Fig. 3

Light microscopy images of live (a) and fixed-attached Hydra polyp (b), and secreted footprint (c). a Overview of the basal disc of a live attached polyp taken through inverted microscopy. Individual basal disc cells (arrowheads) are in focus along the outer margin. b Longitudinal semi-thin section stained with the basic dye methylene blue and Azur II. The polyp was chemically-fixed when still attached to a substratum. Arrowheads indicate the interface between substratum and polyp where the adhesive is secreted. c Footprint deposited by the basal disc of a Hydra polyp stained with crystal violet. Imprints derived from individual cells are visible in the centre of the footprint while at the periphery fungi can be observed [arrows]. Inset is a magnification of a central area of the footprint where the flat area [asterisks] and the rims [arrowheads] can be seen in a better detail. The fungi are contamination and/or symbionts of Hydra culture. Scale bars 100 μm (a, c), 50 μm (b). Abbreviations: s, substratum; bd, basal disc; ec, ectoderm; m, mesoglea; en, endoderm; pe, peduncle