Megascolecidae

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Template:Short description Template:Automatic taxobox Megascolecidae is a family of earthworms native to Madagascar, Australia, New Zealand, Asia, and North America.<ref>Template:Cite web</ref> At up to 2 meters in length,<ref name="Fahri 1–14">Template:Cite journal</ref> their large size distinguishes the Megascolecidae from other earthworm families. They are an essential part of maintaining soil structure, minor carbon sequestration, and maintaining terrestrial ecosystems.

Physiological features

Different species of the Megascolecidae have different physiological features, but some similarities of physiological features can be found between species.<ref>Template:Cite journal</ref> The family contains relatively large individuals. The length of earthworms can vary from Template:Cvt to Template:Cvt.<ref name="Fahri 1–14"/> The number of spermathecal pores is normally paired, but multiples can be present in some species. The location of spermathecal pores and how they are positioned in different segmental locations is used in the identification of different megascolecidids.<ref>Template:Cite journal</ref>

Earthworms ingest a variety of organic materials in the soil since they live in terrestrial environments.<ref name="Nozaki 710–715">Template:Cite journal</ref> Earthworms in this family have the ability to decompose lignocellulose, which requires assistance from microorganisms in their digestive system.<ref>Template:Cite journal</ref> Aside from microorganisms, digestive enzymes such as amylase and cellulase, and proteins can be found in different regions of the gut. Chemical digestion mainly occurs in the intestinal caeca of earthworms, which have higher protease activity than other parts of the gut.<ref name="Nozaki 710–715"/>

Genital markings in the Megascolecidae family can be used to distinguish species.<ref name="Wang and Shih 2017"/>

Reproductive system

The Megascolecidae are oviparous, laying eggs to reproduce. They are biparental.<ref name=":3">Template:Cite journal</ref> The ideal condition of reproduction for the megascolecidids is 25 °C, where the eggs hatch the quickest and have the highest cocoon production.<ref name=":0">Template:Cite journal</ref>

The male reproductive organ of the Megascolecidae includes testes, seminal vesicles, spermathecae, prostate glands,<ref>Template:Cite web</ref> and spermathecal pores.<ref>Template:Cite journal</ref> The sperm can be found in testes and seminal vesicles, but cannot be found in spermathecae.<ref name=":3" /> The female reproductive organ consists of female pores, which normally occur in pairs.<ref name="Wang and Shih 2017">Template:Cite journal</ref> Both male and female reproductive organs are present in earthworms because they are monoecious. To breed, two earthworms exchange sperm. Long after they are separated, the egg case is secreted. It forms a ring around the worm, then the worm removes the ring from its body and injects its own eggs and the other worm's sperm into it. Afterwards, the egg case is sealed and ready to hatch, grow, and become a cocoon.<ref>Template:Cite web</ref>

Lifecycle

The Megascolecidae lifecycle takes around 50–57 days, depending on the external environments and habitat. The rate of growth during the first 14 days is very low, however; after 21–28 days, the rate of growth increases and then cycles up and down throughout the worm's life with no pattern.<ref name=":1"/> The growth rate of these worms is correlated to the temperature of their environment. As temperatures increase from 30 °C, a significant growth rate and decreasing the time to sexual maturity are seen. The ideal living temperature of megascolecidids is around 15–30 °C.<ref>Template:Cite journal</ref> Overall mean growth can range from 1.34–1.79 mg/day, depending on the abundance of worms, environmental conditions, and size.<ref name=":1">Template:Cite journal</ref> The cocoon production of Megascolecidae species also is correlated with the temperature of the environment.<ref>Template:Cite journal</ref>

Distribution and habitat

Megascolecidae species can be found in Australia, New Zealand, Asia, North America, South America, and Europe.<ref>Template:Cite journal</ref> The intercontinental presence of Megascolecidae species can be explained by the Permanence of Continent Theory, which provides the explanation of most Cenozoic distributions; this theory, though, does not explain the presence of European Megascolecidae in North America. The intercontinental distribution of Megascolecidae has two different theories that explains its phenomenon; land bridges and continental drift.<ref name=Reynolds1995>Reynolds, J.W. 1995. The distribution of earthworms (Annelida, Oligochaeta) in North America. Pp. 133- 153 In: Mishra, P.C., N. Behera, B.K. Senapati and B.C. Guru (eds.). Advances in Ecology and Environmental Sciences. New Delhi: Ashish Publishing House, 651 pp.</ref>

The Megascolecidae family originated in Australia.<ref>Template:Cite journal</ref> Australia has a number of species that are native to different parts of the country; Anisochaeta sebastiani is an example. This species can be found from Queensland to Tasmania.<ref>Template:Cite journal</ref> Fifty-three known species of these earthworms can be found in Western Australia; Graliophilus georgei and G. secundus are some examples.<ref>Template:Cite journal</ref> G. zeilensis can be found in the Northern Territory, specifically in Mount Zeil, West MacDonnell Ranges. Graliophilus zeilensis also can be found on the highest point of the mountain where average rainfall of the region is 250 mm annually. This distinguishes them from other species from Graliophilus.<ref name=":2">Template:Cite journal</ref>

Metaphire and Amynthas are two common genera belonging to Megascolecidae. They can be found in different countries in Asia.<ref>Template:Cite journal</ref>

Eight different species of Metaphire can be found in Malaysia: M. sedimensis, M. hijaunensis, M..e songkhlaensis, M. pulauensis, M. pulauensis, M. fovella, M. balingensis, and M. strellana. These species are commonly found in soil containing medium to high organic material. such as loamy soil.<ref>Template:Cite journal</ref>

In Indonesia, 9 different genera can be found; Amynthas, Archipheretima, Metaphire, Metapheretima, Pheretima, Pithemera, Planapheretima, Pleinogaster, and Polypheretima. Pheretimoid is the biggest group of species, which consists of 65 species. Some intrageneric groups are restricted to mainland Asia, but others are native to Indo-Australian Archipelago.<ref>Template:Cite journal</ref>

The ideal habitat for Megascolecidae is a terrestrial environment with soil and with a high content of organic material, such as loamy soil,<ref name=":1" /> cattle or pig manure, and aerobically digested sewage sludge.<ref name=":0" /> Megascolecidae species grow and produce more cocoons during the summer than the winter, because their lifecycle is highly correlated to the temperature and humidity of the environment.<ref name=":1" /> Some Megascolecidae species have adapted to colder temperatures and drier areas, though, which enables them to live in higher-altitude regions of the land.<ref name=":2" />

Ecology

Megascolecidae form an important part of the soil ecosystem, in that they indicate soil health and maintain soil productivity. The abundance of earthworms is highly correlated to soil pH, texture, water content, and temperature.<ref name="Structure: Earthworms">Template:Citation</ref> Earthworms have the ability to biomonitor soil pollutants.<ref>Template:Cite journal</ref> This is because of earthworms' burrowing habit serves to facilitate water flow and agrochemicals through the soil profile, so are able to perform carbon sequestration and reduce soil pollutants].<ref name="Structure: Earthworms"/> Invasive earthworms can have a significant impact causing changes in soil profiles, nutrient and organic matter content and other soil organisms or plant communities. In most cases the disturbed areas includes agricultural systems or previously areas that are lacking of earthworms would see the biggest impact of the invasive earthworms.<ref>Template:Cite journal</ref> The impact of earthworms on soil structure is due to the rate of net nitrogen mineralization.<ref>Template:Cite journal</ref>

Genera

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References

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