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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Rhyacodrilus

Rhyacodrilus Bretscher, 1901 (ref. ID; 1257, 3692, 6913, 6972, 7201)

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

Family Tubificidae: Subfamily Rhyacodrilinae Hrabe, 1963 (ref. ID; 6913) reported author and year? (ref. ID; 6585, 7824)

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 abundant. Prostomium without ciliated pit. Vasa deferentia long, distinct from their wide atria. (ref. ID; 1663)

ref. ID; 6972

The taxonomy of this genus has become confused. Some new species, mostly in the Soviet literature, have been defined on the basis of the presence of penial structures which have also been described in more recent accounts of Rhyacodrilus coccines, as indicated by Brinkhurst and Wetzel (1984). In a collection from California examined in June 1989 there were two forms, one apparently R. coccineus, complete with hair and pectinate dorsally. The other appears from whole mounted specimens and dissections to be an identical taxon apart from the absence of the dorsal hair and pectinate chaetae, which are replaced by bifid chaetae similar to the ventrals. This variation, usually with scarce intermediate forms, is well known within the Tubificinae, but has not previously been reported in other subfamilies (Chapman and Brinkhurst 1987). The Rhyacodrilinae have the same range of dorsal chaetae as the Tubificinae, whereas hair and pectinate chaetae are totally absent in some other subfamilies. The discovery of the California material suggests that Rhyacodrilus species without hair and pectinate chaetae need to be closely compared with those that possess them. (ref. ID; 6972)
  1. Rhyacodrilus altaianus Michaelsen, 1935 (ref. ID; 3692)
  2. Rhyacodrilus amphigenus Juget, 1987 (ref. ID; 6585 original paper)
  3. Rhyacodrilus balmensis Juget, 1959 (ref. ID; 6585)
  4. Rhyacodrilus brevidentatus Br., 1965 (ref. ID; 6651) reported author and year? (ref. ID; 5939)
  5. Rhyacodrilus coccineus (Vejdovsky, 1875) (ref. ID; 1257, 3692, 5939, 6208, 6585, 7201, 7854)
    Syn; Branchiura coccinea Michaelsen, 1900 (ref. ID; 6208); Ilyodrilus coccineus Stolc., 1886 (ref. ID; 6208); Taupodrilus simplex Benham, 1903 (ref. ID; 6208)
  6. Rhyacodrilus coccineus f. inaequalis (Michaelsen, 1905) (ref. ID; 3692, 7201)
  7. Rhyacodrilus ekmani f. profundalis Lastockin, 1937 (ref. ID; 3692)
  8. Rhyacodrilus ekmani f. typica Piguet, 1928 (ref. ID; 3692)
  9. Rhyacodrilus falciformis Bretscher, 1875 (ref. ID; 1257) or 1901 (ref. ID; 3692, 5939, 6585, 6618, 6651, 6653)
  10. Rhyacodrilus fultoni Brinkhurst, 1982 (ref. ID; 7824) reported year? (ref. ID; 7254)
  11. Rhyacodrilus hiemalis Ohtaka, 1995 (ref. ID; 6651, 7098, 7854) reported author and year? (ref. ID; 6648)
  12. Rhyacodrilus isossimovi Cekanovskaya, 1975 (ref. ID; 7201) reported author and year? (ref. ID; 6660)
  13. Rhyacodrilus komarovi Timm, 1990 (ref. ID; 6651, 7854)
  14. Rhyacodrilus korontneffi (Michaelsen, 1905) (ref. ID; 3692, 7201)
    Syn; Clitellio korotneffi Michaelsen, 1905 (ref. ID; 7201); Taupodrilus korotneffi Michaelsen, 1908 (ref. ID; 7201)
  15. Rhyacodrilus leonidi Sokol'skaja, 1976 (ref. ID; 7854)
  16. Rhyacodrilus lepnevae Malevich, 1949 (ref. ID; 3692)
  17. Rhyacodrilus levadinovae Sokolskaya (ref. ID; 7254)
  18. Rhyacodrilus levanidovae Sok., 1973 (ref. ID; 6651)
  19. Rhyacodrilus lindbergi Hrabe, 1976 (ref. ID; 6585)
  20. Rhyacodrilus montana (ref. ID; 1861, 5939)
  21. Rhyacodrilus montanus (Brinkhurst, 1965) (ref. ID; 6651)
  22. Rhyacodrilus multispinus Michaelsen, 1905 (ref. ID; 7201)
    Syn; Clitellio multispinus Michaelsen, 1905 (ref. ID; 7201); Taupodrilus multispinus Michaelsen, 1908 (ref. ID; 7201)
  23. Rhyacodrilus multispinus f. multiovata Burov, 1936 (ref. ID; 3692)
  24. Rhyacodrilus multispinus f. typica (Michaelsen, 1905) (ref. ID; 3692)
  25. Rhyacodrilus palustris (Ditlevsen, 1904) (ref. ID; 3692, 6913)
  26. Rhyacodrilus prostatus Knollner, 1935 (ref. ID; 3692)
  27. Rhyacodrilus punctatus Hrabe, 1931 (ref. ID; 5939)
  28. Rhyacodrilus riabuschinskii Michaelsen, 1929 (ref. ID; 3692, 7854)
  29. Rhyacodrilus sibiricus Semermoi (ref. ID; 7098) or Semernoj, 1971 (ref. ID; 7854) reported year? (ref. ID; 7201)
  30. Rhyacodrilus simplex Benham, 1903 (ref. ID; 7824)
  31. Rhyacodrilus sinicus (Chen, 1940) (ref. ID; 3692, 7854)
  32. Rhyacodrilus sodalis (Eisen, 1879) (ref. ID; 5939, 7854)
  33. Rhyacodrilus sokolskajae Semermoi (ref. ID; 7098) or Semernoj (ref. ID; 7201, 7854)
  34. Rhyacodrilus stephensoni Cernosvitov, 1941 (ref. ID; 6660) or 1942 (ref. ID; 3692)
  35. Rhyacodrilus subterraneus Hrabe, 1963 (ref. ID; 6585)
  36. Rhyacodrilus suputensis Timm, 1990 (ref. ID; 6651, 7854)
  37. Rhyacodrilus svetlovi Sok., 1976 (ref. ID; 6651)

