The Fundamental Question: Do Worms Need Air to Survive?

The answer is unequivocally yes. Worms absolutely require oxygen to survive, just like virtually all living organisms on Earth. Oxygen is essential for cellular respiration, the process through which worms convert nutrients into energy to power their vital functions. Without adequate oxygen supply, worms cannot maintain their metabolic processes and will eventually suffocate and die. However, what makes worms fascinating is not whether they need oxygen, but rather how they obtain it from their environment.

Unlike mammals with lungs or fish with gills, earthworms have evolved a remarkably efficient respiratory system that operates entirely through their skin. This process, known as cutaneous respiration, allows worms to extract oxygen directly from the air and moisture in soil without any specialized respiratory organs. The elegance of this system lies in its simplicity, yet it also imposes specific environmental requirements that determine where and how worms can survive.

Cutaneous Respiration: How Worms Breathe Through Their Skin

Cutaneous respiration is the process by which earthworms exchange gases directly through their body surface. This method of breathing relies on several interconnected biological components working in harmony. The worm’s skin, technically called the epidermis, serves as the primary respiratory organ. This outer layer is remarkably thin and permeable, allowing gases to pass through relatively easily compared to the skin of most other animals.

The process begins when oxygen from the surrounding environment comes into contact with the worm’s moist skin surface. Oxygen molecules dissolve in the thin layer of moisture covering the skin, then diffuse through the epidermal cells. Just beneath the skin lies a dense network of capillaries, tiny blood vessels that form an extensive circulatory system throughout the worm’s body. These capillaries contain hemoglobin, the same oxygen-carrying protein found in human blood, which binds to oxygen molecules and transports them to cells throughout the worm’s body.

The Critical Role of Moisture in Worm Respiration

Moisture plays an absolutely vital role in enabling earthworms to breathe. The skin must remain continuously moist because oxygen can only diffuse through the skin when it is dissolved in water. Dry skin creates an impermeable barrier that prevents gas exchange, effectively suffocating the worm. To maintain this essential moisture, earthworms secrete a slimy mucus from specialized glands in their skin. This mucus serves multiple purposes: it keeps the skin wet, helps trap and dissolve oxygen from the air, and provides some protection against environmental hazards.

The moisture requirement explains many characteristic worm behaviors. Earthworms remain in damp soil during daylight hours and are most active at night or during rainy periods when surface moisture levels are high. In dry weather, worms burrow deeper into the soil where moisture content remains stable. This behavioral adaptation to moisture availability is not optional but essential for survival, as a dried-out worm will die within hours from suffocation.

The Capillary Network and Oxygen Transport

The earthworm’s circulatory system is remarkably sophisticated for such a seemingly simple creature. Worms possess a closed circulatory system, meaning their blood flows through vessels rather than freely bathing internal organs. This system includes five pairs of hearts that pump blood throughout the body, maintaining circulation from head to tail. The network of capillaries just beneath the skin surface is particularly dense, maximizing the surface area available for oxygen absorption.

Once oxygen diffuses into these capillaries, hemoglobin in the blood immediately binds to it. This hemoglobin is dissolved directly in the blood plasma rather than contained within red blood cells as in vertebrates, but it functions similarly to transport oxygen to tissues throughout the worm’s body. Simultaneously, carbon dioxide produced by cellular metabolism diffuses from the blood through the capillaries and out through the skin, completing the gas exchange cycle. The worm’s constant movement helps circulate oxygenated blood efficiently throughout its segmented body.

Oxygen Availability in Different Environments

The amount of oxygen available to earthworms varies significantly depending on their environment. Understanding these variations helps explain worm behavior and habitat preferences. Soil, the natural habitat for most earthworm species, contains oxygen in the air spaces between soil particles. Well-aerated soil with good structure provides abundant oxygen, while compacted or waterlogged soil can become oxygen-depleted and hostile to worm populations.

Soil Oxygen Dynamics

Soil porosity, the volume of air-filled space within soil, directly determines oxygen availability for worms. Healthy, well-structured soil typically contains numerous pores and channels that allow air circulation. Organic matter in soil improves its structure, creating larger pores that facilitate better oxygen exchange. Sandy soils generally provide excellent aeration but may lack moisture retention, while clay soils retain moisture but can become compacted and oxygen-poor if not properly managed.

