Morphology of a sterile, tetraploid, hybrid whiptail lizard (Squamata, Teiidae, Cnemidophorus). American Museum novitates ; no. 3228
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Date
1998
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New York, NY : American Museum of Natural History
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Abstract
"Experimental hybridization with whiptail lizards has been conducted in order to improve understanding of the evolution of parthenogenesis in vertebrates and the effects of horizontal gene transfer in Cnemidophorus, the systematics of which has been confused owing to the reticulate phylogeny within the genus. Here we describe the external morphology and reproductive tissue histology of a sterile tetraploid hybrid between C. sonorae (triploid, unisexual) X C. tigris (diploid, bisexual), and compare her to her parents and siblings that developed from unfertilized eggs (normally cloned C. sonorae). This may help to identify F³ hybrids that are found in nature and may help to determine whether they are sterile without conducting extensive laboratory breeding programs. Considering that the maternal parent (C. sonorae) represented a clone that was of hybrid origin itself, the four genomes in the tetraploid hybrid historically were derived from three hybridization events among three bisexual species of Cnemidophorus, probably as follows: [(inornatus [female] X burti [male]) X burti [male] ] X tigris [male]. The tetraploid inherited 100% of its mother's genes and morphologically was very similar to her and her cloned offspring, particularly in scalation. Nevertheless, it was slightly larger than its siblings at hatching, grew faster than its siblings, attained a larger size, and, beginning at an age of six months, developed dorsal spots reflecting paternal traits in its color pattern. However, if this lizard had been found in nature, without any knowledge of its life history and in the absence of genetic data, it could easily have been misidentified as Cnemidophorus exsanguis, which it resembled more closely than its parental species. Although she reached adult size and lived for more than two years beyond the age at which her cloned siblings produced offspring (nine months), the tetraploid never reproduced. Her ovaries were abnormally small, had poorly defined follicular epithelium with little vascularization, and had either empty or fluid-filled follicles devoid of oocytes. She also had numerous abnormally large mesonephric tubules and few or no cilia in the median oviduct. These traits should be examined in other specimens hypothesized to be sterile F³ hybrid females"--P. 2.
Description
16 p. : ill. (some col.) ; 26 cm.
Includes bibliographical references (p. 14-16).
Includes bibliographical references (p. 14-16).
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