EEB267H1 Lecture Notes - Lecture 6: Rete Mirabile, Actinopterygii, Haikouella
1 Mar 2013
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Chondrichthyes actinopterygii sarcopterygii calcium salts in cartilaginous endoskeleton jaws skull proto-vertebrae, true gills, two eyes, olfactory lobes many molecular characters dorsal hollow nerve cord, notochord, post-anal tail. Another type of hard tissue composed of: a matrix of (mainly) collagen fibers and other proteins. + hydroxyapatite crystals 3(ca3po4)2 . ca(oh)2 (~ 70% of the weight, rigid, hard) + water (~ 5%) produced by specialized cells called osteoblasts. Blood vessels, nerve fibers run throughout the bone in canals. Specialized cells called osteoclasts are responsible for breaking bone down. Osteoblasts then produce new bone matrix to replace the digested area (in other words, bone can repair itself). The evolution of bone: it"s older than we thought bone is found in a number of extinct fishes that existed before osteichthyes originated. This is why bone isn"t an autapomorphy for the bony fishes : [ -------- extinct jawless fishes --- ] [ -------- gnathostomata --------------- ]
