THE EFFECTS OF USED MOTOR OIL, SILT, AND THE WATER MOLD SAPROLEGNIA-PARASITICA ON THE GROWTH AND SURVIVAL OF MOLE SALAMANDERS (GENUS AMBYSTOMA)

Amphibians appear to be declining worldwide. One cause of their declin e may be used crankcase oil which leaks from motor vehicles and washes into ponds. Once in ponds, the oil may either be directly toxic to am phibians, or may indirectly affect them by disrupting food chains. The effects of oil may also be compounded by naturally occurring material s in the water column such as silt. Silt may interfere with respiratio n across gill surfaces. This study examined the effects of oil and sil t on the growth and metamorphosis of larval mole salamanders, Ambystom a opacum and A. tigrinum tigrinum. In Experiment One it examined ponds with and without silty water and oil pollution to determine their sui tability as habitats for salamander larvae. In Experiment Two it studi ed the effects of low levels of oil combined with silt on animals rais ed in the laboratory and fed prey items not raised in oil. In Experime nt Three, it explored the effects of oil at an ecosystem level by rais ing the salamanders in the field in plastic micromesocosms that mimick ed small ponds. Finally, in Experiment Four, in the laboratory, it exa mined the short-term survival of salamanders in high concentrations of oil. This study found that ponds containing oil and silt produce sala manders of reduced size and weight. Furthermore, while salamanders are relatively robust to the short term effects of large concentrations o f used motor oil, oil has deleterious effects on the community and the refore exerts an indirect negative effect on salamanders. In the micro -mesocosms containing oil, salamanders were smaller and weighed less t han animals not raised in oil. Furthermore, silt results in reduced gr owth, earlier metamorphosis, and increased susceptibility to the water mold Saprolegnia parasitica.