In vitro accumulation of mineral components by invertebrate cartilage

In vitro mineralization of the gill cartilage of Limulus (horse-shoe crab) has been reported previously (Eilberg et al. 1975). The present study demonstrates that cranial cartilage of Loligo (squid) and odontophore cartilage of Busycon (marine snail) also mineralize in vitro in hydroxyapatite-metastable media, but not in carbonate-metastable media. In all three of these cartilages, light phase-contrast microscopy revealed that the mineral phase occured in the form of spherical or ovoid granules ranging between 2 and 9 mum in diameter. During mineralization, the granules appeared successively in the perichondrium, in the matrix, and finally, within chondrocytes. Mineralization occurred more rapidly in Eusycon odontophore cartilage which has a significantly higher content of phosphatidyl serine than in Limulus gill or Loligo head cartilages. In all tissues the mineralization process is related to temperature, taking place most actively at 37 degrees C and only weakly at 50 degrees C.