Rhyacodrilus amphigenus Juget, 1987 (ref. ID; 6585 original paper)

Descriptions

Length 3-6 mm, up to 50 segments, width up to 0.28 mm. Prostomium conical, 90-120 µm long, 70-100 µm broad at peristomium. Clitellum not observed.
  • Setal formula: Anterior dorsal bundles with 1 or 2 hair setae, the longest up to 250 µm, and 1 to 3 pectinate setae, 55-67 µm long with upper tooth thinner and slightly shorter than lower and few intermediate teeth. Anterior ventral bundles with 3-5 (exceptionaly 6) bifid setae as long as the pectinate setae, with teeth equal in breadth but with upper tooth 1.5-2.5 times the length of the lower. Posterior dorsal bundles with 1-4 sigmoid simple-pointed setae, 55-60 µm long, with dorsal nodulus. Posterior ventral bundles with 1-4(5) bifid setae as long as posterior dorsal setae with upper tooth thinner but as long as the lower. In segments X to XVI, the the dorsal bundles contain simple-pointed or faintly bifid setae with rudimentary upper tooth and 1 (often absent) hair like seta. Penial setae, 1 to 2 per bundle, 66-72 µm long, up to 5 µm wide, with distal nodulus (ratio tip-nodulus/total length: 0.25); tip of setae with strongly reduced (sometimes missing) upper tooth. Globular coelomocytes, 12-24 µm in diameter numerous in body cavity. The male genitalia resemble those of Rhyacodrilus coccineus. Atria piriform, 120 µm long, 80 µm wide, atrial wall up to 15 µm, with penetration of the posterior wall by the vasa deferentia, with short pseudopenis and diffuse prostate gland. Spermathecae with subspherical ampullae, 60 to 100 µm in diameter; wall of spermathecal ampulla 5-6 µm. The ampullae do not contain sperm bundles but granulous "secretions" the greatest of which are concentrated at apical pole. Spermathecal ducts short and widened in distal part, opening in ventral setal line. Clitellum absent, spermathecae frequently absent and reproductive system variable in location, discussed below. (ref. ID; 6585)

    Remarks

    The absence of clitellum, the frequent absence of spermathecae and the high variability concerning the location of the reproductive organs probably indicate a predominantly asexual reproductive habit, already noted by Timm & Popchenko, 1978 (in Brinkhurst & Wetzel 1984) about Umbadrilus saamicus Timm, 1978, from the Kola Peninsula (U.S.S.R.). Atria and male pores are located in X, XI or XII and spermathecae and spermathopores in IX, X or XI; about 10% of the specimens from the underflow of the Rhone have male pores in X or XII. Autotomy of the posterior segments is frequent between XII an XXIII.
  • Cyst formation, perhaps induced by modification of the hydrological environment, seems to be an original feature in the life history of this stygobiont species. The cysts are composed of silts, sand and detritus cemented by mucus and were found sometimes associated with cysts produced by a species of the genus Aeolosoma which occurs in the same interstitial waters. The posterior dorsal bundles resemble those of only Rhyacodrilus lindbergi Hrabe, 1976 described from the cave Grutas das Alcobertas in Portugal; but Rhyacodrilus amphigenus has pectinate chetae anteriorly. The male genitalia and the shift in the position of the genital system associates Rhyacodrilus amphigenus with Rhyacodrilus coccineus, but it is more often asexual than the latter. (ref. ID; 6585)

