The actions of methoprene acid on a developing urodele.
The objective of this study was to characterize the biological
actions of methoprene acid (MA), a metabolite of the insecticide
methoprene, on a developing axolotl, Ambystoma mexicanum, and to assess
levels of developmental stability following treatment of embryos and
hatchlings. We tested the null hypotheses that (1) MA would produce no
developmental malformations similar to those produced by the positive
control, retinoic acid (RA) and (2) the degree of vulnerability to
treatment would not differ between embryos and hatchlings. Animals were
exposed to 1 of 4 concentrations of MA (0, 30, 150, and 300 ug/L), or RA
(0, 0.3, 1.5, 3.0 ug/L), depending on the respective treatment group.
Additionally, half the subjects were treated from blastula stage to
hatching only, while the second half were treated beginning at hatching
for the duration of the experiment. The experiment was terminated when
all animals reached full hind limb development. Developmental stability
was determined by measuring fluctuating asymmetry of the hind limbs,
forelimbs, and eyes. Craniofacial and limb malformations that were
previously characterized as retinoid-like were seen in both MA- and RA-
treated animals. Effects on developmental stability were consistently
observed as fluctuating asymmetry of the forelimbs and hind limbs in MA-
and RA- treated animals.
Elena M. Lopez and David O. Norris *. Department of EPO Biology,
University of Colorado, Boulder.
* Denotes membership in the Colorado-Wyoming Academy of Science.