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Publications
Lefcort, H., Vancura, J. A. 2006. Correlating invertebrate diversity and abundance to heavy metal levels in watersheds within the Mt. Coeur d'Alene area. U. S. Forest Service Report. 52 pages.
Lefcort, H., Ben-Ami, F., Heller, J. 2006. Terrestrial snails use predator-diet to asses danger. Journal of Ethology 24:97-102.
Some aquatic snails are able to use chemical cues (kairomones) to differentiate between predators that have fed on snails and predators that have eaten other prey. However, it is unknown if terrestrial snails are able to differentiate between snail-fed predators and predators that have not recently consumed snails. Here we document diet-based chemical discrimination of a predator, the ground beetle Carabus carabus, by a terrestrial snail Theba pisana. When exposed to the feces of snail-fed beetles, snails initially stopped all movements and then increased climbing speed. The snails also decreased time to deposition of their egg clutch. The snails did not react to an extract of crushed snails. Snails had only a partial reaction to the feces of beetles that had fed on chicken (Gallus domesticus) livers - they decreased climbing speed but did not alter egg laying times. These responses may be adaptive in that they allow snails to differentiate between individual beetles that may pose an immediate threat and beetles that may not. This is one of only a few studies to examine predator-diet effects on reproductive behavior.
Lefcort, H., Abbott, D. P., Cleary, D. A., Howell, E., Keller, N. C., Smith, M. M. 2004. Aquatic snails from mining sites have evolved to detect and avoid heavy metals. Archives of Environmental Contamination and Toxicology 46:478-484.
Toxicants in polluted environments are often patchily distributed. Hence, rather than being passive absorbers of pollution, some organisms have evolved the ability to detect and avoid toxicants. We studied the avoidance behavior of Physella columbiana, an aquatic pulmonate snail, in a pond that has been polluted with heavy metals for 120 years. Populations of this snail are rare at reference sites and are only robust at heavy metal polluted sites. We hypothesized that the snails are able to persist because they have evolved the ability to minimize their exposure to metals by actively avoiding metals in their environment.
Using a Y-maze flow tank we tested the avoidance behavior of the snails to heavy metal-polluted sediments and single-metal solutions of cadmium, zinc, or lead. We also tested the avoidance behaviors of the snail's lab reared offspring raised in nonpolluted conditions. In addition, we tested the avoidance behavior of a small population of the snails from a reference pond.
We found that, although all the snails we tested were able to detect very low concentrations of heavy metals, snails from the polluted site were the most sensitive, their offspring were somewhat less sensitive, and snails from the reference site were the least sensitive. This suggests that the ability of polluted site snails to avoid heavy metals is both genetic and environmental. The concentrations of metals that the snails from the polluted site avoided are below the levels found at hot spots within their natal pond. The snails may be able to persist at this site because they reduce their exposure by moving to less polluted sections of the pond.
One application of our findings is the use of aquatic snails and our Y-maze design as an inexpensive pollution detector. Environmental pollutants such as lead, zinc and arsenic are a problem throughout the world. People in lesser developed countries often lack sophisticated pollution detection devices. We have developed a behavioral assay of aquatic pollution that is easy to use, extremely sensitive (detection below 10 ppb), and can be constructed for less than US $100. Pulmonate snails are widely distributed in tropical, sub-tropical and temperate parts of the globe and they are often very common in polluted waters. For countries such as India and Bangladesh, which must test thousands of shallow wells for possible contamination with heavy metals, our assay would be a good initial test. Once snails detected metals, then those samples could be confirmed by spectrometers. We encourage scientists in lesser developed nations to consider our assay as an option.
McLaughlin N. J., McLaughlin DI, Lefcort H. 2003. The influence of socio-economic factors on Helicobacter pylori infection rates of students in rural Zambia. Central African Journal of Medicine, 49:38-41.
