBOHYDRATES OF THE BANGIOPHYCIDAE (RHODOPHYTA)1

“…These data are identical to our previous results obtained with R. marinus (3608) from Hawaii (USA) (Karsten et al 1999). Rhodosorus also has one other distinctive character that separates it from all other unicellular red algal genera, that is, chloroplast rotation (Pickett‐Heaps et al 2001, Wilson et al 2002). Based on Müller et al (2001) we placed the above genera in the Stylonematales.…”