Figure 5
Osteocyte characteristics. (a) Representative images obtained using BSEM show the differences in lacunar number and size. (b) The number of osteocyte lacunae per bone area (N.Ot.Lc/B.Ar) was significantly lower in the sperm whales than that in the other whale species. (c) Osteocyte lacunar area (Lc.Ar) was smaller in the sperm whales. *P < 0.05. (d) Toluidine blue-stained sections of undecalcified bone specimens revealed that the harbour porpoise had several osteocytes with 2 cell nuclei, the orca had typically shaped osteocytes and the sperm whale showed only small and empty lacunae; 400x magnification. (e) Percentage of occupied (viable) lacunae was significantly decreased in the sperm whales. **P < 0.001. (f) Images of the osteocyte lacunar connections performed via acid etching of the acrylate embedded specimens followed by scanning electron microscopy (SEM); the images show a well-developed lacunocanalicular system in the orca (left image), whereas poor connections via canaliculi are observed among osteocytes in the sperm whale bone (right image).
