Burrowing into earthworms

Earthworm dissection lab Emily Myers-Pap-biology-vu

Lumbricus Terrestris

An earthworm is a tube-shaped, segmented animal commonly found living in soil, that feeds on live and dead organic matter. Its digestive system runs through the length of its body. It conducts respiration through its skin. An earthworm has a double transport system composed of coelomic fluid that moves within the fluid-filled coelom and a simple, closed blood circulatory system. It has a central and a peripheral nervous system. The central nervous system consists of two ganglia above the mouth, one on either side, connected to a nerve cord running back along its length to motor neurons and sensory cells in each segment. Large numbers of chemoreceptors are concentrated near its mouth. Circumferential and longitudinal muscles on the periphery of each segment enable the worm to move. Similar sets of muscles line the gut, and their actions move the digesting food toward the worm's anus.

Earthworm circulatory system

The earthworm like many more complex organisms has a closed circulatory system, meaning that its blood is confined to blood vessels and its blood is recirculated so it gets maximum use. An earthworm has neither lungs nor gills but uses its body's great surface area to absorb oxygen from the soil. The oxygen is taken in by the dorsal blood vessel and travels to the five aortic arches (hearts) by the esophogus where it is pumped to the lower, ventral blood vessel. The ventral blood vessel pumps the blood to all segments and organs in need of oxygen. In each segment, there is a small blood vessel that sends the blood from the ventral blood vessel back to the dorsal blood vessel, thus completing the loop
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Evolution of earthworms

Since annelids are soft-bodied, their fossils are rare – mostly jaws and the mineralized tubes that some of the species secreted. Although some late Ediacaran fossils may represent annelids, the oldest known fossil that is identified with confidence comes from about 518 million years ago in the early Cambrian period. Fossils of most modern mobile polychaete groups appeared by the end of the Carboniferous, about 299 million years ago. Scientists disagree about whether some body fossils from the mid Ordovician, about 472 to 461 million years ago, are the remains of oligochaetes, and the earliest certain fossils of the group appear in the Tertiary period, which began 65 million years ago.

Earthworm habitat

While, as the name earthworm suggests, the main habitat of earthworms is in soil, the situation is more complicated than that. The brandling worm Eisenia fetida lives in decaying plant matter and manure. Arctiostrotus vancouverensis from Vancouver Island and the Olympic Peninsula is generally found in decaying conifer logs. Aporrectodea limicola, Sparganophilus spp., and several others are found in mud in streams. Some species are arboreal, some aquatic and some euryhaline (salt-water tolerant) and littoral (living on the sea-shore, e.g. Pontodrilus litoralis). Even in the soil species, special habitats, such as soils derived from serpentine, have an earthworm fauna of their own.

Predators of earthworms

Man kills billions by plowing the fields and some that are used for fish bait

Moles ,birds ,

Some species of ants,scorpions,Millipedes

and various other large insects ,

Raccoons ,armadillos ,groundhogs,chipmunks,Monkeys