There's a large amount of literature on amphibians in which the urodeles
(salamanders ) can regenerate limbs throughout life, but anurans (frogs)
lose the ability at metamorphosis. The literature looks at differences
between these groups responsible for the major differences in regenerative
abilities.

1880's: "There's lots of good fish in the sea"   W.S. Gilbert
1990's:  Many fish stocks depleted due to overfishing, habitat loss,
         and pollution.       \ \
                             \ \ \
               - -      _ - \ \ \ \ ----\
                  - _ -                    \
                  - -                (   O   \
                _ -  -_                   __ /
               -       -                    /
                         -///  _ ______ ___/
                        ///          /
Judith S. Weis   Department of Biological Sciences
   Rutgers Univ.  Newark NJ 07102      [log in to unmask]