Department of Zoology at ANDC/Zoology Museum/Museum specimens/Annelida/Pheretima

Pheretima Date & Time : 22, December 2024 22:20 Systematic Position Phylum: Annelida Class: Oligochaeta Genus: Pheretima Species: posthuma Common Name: Earthworm Distribution Found in moist soil all over the world Habit and habitat These are nocturnal in habit and live in damp, moist, humus-rich soil of lawns, gardens etc. In dry weather they burrow deeper into the soil to avoid dryness. Their niche is a herbivore and macro-decomposer and is important as a source of food for birds. It also helps in soil aeration and increasing soil fertility. Identifying features Body is long, narrow and cylindrical. Length may reach upto 150 mm. Body colour is brown. Anterior end is pointed while the posterior end is blunt. Body is divided into 100-140 segments called metameres. The anteriormost segment is called Prostomium. Mouth is a crescentic aperture, present at anterior end. The segment containing mouth is called peristomium. Setae are present at all the segments except-1st and last. Each seta is embedded in a setal sac. A glandular band called Clitellum is situated in 14th to 16th segments. It forms coccon during the reproduction. female genital pore is situated in 14th segment (ventral surface)while male genital pore is present in 18th segment. The earthworm feeds on organic matter in the soil. The food is sucked by the pharynx and the oesophageal glands add calcite to neutralise acidity of the soil. The food is then grinded by the horny lining of the gizzard and is absorbed in the intestine. Undigested food material passes out the anus and is deposited as worm castings. The earthworm 'breathes' by the diffusion of gases through its moist skin. The blood contains haemoglobin which transports oxygen throughput the body. Circulatory system is of closed type. Earthworms have no sense organs but they can sense light intensity by small light-sensitive cells found mainly on the uppers skin surface of their body. They can also sense vibrations and chemicals by the means of tactile or chemo-receptors. The earthworms exhibit undulating movement which takes place by alternate contration and relaxation of circular and longitudinal muscles of each segment. Earthworms are hermaphrodites but they reproduce by cross-fertilization. |}|}|}|}|}|}|}|}|}|}|}|}|}|}|}|}|}|}