Ironically, earthworms themselves are among the most important engineers of soil aeration. As they tunnel through soil, they create extensive networks of burrows that allow air to penetrate deep into the ground. These tunnels persist even after worms have moved on, serving as conduits for air movement and water infiltration. The worm’s burrowing activity continuously mixes soil particles, preventing compaction and maintaining the porous structure essential for oxygen circulation.

Water and Oxygen: A Delicate Balance

Water’s relationship with oxygen availability in soil presents a paradox for earthworms. While worms require moisture for cutaneous respiration, excessive water can be deadly. When heavy rain saturates soil, water fills the air spaces between soil particles, displacing oxygen. In waterlogged conditions, oxygen cannot diffuse effectively through the saturated soil, and dissolved oxygen levels in the water itself are relatively low compared to air.

This explains the common phenomenon of earthworms appearing on sidewalks and paved surfaces after heavy rainfall. Scientists have debated whether worms emerge because they risk drowning in saturated soil or because they take advantage of the wet surface conditions to travel more efficiently than they can underground. Research suggests both factors play a role. Worms can survive in water for several days if it contains sufficient dissolved oxygen, but prolonged submersion in oxygen-poor water will cause suffocation.

Temperature Effects on Worm Oxygen Requirements

Temperature profoundly affects both oxygen availability and worm metabolic demands. As temperature increases, so does the metabolic rate of earthworms, meaning they require more oxygen to sustain their bodily functions. Simultaneously, warmer conditions reduce the amount of oxygen that can dissolve in the moisture film on the worm’s skin and in surrounding soil water. This creates a double challenge during hot weather: worms need more oxygen precisely when less is available.

Recent research has revealed surprising interactions between temperature and oxygen in worm survival. Studies on the microscopic worm Caenorhabditis elegans have shown that cold temperatures can make oxygen toxic to worms, while low oxygen levels can protect worms from cold damage. This counterintuitive finding suggests that worms have evolved complex physiological responses to environmental stresses. At very low temperatures, oxygen that would normally support life becomes harmful, yet oxygen deprivation can trigger protective mechanisms that help worms survive extreme cold.

During winter, earthworms in temperate climates burrow below the frost line where temperatures remain more stable. Their metabolic rate slows dramatically, reducing oxygen requirements and allowing them to survive in a state similar to hibernation for months. This dormancy depends on maintaining minimal but adequate oxygen levels in their deep soil refuges.

Signs of Oxygen Deprivation in Worms

Recognizing oxygen stress in earthworm populations is important for gardeners, composters, and anyone maintaining worm-dependent systems. Oxygen-deprived worms exhibit several characteristic behaviors and physical changes that signal environmental problems requiring intervention.

The most obvious sign is escape behavior. When worms sense inadequate oxygen in their environment, they instinctively try to leave, crawling upward toward the surface or attempting to exit their container. In vermicomposting bins, finding worms climbing the walls or clustering near air holes indicates oxygen problems. This behavior is a survival mechanism, as worms seek areas with better air circulation.

Physical and Behavioral Indicators

Beyond escape attempts, oxygen-stressed worms show reduced activity levels. Rather than their normal active tunneling and feeding behavior, oxygen-deprived worms become sluggish and listless. They may clump together in groups, possibly in an attempt to find microenvironments with slightly better oxygen availability. Their color may also change, becoming paler as oxygen deprivation affects their hemoglobin and overall health.

In severe cases of oxygen deprivation, worms enter a state of dormancy where they curl up and significantly reduce their metabolic activity to conserve what little oxygen they can obtain. This represents a last-ditch survival mechanism. If oxygen deprivation continues beyond a few hours to a couple of days, depending on temperature and worm species, death becomes inevitable. Dead worms in an environment typically indicate either oxygen starvation or moisture problems, which are often interconnected issues.

Oxygen Requirements in Vermicomposting

Vermicomposting, the practice of using worms to convert organic waste into nutrient-rich compost, depends fundamentally on maintaining adequate oxygen levels. Unlike traditional hot composting which relies primarily on microbial action, vermicomposting centers on the activity of composting worms, typically red wigglers (Eisenia fetida). These worms need continuous access to oxygen to survive and process organic material efficiently.

