Fig. 15

Histology of the mantle folds of adult Nodipecten nodosus. a Acid mucopolysaccharide-secreting cells spread over the outer mantle epithelium. AB. b Two distinct types of secretory cells in the inner epithelium of the outer mantle fold: Alcian Blue-positive (acid mucopolysaccharides) and PAS-positive (neutral mucopolysaccharides; magenta color) cells. c Detail of the periostracal groove with two glandular folds responsible for periostracum secretion at the bottom of the groove. Toluidine blue and basic fuchsin (TB). d Ciliated epithelium (arrow) of the outer surface of the middle mantle fold. Hematoxylin and eosin (HE). e Middle fold tentacle displaying muscle and nervous fibers and a pigmented epithelium. TB. f PAS-positive mucous cells (arrows) in the middle fold tentacle (nuclei stained with hematoxylin). g Section through the pallial eyes showing its general structure. TB. h Outer epithelium of the inner mantle fold with sparse tufts of cilia (arrows). HE. Abbreviations: co, cornea; gl, periostracal glands; le, lens; mf, middle mantle fold; mu, tentacle muscles; ne, tentacle nerve; of, outer mantle fold; pg, periostracal groove; pi, pigmented epithelium; re, retina; rl, reflector layer; te, tentacles