Although prevalence of disease in sub-Saharan Africa is often quite high, relatively little is known about the health of many populations. While much attention is often given to dramatic diseases such as AIDS, malaria, and tuberculosis, other diseases can also be very debilitating. We examined primary and secondary students to determine rates H. pylori. We then correlated these rates to socioeconomic factors such as income and tobacco use. We also explored the correlation of H. pylori to HIV and malaria.
H. pylori infection was common (60.9%) and was consistent with rates found in other African countries. We found no significant correlation between disease and socioeconomic variables. High school students in the community had an HIV positive rate of 9.2% with the rate increasing with age and 77.8% of the students reported that they had been treated for malaria.
Lefcort, H, and Eiger, S. M. 2003. Prepatory vs. practice homework: A test using university biology students. Journal of College Science Teaching 33:16-18.
The appropriate use of homework is unclear. We compared the performance of two different types of homework-preparatory (before class) and practice (after class). We also tested student performance and satisfaction against previous years classes when no homework was assigned. We tested 71 freshman students in a university ecology class. We found no difference in performance between students given preparatory versus practice homework. Satisfaction also did not alter when homework was assigned. However, overall student performance increased when compared to previous years classes where no homework of any kind was assigned.
Lefcort, H, Aguon, M. Q., Bond, K. A., Chapman, K. R., Chaquette, R., Clark, J., Kornachuk, P., Lang, B. Z., Martin, J. C. 2002. Indirect Effects of Heavy Metals on Parasites May Cause Shifts in Snail Species Compositions. Archives of Environmental Contamination and Toxicology 43:34-41.
We studied the direct and indirect effects of pollution on the distributions and abundances of two closely related species of pulmonate freshwater snails. Physella columbiana is more numerous at heavy-metal-polluted lakes while Lymnaea palustris is more numerous at reference lakes. Both species are present at all sites as are predacious bluegill sunfish (Lepomis macrochirus).
The direct effects examined included the snails' growth and reproduction in both the presence and absence of heavy metals and their short term survival when exposed to large concentrations of heavy metals. The indirect effects were the species' ability to elude capture by sunfish and the diversity and abundance of parasites within the snails.
We found that heavy metals had little direct effect on growth and reproduction and that both species acquired similar levels of metals in their tissues. Interestingly, P. columbiana (the more abundant species in polluted lakes) actually exhibited higher recruitment in the absence of metals than did L. palustris (reference lakes). L. palustris has life history characteristics that favor increased growth and reduced reproduction. These characteristics resulted in decreased predation of adults by gape-limited predators and a greater ability to cope with heavy parasite burdens. P. columbiana exhibited slower growth which resulted in increased predation although higher reproduction rates may compensate.
The major effect of heavy metals on species distributions was an indirect one on the snailsÕ parasites. Parasites appeared to be very susceptible to metals and this resulted in lower parasite diversity and intensities at polluted sites for both species of snails. P. columbiana may only be able to outcompete L. palustris at polluted sites due to the indirect effects of heavy metals; the negative effect of heavy metals on parasites and a proposed negative effect of metals on the foraging ability of sunfish that favors the faster reproducing P. columbiana.
Lefcort, H, Ammann, E, Eiger, S. M. 2000. Antipredatory behavior as an index of heavy-metal pollution? A test using snails and caddisflies. Archives of Environmental Contamination and Toxicology 38:311-316.
The loss of behaviors that organisms use to avoid predation may serve as a sensitive indicator of pollution. We tested the hypothesis that a correlation exists in the field between heavy metal levels and antipredator behaviors. We examined the antipredator behavior of aquatic caddisfly larvae and snails at sites in the Coeur d'Alene basin of Northern Idaho which varied in their levels of heavy metals.
We tested the antipredator response of Physella columbiana snails at 10 polluted lakes downstream from the Bunker Hill Environmental Protection Agency (EPA) Superfund cleanup site. We then compared their behavior to snails at 14 reference lakes. We placed the snails in a plastic testing apparatus, exposed them to an extract of crushed snail, and then monitored their movements to a normally preferred shaded area.
