Dr Peter Macreadie

Geraldi, N.R. & Macreadie, P.I. 2013, 'Restricting prey dispersal can overestimate the importance of predation in trophic cascades', PLoS One, vol. 8, no. 2, p. e55100.

Macreadie, P.I., Allen, K., Kelaher, B.P., Ralph, P.J. & Skilbeck, C.G. 2012, 'Paleoreconstruction of estuarine sediments reveal human-induced weakening of coastal carbon sinks', Global Change Biology, vol. 18, no. 3, pp. 891-901.
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Human activities in coastal areas frequently cause loss of benthic macrophytes (e.g. seagrasses) and concomitant increases in microalgal production through eutrophication. Whether such changes translate into shifts in the composition of sediment detritus is largely unknown, yet such changes could impact the role these ecosystems play in sequestrating CO2. We reconstructed the sedimentary records of cores taken from two sites within Botany Bay, Sydney the site of European settlement of Australia to look for human-induced changes in dominant sources of detritus in this estuary. Cores covered a period from the present day back to the middle Holocene (6000years) according to 210Pb profiles and radiocarbon (14C) dating. Depositional histories at both sites could not be characterized by a linear sedimentation rate; sedimentation rates in the last 3050years were considerably higher than during the rest of the Holocene. C:N ratios declined and began to exhibit a microalgal source signature from around the time of European settlement, which could be explained by increased nutrient flows into the Bay caused by anthropogenic activity. Analysis of stable isotopic ratios of 12C/13C showed that the relative contribution of seagrass and C3 terrestrial plants (mangroves, saltmarsh) to detritus declined around the time of rapid industrial expansion (1950s), coinciding with an increase in the contribution of microalgal sources. We conclude that the relative contribution of microalgae to detritus has increased within Botany Bay, and that this shift is the sign of increased industrialization and concomitant eutrophication.

Macreadie, P.I., Geraldi, N.R. & Peterson, C.H. 2012, 'Preference for feeding at habitat edges declines among juvenile blue crabs as oyster reef patchiness increases and predation risk grows', Marine Ecology Progress Series, vol. 466, pp. 145-153.
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Both habitat patchiness and behaviorally-mediated indirect effects (BMIEs; predator-induced changes in prey behavior that affect the prey+s resources) are important in many food webs, but the relationships between these 2 factors have yet to be investigated. To explore effects of habitat patchiness and variation in perceived risk of predation on food-web dynamics, we conducted a factorial experiment in a model aquatic food chain of predator-prey-resource using 2 contrasting predators (adult blue crab Callinectes sapidus and toad fish Opsanus tau), juvenile blue crab as prey, and mussel Geukensia demissa as resource. Both predator presence and habitat patchiness influenced the prey+s preference for consuming resources at patch edges instead of interiors. The preference of prey for consuming resources at habitat edges was 4 times stronger in continuous oyster reef habitat than in smaller habitat patches. This suggests that interior resources in continuous habitat experience a refuge from consumption, but this refuge is largely lost in patchy habitat. The mere presence of predators reduced the prey+s preference for consuming resources at habitat edges. This BMIE was significant for the ambush predator (toadfish) and the treatment containing both predators, but not for the actively hunting predator (adult blue crab). We conclude that habitat patchiness and predator presence can jointly affect resource distribution by inducing shifts in prey foraging behavior, revealing a need to incorporate BMIEs into habitat fragmentation studies. This conclusion has broad and growing relevance as anthropogenic factors increasingly modify predator abundances and fragment coastal habitats.

