The effect of lead poisoning on the reproductive behaviors and sex characteristics of male fathead minnows Anna Field Brookfield Central High School
Abstract In this experiment, the class observed lead poisoned fathead minnows in order to determine whether lead has any effect on their reproductive behaviors and sex characteristics. In order to answer this question, four tanks of water were stationed around the room and two were poisoned with lead. Each tank was divided into three sections, each containing a plastic breeding chamber and one fathead minnow of each gender. The students spent 0 minutes observing each section and recorded data regarding the minnow s sex characteristics and reproductive behaviors. The sex characteristics that the students observed included dorsal fin spot, head pad, side bars, and tubercles. After observing sex characteristics, reproductive behaviors, nest preparation, spawning, hovering, chasing, and patrol were recorded. At the end of the experiment, students used the data that they collected to determine which two tanks were poisoned and whether lead poisoning affects the reproductive behavior and sex characteristics of a fathead minnow. Based on the data gathered throughout the course of the experiment, I can conclude that some reproductive behaviors are affected by lead poisoning. For example, the poisoned minnows hovered two times more than the non-poisoned minnows. Although the most common behavior, hovering, was affected by lead, some of the less common behaviors were observed in larger quantities in the lead poisoned tanks. Students discovered this when observing chasing because the lead poisoned minnows chased more than the non-poisoned minnows. I also found that lead poisoning did not have an effect on fathead minnow sex characteristics except for lack of tubercle formation in the minnows in Tank B. Overall, after testing the effect of lead on the reproductive behaviors and sex characteristics of fathead minnows, the conclusion can be drawn that only some reproductive behaviors and no sex characteristics of the fathead minnows are affected by lead.
Introduction In this experiment, our class observed fathead minnows and determined whether they were lead poisoned based on sex characteristics and reproductive behaviors. Multiple items in homes and cities contain lead and can cause lead poisoning. Most houses that are more than 40 years old have lead paint covering the walls. For this reason, the people who inhabit these houses are constantly exposed to lead, which has been proven to be dangerous. Lead poisoning can result in delayed movement, poor speech and language, learning disabilities, behavioral problems, and coordination deficiencies (Dewalt et. al, 0). Lead poisoning occurs not only in the United States, but in many countries across the globe. In the Amazon, lead is used to make fishing supplies, which is occasionally used to clean human teeth (Fraser 03). Researchers found that this resulted in lead poisoning and the affected people of the Amazon experienced a decrease in IQ and various brain functions. However, it was observed that these symptoms dwindled when people started making the fishing supplies out of different metals (Fraser 03). There is also a type of pottery in Mexico that requires lead paint. The potters experienced similar symptoms to the people of the Amazon when they put their pottery in the kiln and it released toxic lead fumes throughout their homes (English 0). Overall, lead is a prevalent problem all over the world. Fathead minnows are a good model for this experiment because they are living things with simple body structures that can be easily manipulated. A fathead minnow s actions are also easy to observe and interpret. Research reveals that lead has a negative effect on the reproductive behaviors of fathead minnows. Female fathead minnows exposed to lead oviposited less, laid fewer eggs, and had embryos that had developed abnormally (Marine and Freshwater Biomedical Core Center 993).
Male fathead minnows exposed to lead experienced a decrease in sex characteristics (Marine and Freshwater Biomedical Core Center 993). This included banding, which are the stripes on the fish s fins, and tubercle formation or dots around the fathead minnow s eyes. Research has revealed that fathead minnows poisoned with drugs or lead experience a decrease in reproductive behaviors and sex characteristics. I hypothesised that if fathead minnows are poisoned with lead then they will show fewer reproductive behaviors and sex characteristics because lead causes movement, coordination, and mental problems in humans. Materials 4 aquariums 8 plastic tank dividers with holes A thermometer siphon which is plastic tubing 6 in in length and ¼ in inner diameter male fathead minnows female fathead minnows container of TetraMin fish food 0mL pipette 000pm of a lead nitrate solution 0 gallons of dechlorinated water Procedure There are four water filled tanks set up around the room and each are divided into three sections comprised of a pair of opposite gender fathead minnows and one breeding chamber. Two of these tanks are exposed to a 000pm lead nitrate solution and the other two, the control
tanks, are filled with clean water. When the students begin the experiment they first feed each section of fish one pipette of fish food and wait five minutes before they start observing. When observing, each member of the group has a job. There are the observers, a timer, and the recorders. While the fish are eating their food, the group will look at the minnows in order to determine which sex characteristics they exhibit. After five minutes has passed, the timer will give the observers and recorders a 0 second warning. Once the timer starts, the observers will call out the male minnow s reproductive behaviors and the recorders will tally the different actions. Once the observers have been observing for minutes, the timer will stop and the process will be repeated for the other tanks. This will happen every day for three days. This is a picture of the tank. It is divided into three sections with a male and female fathead minnow in each. The white half tubes are the breeding chambers.
