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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Limnodrilus

Limnodrilus Claparede, 1862 (ref. ID; 1257, 3692, 6913, 7254)

Family Tubificidae (ref. ID; 1257, 5876, 5939, 6208, 7787, 7854)

Family Tubificidae: Subfamily Tubificinae Eisen, 1879 (ref. ID; 6913) reported author and year? (ref. ID; 5857, 6648)

ref. ID; 1663

Dorsal and ventral setae different. Ventral setae bifurcate, dorsal setae bifurcate or mixture of two or three types. Four bundles of an indeterminate number each per segment. Worm usually reddish. Coelomocytes sparse or absent. Without gills. Single solid prostates attached to atria by narrow stalk. Vasa deferentia as long as or longer than atria. Atria much wider than vasa deferentia. Penis sheaths thick-walled, cuticular, and surrounded by spiral muscles. Common and widely distributed. In stagnant water. Often in tubes. (ref. ID; 1663)

ref. ID; 1923

Ventral setae ordinarily cleft; spermatheca if present usually open on segment 10; usually reddish in appearance, commonly more than 25 mm in length, many live in tubes. Body surface not covered with many cuticular papillae. Dorsal bundles without hair setae. Setae distinctly cleft; sperm ducts each with one definite prostate gland. (ref. ID; 1923)

