The histochemistry and structure of tentacle cartilage tissues in the marine polychaete, Sabella melanostigma

The cartilages (or "chondroid" tissue) in tentacles of the polychaete annelid, Sabella melanostigma, have been examined by electron microscopy and a series of histochemical techniques for the demonstration of mucopolysaccharides and protein end-groups. The ultrastructural studies indicated that the cartilages possess an investing layer of dense connective tissue which differs significanly from the matrix material secreted between the chondrocytes. The cartilage matrix was positive for acidic mucins with levels of sulfation above those of mammalian chondroitins A and C. This matrix as well as the investing connective tissue were intensely PAS-positive. Sabella cartilage was also stained intensely by methods for demonstrating tryptophan, tyrosine, side-chain carboxyl groups, disulfide groups, and amino groups. It was not stained by the procedure for sulfhydryl groups. Some evolutionary aspects of cartilage and chondroid tissues were discussed.