Fig. 7

Histological details of the epistome area of Stephanella hina. Semithin sections. All images are cross-sections (or slightly oblique) except E, which is a longitudinal image. With the exception of the latter, the epistomial epidermis always faces up towards the oral side of the animal and the anal side facing down. a The epistome epidermis is prominent and shows distinct epidermal secretions that ultimately enter the mouth area in the lophophoral base. b Less prominent epistome epidermis with fewer epidermal secretions. c An epistome epidermis with the median part apparently forming secretion droplets. Below that area, a conspicuous extracellular matrix seems to be present. d Section through the cerebral ganglion slightly below the epistome showing similar epidermal secretions occurring in the epidermal lining of the gut. e Longitudinal sections showing few secretion events in the epistome but synchronously in the foregut epithelium slightly below the cerebral ganglion. f An epistome showing prominent cells containing multiple inclusions but lacking any epidermal secretions. g Inconspicuous epistome with few, small secretions. Abbreviations: cg - cerebral ganglion, eds - epidermal secretions, ep - epistome, epc - epistome coelom, epm - epistome musculature, gh - ganglionic horn, glu - ganglion lumen, loc - lophophoral concavity, mo - mouth opening, t - tentacle, tc - tentacle coelom