Why Worm Bins Need Air Holes

Air holes in vermicomposting bins serve multiple critical functions. Most obviously, they allow fresh air to enter the bin, providing oxygen for the worms. Equally important, air holes allow carbon dioxide to escape. Worms produce carbon dioxide as a metabolic waste product during respiration. Without adequate ventilation, carbon dioxide accumulates in the bin, creating toxic conditions that can poison worms even if oxygen is technically present.

The design and placement of air holes significantly impact bin performance. Holes should be distributed across the sides and lid of the bin to create cross-ventilation. The bottom should also have drainage holes to prevent water accumulation, as excess moisture not only creates anaerobic conditions but can also lead to the growth of harmful microorganisms. However, these holes must be sized appropriately: large enough to allow air circulation but small enough to prevent worms from escaping and to exclude pests.

Maintaining Optimal Oxygen Levels in Worm Bins

Several factors influence oxygen availability in vermicomposting systems. Bedding material plays a crucial role in maintaining proper aeration. Shredded newspaper, cardboard, coconut coir, and similar materials create a loose, porous structure that allows air to circulate throughout the bin. This bedding should be kept moist but never soggy, ideally at about eighty percent moisture content, similar to a wrung-out sponge.

Overfeeding represents one of the most common causes of oxygen problems in worm bins. When too much food is added at once, it begins to decompose rapidly, consuming oxygen and producing heat. This creates anaerobic pockets within the bin where beneficial aerobic decomposition cannot occur. The result is foul odors, typically described as rotten or putrid, which indicate anaerobic bacterial activity. To prevent this, food should be added gradually in amounts the worms can process quickly, typically every few days rather than in large weekly additions.

Temperature and Moisture Management

Temperature control in vermicomposting bins indirectly affects oxygen availability. The ideal temperature range for red wigglers is between fifty-five and seventy-seven degrees Fahrenheit. At higher temperatures, worm metabolism accelerates, increasing oxygen demand. High temperatures also promote rapid microbial decomposition of organic matter, which competes with worms for available oxygen. In extreme cases, bins can overheat, creating conditions that suffocate worms.

Moisture management requires careful attention to maintain the balance worms need. The bedding and contents should feel damp to the touch but should not release water when squeezed. Too much moisture fills air spaces in the bedding, creating anaerobic conditions. Too little moisture prevents worms from breathing effectively through their skin. Regular monitoring and adjustment of moisture levels, either by adding dry bedding or lightly misting with water, helps maintain optimal conditions.

How Different Worm Species Adapt to Oxygen Availability

Not all worms have identical oxygen requirements or adaptations. Different species have evolved strategies suited to their particular ecological niches. Understanding these differences helps in selecting appropriate worms for specific purposes and environments.

Composting Worms vs. Earthworms

Red wiggler worms, the most popular choice for vermicomposting, thrive in environments rich in organic matter where they live near the surface. These worms are adapted to the fluctuating conditions found in leaf litter and manure piles, where oxygen levels can vary significantly. They tolerate a wider range of oxygen concentrations than some other species and can even survive brief periods of low oxygen by reducing their metabolic activity.

In contrast, deep-burrowing earthworms like nightcrawlers (Lumbricus terrestris) create permanent vertical burrows deep in mineral soil. These worms maintain their burrows meticulously, lining them with mucus that helps prevent collapse. The burrows provide a stable microenvironment with relatively consistent oxygen availability from surface air that diffuses down through the tunnel system. These species are less tolerant of the variable conditions in compost piles but excel at aerating garden soil.

Parasitic Worms and Oxygen Adaptation

Some parasitic worms have evolved remarkable adaptations to survive in the low-oxygen environment of animal intestines. These worms possess a unique molecule called rhodoquinone that allows them to continue using their electron transport chain for energy production even when oxygen is scarce or absent. This biochemical adaptation enables them to thrive in environments where most animals would quickly die from oxygen starvation. Researchers are studying these mechanisms to develop new antiparasitic drugs that could target this unique respiratory pathway.

Practical Applications: Creating Optimal Conditions for Worms

Whether maintaining a vermicompost bin, encouraging worms in garden soil, or using worms for agricultural improvement, creating conditions with adequate oxygen availability is essential for success. Practical strategies can ensure worm populations thrive and perform their beneficial functions effectively.