Sherman, C.D., Stanley, A.M., Keough, M.J., Gardner, M.G. & Macreadie, P.I. 2012, 'Development of twenty-three novel microsatellite markers for the seagrass, Zostera muelleri from Australia', Conservation Genetics Resources, vol. 4, no. 3, pp. 689-693.
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Seagrasses are one of the most productive and economically important habitats in the coastal zone, but they are disappearing at an alarming rate, with more than half the world's seagrass area lost since the 1990s. They now face serious threat from climate change, and there is much current speculation over whether they will survive the coming decades. The future of seagrasses depends on their ability to recover and adapt to environmental change-i.e. their 'resilience'. Key to this, is understanding the role that genetic diversity plays in the resilience of this highly clonal group of species. To investigate population structure, genetic diversity, mating system (sexual versus asexual reproduction) and patterns of connectivity, we isolated and characterised 23 microsatellite loci using next generation sequencing for the Australian seagrass species, Zostera muelleri (syn. Z. capricorni), which is regarded as a globally significant congeneric species. Loci were tested for levels of variation based on eight individuals sampled from Lake Macquarie, New South Wales, Australia. We detected high to moderate levels of genetic variation across most loci with a mean allelic richness of 3.64 and unbiased expected hetrozygosity of 0.562. We found no evidence for linkage disequilibrium between any loci and only three loci (ZosNSW25, ZosNSW2, and ZosNSW47) showed significant deviations from Hardy-Weinberg expectations. All individuals displayed a unique multi-locus genotype and the combined probability of identity across all loci was low (P (ID) = 1.87 x 10(-12)) indicating a high level of power in detecting unique genotypes. These 23 markers will provide an important tool for future population genetic assessments in this important keystone species.

Booth, D.J., Bond, N. & Macreadie, P.I. 2011, 'Detecting range shifts among Australian fishes in response to climate change', Marine and Freshwater Research, vol. 62, no. 9, pp. 1027-1042.
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One of the most obvious and expected impacts of climate change is a shift in the distributional range of organisms, which could have considerable ecological and economic consequences. Australian waters are hotspots for climate-induced environmental changes; here, we review these potential changes and their apparent and potential implications for freshwater, estuarine and marine fish. Our meta-analysis detected <300 papers globally on 'fish' and 'range shifts', with similar to 7% being from Australia. Of the Australian papers, only one study exhibited definitive evidence of climate-induced range shifts, with most studies focussing instead on future predictions. There was little consensus in the literature regarding the definition of 'range', largely because of populations having distributions that fluctuate regularly. For example, many marine populations have broad dispersal of offspring (causing vagrancy). Similarly, in freshwater and estuarine systems, regular environmental changes (e. g. seasonal, ENSO cycles - not related to climate change) cause expansion and contraction of populations, which confounds efforts to detect range 'shifts'. We found that increases in water temperature, reduced freshwater flows and changes in ocean currents are likely to be the key drivers of climate-induced range shifts in Australian fishes. Although large-scale frequent and rigorous direct surveys of fishes across their entire distributional ranges, especially at range edges, will be essential to detect range shifts of fishes in response to climate change, we suggest careful co-opting of fisheries, museum and other regional databases as a potential, but imperfect alternative.

Jenkins, G.S., Syme, A. & Macreadie, P.I. 2011, 'Feeding Ecology Of King George Whiting Sillaginodes Punctatus (Perciformes) Recruits In Seagrass And Unvegetated Habitats. Does Diet Reflect Habitat Utilization?', Journal Of Fish Biology, vol. 78, no. 5, pp. 1561-1573.
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This study investigated the feeding ecology of King George whiting Sillaginodes punctatus recruits to determine how diet composition varies between habitat types (seagrass and unvegetated habitats), and between sites separated by distance. Broad-scale sa