Results The effect of lead on the reproductive behaviors of male fathead minnows Tank A Tank B Tank C Tank D Type of Reproductive Characteristic N H S C P N H S C P N H S C P N H S C P # of Times Characteristic was Observed 8 0 3 3 9 4 9 9 6 9 4 4 3 3 4 9 3 9 Key of Reproductive Behaviors (Definitions from Student Worksheet #4C) N=Nest Preparation-Touching the ceiling of the breeding chamber with its body (nibbling with its mouth or brushing it with its dorsal head pad) to clean the ceiling and possibly place a mucous layer on the ceiling of the breeding chamber so eggs stick to it. H=Hover-Swimming above the halfway point of the breeding chamber without touching the ceiling. S=Spawning-Release of eggs by the female and milt by the male, usually after the male and female swim side-by-side and he flips her over so the eggs are deposited on the ceiling inside the breeding chamber. C=Chasing-Male swims rapidly after the female or another male outside the breeding chamber; sometimes the female may swim after the male. P=Patrol-Swimming behavior outside the breeding substrate. It may or may not include chasing. Key of Sex Characteristics Dorsal Fin Spot-The line on the minnow s fin Head Pad-The hard, raised part of the minnow s forehead Side Bars-Strips on the side of the minnow
Tubercles-The dots around the minnow s eyes Tank A Male fathead minnow sex characteristics Section Dorsal Fin Spot Head Pad Side Bars Tubercles A yes yes yes yes B yes yes yes yes C yes yes yes yes Tank B Section Dorsal Fin Spot Head Pad Side Bars Tubercles A yes yes yes no B yes yes yes no C yes yes yes no
Tank C Section Dorsal Fin Spot Head Pad Side Bars Tubercles A yes yes yes yes B yes yes yes yes C yes yes yes yes Tank D Section Dorsal Fin Spot Head Pad Side Bars Tubercles A yes yes yes yes B yes yes yes yes C yes yes yes yes Our data revealed that the poisoned tanks had a lower number of reproductive behaviors but lead poisoning did not affect the fathead minnows sex characteristics. All of the fathead minnows exhibited all of the sex characteristics except for the tubercles in Tank B. Based on this, I concluded that lead poisoning did not affect the sex characteristics of fathead minnows. While sex characteristics were not affected, lead did affect the reproductive behaviors of fathead minnows. Reproductive behaviors in Tanks A and B dramatically surpassed Tanks C and D in regard to quantity of hovering. The minnows in Tank A hovered 8 times and the minnows in Tank B hovered times. These numbers are more than double the 9 times the minnows hovered in Tanks C and D. While the difference was not quite as drastic when it came to nesting, Tanks A and B still had a greater nesting number than Tanks C and D. Tank A minnows nested times and minnows in Tank B nested 39 times while Tank C minnows nested 6 times and Tank D minnows nested 34 times. Nesting and hovering were the most common reproductive
behaviors as the number of times the fathead minnows spawned, chased, and patrolled was quite low. Tank A did not spawn, Tank B spawned 4 times, and Tank D spawned 3 times, while Tank C exceeded all of the tanks and spawned times. Similar results arose when observing chasing as Tanks A, B, and D had very low numbers while Tank C chased more than all of the other tanks combined. While observing patrol, it was discovered that Tanks A and C had very similar numbers. Tanks B and D also had similar statistics. Based on these results, it could be concluded that Tanks C and D were poisoned because, overall, the fathead minnows that they contained did not present as many reproductive behaviors as the minnows in Tanks A and B. Conclusion From the data collected during this experiment, I can conclude that lead poisoning causes a decrease in some reproductive behaviors among fathead minnows but does not affect sex characteristics. The most common reproductive behaviors, hovering and nesting, were observed in the highest quantities in Tanks A and B but other reproductive behaviors showed little correlation between lead poisoning and a decrease in reproductive behaviors. My hypothesis for this experiment was, if fathead minnows are poisoned with lead then they would show fewer sex characteristics and reproductive behaviors because lead causes movement, coordination, and mental problems in humans (Weber et. al, 03). I reject this hypothesis because, while some reproductive behaviors were fewer when exposed to lead, the poisoned minnows did not have a lower number of spawning, chasing, or patrol when compared to the non-lead-exposed minnows. For example, the lead poisoned minnows chased 44 and 9 times while the non-lead-poisoned minnows chased and 9 times. Also, when spawning, the non-lead-poisoned minnows had 4 and 0 while the lead poisoned minnows had and 3. Also, there was no correlation between sex characteristics and whether or not the fish was poisoned.
Some errors that could have occurred throughout the course of the experiment include different groups having different definitions of hovering or other reproductive behaviors. This would result in skewed data. Another potential source of error includes fish dying. Fathead minnows do not live long so if fish are not moving then it may not be a result of lead poisoning but of some other disease. This experiment could be improved if the class observed together so that everyone would have the same interpretations of reproductive behaviors. It could also be improved if animals with longer life spans were used. Additional Questions The data that was collected regarding the effects of lead poisoning on the reproductive behaviors and sex characteristics of fathead minnows led me to form more questions related to the topic. Since lead has a partial impact on minnows, I wondered if other materials such as drugs or alcohol would have an effect on the reproductive behaviors or sex characteristics of fathead minnows. Another question that I would like to further explore is whether the temperature of water affects fathead minnows. Overall, this experiment has caused me to ask questions to deepen my knowledge on the sex characteristics and reproductive behaviors of fathead minnows. Works Cited English, Bella. (0). Nonprofit Helps Artisans in Mexico Get Lead Out. Retrieved from http://www.bostonglobe.com/arts/theater-art/0///nonprofit-helps-ceramicartisans-mexico-convert-lead-free-glazes/yjsuv0rhd3jwz8o6ik4doj/story.html Fraser, Barbara. (03). Surprising Source of Lead in the Amazon. Retrieved from http://www.bostonglobe.com/arts/theater-art/0///nonprofit-helps-ceramicartisans-mexico-convert-lead-free-glazes/yjsuv0rhd3jwz8o6ik4doj/story.html
Marine and Freshwater Biomedical Core Center. (993). Exposure to sublethal levels of waterborne lead alters reproductive behavior patterns in fathead minnows. (Pimephales promelas). Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/847408 Weber, D., Hesselbach, R., Kane, A., Petering, D., Petering, L., Berg, C. (0). Minnows as a Classroom Model for Environmental Health. Retrieved from chromeextension://mloajfnmjckfjbeeofcdaecbelnblden/http://www4.uwm.edu/cehsc/news/upload /MinnowsClassroomModel.pdf