Remodelling of the vertebral axis during metamorphic shrinkage in the pearlfish
Parmentier E, Lecchini D &Vandewalle P
Journal of Fish Biology 64, 159-169. 2003
Metamorphosis is characterised by a reduction of the body length in some leptocephalous larvae and anuran tadpoles. However, an important body shortening also exists between the larval and juvenile stage in several species of Carapidae. Morphological observations of the vertebral axis have been realised on the pearlfish, Carapus homei, a species living inside sea cucumbers. C. homei has a particular metamorphosis from at least two points of view : 1) contrary to leptocephalous and tadpoles, osseous vertebrae are present before the metamorphosis; 2) it involves a pronounced and progressive decalcification of all vertebral centra following an anterio-posterior gradient, the complete disappearance of the posterior vertebrae and associated structures, and progressive anterio-posterior shortening of the vertebral centra. This degradation might provide the necessary metabolites required for the development of the components of the remaining vertebrae. A model requiring gradients is proposed to explain this metamorphosis.
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