Frog limb deformities: An ?eco-devo? riddle wrapped in multiple hypotheses surrounded by insufficient data

Synergism between trematode infection and pesticide exposure: A link to amphibian limb deformities in nature?

“…Included within these reports are accounts of increases in developmental deformities (12)(13)(14). Amphibian deformities, in particular those related to limb development, have now been reported in 43 states in the U.S. and in five Canadian Provinces, as well as in several other countries around the world (13). The widespread nature and apparent increase in the prevalence of deformities have led to substantial interest from scientists and the general public.…”

“…The types of deformities I observed encompass those seen in other studies reporting increases in abnormalities from around North America (12)(13)(14)(16)(17)(18)(19)(20)(21). The strong context dependence observed in this study may help explain the disparities among the observations of deformities under natural conditions and those experimentally induced under laboratory conditions that have been reported in numerous studies (13).…”

“…The strong context dependence observed in this study may help explain the disparities among the observations of deformities under natural conditions and those experimentally induced under laboratory conditions that have been reported in numerous studies (13). Moreover, it was clear that tadpoles possess the ability to prevent the formation of, or to shed, metacercarial cysts.…”

“…In addition, for some populations, unprecedented mortality has been documented (7)(8)(9)(10)(11). Included within these reports are accounts of increases in developmental deformities (12)(13)(14). Amphibian deformities, in particular those related to limb development, have now been reported in 43 states in the U.S. and in five Canadian Provinces, as well as in several other countries around the world (13).…”

“…Hypotheses proposed to explain the deformities fall into two broad camps: chemical contaminants (16,17) and trematode infection (18)(19)(20)(21). Although preliminary laboratory experiments suggest that infection by some species of trematode or exposure to certain contaminants can cause some deformities, there are often inconsistencies between observations of deformities occurring under natural conditions and those that result from laboratory manipulations (13). Moreover, no experimental manipulations have been conducted in the field, and no studies have attempted to examine synergistic effects of trematode infection and exposure to chemical contaminants.…”