We also tested the behavior of caddisfly larvae from 36 sites from a total of six streams/rivers adjacent to the Superfund site. Sites were located upstream and downstream of abandoned mines. We located active larvae of four genera, simulated predation by grasping the animals between thumb and forefinger (the larvae respond to being grasped by withdrawing into their case), lifted them from the water for three seconds, and then placed them in an adjacent slower section of the stream. We then recorded how long it took each larvae to partially emerge from its case and attempt to move away.
Unlike reference site snails, snails from heavy-metal polluted environments failed to exhibit antipredator behaviors in response to crushed conspecifics. These results are consistent with previous laboratory studies. We found no effect of heavy metals on the antipredatory behavior of caddisfly larvae.
Lefcort, H, Thomson, S. M., Cowles, E. E., Harowicz, H. L., Livaudais, B. M., Roberts, W. E., Ettinger, W. F. 1999. The importance of fear: predator and heavy metal mediated competition between tadpoles and snails. Ecological Applications 9:1477-1489.
ABSTRACT
We examined how the effects of competition between snails (Lymnaea pulustris) and Columbia spotted frog (Rana luteiventris) tadpoles are mediated by predatory bluegill sunfish (Lepomis macrochirus) and heavy metals. We raised snails and tadpoles in outdoor mini-ecosystems containing lead, zinc and cadmium-contaminated soil from the EPA Superfund site in the Silver Valley of northern Idaho. To some treatments we added water from the tanks of sunfish that had fed on tadpoles and snails.
Unexpected indirect effects occurred in polluted environments. We found a habitat shift by snails and tadpoles due to the response of tadpoles towards predacious fish-odor. This shift decreased tadpole ingestion of metal-rich sediments, and increased metal ingestion by snails. Heavy metals and fish-odor therefore altered competitive interactions between snails and tadpoles.
Metal-exposed tadpoles metamorphosed at an older age than nonmetal-exposed animals. Metal exposure did not affect snail survival, growth, or recruitment. In the absence of heavy metals tadpoles reduced snail recruitment. Because heavy metals disproportionately harmed tadpoles, the negative effects of tadpoles on snails were ameliorated in polluted environments. The presence of snails did not alter tadpole development but did increase metal loads in tadpoles.
We also tested the ability of snails to detect and respond to chemical cues emanating from crushed snails, an extract of crushed snails and sunfish. Snails changed their behavior in response to crushed snails, but not to sunfish. Heavy metal-exposed snails did not alter their behavior.
Tadpoles altered their behavior when exposed to sunfish that had fed on tadpoles but did not respond to sunfish that had not fed on tadpoles.
We found that heavy metal toxicants and predator odor cause behavioral changes and can alter competitive interactions between snails and tadpoles. We also showed that due to indirect effects, pollution exposure for a given species may be modified both by the presence of competitors, and also by species that are neither competitors nor predators.
Lefcort, H, Meguire, R. A., Wilson, L. H., Ettinger, W. F. 1998. Heavy metals alter the survival, growth, metamorphosis, and antipredatory behavior of Columbia spotted frog (Rana luteiventris) tadpoles. Archives of Environmental Contamination and Toxicology 35:447-456.
ABSTRACT
Amphibians populations appear to be declining around the world. Although there is no single cause, one factor may be pollution from heavy metals. As a result of mining in the Silver Valley of Idaho, heavy metals have been released into habitats containing many species of sensitive organisms, including spotted frogs (Rana luteiventris). While the gross extent of pollution has been well documented, the more subtle behavioral effects of heavy metals such as lead, zinc and cadmium are less well studied.
We tested the effects of heavy metals on the short term survival (LC50) of spotted frog tadpoles. Compared to single metals, metals presented together were toxic at lower doses.
We also raised the tadpoles in outdoor mini-ecosystems containing either a single heavy metal or soil from an EPA Superfund site in the Silver Valley known to be composed of numerous heavy metals. Exposure to Silver Valley soil resulted in delayed metamorphosis.
