Spontaneous Triploidy in the Stone Loach Noemacheilus barbatulus (Balitoridae)

Polyploidy is generally considered to be rare among sexually reproducing animals. Benfey listed only a few cases of spontaneous triploidy in natural or domesticated fish populations, in contrast to the listings of experimentally induced fish triploids. In general, animal triploids are thought to stem from a failure of the egg to exclude the second polar body nucleus, followed by homospecific (autotriploidy) or heterospecific insemination (allotriploidy) and fertilization. Although different types of polyploidy have been reported among lower vertebrates, sustaining triploid-populations appear to be linked invariably to interspecific hybridization. In most cases, triploids have been indistinguishable in external morphology from normal diploids. This suggests that triploids may be easily overlooked and more common in nature than currently believed. Very possibly, more extensive population sampling will identify additional spontaneously arisen triploids. In this note, we report the finding of a triploid in the hillstream loach Noemacheilus barbatulus. This is the first documented case of a triploid individual in the cobitoid family Balitoridae.