ref. ID; 6208

All previous accounts of this genus use the length of the penis tube as the diagnostic character separating the four commoner species, but I have found this unsatisfactory both because the lengths of the tube is mature specimens overlap considerably and also because the tube develops slowly, immature worms having very short tubes, and this could lead to considerable confusion. The shape of the chaetae and the distal end of the penis tube have provided suitable alternative character. (ref. ID; 6208)
  1. Limnodrilus amblysetus Brinkhurst et al., 1990 (ref. ID; 6648, 6972 original paper)
    Syn; Limnodrilus silvani Eisen, 1879: Liang, 1987 (ref. ID; 6972)
  2. Limnodrilus angustipenis Brinkhurst & Cook (ref. ID; 6913) reported author and year? (ref. ID; 5939)
  3. Limnodrilus arenarius Michaelsen, 1926 (ref. ID; 3692)
    See; Isochaetides arenarius (ref. ID; 7201)
  4. Limnodrilus aurostriatus Southern, 1909 (ref. ID; 1928 original paper)
  5. Limnodrilus aurostriatus Southern, 1909
    See; Limnodrilus hoffmeisteri (ref. ID; 1257)
  6. Limnodrilus baicalensis Michaelsen, 1901 (ref. ID; 3692)
    See; Isochaetides baicalensis (ref. ID; 7201)
  7. Limnodrilus bulbiphallus Block & Goodnight, 1972 (ref. ID; 7787 original paper)
  8. Limnodrilus caparedeianus Ratzel (ref. ID; 6600)
  9. Limnodrilus claparedeanus Ratzel, 1868 (ref. ID; 1257, 3692, 6208, 7854) reported author and year? (ref. ID; 6583)
  10. Limnodrilus claparedeianus Ratzel, 1868 (ref. ID; 6913)
  11. Limnodrilus claparedianus Ratzel, 1868 (ref. ID; 7098) or 1869 (ref. ID; 1923) reported author and year? (ref. ID; 5939)
  12. Limnodrilus cervix Brinkhurst (ref. ID; 6913) reported author and year? (ref. ID; 5939)
  13. Limnodrilus dybowskii (Grube) Michaelsen, 1926
    See; Lycodrilus dybowskii (ref. ID; 7201)
  14. Limnodrilus grandisetosus Nomura, 1932 (ref. ID; 3692, 6972, 7854)
  15. Limnodrilus helveticus Piguet, 1913 (ref. ID; 3692)
  16. Limnodrilus heterochaetus Michaelsen, 1926
    See; Tubificoides heterochaetus (Michaelsen, 1926) n. comb. (ref. ID; 5945, 7248)
  17. Limnodrilus hoffmeisteri Claparede, 1862 (ref. ID; 1257, 1861, 1911, 1923, 1928, 2378, 6208, 6913, 7254, 7854) reported year? (ref. ID; 3446, 3704, 3955) reported author and year? (ref. ID; 5855, 5939, 6583, 7787, 7817)
    Syn; Limnodrilus aurostriatus Southern, 1909 (ref. ID; 1257); Limnodrilus parvus Southern, 1909 (ref. ID; 6208); Limnodrilus spiralis (ref. ID; 5939)
  18. Limnodrilus hoffmeisteri f. parva Southern, 1908 (ref. ID; 3692)
  19. Limnodrilus hoffmeisteri f. typica Claparede, 1862 (ref. ID; 3692)
  20. Limnodrilus infundibuliferus Isossimov, 1972
    See; Tubifex kessleri (ref. ID; 7201)
  21. Limnodrilus lastockini Jaroschenko, 1948 (ref. ID; 3692)
  22. Limnodrilus longus Bretscher, 1901 (ref. ID; 1257, 1928)
  23. Limnodrilus maumeensis Brinkhurst & Cook (ref. ID; 6913)
  24. Limnodrilus mauneensis (ref. ID; 5939)
  25. Limnodrilus michaelseni Lastockin, 1936 (ref. ID; 3692)
  26. Limnodrilus neotropicus Cernosvitov, 1939 (ref. ID; 6913, 7787)
  27. Limnodrilus newaensis Michaelsen, 1902 (ref. ID; 3692) or 1903 (ref. ID; 7201)
    See; Tubifex newaensis (ref. ID; 7201)
  28. Limnodrilus parvus Southern, 1902 (ref. ID; 6208) or 1909 (ref. ID; 1257, 1928 original paper)
    See; Limnodrilus hoffmeisteri (ref. ID; 6208)
    Syn; Limnodrilus hoffmeisteri f. parvus (ref. ID; 1257)
  29. Limnodrilus profundicola (Verrill, 1871) (ref. ID; 6653, 7854) reported year? (ref. ID; 1911, 3704, 3955) or Verril (ref. ID; 7817) reported author and year? (ref. ID; 5939, 6583)
  30. Limnodrilus psammophilus (ref. ID; 5939)
  31. Limnodrilus pseudogaster Dahl, 1960
    See; Tubificoides pseudogaster (ref. ID; 5945)
  32. Limnodrilus rubripenis (ref. ID; 5939)
  33. Limnodrilus schizochaetus (Michaelsen, 1901)
    See; Lycodrilides schizochaetus (ref. ID; 7201)
  34. Limnodrilus silvani Eisen, 1879 (ref. ID; 6651) reported year? (ref. ID; 6597) reported author and year? (ref. ID; 5939)
    See; Limnodrilus amblysetus (ref. ID; 6972)
  35. Limnodrilus spiralis
    See; Limnodrilus hoffmeisteri (ref. ID; 5939, 7248)
  36. Limnodrilus udekemianus Claparede, 1861 (ref. ID; 1923) or 1862 (ref. ID; 1257, 3692, 6208, 6651, 6653, 6913, 7254, 7854) reported year? (ref. ID; 1928, 3446) reported author and year? (ref. ID; 5855, 5939)

Limnodrilus amblysetus Brinkhurst et al., 1990 (ref. ID; 6648, 6972 original paper)

Synonym

Limnodrilus silvani Eisen, 1879: Liang, 1987 (ref. ID; 6972)

