Tubifex tubifex is a slender segmented worm that may grow up to 20 cm in length. The number of body segments may number between 34-120 and have on each side an upper and lower bundle of chitinous bristles (setae), these are used for burrowing. The worm may appear red in colour owing to the possession of the respiratory pigment haemoglobin. The species is a hermaphrodite, with a complex reproductive system.Oligochaetes are segmented, bilaterally symmetrical, cylindrical worms, with tapering ends. Typically each body segment possesses four bundles of setae (chitinous bristles projecting from the body). The setae vary considerably in size and shape, and between families, so are consequently used extensively in identification. Examination under a microscope and of internal anatomy is likely to be required for accurate identification (see Brinkhurst, 1982), and attention paid to the rather complex reproductive organs. The number of gonads, the position of one gonad relative to the other, and the body segments in which they occur are used to define families. In the Tubificidae the form of the male duct is used to define genera.