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No. 14: Winter 1981 Supplement

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Eyes of deep-sea fish have spare parts

The sunlight that filters down into the depths of the sea is exceedingly weak. It is so dark down there that one would expect deep-sea fish to be blind like many cave-dwelling animals. They are not blind; rather many have eyes of fantastic size and novel construction. An unusual feature of some deep-sea eyes is a layered retina. In the conger eel, five layers of photoreceptors are plastered on top of one another. Yet, experiments with conger eel eyes reveal that only one layer of photoreceptors is active at any one time. R. Shapley and J. Gordon, who carried out these experiments at the Plymouth Lab., surmise that the extra retinal layers are being held in reserve, much like the rows of spare teeth found in sharks' mouths. If so, deep-sea fish are the only animals that have evolved spare stores of visual pigments.

(Anonymous; "The Mystery of the Non-Functioning Receptors," New Scientist, 88:366, 1980.)

Comment. Why haven't cave-dwelling fish taken the same evolutionary route?

From Science Frontiers #14, Winter 1981. 1981-2000 William R. Corliss

Science Frontiers Sourcebook Project Reviewed in:


  • "A sourcebook of unexplained phenomena is therefore a valuable addition to a collection of scientific literature. William R. Corliss has provided this in the past with his source books of scientific anomalies in several subjects, and now he has provided it for astronomy. He has done an excellent job of collecting and editing a large amount of material, taken in part from scientific journals and in part from scientific reporting in the popular or semi-scientific press." -- "The Mysterious Universe: A Handbook of Astronomical Anomalies", reviwed by Thomas Gold, Cornell University, in Icarus, vol.41, 1980

  • "An interesting, systematic presentation of unusual weather [..] This book is recommended for a general audience" --"Corliss, William R., Tornados, Dark Days, Anomalous Precipitation, and Related Weather Phenomena, Sourcebook Project, 1983.", revieweed in Choice, September 1983
  • "..the science is necessarily somewhat speculative, but Corliss's symthesis is based on reputable sources." -- "Corliss, William R. (Compiler). Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena" reviwed by Joseph M. Moran, Univ. of Wisconsin in Science Books and Films, Sep/Oct 1983

  • "Before opening the book, I set certain standards that a volume which treads into dangerous grounds grounds like this must meet. The author scrupulously met, or even exceeded those standards. Each phenomenon is exhaustively documented, with references to scientific journals [..] and extensive quotations" -- "Book Review: The moon and planets: a catalog of astronomical anomalies", The Sourcebook Project, 1985., Corliss, W. R., Journal of the Royal Astronomical Society of Canada, Vol. 81, no. 1 (1987), p. 24., 02/1987