We tested the ability of metal-exposed tadpoles to detect and respond to chemical cues emanating from predacious rainbow trout. We found that high levels of Silver Valley soil, medium levels of zinc, and medium and high levels of lead resulted in a decreased fright response. Low levels of cadmium, zinc, and lead did not cause a significant effect but low levels of soil did result in a decreased fright response. Heavy metals may alter interactions between tadpoles and their predators.
Lefcort, H. 1998. A chemically mediated fright-response in southern toad, Bufo terrestris, tadpoles Copeia 1998:445-450.
ABSTRACT
Laboratory experiments were used to determine if groups of southern toad (Bufo terrestris) tadpoles alter their activity levels and use of refugia when exposed to chemical, but not visual, cues from predacious, two-toed amphiuma (Amphiuma means), and eastern lesser sirens (Siren intermedia intermedia). Amphiuma and sirens hunt by tactile cues. Also explored was the effect of the predator's diet on the behavior of tadpoles and the tadpole's reaction to an extract of crushed toad tadpoles.
Predator-avoidance behavior may occasionally cause some prey to erroneously react to predators that find the prey species distasteful. To examine this behavior, this study tested the tadpole's reaction to warmouth sunfish (Lepomis gulosus) an organism that preys on many tadpoles but not distasteful toad tadpoles. Although many tadpole species school, behavioral tests of tadpoles are often carried out using single tadpoles. Therefore, the effect of group size on tadpole antipredatory behavior was also explored.
Tadpoles decreased their activity levels when exposed to water that had been in contact with sunfish but not sirens, amphiuma or southern leopard frog (Rana utricularia) tadpoles. The tadpoles' response to sunfish may be adaptive in that naive fishes must sample toad tadpoles to learn that they are distasteful. Tadpoles were able to differentiate between predators (sirens and amphiuma) fed toad tadpoles and predators fed leopard frog tadpoles.
The size of tadpole groups influences their response to predators. Tadpoles in groups of eight and twenty decreased movement to a similar degree but lone and paired tadpoles moved even less, often freezing during an entire trial. Future antipredatory behavioral tests of tadpoles that school should be performed on groups of more than two tadpoles.
Lefcort, H., Hancock, K., Maur, K. and Rostal, D. 1997. The effects of used motor oil and silt on the growth, survival, and the ability to detect predators by tiger salamanders, Ambystoma tigrinum. Archives of Environmental Contamination and Toxicology 32:383-388.
ABSTRACT
Amphibians appear to be declining worldwide. One cause of their decline 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 amphibians, or may indirectly affect them by disrupting food chains. The effects of oil may also be compounded by naturally occurring materials in the water column such as silt. Silt may interfere with respiration across gill surfaces.
This study examined the effects of oil and silt on the growth and metamorphosis of larval mole salamanders, Ambystoma opacum and A. tigrinum tigrinum. In Experiment One it examined ponds with and without silty water and oil pollution to determine their suitability as habitats for salamander larvae. In Experiment Two it studied the effects of low levels of oil combined with silt on animals raised in the laboratory and fed prey items not raised in oil. In Experiment Three, it explored the effects of oil at an ecosystem level by raising the salamanders in the field in plastic micro-mesocosms that mimicked small ponds. Finally, in Experiment Four in the laboratory, it examined the short-term survival of salamanders in high concentrations of oil.
This study found that ponds containing oil and silt produce salamanders of reduced size and weight. Furthermore, while salamanders are relatively robust to the short term effects of large concentrations of used motor oil, oil has deleterious effects on the community and therefore exerts an indirect negative effect on salamanders. In the micro-mesocosms containing oil, salamanders were smaller and weighed less than animals not raised in oil. Furthermore, silt results in reduced growth, earlier metamorphosis, and increased susceptibility to the water mold Saprolegnia parasitica.
Lefcort, H. and Durden, L. A. 1996. The effect of infection with Lyme disease spirochetes (Borrelia burgdorferi) on the phototaxis, activity, and questing height of the tick vector Ixodes scapularis. Parasitology113: 97-103.