Descriptions

Lake Biwa material: In immature and fixed state body up to 50 mm long, segments up to 325. Posterior part of body slender, thread-like. Cuticular covering and body wall thick. Prostomium bluntly conical. Segments II-V biannulate, each anterior annulus shorter than posterior one. Both ventral and dorsal chaetal bundles consisting of simple-pointed or bifurcate crotchets only. Chaetae in anterior segments 3-7 per bundle, 110-150 µm long with maximum size in V-VII. Distal end simply pointed in II and III, bearing minute upper tooth from IV to VII on. Chaetae in middle segments 2-4 per bundle, 90-110 µm long, with upper tooth shorter and thinner than lower; in posterior segments 1-2 per bundle, 44-70 µm long, upper tooth becoming almost as long as but still thinner than lower. Nodulus of all chaetae situated about 1/3 from distal end. Chloragogen cells from VI on, thickly covering gut. No coelomocytes. (ref. ID; 6648)

Length 30-50 mm, body slender. Prostmium bluntly conical. Chaetae all bifid to bluntly simple-pointed, anteriorly 3-7 per bundle, 87-110 µm long, nodulus slightly proximal. Posterior chaeta(e) 1, at most 2, bifid, nodulus distal, upper teeth short and thick but appear thinner and shorter than lower. Vasa deferentia long, atria wider than vasa deferentia, narrowing to short ejaculatory ducts also wider than vasa. Penes with cuticular penis sheaths with flared bases and rounded platelike ectal ends. Spermathecae with short ducts, irregularly oval to elongate ampullae, spermatozeugmata tadpole-shaped. Posterior end of intact worms unusually long and thin. (ref. ID; 6972)

Remarks

Lake Biwa material: The present species was previously known only from China. According to the original account of L. amblysetus (Brinkhurst et al., 1990), all chaetae are bifid or bluntly simple-pointed, and the nodulus of anterior chaeta is situated in a slightly proximal position. However, re-examination of the paratypes (from Hubei Province) reveals that chaetae in some most anterior segments are sharply simple-pointed and all chaetae have a distal nodulus. In the paratypes, the chaetae attain their maximum size in V. Thus, the chaetal condition of the paratypes coincides well with the present lake Biwa material. This species resembles the congeners. L. grandisetosus Nomura and L. udekemianus Claparede, in having slender posterior body, but their chaetal forms are different from each other and diagnostic. (ref. ID; 6648)

The senior author initially identified this species as L. silvani because of the spade-shaped penis sheath despite the unusual blunt teeth of the anterior chaetae, which are distinctly bifid in American specimens of that species. Comparison shows that the penis sheath of L. amblysetus resembles that of L. grandisetosus rather than that of L. silvani. The relationship of these taxa will be discussed later. (ref. ID; 6972)

Material examined

One immature individual, off Wani (the northern lake), 5 m depth, mud, 25th October, 1992. One immature individual, off Ayame-hama (the northern lake), 10 m depth, mud, 30th January, 1992. Three immature individuals, off Karasaki (the southern lake), 1.5 m depth, 14th February, 1994. One immature individual, off Shina (the southern lake), 2.5 m depth, 14th February, 1994. Five immature individuals, off Shimosakamoto (the southern lake), 2.0-2.5 m depth, 23rd October, 1992, 14th February, 1994. Three mature individuals, Lake Chenhu, Hanyang, Hubei Province, People's Republic of China, 8th June, 1983 (paratypes) (R.O. Brinkhurst collection). (ref. ID; 6648)

  • Holotype: USNM122718, a whole specimen in alcohol from Liang Yanling collection, Yangtze River basin main channel and oxbow lakes, Sandouping, Hubei Province, 31 May 1985, Liang Yanling collection. (ref. ID; 6972)
  • Paratypes: USNM122719, 9 specimens in 70% alcohol from the same locality, and also floodplain Lake Chenhu, Hanyang, Hubei Province, 8 June 1983. Also 3 whole mounted dissections, R.O. Brinkhurst collection. (ref. ID; 6972)

    Limnodrilus aurostriatus Southern, 1909 (ref. ID; 1928 original paper)

    Diagnosis

    The species seems to be most nearly related to L. hoffmeisteri Claparede. The chief differences are; (1) The pharynx reaches back to the 5th segment, (2) Integumental vessels not branched, (3) Shape of the setae and penis-sheath and (4) Shape of the spermatheca and spermatophores. (ref. ID; 1928)

