Мегасколециды: Биология, Распространение и Жизненный Цикл

Family of annelid worms

Megascolecidae is a family of earthworms native to Madagascar, Australia, New Zealand, Asia, and North America. All species of the Megascolecidae belong to the Clitellata class. The Megascolecidae comprise a large family of earthworms and they can grow up to 2 meters in length. The intercontinental distribution of Megascolecidae species favours the continental drift theory. 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 ecosystem balance. The Megascolecidae are one of many families in the Annelida phylum. They live in a terrestrial environment and have a preference for soil with high biomass content, high humidity, and warm temperature. Many different genera of the Megascolecidae have been described, but the total number of species is still unsettled.

Different species of the Megascolecidae have different physiological features, but some similarities of physiological features can be found between species. The family contains relatively large individuals. The length of earthworms can vary from to
Earthworms ingest a variety of organic materials in the soil since they live in terrestrial environments. Earthworms in this family have the ability to decompose lignocellulose, which requires assistance from microorganisms in their digestive system. 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. The ideal condition of reproduction for the megascolecidids is 25 °C, where the eggs hatch the quickest and have the highest cocoon production. The male reproductive organ of the Megascolecidae includes testes, seminal vesicles, spermathecae, prostate glands, and spermathecal pores. The sperm can be found in testes and seminal vesicles, but cannot be found in spermathecae. 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.

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. Overall mean growth is 1.79 mg/day, 1.57 mg/day, and 1.34 mg/day depending on the abundance of worms and environment condition and size. The cocoon production of Megascolecidae species also is correlated with the temperature of the environment.

Megascolecidae species can be in Australia, New Zealand, Asia, North America, South America, and Europe. 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. Australia has 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. Fifty three known species of these earthworms can be found in Western Australia; Graliophilus georgei and G. secundus are some examples. G. zeilensis can be found in the Northern Territory, specifically in Mount Zeil, West MacDonnell Ranges. G. 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. Metaphire and Amynthas are two common genera belonging to the Megascolecidae family. They can be found in different countries in Asia. 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. 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. The ideal habitat for Megascolecidae is a terrestrial environment with soil with a high content of organic material, such as loamy soil, Earthworms have the ability to biomonitor soil pollutants. 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]. The impact of earthworms on soil structure is due to the rate of net nitrogen mineralization.