Fig. 4

Organization of tentacles in Hemithiris psittacea. Semi-thin cross sections (a, b); Z-projections after mono- (c, d) and double- (e) immunostaining against alpha acetylated-tubulin (grey) and serotonin (magenta); and staining with phalloidin (blue) (g); thin sections (f, h). a Outer tentacle. b Inner tentacle. c Z-projection of peritoneal nerves in outer tentacles. d Z-projection of peritoneal nerves in inner tentacles. e Z-projection of inner tentacle. f Cross section of the base of an outer tentacle: the large cell (ppk) with electron-lucent cytoplasm is visible. g Z-projection of the base of outer tentacles: perikarya of peritoneal cells (ppk) are visible. h Cross section of the lateral side of an inner tentacle: large peritoneal neurites (pn) contain electron-lucent cytoplasm. Abbreviations: ac – amoebocyte; af – abfrontal zone; cn – cross nerve; ecm – extracellular matrix; f – frontal zone; fn – frontal tentacular nerve; frg – frontal groove; lf – laterofrontal zone; lfn – laterofrontal tentacular nerve; pe – peritoneal cell of coelomic lining; pn – peritoneal neurite; ppk – peritoneal perikarya; sa – second accessory nerve; tc – tentacular coelom; tv – tentacular blood vessel