    Etymology

    We have given the specific name amphigenus (gr. amphi; on one hand and the other hand, and genos origin), because of the disparities affecting the shape of somatic setae, especially the anterior and posterior dorsal setae, in the same way as the physiology (characterized by anabiosis stages). (ref. ID; 6585)

    Ecological notes

    Rhyacodrilus amphigenus is a stygobiont limivorous species found in the phreatic sheet of the alluvial plain of the French upper Rhone, chiefly on the right bank of the river, downstream of the confluence Ain-Rhone. (ref. ID; 6585)

    Material examined

    20 whole mounted specimens on 8 slides, from the alluvial plain of the river Rhone, deposed in the author's collection. (ref. ID; 6585)

    Rhyacodrilus coccineus (Vejdovsky, 1875) (ref. ID; 1257, 3692, 5939, 6208, 6585, 7201, 7854)

    Synonym

    Branchiura coccinea Michaelsen, 1900 (ref. ID; 6208); Ilyodrilus coccineus Stolc., 1886 (ref. ID; 6208); Taupodrilus simplex Benham, 1903 (ref. ID; 6208)

    Descriptions

    Hair chaetae thin, relatively long, 3-5 per bundle anteriorly, 1-2 in the mid region, none posteriorly. Dorsal crotchets thin, and straight proximal to the nodulus, the latter a quarter to one third of the length from the distal end. Teeth diverging at about 45 degrees with a series of very fine intermediate teeth between them. There are usually five chaete per bundle anteriorly and 2-3 in post-clitellar segments. The ventral chaetae are slightly more sigmoid with fine distal teeth diverging at less than 45 degrees. The upper tooth is thinner and slightly longer than the lower, and the nodulus about one third the way from the distal end. The penial setae in segment 11 are straight and either simple ended or with very reduced teeth. They are from 3-5 in number, and are characteristically grouped with their proximal ends widely separated but their distal ends close together. The chaetae of the posterior segments are all similar, with the upper tooth thinner ans shorter than the lower. (ref. ID; 6208)