Garden Soil Management

Building and maintaining healthy garden soil that supports robust earthworm populations begins with improving soil structure and organic matter content. Adding compost, aged manure, or other organic materials increases soil porosity and provides food for worms. Avoiding excessive tillage prevents soil compaction and preserves the natural burrow systems that worms create. Mulching the soil surface helps retain moisture at levels ideal for worm activity while moderating temperature extremes.

Chemical inputs can significantly impact worm populations. Many synthetic fertilizers, pesticides, and herbicides are toxic to earthworms or make soil conditions inhospitable. Organic gardening practices that avoid these chemicals support healthier, more abundant worm populations. Similarly, avoiding soil compaction from foot traffic or machinery preserves the air spaces worms need. In areas where soil has become compacted, techniques like broad-forking can help restore aeration without the destructive mixing of deep tillage.

Troubleshooting Oxygen Problems in Worm Systems

When problems arise in vermicomposting systems or garden worm populations, oxygen availability should be among the first factors investigated. In worm bins, if worms are attempting to escape or clustered at the top near air holes, immediately check moisture levels and ensure adequate ventilation. Adding dry, fluffy bedding material can help absorb excess moisture and restore air spaces. Gently fluffing or turning the bin contents incorporates fresh oxygen throughout, though this should be done carefully to avoid disturbing the worms excessively.

If the bin smells bad, anaerobic conditions have developed. Remove any large amounts of uneaten food, which may be decomposing anaerobically. Add fresh bedding and increase ventilation. Consider whether the bin is too large for the worm population, as insufficient worms cannot process food quickly enough before it begins to rot. In outdoor garden situations, if worm populations decline, examine whether watering practices are creating waterlogged conditions or whether soil compaction has developed that limits oxygen penetration.

The Ecological Importance of Worm Respiration

Understanding worm respiration extends beyond practical gardening or composting concerns to fundamental ecological processes. The oxygen requirements and breathing mechanisms of earthworms connect to broader environmental functions that affect soil health, nutrient cycling, and ecosystem productivity.

Worm burrows serve as conduits not just for worm movement but for air, water, and root penetration throughout soil profiles. These burrows can persist for years, creating semi-permanent channels that dramatically improve soil aeration far beyond what the current worm population would suggest. Research has shown that worm channels can increase water infiltration rates by factors of ten or more compared to soil without earthworms. This improved infiltration reduces runoff and erosion while helping recharge groundwater supplies.

Worms, Oxygen, and Soil Microbiomes

The relationship between worm respiration and soil microorganisms is complex and mutually beneficial. Worms require aerobic conditions with adequate oxygen, and their burrowing activity creates these conditions throughout soil. Beneficial aerobic bacteria and fungi that decompose organic matter and cycle nutrients also require oxygen-rich conditions. As worms tunnel and consume organic material, they inoculate it with microorganisms from their gut, many of which continue working in worm castings after excretion.

The gut of an earthworm contains a unique microbiome that can modify microbial populations in remarkable ways. Studies have shown that harmful bacteria like E. coli are eliminated as organic matter passes through a worm’s digestive system. The processed material, called vermicast or worm castings, is teeming with beneficial microorganisms that improve soil health and plant growth. This process depends on the aerobic metabolism of both the worm and the microorganisms in its gut, all of which require adequate oxygen to function properly.

Scientific Research on Worm Oxygen Requirements

Scientific investigation into how worms use oxygen continues to reveal fascinating insights with practical applications. Research spans from fundamental questions about cellular respiration to applied studies on optimizing vermicomposting systems. These studies not only advance our understanding of worm biology but also inform practices in agriculture, waste management, and even medicine.

Recent research has explored the limits of worm survival under oxygen stress. Scientists have discovered that some worm species can enter a state of suspended animation when oxygen levels drop critically low, dramatically slowing their metabolism to conserve energy. This state is not sustainable indefinitely, but it can buy time until oxygen availability improves. Understanding the molecular mechanisms underlying this adaptation could have implications for medical applications, such as preserving organs for transplant or treating conditions involving oxygen deprivation.

Climate Change and Worm Respiration

Climate change poses complex challenges for earthworm populations related to their oxygen requirements. Rising temperatures increase metabolic rates and oxygen demand while simultaneously reducing oxygen solubility in soil moisture. More frequent extreme weather events, including both droughts and intense rainfall, create conditions that challenge worm survival. Droughts cause soil desiccation that prevents cutaneous respiration, while heavy rainfall can create prolonged waterlogging that depletes soil oxygen.

