Ardissonea crystallina A, B external and internal views of valve poles from, respectively Majuro (M1) and Guam (GU44J-4), showing pseudoseptum (B arrow) C internal SEM view (60° tilt) of broken valve showing internal costae including longitudinal costa subtending the annulus (arrowhead) and continuous rim on valve (arrow) (Chuuk: TK4) D, E pole of frustule in girdle view and tilted to 45° to confirm identity; showing the asymmetrical gaps between the pseudoseptum and valvocopula (arrows) (GU75A-4) F, G polar portions of valvocopulae from advalvar side and abvalvar sides, respectively, arrow on F showing where pores along edge of pars interior move to the back of the gap, arrowhead on G showing that slits do not form an open comb (Chuuk: TK4) H polar view of pole with valvocopula showing the asymmetrical gaps (TK4) I, J poles of copulae from wild material (TK4) and culture (GU44AV-8), respectively, arrows indicating fused bases of fimbriae away from the pole. Scale bars: 10 µm (D, E, I); 5 µm (A–C, F–H, J).