part of start stage end stage median fin fold cleft cell Wedge-shaped epidermal cell positioned along the apex of the developing fin fold. Each cleft cell retains a wedge-shaped form during fold formation and develops a basal cleft-shaped invagination. Invaginations are aligned in neighboring cleft cells so that these cells cap the distal boundary of the subepidermal space where collagenous extracellular fibres called actinotrichia run anteroposteriorly along the length of the fin fold. Ceri ZFA:0005786 2014-03-25T09:31:29Z zebrafish_anatomy epidermal cell segmentation:26+ somites larval:day 5