Macreadie, P.I., Geraldi, N.R. & Peterson, C.H. 2011, 'How small-scale variation in oyster reef patchiness influences predation on bivalves', Marine Ecology Progress Series, vol. 429, pp. 87-91.
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As oyster fishing continues to degrade reef habitat along the US Atlantic coast, oyster reefs appear increasingly fragmented on small spatial scales. In outdoor mesocosms, experiments tested how consumption of representatives of 4 different bivalve guilds by each of 3 mesopredators varies between continuous and fine-scale patches of oyster reef habitat. The mesopredator that fed least (stone crab) exhibited no detectable change in consumption on any bivalve (ribbed mussel, bay scallop, hard clam, and 3 size classes of eastern oyster). Consumption of bay scallops by both blue crabs and sheepshead fish was greater in small patches than in continuous oyster reef habitat. Of the bivalve guilds tested, only the scallop possesses swimming motility sufficient to reduce predation, an escape response that would likely leave the bivalve protected within structured habitat in larger continuous oyster reefs. Sheepshead consumed more small oysters in the continuous habitat than in the fine patches, while no other predator-prey interaction exhibited differential feeding as a function of habitat patchiness. Consequently, predation by mesopredators on bivalves can vary with the scale of oyster reef patchiness, but this process may depend upon the bivalve guild. Understanding the role of habitat patchiness on fine scales may be increasingly important in view of the declines in apex predatory sharks leading to mesopredator release, and global climate change directly and indirectly enhancing stone crab abundances, thereby increasing potential predation on bivalves.

Macreadie, P.I., Bishop, M.J. & Booth, D.J. 2011, 'Implications of climate change for macrophytic rafts and their hitchhikers', Marine Ecology Progress Series, vol. 443, pp. 285-292.
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Most models predicting changes to species distributions under future climate scenarios ignore dispersal processes, despite their importance in determining community structure in both terrestrial and aquatic systems ('supply-side ecology'). In the marine environment, facilitation of long-distance dispersal of coastal organisms by macrophytic rafts may be severely modified by climate impacts on raft supply, quality, and persistence, and on transport processes. Increasing storminess in the coastal zone, higher water temperatures, and changes in water circulation represent some of the key mechanisms that will directly affect rafts, while increases in herbivore metabolism due to higher water temperatures are likely to indirectly reduce raft longevity through raft consumption. Accurate predictions of climate impacts on coastal biodiversity will be contingent on resolution of factors influencing rafting so that this and other dispersal mechanisms can be incorporated into species distribution models.

Macreadie, P.I., Fowler, A.M. & Booth, D.J. 2011, 'Rigs-to-reefs: will the deep sea benefit from artificial habitat?', Frontiers in Ecology and the Environment, vol. 9, no. 8, pp. 455-461.
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As a peak in the global number of offshore oil rigs requiring decommissioning approaches, there is growing pressure for the implementation of a +rigs-to-reefs+ program in the deep sea, whereby obsolete rigs are converted into artificial reefs. Such decommissioned rigs could enhance biological productivity, improve ecological connectivity, and facilitate conservation/restoration of deep-sea benthos (eg cold-water corals) by restricting access to fishing trawlers. Preliminary evidence indicates that decommissioned rigs in shallower waters can also help rebuild declining fish stocks. Conversely, potential negative impacts include physical damage to existing benthic habitats within the +drop zone+, undesired changes in marine food webs, facilitation of the spread of invasive species, and release of contaminants as rigs corrode. We discuss key areas for future research and suggest alternatives to offset or minimize negative impacts. Overall, a rigs-to-reefs program may be a valid option for deep-sea benthic conservation.

Macreadie, P.I., Connolly, R., Jenkins, G.P., Hindell, J.S. & Keough, M.J. 2010, 'Edge patterns in aquatic invertebrates explained by predictive models', Marine and Freshwater Research, vol. 61, pp. 214-218.
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Predictive frameworks for understanding and describing how animals respond to habitat fragmentation, particularly across edges, have been largely restricted to terrestrial systems. Abundances of zooplankton and meiofauna were measured across seagrass+sand edges and the patterns compared with predictive models of edge effects. Artificial seagrass patches were placed on bare sand, and zooplankton and meiofauna were sampled with tube traps at five positions (from patch edges: 12, 60 and 130 cm into seagrass; and 12 and 60 cm onto sand). Position effects consisted of the following three general patterns: (1) increases in abundance around the seagrass+sand edge (total abundance and cumaceans); (2) declining abundance from seagrass onto sand (calanoid copepods, harpacticoid copepods and amphipods); and (3) increasing abundance from seagrass onto sand (crustacean nauplii and bivalve larvae). The first two patterns are consistent with resource-distribution models, either as higher resources at the confluence of adjacent habitats or supplementation of resources from high-quality to low-quality habitat. The third pattern is consistent with reductions in zooplankton abundance as a consequence of predation or attenuation of currents by seagrass. The results show that predictive models of edge effects can apply to aquatic animals and that edges are important in structuring zooplankton and meiofauna assemblages in seagrass

