Figure 1.

Life cycle of the European eel Anguilla anguilla. (a,b) Silver eels travel to the Sargasso Sea to spawn. Larvae (leptocephalus) are transported back to European fresh water where they develop into glass eels and eventually yellow eels. (c) Photographs of the eels show the morphological change during maturation. Note the increase in eye size. Scale bar, 2 cm. (d) Images obtained by microcomputed tomography (µ-CT) point out severe bone loss in skulls during maturation among yellow (Y), silver (S), and artificially matured eels (AM) in both sexes. Red colouring indicates the cutting plane for histologic analysis of the skull base. Scale bar, 1 cm. (e) Representative three-dimensional reconstructions of µ-CT scans equally show the dramatic bone loss in vertebral bodies among the three groups. Scale bar, 1 mm. (f) Overall mineralization (tissue mineral density, TMD) obtained by µ-CT did not change significantly with maturation. (Online version in colour.)