Earthworms are a type of invertebrate (animals without a backbone) found in the soil worldwide where soil conditions allow. They are segmented externally, meaning you can see their segments, but they also have internal segments that match these external ones. Their body design is very much a tube within a tube design. Earthworms are broken down into three groups depending on where they live. You have the epigeic. These species live in the leaf litter above the soil where they eat decomposing organic matter. You then have the endogeic. These individuals live within the top 10-30 cm (4-12 in). The last kind are the aneic. These are the deep-dwelling species. They create long verticla burrows in which they travel up and down to feed every night. It allows them to pull leaves a little down to the depths of the soil.
Earthworms have major benefits for soil fertility. They help organic material like leaves decompose and convert it into rich humus. This helps by providing significant nutrients to the soil. While the earthworm is moving and living its life, it also eats fine grains of sand. These grains then enter the worms' gizzard, a special organ used to breakdown particles. The fine grains of sand are then ground down into an even finer paste before they are excreted. This process unlocks numerous chemicals that were locked within the grains of sand. There is also the benefit of creating tunnels throughout the topsoil that provide extensive benefits to the soil. The tunnels provide great access for drainage and aeration of the soil.
Let's look at some of the largest of these incredible creatures.
The Giant Palouse Earthworm
It is found in East Washington and North Idaho in the US. These earthworms can burrow to a depth of 4.6 m (15 ft). Originally thought to have gone extinct in the 1980's, an adult and a juvenile were discovered in 2010. The juvenile suggests that there is still a population breeding, which is great news. Adults can grow to a size of about 20 cm (8 in). During summer droughts in their native habitats, the worms are believed to dig deep and enter a state of estivation.
The Oregon Giant Earthworm
Little is known about this species, found only in the state of Oregon in the US. It is closely related to the previous species, the Giant Palouse Earthworm. However, the Oregon species is significantly larger, growing to a length of over 91 cm (3 ft). Little is known about this species, and the last individual was found in 2008. It seems they have a very narrow tolerance for soil conditions, which leads scientists to think they are highly endangered, but no large-scale study has been done to find out if that's the case.
The Giant Gippsland Earthworm
One of the largest species of earthworms, they average 1 m (3.3 ft) in length. However, they have been recorded to go as long as 3 m (9.8 ft). They are native to the Australian region of Gippsland in Victoria. They spend most of their lives below a depth of 52 cm (20 in), and they require wet soil to breathe or respire. If they move fast enough underground, gurgling noises can be heard above ground as the fluid in their tunnels moves around them. Their native habitat is grasslands. Cultivation and heavy cattle grazing negatively impact them, so they are only found in small, isolated colonies now.
The Mekong Giant Earthworm
As the name suggests, these giants are found on the banks of the Mekong river in Southeast Asia. These seem to be the largest earthworms known, as they can grow to a length of 2.9 m (10 ft). The other giant earthworms we have looked at in this article all inhabit pastureland; the Mekong giant An earthworm is different in that it survives in the extremely wet mud on the banks of the Mekong River. Little is known about the worms' soil preferences or numbers.
What do you think of earthworms? They are an incredibly important species to the terrestrial fauna and flora around the world. In fact, they are most likely on the same level of importance as bees.