Early observations suggest that parasites cause amphibian deformities

Nine years before the Minnesota students made their startling discovery, Stephen Ruth was exploring ponds in Northern California when he found Pacific tree frogs (Pseudacris regilla) and long-toed salamanders (Ambystoma macrodactylum) with extra limbs, missing limbs, and other deformities.

He asked Stanley Sessions, an expert in amphibian limb development, to examine his specimens. Sessions found that the deformed amphibians all contained a parasite, now known to be Ribeiroia ondatrae, a trematode flatworm. Sessions and Ruth hypothesized that the parasite caused the deformities. As an initial test of this hypothesis, they implanted small glass beads near the developing limb buds of tadpoles. These beads were meant to mimic the effects of Ribeiroia, which produces cysts near the areas where limbs form in a tadpole as it transitions into an adult frog. In a 1990 paper, Sessions and Ruth reported that the beads caused deformities similar to (but less severe than) those Ruth had found.

More on the topic Early observations suggest that parasites cause amphibian deformities:

1. The studies of amphibian deformities that we discussed earlier in this chapter illustrate several ways in which ecologists seek to answer questions about the natural world.
2. In addition to the parasites outlined in this section, there are other parasites that are rarely seen in rats maintained in well-managed facilities.
3. A field experiment suggests that multiple factors influence frog deformities
4. CONCEPT 13.2 Hosts have mechanisms for defending themselves against parasites, and parasites have mechanisms for overcoming host defenses.
5. Deformity and Decline in Amphibian Populations: A Case Study
6. A laboratory experiment tests the role of parasites
7. Some Concluding Observations
8. Observations
9. Parasites can drive host populations to extinction
10. Concluding Observations
11. Concluding Observations
12. Parasites can influence host population cycles
13. Selected Observations by Dr. Cucliciu
14. The continuity thesis: some critical observations