ABSTRACT
Little is known about the effects of infection with Borrelia burgdorferi, the bacterium that causes Lyme disease, on its tick vectors. The purpose of this study was to determine the behavioural and ecological effects of infection by the bacterium in nymphal and adult black-legged (Ixodes scapularis) ticks. We found that the effects of infection were more pronounced in adults than in nymphs. Compared to uninfected adults, infected adults were less able to overcome physical obstacles, avoided vertical surfaces, were less active and quested at lower heights. Infected nymphs showed increased phototaxis and attraction to vertical surfaces. Infected nymphs also showed trends toward increased questing height and a greater tendency to overcome physical obstacles although these trends were not statistically significant. These altered behaviours in an infected tick may affect survival or pathogen transmission and may reflect kin selection in the bacterial pathogen.
Lefcort, H., Ben-Ami, F., Heller, J. In Press. Terrestrial Snails Use Predator-Diet to Asses Danger. Journal of Ethology.
Abstract
Some aquatic snails are able to use chemical cues (kairomones) to differentiate between predators that have fed on snails and predators that have eaten other prey. However, it is unknown if terrestrial snails are able to differentiate between snail-fed predators and predators that have not recently consumed snails. Here we document diet-based chemical discrimination of a predator, the ground beetle Carabus carabus, by a terrestrial snail Theba pisana. When exposed to the feces of snail-fed beetles, snails initially stopped all movements and then increased climbing speed. The snails also decreased time to deposition of their egg clutch. The snails did not react to an extract of crushed snails. Snails had only a partial reaction to the feces of beetles that had fed on chicken (Gallus domesticus) livers - they decreased climbing speed but did not alter egg laying times. These responses may be adaptive in that they allow snails to differentiate between individual beetles that may pose an immediate threat and beetles that may not. This is one of only a few studies to examine predator-diet effects on reproductive behavior.
Lefcort, H., Abbott, D. P., Cleary, D. A., Howell, E., Keller, N. C., Smith, M. M. 2004. Aquatic snails from mining sites have evolved to detect and avoid heavy metals. Archives of Environmental Contamination and Toxicology 46:478-484.
ABSTRACT
Toxicants in polluted environments are often patchily distributed. Hence, rather than being passive absorbers of pollution, some organisms have evolved the ability to detect and avoid toxicants. We studied the avoidance behavior of Physella columbiana, an aquatic pulmonate snail, in a pond that has been polluted with heavy metals for 120 years. Populations of this snail are rare at reference sites and are only robust at heavy metal polluted sites. We hypothesized that the snails are able to persist because they have evolved the ability to minimize their exposure to metals by actively avoiding metals in their environment.
Using a Y-maze flow tank we tested the avoidance behavior of the snails to heavy metal-polluted sediments and single-metal solutions of cadmium, zinc, or lead. We also tested the avoidance behaviors of the snailÕs lab reared offspring raised in nonpolluted conditions. In addition, we tested the avoidance behavior of a small population of the snails from a reference pond.
We found that, although all the snails we tested were able to detect very low concentrations of heavy metals, snails from the polluted site were the most sensitive, their offspring were somewhat less sensitive, and snails from the reference site were the least sensitive. This suggests that the ability of polluted site snails to avoid heavy metals is both genetic and environmental. The concentrations of metals that the snails from the polluted site avoided are below the levels found at hot spots within their natal pond. The snails may be able to persist at this site because they reduce their exposure by moving to less polluted sections of the pond.
One application of our findings is the use of aquatic snails and our Y-maze design as an inexpensive pollution detector. Environmental pollutants such as lead, zinc and arsenic are a problem throughout the world. People in lesser developed countries often lack sophisticated pollution detection devices. We have developed a behavioral assay of aquatic pollution that is easy to use, extremely sensitive (detection below 10 ppb), and can be constructed for less than US $100. Pulmonate snails are widely distributed in tropical, sub-tropical and temperate parts of the globe and they are often very common in polluted waters. For countries such as India and Bangladesh, which must test thousands of shallow wells for possible contamination with heavy metals, our assay would be a good initial test. Once snails detected metals, then those samples could be confirmed by spectrometers. We encourage scientists in lesser developed nations to consider our assay as an option.