Research into how earthworm populations will respond to changing climate conditions is ongoing. Some species may be able to adapt by adjusting their behavior, burrowing deeper during unfavorable conditions. Others may shift their geographic ranges toward more suitable climates. Understanding these dynamics is important because earthworms provide essential ecosystem services, and their decline could have cascading effects on soil health, agricultural productivity, and carbon cycling in soils.

Pro Tips for Maintaining Healthy Worm Populations

Successful worm management, whether in composting systems or garden environments, benefits from attention to details that optimize oxygen availability and overall conditions. These professional tips draw on both scientific understanding and practical experience to help ensure thriving worm populations.

Layer bedding materials strategically: In vermicomposting bins, alternate layers of different bedding materials with varying textures. Shredded newspaper, cardboard strips, and coconut coir each have different structures that create air spaces. Combining them ensures a consistently porous environment that allows oxygen circulation throughout the bin while maintaining appropriate moisture levels.
Feed worms in designated zones: Rather than spreading food throughout the entire bin, create feeding pockets by burying food scraps in specific areas. This concentrates worm activity and makes it easier to monitor how quickly food is being processed. It also prevents overfeeding and the anaerobic conditions that develop when excess food decomposes faster than worms can consume it.
Monitor bin weight as an oxygen indicator: A properly maintained vermicompost bin should feel light for its size because the bedding contains significant air space. If the bin feels heavy and dense, it likely contains too much moisture and insufficient aeration. Adding dry bedding and gently fluffing the contents can restore proper structure.
Create aeration columns in larger systems: For larger vermicomposting operations or worm beds, vertical columns of coarse material like wood chips or rolled corrugated cardboard extending from bottom to top help ensure oxygen reaches all levels. These columns create permanent air channels while also providing structural support that prevents compaction.
Use the smell test regularly: A healthy worm bin should smell earthy and pleasant, like a forest floor after rain. Any sour, rotten, or ammonia-like odors indicate anaerobic conditions or other problems requiring immediate attention. Catching issues early through regular smell checks prevents serious problems that could harm or kill the worm population.
Adjust practices seasonally: Worm oxygen requirements and environmental conditions change with seasons. In summer, bins may need more frequent additions of dry bedding to maintain structure as higher temperatures increase decomposition rates. In winter, reduced activity means less frequent feeding, and indoor bins may need extra ventilation if heating systems reduce air circulation.
Encourage natural soil structure in gardens: The best way to support garden earthworm populations is to build soil structure that provides consistent oxygen availability. This means adding organic matter regularly, minimizing tillage that disrupts burrow systems, preventing compaction through careful traffic management, and maintaining moisture without creating waterlogged conditions. Healthy soil that supports worms will, in turn, be improved by those worms in a beneficial cycle.

Frequently Asked Questions

Can worms survive completely underwater?

Worms can survive underwater for limited periods if the water contains adequate dissolved oxygen. Some species can live submerged for several days or even weeks in well-oxygenated water. However, most water contains significantly less oxygen than air, so worms will eventually suffocate if they cannot access air-saturated conditions. Still water with low oxygen content will kill worms much faster than moving, aerated water. The ability to survive temporary flooding is an important adaptation for worms living in areas prone to heavy rainfall.

How long can worms survive without oxygen?

The survival time for worms without sufficient oxygen varies by species, temperature, and individual health, but generally ranges from a few hours to about two days. At cooler temperatures where metabolism slows, worms may survive slightly longer in low-oxygen conditions. When oxygen becomes critically scarce, some worms can enter a temporary state of reduced metabolic activity that extends survival time, but this is not a long-term solution. Complete absence of oxygen will kill most worms within hours as their cells cannot produce the energy needed for survival.

Why do worms come to the surface during rain?

Scientists have proposed several explanations for this common behavior. The traditional theory suggests that heavy rain saturates soil, filling air spaces with water and reducing oxygen availability, forcing worms to surface to breathe. However, research shows worms can survive in saturated soil for days if necessary. Alternative explanations include that worms take advantage of wet surface conditions to travel farther and faster than they can underground, potentially colonizing new areas. The moist surface also allows breeding encounters with other worms. The behavior likely involves multiple motivations depending on circumstances.

