EEB267H1 Lecture Notes - Lecture 4: Holocephali, Ichthys, Dentin
25 Mar 2018
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Cartilage: chondros (cartilage); produced by specialized cells called chondrocytes a matrix of collagen fibers (proteins) Proteoglycans (proteins coupled with long strings of sugars e. g. chondroitin) Cartilage= matrix of collagen fibers+proteoglycans+75% water; flexible and light; no ca salt. The holocephali (chimaeras, ratfish, rabbitfish, spookfish): holos(entire) + kephale (head), cold deep marine fishes; green shine eyes; swim using pectoral fins like wings or slow undulating body; their whiplike tails are of little use for swimming. 3 pairs of continuously growing tooth-plates (dentine) = rigid surface for grinding hard prey items; predators primarily on molluscs (echinoderms, cephalopods, small fish) In the basal chordata, the chondrocytes are not part of the matrix ( they are outside of it) so this type of cartilage is acellular and is therefore nonliving . In vertebrates, the chondrocytes deposit the matrix around themselves, because these cells are now part of the matrix, cartilage is considered to be a living tissue in vertebrates.