McLaughlin N. J., McLaughlin DI, Lefcort H. 2003. The influence of socio-economic factors on Helicobacter pylori infection rates of students in rural Zambia. Central African Journal of Medicine, 49:38-41.
ABSTRACT
Although prevalence of disease in sub-Saharan Africa is often quite high, relatively little is known about the health of many populations. We conducted two studies on an understudied rural Zambian population. One, we surveyed a hospital population for prevalence of anemia, malaria, and HIV. Two, we examined high school students and determined rates of anemia, malaria, HIV, H. pylori and then we correlated rates of infection to socioeconomic factors such as income and tobacco use.
Of patients admitted to the hospital for any reason, rates of HIV infection were over 65% for all three years that were sampled. High school students in the community had an HIV positive rate of 9.2% with the rate increasing with age.
Rates of malaria in the hospital population were 48.5% in children and 30.7% in adults. Anemia rates were 38.7% in children and 25.4% in adults. 77.8% of high school students reported that they had been treated for malaria.
H. pylori infection also common (60.9%) although it was consistent with rates found in other African countries. We found no significant correlation between disease and socioeconomic variables. HIV prevalence levels did not increase from 1997 to 1999.
Lefcort, H, and Eiger, S. M. 2003. Prepatory vs. practice homework: A test using university biology students. Journal of College Science Teaching 33:16-18.
ABSTRACT
The appropriate use of homework is unclear. We compared the performance of two different types of homework Š preparatory (before class) and practice (after class). We also tested student performance and satisfaction against previous years classes when no homework was assigned. We tested 71 freshman students in a university ecology class. We found no difference in performance between students given preparatory versus practice homework. Satisfaction also did not alter when homework was assigned. However, overall student performance increased when compared to previous years classes where no homework of any kind was assigned.
Lefcort, H, Aguon, M. Q., Bond, K. A., Chapman, K. R., Chaquette, R., Clark, J., Kornachuk, P., Lang, B. Z., Martin, J. C. 2002. Indirect Effects of Heavy Metals on Parasites May Cause Shifts in Snail Species Compositions. Archives of Environmental Contamination and Toxicology 43:34-41.
Abstract
We studied the direct and indirect effects of pollution on the distributions and abundances of two closely related species of pulmonate freshwater snails. Physella columbiana is more numerous at heavy-metal-polluted lakes while Lymnaea palustris is more numerous at reference lakes. Both species are present at all sites as are predacious bluegill sunfish (Lepomis macrochirus).
The direct effects examined included the snailsÕ growth and reproduction in both the presence and absence of heavy metals and their short term survival when exposed to large concentrations of heavy metals. The indirect effects were the speciesÕ ability to elude capture by sunfish and the diversity and abundance of parasites within the snails.
We found that heavy metals had little direct effect on growth and reproduction and that both species acquired similar levels of metals in their tissues. Interestingly, P. columbiana (the more abundant species in polluted lakes) actually exhibited higher recruitment in the absence of metals than did L. palustris (reference lakes). L. palustris has life history characteristics that favor increased growth and reduced reproduction. These characteristics resulted in decreased predation of adults by gape-limited predators and a greater ability to cope with heavy parasite burdens. P. columbiana exhibited slower growth which resulted in increased predation although higher reproduction rates may compensate.
The major effect of heavy metals on species distributions was an indirect one on the snailsÕ parasites. Parasites appeared to be very susceptible to metals and this resulted in lower parasite diversity and intensities at polluted sites for both species of snails. P. columbiana may only be able to outcompete L. palustris at polluted sites due to the indirect effects of heavy metals; the negative effect of heavy metals on parasites and a proposed negative effect of metals on the foraging ability of sunfish that favors the faster reproducing P. columbiana.
Publications