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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Monadrilus

Family Tubificidae (ref. ID; 6208)
  1. Monadrilus palliolatus Brinkhurst, 1960 (ref. ID; 6208 original paper)

Monadrilus palliolatus Brinkhurst, 1960 (ref. ID; 6208 original paper)

Descriptions

This species is now recognized to be a Capitelled Polychaete, probably Capitellides giardi Mesnil. On March 23, 1959, a large number of worms were collected in muddy sand on the sea-shore at Port St. Mary, Isle of Man, in the hope of obtaining Clitellio arenarius. The worms appeared to be most abundant where a small fresh-water stream ran across the shore between some large stones. They proved to be unlike any worm I have seen described. Unfortunately only one fully mature specimen has so far come to hand and so the details of the genitalia are not complete. The chaetae are, however, strikingly different from those observed in any other Tubificid in that they are hooded, as is known to occur in some Polychaetes. The species is tentatively ascribed to the Tubificidae in that there are genital chaetae present in segments 9 and 10 - other species of Tubificidae are known to have the genital organs in segments other than 10, 11, 12, viz, Aulodrilus species, and Ilyodrilus bedoti Piguet. The chaetae are absent from segment 1 as is usual, and from segment 2-8 inclusive they are all modified crotchets with lancelike ends. These number 12-14 in mature specimens, 7-9 in immature individuals. They change abruptly in segment 9 to more conventional crotchets with a varying number of intermediate teeth, but the whole head of the chaeta is covered with sheath. There may be as many as 16 per bundle. The most striking feature of the worm is the genital chaetae, 2 per bundle on the ventral aspects of segments 9 and 10 (with a minute third chaeta developing in one of the bundles. These genital chaetae are all similar - they are broad, simple-ended chaetae with a slight nodulus, and in the single mature specimens they point posteriad in segment 9, anteriad in segment 10. The prostomium and first segment form a conical projection set on the dorsal surface of segment 2. The segments are divided at about the level of the chaetae in the first eight segments (i.e. the two parts of the segment are equal in width) but the posterior segments are divided more anteriorly. The mature specimen was approximately 6 cm long. (ref. ID; 6208)