    Descriptions

    These worms are 25-30 mm long, and very slender. They are bright red in front. The tail is paler in colour; and each segment has two golden rings formed by pigment-bearing glands in the epidermis. The front ring is in a line with the setae, the second at the posterior margin of the segment. The segments are biannulate; and the epidermis is covered with clear glands. There are 6-8 setae in each bundle. The teeth of the setae are nearly equal in length; but the lower tooth is the thicker. In the anterior setae the teeth are almost parallel; but in the posterior setae they diverge much more. The oesophagus begins in the 5th segment, and is covered with dark peritoneal cells. The brain is almost square. In a state of rest, the posterior margin is almost straight, but when contracted it is slightly concave. The anterior border is slightly conical; and the median outgrowth is only represented by a slender branching nerve. The commissures are very wide, and project far in front of the brain. There are contractile vessels in the 8th and 9th segments. In the posterior segments there is only a single integumental commissure between the dorsal and ventral vessels. It lies at the back of the segment, and does not branch, thus differing markedly from L. hoffmeisteri Claparede. The first nephridia are in the 6th segment. The anterior nephridia are enveloped in a compact mass of bladder-like cells. The duct is widened at the pore. The post-clitellar nephridia are not enveloped in these cells. The spermatheca consists of a large sac which leads by a narrow passage into a wide duct. The duct is proportionately much smaller than in L. parvus. The spermathecae each contain 2 or 3 spermatophores. These are compact, oval bodies, with rounded ends. At the broad end is a clear oval space containing several shining granules. The atrium is very long and slender, and is swollen in the middle, where it receives the prostate gland. The penis is 8-9 times as long as the proximal end is broad. It is curved distally, and terminates in a funnel-like enlargement, which is twisted on one side into a sharp-pointed beak. (ref. ID; 1928)

    Limnodrilus bulbiphallus Block & Goodnight, 1972 (ref. ID; 7787 original paper)

    Descriptions

    Live specimens are reddish-brown in color and blend with the substrate in which they live. Preserved mature specimens are 10-18 mm long and 0.52-0.83 mm in diameter. The number of segments range from 33-87. (The small number of segments may be misleading as these worms were, at the time of collection, regenerating new segments. This may suggest that posterior ends had been severed and would account for low number of segments.) The prostomium is approximately as long as it is wide. Dorsal and ventral setae are similar in number, size, and shape. The sigmoid setae appear in segment two and are arranged in four distinct bundles, two dorsal and two ventral. Anteriorly, each bundle contains 4-8 bifid setae; posteriorly, each bundle contains 2-6. The upper tooth is as long or slightly longer than the lower tooth in both anterior and posterior setae. There is little difference in width of the teeth. The clitellum develops on segments 10-12. The male genital system, all structures paired, is characterized by a peculiarly shaped penis sheath. The sheath, approximately 0.04 mm wide at the base and upwards of 0.52 mm in length, has a peculiar bulge that appears just behind the head structure. Except in occasional specimens, the sperm duct is not curved by this bulge but follows a straight line within the sheath to an opening at the end of the penis. The base of this thin-walled chitinous sheath is approximately 0.04 mm wide. From the base, the wall narrow slightly to approximately 0.03 mm at a point about 0.12 mm from the end of the sheath. The bulge appears as the walls widen to around 0.08 mm. At this point, the walls quickly narrow to a widh of 0.03 mm, and then flare outward as lips, forming what has traditionally been described as the head. The flared end of the head resembles the end of trumpets, while the entire head would resemble a cuspidor in shape. The outward flaring of the lips is variable, and such variations may be accounted for in the position that the sheath is viewed through the microscope. The sheath is located ventrally in segments 11 and 12. A slightly developed spiral musculature forms aroud it. The ejaculatory duct, ca. 0.60 mm long and 0.06 mm wide, joins the atrium which appears as a swelling, approximately 0.12 mm wide, 0.32 mm long, along the genital tract. The prostate, in mature specimens, measures ca. 0.16 mm long and 0.07 mm wide. Spermatophores (perhaps better, spermatozeugma) are easily seen in the spermatheca, which is in segment 9 and 10, of mature specimens. The spermatheca is tubular in shape, and the spermatozeugma are short and broad. A pair of female pores are located ventrally in segment 11. Egg sac development extends to segment 14. (ref. ID; 7787)

