Kiera Jefferson
Benthic macroinvertebrates, including aquatic earthworms, are small aquatic animals that are commonly used as indicators of the biological condition of waterbodies. Aquatic earthworms closely resemble terrestrial earthworms, with long, cylindrical bodies ranging from 1-30mm in length. They are collector/gatherers that feed on bacteria, protozoa, algae, and dead organic matter. Earthworms have been recognized as candidate bio-monitor organisms for soil pollutants due to their ability to bioaccumulate toxins. However, they are not suitable for detecting all types of chemical substances in the soil. The presence of pollution-tolerant species, such as aquatic earthworms, can indicate the biological condition of a waterbody.
| Characteristics | Values |
|---|---|
| Length | 1-30mm long, some may be as long as 150mm |
| Front end | No suckers or eyespots |
| Reproduction | Sexual or asexual |
| Diet | Bacteria, protozoa, algae, and dead organic matter |
| Oxygen absorption | Over their entire surface area |
| Pollution tolerance | Likely to be pollution-tolerant |
What You'll Learn
Aquatic earthworms are bottom-dwelling
Aquatic earthworms closely resemble their terrestrial counterparts, with long, cylindrical, and moderately muscular bodies composed of ring-like segments. They range in length from 1 to 30 mm, although some larger species can reach up to 150 mm. These worms are hermaphrodites, capable of both sexual and asexual reproduction. Unlike their terrestrial relatives, aquatic earthworms lack eyespots and suckers at the anterior end.
Aquatic earthworms are primarily gatherers and collectors, foraging in the upper layer of soft, fine sediment. They feed on bacteria, protozoa, algae, and dead organic matter. Some earthworms create vertical mud tubes in the sediment, protruding their hind end to absorb oxygen. Interestingly, aquatic earthworms can absorb oxygen over their entire surface area, adapting to their aquatic environment.
The presence and abundance of aquatic earthworms and other benthic macroinvertebrates serve as reliable indicators of waterbody health. Healthy aquatic ecosystems typically support a diverse range of macroinvertebrate species, including those intolerant of pollution. When a waterbody exhibits low diversity or abundance of macroinvertebrates, or only pollution-tolerant species are present, it may suggest a decline in ecological health. This relationship between benthic macroinvertebrates and water quality is essential for assessing the biological, chemical, and physical conditions of aquatic ecosystems.
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They are used as indicators of waterbody health
Aquatic earthworms are small benthic macroinvertebrates that live in or around waterbodies and burrow through the upper layer of soft, fine sediment, grazing on bacteria, protozoa, algae, and dead organic matter. They are mostly 1-30mm long, but some can reach up to 150mm.
Benthic macroinvertebrates are commonly used as indicators of the biological condition of waterbodies. They are reliable indicators because they reside in water throughout their lives, are simple to collect, and exhibit varying levels of pollution tolerance. Aquatic earthworms, as part of this group, are used as indicators of waterbody health.
The presence of a diverse range of benthic macroinvertebrates, including pollution-intolerant species, generally indicates a biologically healthy waterbody. Conversely, samples yielding only pollution-tolerant species or exhibiting minimal diversity suggest a less favourable condition. As such, the abundance and variety of aquatic earthworms, alongside other macroinvertebrates, can provide insights into the health of a waterbody.
Earthworms have also been recognised as candidate bio-monitor organisms for soil pollutants. The species Eisenia fetida, for instance, is commonly employed in ecotoxicology and is effective in assessing the chemical toxicity of soil due to its proximity to soil contaminants. Similarly, the effects of cadmium and zinc on the reproduction of Enchytraeus albidus have been studied, highlighting the sensitivity of certain life cycle parameters to metal pollution.
The bio-accumulative abilities of earthworms make them valuable for detecting the cytotoxic effects of specific chemical agents in soil. By selecting appropriate target substances, earthworms can be utilised to evaluate the presence of chemical substances in the environment. For instance, the presence of metallothioneins (MTs) in earthworms can help in the detection and sequestration of cadmium.
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Aquatic earthworms are mostly collector/gathers
Aquatic earthworms are mostly collector/gatherers, feeding on bacteria, protozoa, algae, and dead organic matter found in the upper layer of soft, fine sediment. They burrow through this sediment, grazing as they go. Some species of aquatic earthworm live in vertical mud tubes in the sediment with their hind ends protruding to absorb oxygen.
Aquatic earthworms closely resemble terrestrial earthworms, with long, moderately muscular, cylindrical bodies made up of ring-like segments. They are typically between 1 and 30mm long, though some can reach lengths of 150mm. They have no suckers or eyespots at the anterior (front) end. They are hermaphrodites, capable of reproducing sexually and asexually.
Aquatic earthworms are benthic macroinvertebrates, which are small aquatic animals or aquatic larval insects. Benthic macroinvertebrates are bottom-dwelling organisms that live in or around water bodies for most or all of their lives. They are often found attached to underwater objects like rocks, vegetation, and logs, or burrowed into the sediment at the bottom of the water body.
