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A Cavernicolous Form of the Poeciliid Fish Poecilia sphenops from Tabasco, Mexico
Malcolm S. Gordon and Donn Eric Rosen
Vol. 1962, No. 2 (Jul. 20, 1962), pp. 360-368
Stable URL: http://www.jstor.org/stable/1440903
Page Count: 9
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The first known cavernicolous population of a poeciliid fish, Poecilia sphenops (Cuvier and Valenciennes), is described from a calcium sulfate saturated cave stream in Tabasco, Mexico. The most extreme cave mollies are almost colorless, have thicklipped, terminal, horizontal mouths, and reduced eyes. Several body proportions vary within the cave population in correlation with distance from the cave mouth. These continuous morphological gradients are interpreted as possible evidence for the existence of an undiscovered, truly cavernicolous upstream population of mollies, the known fish possibly being intergrades between this form and the surface-living populations. A detailed physical description of the cave is presented, also a list of all other organisms so far found within the cave and its stream.