Award Date

2004

Degree Type

Thesis

Degree Name

Master of Science in Environmental Science

Department

Environmental Science

Advisor 1

Dr. Shawn Gerstenberger, Ph. D.

First Committee Member

Dr. Chad Cross, Ph. D.

Second Committee Member

Dr. Stan Hillyard, Ph. D.

Graduate Faculty Representative

Dr. Paul Ferguson, Ph. D.

Number of Pages

188

Abstract

The purpose of this study was to assess the effects of environmentally relevant concentrations of perchlorate on the development and growth of Rana pipiens. Ammonium perchlorate is a rocket fuel oxidizer that is known to interfere with the function of the thyroid gland and some of the highest United States surface water concentration exists in the Las Vegas Wash, NV. Perchlorate not only blocks the body’s ability to incorporate iodine into T3 and T4 hormones through the sodium iodine symporter system, but also depletes the thyroid glands’ internal stores of iodine. Many of the steps that regulate metamorphosis in amphibians are also triggered by thyroid hormones therefore we investigated the ability of perchlorate to interfere with the development and metamorphosis of Rana pipiens. Aquaria containing concentrations of 40 ppb, 400 ppb, and 4000 ppb perchlorate with a 0 ppb perchlorate control as well as a magnesium control (since magnesium perchlorate was used) to evaluate the growth and development of Rana pipiens. Measuring snout to vent length, hindlimb length, tail length and total body length weekly on 40 animals per tank allowed the growth of the tadpoles to be monitored throughout the study. Development of the tadpoles was determined by staging 20 animals per dose group according to the Taylor-Kollros Index. Metabolic rate for each dose group was assessed monthly by determining oxygen consumption; while deformities, as well as mortality, were tracked daily. The magnesium control completed metamorphosis during week 10, followed by the 40 ppb and 4000 ppb groups in week 21 with the control and 400 ppb group completing development during week 33. The magnesium control was larger (tail, snout to vent, total body, hindlimb) than all of the other groups during weeks 2-11. The weight adjusted oxygen consumption provided similar results with the magnesium and control groups consuming more oxygen than the other groups, while the 400 ppb group consistently consumed the least oxygen. Experimental problems significantly reduced the number of animals in 400 ppb, magnesium control and 4000 ppb groups thereby causing resource allocation problems. The magnesium control group developed faster than all other groups, which could be due to magnesium’s up-regulation during glycolysis. The increased energy production could be accelerating metamorphosis, and hence attenuating perchlorate’s inhibitory mechanism. Oxygen consumption appears to be a more sensitive biomarker, and is useful for detecting alterations prior to seeing adverse effects on growth and development. The concentrations of perchlorate used in this study did not delay development or metamorphosis in Rana pipiens.

Keywords

Ammonium perchlorate; Amphibian metamorphosis; Las Vegas Wash; Nevada; Northern Leopard Frogs; Rana pipiens; Thyroid glands; Water pollution

Disciplines

Desert Ecology | Environmental Indicators and Impact Assessment | Environmental Sciences | Zoology

Language

English


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