Ecological Archives M080-014-A4

Mari K. Reeves, Peter Jensen, Christine L. Dolph, Marcel Holyoak, and Kimberly A. Trust. 2010. Multiple stressors and the cause of amphibian abnormalities. Ecology 80:423–440.

Appendix D. Supplemental results for predator exclusion and limb amputation experiments.

Predator Exclusion Experiment

Additional abnormalities documented in exclusion cages included one animal with two bleeding but intact limbs, and one with a tumor-like growth in its torso. We also found torn or notched tails on four metamorphs in 2005 and two in 2006. In 2005, only 126 of the 900 tadpoles deployed (14%) reached metamorphosis. This poor survival was due in part to high cage densities and also to the loss of one entire cage, which was removed from the water at the remote site (probably by wildlife). In 2006, we reduced tadpole density to 50 per cage, and only deployed cages at road-accesible sites where we could monitor them. This year 85 of the 450 (19%) tadpoles reached metamorphosis by the end of the season. Metamorphs in the cages were smaller than those outside the cages (mean SVL ± SD: inside = 14 ± 2 mm; outside = 19 ± 1 mm).

Limb Amputation Experiment

We found that more complex injuries produced more complex malformations. For example, two early amputations (with the scalpel) resulted in bony triangles and duplicated limb elements (Fig. D1.B), likely because amputations were more jagged when performed. Clean amputations in the middle of the limb bud resulted in shrunken, but correctly formed, limbs and feet (Fig. D1.A).

   FIG. D1. Skeletal malformations produced by early amputation injury to the developing tadpole limb bud. Right limbs amputated at the limb bud stage. Left limbs left intact for comparison. (A) Micromelia with limited phalange development, (B) Duplicated foot elements with bony triangle between knee and ankle, (C) Micromelia with ectrodactyly, and (D) Ectromelia with limited phalange development.


   FIG. D2. Boxplots of parameter estimates from five-factor skeletal abnormality models.

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