(Müller, 1774)
Description
Small to large smooth pink worms. In anterior dorsal bundles 1-6 very finely pilose hair chaetae, 150-600 µm long, and 2-5 pectinates, 60-125 µm long, with equal main teeth and with shorter but distinct intermediate teeth. Anterior ventral chaetae 3-6 per bundle, 65-150 µm long, with slightly longer upper tooth. Posterior dorsal and ventral bifids slightly thicker and more bent, with shorter and thinner upper tooth, lower one gradually becoming stout and curved. In XI, near male pores, ordinary ventral bifid chaetae, sometimes smaller. Clitellum in XI-XII, spermathecal pores laterally in middle portion of X. Length 10-100 mm, segment number 36-130. Immature individuals hardly distinguishable from juveniles of Potamothrix hammoniensis, Ilyodrilus templetoni, and many others. Note their smoother tail portion with longer segments and weaker intersegmental furrows, as well as stout and curved lower tooth in posterior bifids, somewhat similar to those of the genus Psammoryctides but less robust. When compared with immature Rhyacodrilus coccineus, lack of coelomocytes is important. There occur different morphological and ecological forms; some of them may be genetically isolated from each other, representing separate species (Holmquist, 1983; Sturmbauer et al., 1999). Presumably, ecological forms devoid of hair and pectinate chaetae can exist in slightly saline water (Chapman and Brinkhurst, 1987) - see Tubifex blanchardi. References to "Tubifex tubifex" in older hydrobiological literature, even from as late as the 20th century, where other tubificid species are not mentioned, can be confusing.
Burrowing in sediment.
Distribution
Cosmopolitan, presumably of Holarctic origin.
Ecology
In freshwater, in very different conditions including profundal of clean northern lakes, cool springs, polluted rivers, and periodically brackish estuaries. Tolerant of low oxygen content. Common in new habitats, like dug ponds, ditches and aquaria, as pioneer animal. Can be very abundant in conditions of heavy pollution. In balanced ecological conditions with established communities of diverse tubificids, represented in modest numbers.
Reproduction
Sexual only. Parthenogenesis common, particularly at higher water temperatures. Eggs laid in cocoons with thin colourless shells and two short appendages. Can reproduce in all seasons, and produce several generations a year.
Literature
Müller, 1774: 27 (partim); Brinkhurst and Jamieson, 1971: 453-456 (partim), Figs 8.1A-D, 8.3G-J; Chekanovskaya, 1981: 341-342, Fig. 171; Hrabe, 1981: 83-84, Pl. 13 Figs 9-20 ; Kasprzak, 1981: 174, Fig. 655; Holmquist, 1983: 187-201, Figs 1-4; Chapman and Brinkhurst, 1987: 45-55, Figs 1, 3; Sturmbauer et al., 1999: 967-974.