Etiolated

adjective

1. Of a plant or part of a plant: pale and weak because of sunlight deprivation or excessive exposure to sunlight.
2. Of a plant: intentionally grown in the dark.
3. (by extension) Of an animal or person: having an ashen or pale appearance; also, haggard or thin; physically weak.

   "Birds inhabiting desert regions have an etiolated appearance."

4. Lacking in vigour; anemic, feeble.