Uneven division of the auxospore mother cell (compare to Fig 4C

Uneven division of the auxospore mother cell (compare to Fig 4C), note doughnut-shaped, lightly silicified rudimentary hypovalve (valve EDS spectrum shown in Fig 6A-A1-2); B–a young spherical auxospore with large scale (arrowheads) exposed (compare to Fig 3I and 3J); C–the same large scale showing detail of pitted ornamentation; D–partially collapsed, large auxospore probably captured during partial plasmolysis, note fnins.2015.00094 large diameter of parental theca demonstrating the second round of auxosporulation; E–a partially damaged auxospore with thick wall with siliceous elements (EDS spectrum shown in Fig Pan-RAS-IN-1MedChemExpress Pan-RAS-IN-1 6B-E1-2), jir.2010.0097 note that the small parent cell of this auxospore indicates first round of auxosporulation; F- spinose initial valve covered with thin and pliable remains of the auxospore wall; G–the same specimen as in F at greater magnification showing scaly incunabulae (arrowheads) in the auxospore wall; H–another initial frustule enshrouded in the auxospore wall demonstrating scaly incunabulae in the girdle region (arrowheads); I–individual incunabular scales (arrowheads) disassociated from the auxospore wall (EDS spectrum shown in Fig 6C-I1-2); J–complete initial frustule in girdle view, note epicingulum; K–external view of an initial valve; L–internal view of an initial valve. doi:10.1371/journal.pone.0141150.g005 PLOS ONE | DOI:10.1371/journal.pone.0141150 October 20, 2015 11 /Auxosporulation in ParaliaFig 6. Representative EDS spectra. Spectra acquired from UNC0642 msds locations shown in Fig 5A, 5E and 5I, respectively for vestigial hypovalve, auxospore wall and incunabular scale (locations indicated by boxes). Note difference in vertical scale of the spectra in Fig 6B. Spectra from position 1 are taken from structure shown in Fig 5 and spectra from position 2 from filter substrate which shows no detectable silicon peak. Gold peaks were generated from the conductive coating. doi:10.1371/journal.pone.0141150.gPLOS ONE | DOI:10.1371/journal.pone.0141150 October 20,12 /Auxosporulation in ParaliaFig 7. Acid cleaned initial valves observed in brightfield LM. A B–convex, relatively plain initial valves with single (A) and double (B) elevations, note band of quincunx pores at the valve margin; C through E–a strongly concentrically undulated valve at three different foci: C–focus on valve margin andPLOS ONE | DOI:10.1371/journal.pone.0141150 October 20,13 /Auxosporulation in Paraliastriae; D–focus on peripheral part of the valve face, ribs and stout spines; E–focus near central elevation with smaller spines; F–inside view of initial valve with central elevation; G–outside view of a less convex initial valve, note ribbed margin. doi:10.1371/journal.pone.0141150.gone of the initial valves. This demonstrated the degree of persistence of the heterovalvate endcells with initial thecae. Valves with a range of morphologies intermediate between the initial valves and typical vegetative valves were found (Figs 8?0) and they included: valves with faces carrying depressions and elevations (although less pronounced than on the initial cell valves; Fig 8D?F), with malformed marginal linking spines and imperfect fenestra (Figs 8A?H andFig 8. Post auxospore frustules and valves as observed in SEM. Morphology is intermediate between initial and typical vegetative valves. A–a short chain (probably 3? cells), note strong cingulae and initial valves on the end cells; B–disarticulated post auxospore chain showing 6 valves with imperfect marginal linking spines.Uneven division of the auxospore mother cell (compare to Fig 4C), note doughnut-shaped, lightly silicified rudimentary hypovalve (valve EDS spectrum shown in Fig 6A-A1-2); B–a young spherical auxospore with large scale (arrowheads) exposed (compare to Fig 3I and 3J); C–the same large scale showing detail of pitted ornamentation; D–partially collapsed, large auxospore probably captured during partial plasmolysis, note fnins.2015.00094 large diameter of parental theca demonstrating the second round of auxosporulation; E–a partially damaged auxospore with thick wall with siliceous elements (EDS spectrum shown in Fig 6B-E1-2), jir.2010.0097 note that the small parent cell of this auxospore indicates first round of auxosporulation; F- spinose initial valve covered with thin and pliable remains of the auxospore wall; G–the same specimen as in F at greater magnification showing scaly incunabulae (arrowheads) in the auxospore wall; H–another initial frustule enshrouded in the auxospore wall demonstrating scaly incunabulae in the girdle region (arrowheads); I–individual incunabular scales (arrowheads) disassociated from the auxospore wall (EDS spectrum shown in Fig 6C-I1-2); J–complete initial frustule in girdle view, note epicingulum; K–external view of an initial valve; L–internal view of an initial valve. doi:10.1371/journal.pone.0141150.g005 PLOS ONE | DOI:10.1371/journal.pone.0141150 October 20, 2015 11 /Auxosporulation in ParaliaFig 6. Representative EDS spectra. Spectra acquired from locations shown in Fig 5A, 5E and 5I, respectively for vestigial hypovalve, auxospore wall and incunabular scale (locations indicated by boxes). Note difference in vertical scale of the spectra in Fig 6B. Spectra from position 1 are taken from structure shown in Fig 5 and spectra from position 2 from filter substrate which shows no detectable silicon peak. Gold peaks were generated from the conductive coating. doi:10.1371/journal.pone.0141150.gPLOS ONE | DOI:10.1371/journal.pone.0141150 October 20,12 /Auxosporulation in ParaliaFig 7. Acid cleaned initial valves observed in brightfield LM. A B–convex, relatively plain initial valves with single (A) and double (B) elevations, note band of quincunx pores at the valve margin; C through E–a strongly concentrically undulated valve at three different foci: C–focus on valve margin andPLOS ONE | DOI:10.1371/journal.pone.0141150 October 20,13 /Auxosporulation in Paraliastriae; D–focus on peripheral part of the valve face, ribs and stout spines; E–focus near central elevation with smaller spines; F–inside view of initial valve with central elevation; G–outside view of a less convex initial valve, note ribbed margin. doi:10.1371/journal.pone.0141150.gone of the initial valves. This demonstrated the degree of persistence of the heterovalvate endcells with initial thecae. Valves with a range of morphologies intermediate between the initial valves and typical vegetative valves were found (Figs 8?0) and they included: valves with faces carrying depressions and elevations (although less pronounced than on the initial cell valves; Fig 8D?F), with malformed marginal linking spines and imperfect fenestra (Figs 8A?H andFig 8. Post auxospore frustules and valves as observed in SEM. Morphology is intermediate between initial and typical vegetative valves. A–a short chain (probably 3? cells), note strong cingulae and initial valves on the end cells; B–disarticulated post auxospore chain showing 6 valves with imperfect marginal linking spines.