Macreadie, P.I., Connolly, R., Keough, M.J., Jenkins, G.P. & Hindell, J.S. 2010, 'Short-term differences in animal assemblages in patches formed by loss and growth of habitat', Austral Ecology, vol. 35, no. 5, pp. 515-521.
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Ecological theory predicts that habitat growth and loss will have different effects on community structure, even if they produce patches of the same size. Despite this, studies on the effects of patchiness are often performed without prior knowledge of the processes responsible for the patchiness. We manipulated artificial seagrass habitat in temperate Australia to test whether fish and crustacean assemblages differed between habitats that formed via habitat loss and habitat growth. Habitat loss treatments (originally 16 m2) and habitat growth treatments (originally 0 m2) were manipulated over 1 week until each reached a final patch size of 4 m2. At this size, each was compared through time (0+14 days after manipulation) with control patches (4 m2 throughout the experiment). Assemblages differed significantly among treatments at 0 and 1 day after manipulation, with differences between growth and loss treatments contributing to most of the dissimilarity.

Macreadie, P.I., Hindell, J., Keough, M., Jenkins, G.S. & Connolly, R. 2010, 'Resource Distribution Influences Positive Edge Effects In A Seagrass Fish', Ecology, vol. 91, no. 7, pp. 2013-2021.
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According to conceptual models, the distribution of resources plays a critical role in determining how organisms distribute themselves near habitat edges. These models are frequently used to achieve a mechanistic understanding of edge effects, but becaus

Smith, J.E., Macreadie, P.I. & Swearer, S.E. 2010, 'An osmotic induction method for externally marking saltwater fishes, Stigmatopora argus and Stigmatopora nigra, with calcein', Journal Of Fish Biology, vol. 76, no. 4, pp. 1055-1060.
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Calcein marking via osmotic induction and overnight immersion was compared in saltwater fishes. Immersion in a salt solution for 10 min followed by 30 min in a 500 mg l^-1 calcein solution produced the highest fluorescent mark in 40 min with no effect on survival.

Macreadie, P.I., Hindell, J.S., Jenkins, G.P., Connolly, R. & Keough, M.J. 2009, 'Fish responses to experimental fragmentation of seagrass habitat', Conservation Biology, vol. 23, no. 3, pp. 644-652.
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Understanding the consequences of habitat fragmentation has come mostly from comparisons of patchy and continuous habitats. Because fragmentation is a process, it is most accurately studied by actively fragmenting large patches into multiple smaller patches. We fragmented artificial seagrass habitats and evaluated the impacts of fragmentation on fish abundance and species richness over time (1 day, 1 week, 1 month). Fish assemblages were compared among 4 treatments: control (single, continuous 9-m² patches); fragmented (single, continuous 9-m² patches fragmented to 4 discrete 1-m² patches); prefragmented/patchy (4 discrete 1-m² patches with the same arrangement as fragmented); and disturbance control (fragmented then immediately restored to continuous 9-m² patches). Patchy seagrass had lower species richness than actively fragmented seagrass (up to 39% fewer species after 1 week), but species richness in fragmented treatments was similar to controls. Total fish abundance did not vary among treatments and therefore was unaffected by fragmentation, patchiness, or disturbance caused during fragmentation. Patterns in species richness and abundance were consistent 1 day, 1 week, and 1 month after fragmentation. The expected decrease in fish abundance from reduced total seagrass area in fragmented and patchy seagrass appeared to be offset by greater fish density per unit area of seagrass. If fish prefer to live at edges, then the effects of seagrass habitat loss on fish abundance may have been offset by the increase (25%) in seagrass perimeter in fragmented and patchy treatments. Possibly there is some threshold of seagrass patch connectivity below which fish abundances cannot be maintained. The immediate responses of fish to experimental habitat fragmentation provided insights beyond those possible from comparisons of continuous and historically patchy habitat.

