Ontogeny of the tessellated skeleton: insight from the skeletal growth of the round stingray Urobatis halleri

• DOI: 10.1111/j.1469-7580.2009.01116.x
• Publication Date: 2009-07-18T06:52:40Z
• Authors: Mason N. Dean; Chris G. Mull; Stanislav N. Gorb; Adam P. Summers
• Keywords: Perichondrium; Endochondral ossification; Skeleton (computer programming); Columnar Cell

The majority of the skeleton elasmobranch fishes (sharks, rays and relatives) is tessellated: uncalcified cartilage overlain by a superficial rind abutting, mineralized, hexagonal blocks called tesserae. We employed diversity imaging techniques on an ontogenetic series jaw samples to investigate development tessellated in stingray (Urobatis halleri). compared these data with cellular changes that characterize calcification bony skeletons. Skeletal growth characterized appearance tesserae as well chondrocyte shape, arrangement density. Yolk sac embryos (35-56 mm disc width, DW) have untessellated lower tissue wrapped perichondrium densely packed chondrocytes. Chondrocyte density decreases dramatically after yolk absorption (histotroph stage: 57-80 until formation tesserae, which are first visible using our thin (approximately 60 microm), sub-perichondral plaques. During histotroph stage, flattened chondrocytes align parallel at periphery, where we believe they incorporated into developing form cell-rich laminae observed within tesserae; older animals peripheral cells phase rounder less uniformly oriented. By parturition 75 DW), cell number adjoining pairs (an indicator division) dropped than third their initial values; remain low continue grow size. simple solution conundrum endoskeleton external mineralization no remodeling. Although see parallels endochondral ossification (e.g. decreasing age), lack hypertrophy fact (not case mammalian cartilage) suggest similarities end there.