    Relationship to other species of Limnodrilus

    According to Brinkhurst's (1971) recent key to the family Tubificidae, L. bulbiphallus belongs to the subfamily Tubficinae. The worm has an atrium, prostate, and spermatozeugma which are characteristic of this subfamily. The new species is placed in the genus Limnodrilus because it has a cuticular, cylindrical penis sheath which is surrounded by spiral muscles. Specific characters in the genus Limnodrilus are found for the most part in the shape of the penis sheath (Brinkhurst 1971; Brinkhurst & Cook 1966; Kennedy 1969). The sheath of L. bulbiphallus has two characteristics that are similar to two other species other genus: the bulge and the flared trumpet-like lips. L. neotropicus Cernosvitov is described as having a swollen distal end on the sheath of "bainha termina com dilatacao globosa" (Cernosvitov 1939; Marcus 1942). This species, from Lake Titicaca, South America, does not resemble L. bulbiphallus in that the distal dilation of L. neotropicus forms into a lateral opening while the sheath of L. bulbiphallus forms the bulge, narrows, and flares outwards like a trumpet. Also, the length to width ratios are different for the two sheaths (measured from below the distal bulges): L. neotropicus, 4 to 5 times longer than wide; L. bulbiphallus, up to or greater than 12 times longer than wide. The flared lips of L. bulbiphallus resemble the universally distributed L. hoffmeisteri (straight head variant). The most obvious distinction from L. hoffmeisteri is the shape of the distal end of the penis sheath - the bulge. The length to width ratios are about the same. This new species, with its thin-walled chitinous sheath and its peculiar bulge, has been found by our expeditions to British Honduras in both 1970 and 1971. Curiously enough, a record of L. hoffmeisteri does not occur for the Belize River. The closenes of the bulge to the anterior end of the sheath suggests that this curious swelling is, indeed, part of the head structure. This would give further evidence for considering L. bulbiphallus distinct from L. hoffmeisteri. Except for this obvious distinctions, L. bulbiphallus that characteristics typical of other species of Limnodrilus. It appears, however, that the organism is considerably smaller than its close relatives. For instance, preserved mature specimens of L. bulbiphallus measure 8-10 mm in length, while L. hoffmeisteri ranges from 20 to 35 mm. (ref. ID; 7787)

    Ecology and distribution

    Specimens of L. bulbiphallus were collected among the benthos of the Belize River of British Honduras during the summers of 1970 and 1971. The Belize River empties into the sea just north of Belize City, a city of 40,000. The Haulover Creek, used for the disposal of raw sewage, runs through the city and enters the river near its mouth. The headwaters of the Belize River flow from two branches: the western branch flows into British Honduras from Guatemala, while the eastern forms its headwaters in the Maya mountains. A more complete description of the surrounding vegetation, soils, and the drainage systems that contribute to the river system is reviewed in Wright et al. (1959). (ref. ID; 7787)

    Deposited specimens

  • Holotype: United States National Museum (USNM). Collected in the Belize River, British Honduras, Central America near the village of Boom. Water temperature: 26-34 degrees C. Substrate: clay and mud silt often enriched with organic matter. Salinity: negligible. Collected by: E.M. Block, R.J. Hall, and V.J. Gonzalez. (ref. ID; 7787)
  • Paratypes: Deposited with R.O. Brinkhurst, University of Toronto, Canada; C.J. Goodnight and E.M. Block, Western Michigan University, Kalamazoo Michigan. (ref. ID; 7787)