Benthic macroinvertebrates are commonly used as indicators of the biological condition of water bodies. They are reliable indicators because they respond predictably to human disturbances, are easy to collect and identify, and have limited mobility. A healthy water body will typically support a wide variety of benthic macroinvertebrates, including many that are intolerant of pollution. Therefore, a sample that yields only pollution-tolerant species may indicate a less healthy water body.
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They can reproduce sexually or asexually
Aquatic earthworms are hermaphroditic and can reproduce both sexually and asexually. They have long, moderately muscular, cylindrical bodies composed of ring-like segments and range in length from 1-30mm, with some growing up to 150mm. They are bottom-dwelling and are found in and around water bodies during some part of their lives. They are often found attached to rocks, vegetation, logs, or burrowed in the bottom sand and sediments.
Aquatic earthworms closely resemble terrestrial earthworms, but the front end of the worm has no suckers or eyespots. They undergo no metamorphosis as they age, so juveniles are only distinguishable from adults by their smaller size. They feed by burrowing through the upper layer of soft, fine sediment and grazing on bacteria, protozoa, algae, and dead organic matter. Some live in vertical mud tubes in the sediment, with their hind end protruding to absorb oxygen.
Aquatic earthworms are considered benthic macroinvertebrates, which are small aquatic animals and the aquatic larval stages of insects. Benthic macroinvertebrates are commonly used as indicators of the biological condition of water bodies. They are reliable indicators because they are relatively easy to collect, have limited mobility, and differ in their tolerance to pollution.
The abundance and variety of benthic macroinvertebrates in a water body can indicate its biological health. Generally, a healthy water body supports a wide variety and a high number of macroinvertebrate taxa, including those intolerant of pollution. On the other hand, samples yielding only pollution-tolerant species or with low diversity and abundance may indicate a less healthy water body.
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They are similar in appearance to terrestrial earthworms
Aquatic earthworms closely resemble terrestrial earthworms. They have long, moderately muscular, cylindrical, and segmented bodies composed of ring-like segments. Most aquatic earthworms range in length from 1-30mm, although some may be as long as 150mm. The anterior (front) end of the worm has no suckers or eyespots. However, they do have simple photoreceptors that help them distinguish between light and dark, allowing them to sense the presence of light and burrow away from it. They tend to avoid bright light due to the sensitivity of the photoreceptors and typically stay buried in the coarse particles of the soil or sediment, inhabiting darker spaces.
Aquatic earthworms are similar to terrestrial earthworms in that they are both hermaphroditic and can reproduce sexually or asexually. They undergo no metamorphosis as they age, so juveniles can only be distinguished from adults by their smaller relative size. Like their terrestrial counterparts, aquatic earthworms are collector/gatherers, burrowing through the upper layer of soft, fine sediment to feed on bacteria, protozoa, algae, and dead organic matter. They can absorb oxygen over their entire surface area, and some have specialised adaptations to cope with low oxygen, such as gills or hemoglobin in their blood, which helps transport oxygen.
The majority of aquatic earthworms are small, slender worms whose organs can be seen through their transparent body wall. They are highly adaptable and can survive in a wide variety of habitats, including freshwater and marine environments. However, they do not fare well in completely oxygen-deficient environments. They play an important role in maintaining healthy ecosystems, particularly in deep or stagnant waters that are naturally low in oxygen. Their high tolerance for low oxygen also means they can survive in the anaerobic conditions caused by severe nutrient pollution, such as sewage discharge, which can kill other organisms.
Aquatic earthworms, like their terrestrial cousins, are often misunderstood and viewed negatively. However, they are critical parts of every ecosystem, and without them, organic materials would build up, causing soils and water to become toxic. They are true ecosystem peacekeepers, ensuring the thriving of other organisms by redistributing sediment, minerals, beneficial bacteria, and oxygen throughout their environments.
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Frequently asked questions
Aquatic earthworms are small, cylindrical worms that range in length from 1-30mm, although some can be as long as 150mm. They closely resemble terrestrial earthworms but lack eyespots and suckers. They are mostly collectors/gatherers that feed on bacteria, protozoa, algae, and dead organic matter.
Aquatic earthworms are considered pollution-tolerant organisms. They are often used as indicators of the biological condition of water bodies, with healthy water bodies typically supporting a diverse range of both pollution-tolerant and intolerant species.
Benthic macroinvertebrates, including aquatic earthworms, are used as indicators because they are relatively easy to collect and identify, have predictable responses to human disturbances, and have limited mobility compared to fish.
Other examples of benthic macroinvertebrates include dragonfly and stonefly larvae, snails, beetles, and other worms.
A high abundance and diversity of benthic macroinvertebrates, including aquatic earthworms, generally indicate a healthy biological condition of the waterbody. In contrast, samples yielding only pollution-tolerant species or low diversity may suggest a less healthy ecosystem.