Warry, F.Y., Hindell, J.S., Macreadie, P.I., Jenkins, G.P. & Connolly, R. 2009, 'Integrating edge effects into studies of habitat fragmentation: a test using meiofauna in seagrass', Oecologia, vol. 159, no. 4, pp. 883-892.
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Habitat fragmentation is thought to be an important process structuring landscapes in marine and estuarine environments, but effects on fauna are poorly understood, in part because of a focus on patchiness rather than fragmentation. Furthermore, despite concomitant increases in perimeter:area ratios with fragmentation, we have little understanding of how fauna change from patch edges to interiors during fragmentation. Densities of meiofauna were measured at different distances across the edges of four artificial seagrass treatments [continuous, fragmented, procedural control (to control for disturbance by fragmenting then restoring experimental plots), and patchy] 1 day, 1 week and 1 month after fragmentation. Experimental plots were established 1 week prior to fragmentation/disturbance. Samples were numerically dominated by harpacticoid copepods, densities of which were greater at the edge than 0.5 m into patches for continuous, procedural control and patchy treatments; densities were similar between the edge and 0.5 m in fragmented patches. For taxa that demonstrated edge effects, densities exhibited log-linear declines to 0.5 m into a patch with no differences observed between 0.5 m and 1 m into continuous treatments. In patchy treatments densities were similar at the internal and external edges for many taxa. The strong positive edge effect (higher densities at edge than interior) for taxa such as harpacticoid copepods implies some benefit of patchy landscapes. But the lack of edge effects during patch fragmentation itself demonstrates the importance of the mechanisms by which habitats become patchy.

Macreadie, I.G., Avery, T.D., Robinson, T.V., Macreadie, P.I., Barraclough, M., Taylor, D.K. & Tiekink, E.R. 2008, 'Design of 1,2-dioxines with anti-Candida activity: aromatic substituted 1,2-dioxines', Tetrahedron, vol. 64, no. 7, pp. 1225-1232.
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In an ongoing effort to rationally design new antimicrobials, 47 new 1,2-dioxines have been synthesised. Broad antifungal structure+activity relationships governing aromatically substituted epoxy-1,2-dioxines 2 and 3 and their parent 1,2-dioxines 1 were assessed primarily against the pathogenic yeast, Candida albicans, with haemolytic activity of selected examples also reported.

Avery, T.D., Macreadie, P.I., Greatrex, B.W., Robinson, T.V., Taylor, D.K. & Macreadie, I.G. 2007, 'Design of endoperoxides with anti-Candida activity', Bioorganic & Medicinal Chemistry, vol. 15, no. 1, pp. 36-42.
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Broad antifungal structure-activity relationships governing epoxy-endoperoxides 2 and 3 and their parent endoperoxides 1 are reported. Their inhibitory activity against Candida albicans in conjunction with hemolytic activity and/or growth inhibition of cultured mammalian cells are reported. This information provided guidance for the further development of endoperoxide and epoxy-endoperoxides as topical antifungal agents

Caine, J., Sankovich, S., Antony, H., Waddington, L., Macreadie, P.I., Varghese, J. & Macreadie, I.G. 2007, 'Alzheimer's Abeta fused to green fluorescent protein induces growth stress and a heat shock response', FEMS Yeast Research, vol. 7, no. 8, pp. 1230-1236.
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The 42 amino acid Alzheimer's A beta peptide is involved in the progression of Alzheimer's disease. Here we describe the effects of intracellular A beta, produced through its attachment to either end of a green fluorescent protein, in yeast. Cells producing A beta exhibited a lower growth yield and a heat shock response, showing that A beta fusions promote stress in cells and supporting the notion that intracellular A beta is a toxic molecule. These studies have relevance in understanding the role of A beta in the death of neuronal cells, and indicate that yeast may be a new tractable model system for the screening for inhibitors of the stress caused by A beta.

