Fig. 2

Chaetal musculature and ultrastructure of the chaetal follicle. a Confocal laser scanning microscopy (CLSM) of phalloidin stained musculature in a male O. japonicus, the z-projection is depth coded, and the inlet shows a higher magnification of a chaetal sac, with chaetal autofluorescence shown in gray. b–g Transmission electron microscopy (TEM) of fully developed and developing chaetae within chaetal follicles of 4-day old trochophore larvae. b Longitudinal section through a fully developed chaeta. c Transverse sections of two neighboring chaeta, within a single chaetal sac. d Detail of chaetal shaft near the base connected to the chaetal musculature via hemidesmosomes. e Two developing chaetae within a chaetal sac f, g Details of developing teeth. Abbreviations: ant anterior, cb chaetoblast, ch chaeta, cm amorphous chaetal material, dp dense plaques, ecm extracellular matrix, fc follicle cell, h hemidesmosomes, if intermediate filaments, lm longitudinal muscles, mc fiber muscle cell, mi mitochondria, mv microvilli, nu nucleus, pm protractor muscle, post posterior, rm retractor muscle, v electron-dense vesicle. Scale bars: a 10 µm, b 5 µm, c 500 nm, d 500 nm, e 1 µm, f 500 nm, and g 1 µm