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Leaping lopsided: a review of the current hypotheses regarding etiologies of limb malformations in frogs

The Anatomical Record Part B: The New Anatomist

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Abstract

Recent progress in the investigation of limb malformations in free-living frogs has underlined the wide range in the types of limb malformations and the apparent spatiotemporal clustering of their occurrence. Here, we review the current understanding of normal and abnormal vertebrate limb development and regeneration and discuss some of the molecular events that may bring about limb malformation. Consideration of the differences between limb development and regeneration in amphibians has led us to the hypothesis that some of the observed limb malformations come about through misdirected regeneration. We report the results of a pilot study that supports this hypothesis. In this study, the distal aspect of the right hindlimb buds of X. laevis tadpoles was amputated at the pre-foot paddle stage. The tadpoles were raised in water from a pond in Minnesota at which 7% of surveyed newly metamorphosed feral frogs had malformations. Six percent (6 of 100) of the right limbs of the tadpoles raised in pond water developed abnormally. One truncated right limb was the only malformation in the control group, which was raised in dechlorinated municipal water. All unamputated limbs developed normally in both groups. Three major factors under consideration for effecting the limb malformations are discussed. These factors include environmental chemicals (primarily agrichemicals), encysted larvae (metacercariae) of trematode parasites, and increased levels of ultraviolet light. Emphasis is placed on the necessary intersection of environmental stressors and developmental events to bring about the specific malformations that are observed in free-living frog populations.

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Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Leaping lopsided: a review of the current hypotheses regarding etiologies of limb malformations in frogs
Series title:
The Anatomical Record Part B: The New Anatomist
Volume
265
Issue:
5
Year Published:
2001
Language:
English
Contributing office(s):
National Wildlife Health Center
Description:
p. 228-245
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
The Anatomical Record Part B: The New Anatomist
First page:
228
Last page:
245
Country:
Canada, United States
State:
California, Maine, Minnesota, Quebec, Vermont
Online Only (Y/N):
N
Additional Online Files(Y/N):
N