    Limnodrilus claparedeanus Ratzel, 1868 (ref. ID; 1257, 3692, 6208, 7854) reported author and year? (ref. ID; 6583)

    Descriptions

    Chaetae similar to those of L. hoffmeisteri, slightly longer and thinner with the nodulus more median, teeth more often rounded. Often having rather more chaetae per bundle - up to 10 in anterior segments. The penis tube is very long, with a thick wall which narrows abruptly just proximal to the head. The head itself of characteristic shape, being set in line with the shaft and having a forward and a backward projection of equal length. 3-4 cm long. (ref. ID; 6208)

    Limnodrilus claparedianus Ratzel, 1868 (ref. ID; 7098) or 1869 (ref. ID; 1923) reported author and year? (ref. ID; 5939)

    Descriptions

    Penis sheath about 20 to 30 times as long as it is broad; proximal prongs with setae only slightly reduced. (ref. ID; 1923)

    Limnodrilus grandisetosus Nomura, 1932 (ref. ID; 3692, 6972, 7854)

    Descriptions

    Length 130 mm, maximum width 0.6 mm, 270 segments. Anterior chaetae mostly paired, though up to 4 may be observed, presumably owing to the development of replacements. Chaetae are bifid, with teeth or less equal, but in IV-X enlarging to giant blunt chaetae. Posterior chaetae single. Vasa deferentia long, atria somewhat comma-shaped, ejaculatory ducts thicker than vasa, fairly long. Penis sheaths short, broad, with flared bases and rounded triangular platelike head, no spiral muscles on sacs. Spermathecal pores opening into slight enlargments of spermathecal ducts. (ref. ID; 6972)

    Remarks

    Ohtaka (1985) confirmed the distinction between this and L. silvani, as noted earlier. The penis sheaths of this species are similar in form to those of L. amblysetus, and there are no spiral muscles on the walls of the penis sacs of these species. This may simply be because they are short. Ohtaka (1985) also noted the description of a Limnodrilus by Stephenson (1929) from Burma. This form has a penis sheath somewhat intermediate in form between those of L. grandisetosus and L. silvani, with the base only slightly flared but longer than the head end, which is sharply pointed ectally and otherwise triangular. There is usually a pair of chaetae anteriorly, rarely 3, but only 1 behind VIII-XI. The anterior chaetae have upper teeth that may be twice as long and thick as the lower, but further back the teeth are more nearly equal. It was the existence of this form in Asia that suggested the synonymy of L. grandisetosus and L. silvani by Brinkhurst (Brinkhurst & Jamieson 1971), but this is now rejected. The chaetal form of the Burmese species suggests an affinity with L. udekemianus which has a short but cylindrical penis sheath, but no clear decision can be made. The description of L. amblysetus raises the possibility that Stephenson's species is independent, but this requires confirmation. Two dissected specimens of L. silvani, collected from Miller Sands, Columbia River, Oregon, by R.J. Diaz, were examined. These had 4 or 5 chaetae per bundle, anteriorly, which are clearly bifid, with upper teeth distinctly longer than lower, posterior chaetae 2 per bundle, with blunt teeth, the upper equal to or slightly longer and thinner than the lower. The penis sheaths are quite cylindrical basally, with a platelike ectal end which is somewhat triangular or pointed. The atria are wide adjacent to the entry of the prostate gland, tapered on either side, with ejaculatory ducts as wide as or a little wider than the vasa deferentia. The spermathecae have specialized ectal portions making up a third of the total length in unmated specimens. These are lined with thick cuticle. These worms have chaetae and penis sheaths that differ sharply from those of L. grandisetosus, as noted by Loden (1977) and Ohtaka (1985). The two species can no longer be synonyms, as suggested by Brinkhurst (Brinkurst and Jamieson 1971). The male ducts of this species are of the Limnodrilus form, with thin ejaculatory ducts, unlike those of L. grandisetosus and L. amblysetus. The male ducts were well described by Eisen (1883). (ref. ID; 6972)

