Fig. 4

Localisation of asterotocin in A. rubens using in situ hybridisation (ISH) and immunohistochemistry (IHC). a Asterotocin precursor transcript-expressing cells (AstPtc) in a radial nerve cord (black arrowheads) and tube feet (white arrowheads). Inset shows the absence of staining with sense probes. b Asterotocin-immunoreactive (Ast-ir) cells (arrowheads in inset) and fibres (white asterisks) in a radial nerve cord. c AstPtc in the circumoral nerve ring (arrowheads and inset). d Ast-ir cells (arrowheads) and fibres (white asterisks) in the circumoral nerve ring. e AstPtc in marginal nerve. f Ast-ir fibres in marginal nerve. g AstPtc in tube foot disc. h Ast-ir in the basal nerve ring (black arrow) and longitudinal nerve tract (grey arrow) of a tube foot. i AstPtc in the peristomial membrane. j AstPtc in the oesophagus. k Ast-ir in the peristomial membrane (square bracket) and oesophagus. l AstPtc in the cardiac stomach. m Ast-ir in the cardiac stomach. n AstPtc in the pyloric stomach. o AstPtc in a pyloric duct. p Ast-ir in the pyloric stomach. q AstPtc in the coelomic epithelium of the body wall. r Ast-ir in the coelomic basiepithelial nerve plexus of body wall. s Ast-ir in the basiepithelial nerve plexus of the apical muscle. t AstPtc in a papula. u Ast-ir in a papula. v AstPtc in the body wall. w Ast-ir in the body wall. x AstPtc in a pedicellaria. y Ast-ir in a pedicellaria. z AstPtc in a spine. z’ Ast-ir in an ambulacral spine. Abbreviations: AM, apical muscle; BNR, basal nerve ring; BNP, basiepithelial nerve plexus; CMLNP, circular muscle layer nerve plexus; CBNP, coelomic basiepithelial nerve plexus; CE, coelomic epithelium; CT, collagenous tissue; Di, disc; Ec, ectoneural region; EE, external epithelium; Hy, hyponeural region; LNT, longitudinal nerve tract; Lu, lumen; MN, marginal nerve; ML, mucosal layer; MuL, muscle layer; Oes, oesophagus; Pa, papula; RHS, radial hemal sinus; TF, tube foot; VML, visceral muscle layer. Scale bars: a, a inset, h, l, m, n, o, p, u = 60 μm; b, d, g, z’ = 40 μm; i, j, l inset, p inset, t, w, x = 30 μm; B inset, c, d inset, e, k, n inset, o inset, s, v, y, z = 20 μm; c inset, f, m inset, q, r = 10 μm