Macreadie, I.G., Johnson, G., Schlosser, T. & Macreadie, P.I. 2006, 'Growth inhibition of Candida species and Aspergillus fumigatus bystatins', FEMS Microbiology Letters, vol. 262, no. 1, pp. 9-13.
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Statins are a class of drugs widely used for lowering high cholesterol levels through their action on 3-hydroxy-3-methylglutaryl-CoA reductase, a key enzyme in the synthesis of cholesterol. We studied the effects of two major statins, simvastatin and atorvastatin, on five Candida species and Aspergillus fumigatus. The statins strongly inhibited the growth of all species, except Candida krusei. Supplementation of Candida albicans and A. fumigatus with ergosterol or cholesterol in aerobic culture led to substantial recovery from the inhibition by statins, suggesting specificity of statins for the mevalonate synthesis pathway. Our findings suggest that the statins could have utility as antifungal agents and that fungal colonization could be affected in those on statin therapy.

Macreadie, P.I., Ross, D.J., Longmore, A.R. & Keough, M.J. 2006, 'Denitrification measurements of sediments using cores and chambers', Marine Ecology Progress Series, vol. 326, pp. 49-59.
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Denitrification is commonly measured using in situ benthic chambers or laboratory incubations of sediment cores. These techniques are similar in principle but differ considerably in cost and practicality. Despite widespread use of both techniques, it is uncertain whether they give comparable results. We compared cores and chambers for measuring fluxes (dissolved oxygen [DO], N2, NH4+, NO3+ and NO2+) and denitrification efficiency at 2 sites in Port Phillip Bay, Victoria, Australia. Overall, denitrification efficiency was not significantly different between cores and chambers, but fluxes of DO, NO3+ and NO2+ differed. Chambers demonstrated higher levels of oxygen consumption and net fluxes of NO3+ and NO2+ out of the sediment, suggesting that denitrification and nitrification were closely coupled. In contrast, there was a greater relative importance for uncoupled denitrification in cores as indicated by reduced oxygen consumption and net fluxes of NO3+ into the sediment. We conclude that cores and chambers give different flux results and therefore are not comparable techniques for measuring denitrification. To ascertain the cause of this, we tested the hypothesis that cores failed to adequately incorporate the impacts of macrofauna on fluxes, due to the small size of cores relative to chambers

Macreadie, P.I., Avery, T., Greatrex, B.W., Taylor, D.K. & Macreadie, I.G. 2006, 'Novel endoperoxides: Synthesis and activity against Candida species', Bioorganic & Medicinal Chemistry Letters, vol. 16, no. 4, pp. 920-922.
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A series of novel endoperoxides were synthesised and tested for inhibitory activity against Candida growth. Despite structural similarities, their activity varied considerably. Several endoperoxides demonstrated potential for development as antifungal agents.

Taylor, D.K., Avery, T.D., Greatrex, B.W., Tiekink, E.R., Macreadie, I.G., Macreadie, P.I., Humphries, A.D., Kalkanidis, M., Fox, E.N., Klonis, N., Tilley, L. 2004, 'Novel endoperoxide antimalarials: Synthesis, heme binding, and antimalarial activity', Journal of Medicinal Chemistry, vol. 47, no. 7, pp. 1833-1839.
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We report the synthesis of a series of novel epoxy endoperoxide compounds that can be prepared in high yields in one to three steps from simple starting materials. Some of these compounds inhibit the growth of Plasmodium falciparum in vitro. Structure-activity studies indicate that an endoperoxide ring bisubstituted with saturated cyclic moieties is the pharmacophore. To study the molecular basis of the action of these novel antimalarial compounds, we examined their ability to interact with oxidized and reduced forms of heme. Some of the compounds interact with oxidized heme in a fashion similar to chloroquine and other 4-aminoquinolines, while some of the compounds interact with reduced heme. However, the level of antimalarial potency is not well correlated with these activities, suggesting that some of the endoperoxides may exert their antimalarial activities by a novel mechanism of action.