    Material examined

    1 specimen, Lake Semba, Ibaraki, Japan, A. Ohtaka collection; 1 specimen, Zhujiang River, Huang-zhu-qi, Guangzhou, Guangdong Province, 1985, Qi Sang collection; 2 specimens, Ge Le Mountain, Middle School 61, near Chongquing, Sichuan Province, 700 m altitude, 11 October 1988, R.O. Brinkhurst collection. (ref. ID; 6972)

    Limnodrilus hoffmeisteri Claparede, 1862 (ref. ID; 1257, 1861, 1911, 1923, 1928, 2378, 6208, 6913, 7254, 7854) reported year? (ref. ID; 3446, 3704, 3955) reported author and year? (ref. ID; 5855, 5939, 6583, 7787, 7817)

    Synonym

    Limnodrilus aurostriatus Southern, 1909 (ref. ID; 1257); Limnodrilus parvus Southern, 1909 (ref. ID; 6208); Limnodrilus spiralis (ref. ID; 5939)

    Descriptions

    L. hoffmeisteri is one of the most abundant and widespread tubificids in the world. It is especially characteristic of polluted or enriched sites. In lakes, it is typically a species of sublittoral or upper profundal zone sediments. (ref. ID; 1861)

    This species is indicative of eutrophic conditions. (ref. ID; 1911)

    Body with less than 140 segments. (ref. ID; 1923)

    There are no hair chaetae in members of this genus and dorsal and ventral chaetae are alike, being simple crotchets without intermediate teeth. In all the species so far recorded from Britain there is a chitinous penis tube in segment 11, and in this species it is usually 11-12 times longer than the width, but immature specimens have tubes as short as L. udekemianus, and I have observed several specimens with the tube as long as that of L. claparedeanus. The tube is thin walled along its length and terminates in an expanded bulb, variously ornamented with flaring lips and commonly set at right-angles to the shaft. The chaetae are broad, sigmoid structures, relatively short, with the teeth equally thick. The upper tooth is often somewhat longer than the lower, or they may be equal; they may be pointed or rounded. There are from 4-8 chaetae per bundle. In the spermathecae (segment 10) the spermatophores are short and broad. The worm can be as long as 4 cm. (ref. ID; 6208)

    Remarks

    Immature: The immatures of L. hoffmeisteri and L. claparedeanus were separated by setal characters alone, as no further differences in the soft anatomy could be found. (ref. ID; 6583)

    Limnodrilus longus Bretscher, 1901 (ref. ID; 1257, 1928)

    Descriptions

    This species is distinguished by the comparative length of the penis-sheath. Bretscher gives 20 to 1 as the proportion (length : breadth). The sheath has a broad and shallow funnel-like expansion at the distal end. The anterior nephridia are enveloped in bladder-like cells. The length is 20-25 mm, and there are 4-7 setae in the anterior bundles. (ref. ID; 1928)

    Limnodrilus parvus Southern, 1902 (ref. ID; 6208) or 1909 (ref. ID; 1257, 1928 original paper)

    See

    Limnodrilus hoffmeisteri (ref. ID; 6208)

    Synonym

    Limnodrilus hoffmeisteri f. parvus (ref. ID; 1257)

