Fig. 3

Location of brachial nerves in the brachium and structure of the main brachial nerve in Hemithiris psittacea. a Schematic cross section of the lophophore brachium. b Semi-thin cross section of the brachium. The location of different nerves is marked by circles of different colors, which correspond to the colors of nerves in Fig. 5. c Semi-thin section of the epithelium, which contains the main brachial nerve (marked by color). The cross nerves, which originate from the main nerve, are indicated by arrowheads. d Z-projections of the brachial fold with the main brachial nerve at the base. Immunostaining against alpha acetylated-tubulin. e Z-projections of the brachial fold: immunostaining against alpha acetylated-tubulin (grey) and serotonin (green). The sensory cells are visible along the edge of the brachial fold. f Z-projections of the base of brachial fold: immunostaining against alpha acetylated-tubulin. The main nerve and a portion of the cross nerves (cn) are visible. g Z-projections of the base of brachial fold: immunostaining against FMRFamide. The empty space, which corresponds to the location of serotonin-like immunoreactive elements of the main nerve, is visible (p5HT-mn). Abbreviations: 5HT-mn – serotonin-like immunoreactive elements of the main brachial nerve; an – accessory brachial nerve; bf – brachial fold; cn – cross nerves; ecm – extracellular matrix; fg – food groove; FMRFamide-mn – FMRFamide-like immunoreactive elements of the main brachial nerve; it – inner tentacle; lc – large canal of the lophophoral coelom; ln – lower brachial nerve; mn – main brachial nerve; ot – outer tentacle; sa – second accessory nerve; sc – small canal of the lophophoral coelom; sec – sensory cells