Do different colored worms have different oxygen needs?

Worm color relates more to species identity and habitat than to oxygen requirements, though different species do have varying tolerances. Red wigglers get their reddish color from high concentrations of hemoglobin, which efficiently transports oxygen and allows them to thrive in organic-rich environments where oxygen levels fluctuate. Pale or white worms that live deep in soil or in aquatic environments may have adapted to consistently low oxygen availability with different respiratory strategies. However, color itself does not determine oxygen needs; rather, it is one indicator among many of a species’ ecological adaptations.

Can worms breathe in dry soil?

No, worms cannot effectively breathe in dry soil because cutaneous respiration requires moisture. Oxygen must dissolve in the moisture layer on the worm’s skin before it can diffuse through to the capillaries beneath. In dry conditions, worms will quickly burrow deeper into soil seeking moisture or, if no moisture is available, will enter a state of dormancy curling up in a mucus cocoon to retain what little moisture remains. Prolonged dry conditions will eventually kill worms through a combination of dehydration and suffocation. This is why worms are most active in damp environments and during humid weather.

How do I know if my compost bin has enough oxygen for the worms?

Several indicators reveal whether your compost bin has adequate oxygen. First, observe worm behavior: active worms distributed throughout the bin suggest good conditions, while worms clustering at air holes or attempting to escape indicate problems. Second, smell the bin: it should have a pleasant, earthy odor, while sour or rotten smells indicate anaerobic conditions. Third, check the physical structure of the contents: properly aerated bins have loose, fluffy bedding with visible air spaces, while oxygen-poor bins feel dense and compacted. Finally, monitor processing rates: if worms are consuming food scraps quickly and producing abundant castings, oxygen is likely sufficient. Slow processing despite adequate worm population may signal oxygen limitations.

Conclusion

Earthworms’ absolute requirement for oxygen, coupled with their unique method of obtaining it through cutaneous respiration, shapes every aspect of their biology and ecology. Understanding this fundamental need provides the foundation for successfully working with worms in any context, from maintaining productive vermicomposting systems to supporting healthy soil ecosystems in gardens and agricultural land. The elegant simplicity of breathing through skin, while requiring specific environmental conditions, has allowed earthworms to become among the most successful and important soil organisms on Earth.

The moisture-dependent nature of cutaneous respiration explains characteristic worm behaviors including their affinity for damp environments, their tendency to burrow during dry periods, and their appearance on surfaces after heavy rain. Managing environments for worms means maintaining the delicate balance of moisture and aeration that allows oxygen to reach them while carbon dioxide can escape. Too much or too little water, compacted soil, or inadequate ventilation in contained systems all lead to oxygen deprivation that stresses or kills worm populations.

The ecological importance of worm respiration extends far beyond the worms themselves. Their oxygen requirements drive burrowing behavior that creates channels throughout soil, dramatically improving aeration, water infiltration, and root penetration. This activity benefits the entire soil ecosystem, supporting diverse communities of aerobic microorganisms essential for nutrient cycling and soil health. The symbiotic relationship between worms and soil microbes, both requiring oxygen-rich conditions, creates the foundation for productive, resilient soils that support plant growth and sequester carbon.

Practical applications of understanding worm oxygen needs span from backyard composting to large-scale agricultural improvements. In vermicomposting, ensuring adequate ventilation, appropriate moisture levels, and proper bedding structure maintains conditions where worms can breathe easily and work efficiently to process organic waste. In gardens and farms, building soil organic matter and structure while avoiding compaction creates environments where natural earthworm populations thrive and provide valuable ecosystem services. These practices, informed by knowledge of how worms breathe, yield benefits that include enhanced soil fertility, improved water management, and reduced environmental impacts.

As research continues to reveal the complexity of earthworm biology, from their remarkable adaptations to low-oxygen conditions to the unique microbiomes in their digestive systems, the practical value of this knowledge grows. Climate change presents new challenges for earthworm populations as temperature and precipitation patterns shift, potentially affecting oxygen availability in soils. Supporting healthy earthworm communities through practices that ensure adequate oxygen and other requirements becomes increasingly important for maintaining the ecosystem services these humble creatures provide. By respecting the simple yet critical need of worms for air, we can partner with them to build healthier soils and more sustainable environmental management systems.

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