    Descriptions

    This species is of comparatively small and slender dimensions, being only 12-15 mm long. The prostomium is rounded; and the breadth at the base exceeds the length. The epidermis is smooth, and the segments not biannulate. There are 3-5, usually 5, setae in the anterior dorsal and ventral bundles. The lower tooth of the seta is slightly longer and thicker than the upper one. The node occurs at the beginning of the distal third. The brain has a rounded outline, and is deeply concave behind. The front is slightly convex, and has a broad median outgrowth. The commissures are also large and broad. The pharynx reaches back to the 5th segment. The intestine is covered with very dark-brown cells. There are prominent contractile vessels in segments 8 and 9. The nephridia are almost completely enveloped in a mass of clear spherical cells. The spermathecae consist of a pear-shaped sack, which leads through a narrow opening into a broad thick-walled duct, opening by a narrow slit on the 10th segment. No spermatophores were observed. The sperm duct commences with a cone-shaped funnel, which leads into a long narrow duct ciliated during the latter part of its course. This passes into a broad atrium lined with very characteristic irregular branched masses of cells. At about the middle of its length it receives the large prostate gland. The penis-sheath is 9-12 times as long as broad. It is curved in a very irregular manner, and becomes very narrow distally, before expanding into a funnel-like mouth. The distal end is of somewhat complex structure. It is sometimes bent at right angles, but usually only slightly curved. The length in all cases was very close to 300 µm, the width 25-35 µm. The width of the proximal and varies; and this accounts for the variation in the relative proportions. The length is slightly less than the width of the body. (ref. ID; 1928)

    This species is described as having a penis tube like that of L. hoffmeisteri but differing from it in that the chaetae have the upper tooth thinner and shorter than the lower, and having rather fewer chaetae per bundle. Cernosvitov (1945) regarded these as closely related species although Hrabe (1938) thought that L. parvus was nothing more than immature L. hoffmeisteri. Forms resembling the description of L. parvus have been observed frequently in the present work. In every instance L. hoffmeisteri was recorded from the same locality, and the parvus specimens were invariably immature with either no penis tube or a very short one, and a poorly developed clitellum. I therefore propose to regard L. parvus as a synonym of L. hoffmeisteri. (ref. ID; 6208)

    Limnodrilus profundicola (Verrill, 1871) (ref. ID; 6653, 7854) reported year? (ref. ID; 1911, 3704, 3955) or Verril (ref. ID; 7817) reported author and year? (ref. ID; 5939, 6583)

    Descriptions

    This species is indicative of eutrophic conditions. (ref. ID; 1911)

    Remark

    Immature: The immatures of this species could clearly be distinguished from L. hoffmeisteri and L. claparedeanus according to a distinct difference in the anatomy of the alimentary canal. The pharynx opens into the gut between segment V and VI in L. profundicola, but between segment IV and V in L. hoffmeisteri and L. claparedeanus. This abrupt widening is readily visible in sufficiently clear preparations. Moreover, the setal equipment of L. profundicola differs from the other two species in several details. The setae near the clitellar region appear rather simple-shaped: the upper and lower teeth are short and rounded, more or less equal in length and shape, the shaft is slender and softly sigmoid. The corresponding setae of L. hoffmeisteri and L. claparedeanus have a curved lower and relatively straight upper tooth, both with pointed ends; the shaft appears somewhat stouter. (ref. ID; 6583)

    Limnodrilus udekemianus Claparede, 1861 (ref. ID; 1923) or 1862 (ref. ID; 1257, 3692, 6208, 6651, 6653, 6913, 7254, 7854) reported year? (ref. ID; 1928, 3446) reported author and year? (ref. ID; 5855, 5939)

    Descriptions

    Penis sheath about 4 to 6 times as long as broad; proximal prongs of setae much reduced. (ref. ID; 1923)

    This species is made conspicuous by the rings of bluish-grey or golden pigment in the posterior segments. Some of the specimens contained large spindle-shaped spermatophores as long as the diameter of the body. The penis-sheath is slightly bent and widened at both ends. (ref. ID; 1928)

    In this species there are about the same number of chaetae per bundle as in L. hoffmeisteri (5-8 anteriorly, 4 in the middle segments falling to 2 posteriorly) but these have the upper tooth larger and much longer than the lower which is occasionally absent. The penis tube is short even in mature specimens, and is usually straight with a simple, or more rarely a sculptured, head. Some worms are as much as 9 cm long, and very thin. (ref. ID; 6208)