Figure 3.

CARD-FISH localization of symbiont 16S rRNA in S. velum gill and ovary transverse sections imaged with confocal microscopy. Symbiont-containing S. velum (a–f,m,p) gill filaments and (g–l,n,o,q,r) ovary. (a–l) Columns left to right: DAPI (blue), Svsym47 signal (red, Alexa 647), merged images. Boxes in (a–c) and (g–i) show enlargement of regions featured in (d–f) and (j–l), respectively. (m–r) Hybridization of S. velum (m,p) gill and (n,o,q,r) ovary sections with the negative control probe NON338. (m–o) DAPI (blue). (p–r) NON338 signal under laser intensities and gain settings for Svsym47-hybridized gill (red, Alexa 647). (o,r) are enlargements of (n,q). Abbreviations: aw: acinal wall; bc: bacteriocyte; gf: gill filament; mo: mature oocyte; n: nucleus; s: symbiont cells. Scale bars: (a,b,m,n,o,p) 100 µm, (c–f) 50 µm, (g,h) 10 µm.