    The species revealed cosiderable variability. Mature but damaged individuals (without tail) were usually at least 13-23 mm long, 0.4-0.8 mm broad in VIII and up to 0.9 mm in clitellum when compressed in whole mounts and consisting of more than 35-60 segments. Body wall smooth and transparent, rarely with sparse dark epidermal glands. Anterior ventral chaetae 4-6 per bundle, 80-115 µm long, with upper tooth of variable length but thinner. Dorsal pectinate chaetae by 3-5, 101-137 µm long (often smaller in II), with teeth usually straighter than in ventral chaetae and with very thin intermediate teeth. Besides these, 1-5 smooth hair chaetae occur, 220-516 µm long (less than 200 µm in II). Posteclatellar body portion, 2-4 bifid chaetae per bundle, accompanied by 1-2 hair chaetae in dorsal bundles. Penial chaetae medially of male pores (usually in XI), 2-5 per bundle, 103-114 µm long, with blunt tips close to each other, sometimes equipped with rudimentary upper tooth. Clitellum covering XI-XII and some parts of X and XIII, sometimes reaching anterior edge of X. Forward shift of the reproductive system has been observed in some cases. Pharynx roof bears 4-6 separate clusters of gland cells fusing into a common mass in posterior part of III. Chromophilous cells laterally on anterior side of 3/4, 4/5, and 5/6. Chloragogen tissue on oesophagus beginning either from V or VI. Intestine dilating gradually in VII-IX. Anterior nephridia in VII and VIII, sometimes also in IX. Numerous coelomocytes in body cavity (including prostomium), round and granulated, 10-21 µm in diameter. No dilated blood vessels observed in forebody; dorsal vessel often thickened in its postclitellar portion. Testes in X, ovaria and atria with male pores in XI; however, in one sectioned specimen they were shifted one segment forward. Another, whole-mounted abnoraml individual had long clitellum in VIII-1/2XII, with paired bundles of penial chaetae in IX and one unpaired bundle in X. Unpaired sperm and egg sacs can reach up to XVII-XXVI; anterior sperm sac often occurs in IX. Compact, bowl-shaped male funnels on 10/11 directed forward, 80-90 µm high and up to 30 µm thick. Short (but longer than atrium), slightly meandering vas deferens 16-35 µm wide, consisting of large epithelial cells, enters anterior surface of atrial ampulla. Ampullae are rounded, 42-66 µm wide, with 1-5 µm thick external muscular layer and about 9 µm thick epithelium. Their lumen is 5-21 µm wide and empty. Ejaculatory ducts 40-70 µm long and 44-63 µm wide, epithelial. Males pores in common transversal groove of epidermis, devoid of clitellar glands, without any penial structures in the typical form. A dense layer of prostatic cells reaches up to 70-160 µm at the top of atrial ampulla, decreasing gradually on the sides; no prostate tissue on ejaculatory duct. Female funnels as 60-140 µm high and about 14 µm thick sparsely ciliate portions of 11/12. A larger tuft of ciliate marks the place where a 35 µm long and up to 16 µm wide canal (oviduct) enters body wall. The canal open with female pore above ventral chaetal line. Spermathecae filling most of X. Ampulla oval, 215-235 µm long and 105-210 µm wide when full of irregular sperm mass. Its wall is epithelial and in most part only 5-9 µm thick; however, anteriorly many 21-37 µm high cells are projecting into ampullar lumen. Duct lies on the lower side of the anterior end of ampulla and opens near 9/10 on ventral chaetal line. It is very short (40-70 µm) and conical, narrowing from 53-90 down to 35-56 µm. Wall of duct consists of thin external musculature (2-5 µm) and of high, transversally extending epithelial cells. Lumen can be 7-19 µm wide in different specimens. A special form, tentatively attributed to R. coccineus, was observed in the Ul'conok, a small tributary stream. 15 individuals, mostly mature, were studied, three of them on sections. The worms were smaller than the rest of R. coccineus, only 7-9 mm long, consisting of 45-54 segments, 0.4 mm wide in VIII and 0.5-0.7 mm on clitellum when mounted under the cover glass. Consequently, chaetae were also shorter (anterior ventral chaetae 68-105 µm, pectinates 58-84 µm, and hair chaetae 150-250 µm). Only two bifids per bundle occurred on the tail, and hair chaetae disappeared soon after clitellm. Pectinates had particularly long and thin teeth. Male funnels were also slightly smaller (3-75 µm in diameter, 21-23 µm thick) while the shape and measurments of vas deferens, female funnels, and spermathecae remained within the variation limits of R. coccineus as given above. However, atria were different. The atria of the R. coccineus (?) from Ul'conok were cub-shaped, 120-150 µm long, without a clear distinction between ampulla and ejaculatory duct. The proximal portion (ampulla) was 35-47 µm wide and covered with prostatic tissue, 45-80 µm thick at the very end but thinner of the sides. Muscular layer was 2-6 µm thick, epithelium 5-12 µm, while lumen reached up to 16 µm in diameter. Vas deferens entered the lower part of ampulla like in a typical R. coccineus. Ampulla narrowed gradually down into ejaculatory duct, about 80 µm long and 21-35 µm wide, its distal end often (but not always) protruding over body surface as pseudopenis with a length of about 32 µm. Presence of pseudopenes, together with prolonged teeth of pectinate chaetae are the main peculiarities of this form. (ref. ID; 7854)

    Notes

    A separate form of this species (forma inaequalis Michaelsen, 1905) is merely noted by Cekanovskaya (1962) with very little comment. Brinkhurst (1981) examined the vial labelled as types of this form (ZMUH (Zoological Museum of the University of Hamburg) V6591). One specimen was a fragment, another a lumbriculid; 14 others were not made available. Two species resembling R. coccineus have recently been described in the Soviet Union (R. sokolskajae Semernoj; R. sibiricus Semernoj, 1971), which differ from the original in regard to the possession of pseudopenes (either protrusible or permanently everted), the difficulty being that Hrabe (1981) has recently described eversible pseudopenes in R. coccineus for the first time. The genus requires reevaluation, made all the more difficult by the absence of types of R. coccineus. The types listed for that taxon by Reynolds and Cook (1976) in Hamburg (ZMUH V6948) are of R. coccineus var. simplex, later Rhyacodrilus (Taupodrilus simplex (Benham)) from New Zealand. (ref. ID; 7201)

    R. coccineus is a widely distributed Holarctic species. Several local forms or closely related species occur in the Far East. Chen (1940) described from Nanking, China, Tubifex sinicus, a worm externally similar to R. coccineus but equipped with short penes in penial sac, as well as with bipartite vasa deferentia more than 5-fold longer than atrium together with penis. These penes can be interpreted as pseudopenes, and the species must be attributed to Rhyacodrilus, as Cekanoskaja (1962) and many others did. Sokol'skaja (1958) found a similar but smaller taxon, with facultatively protruded pseudopenes, several places of the Amur River, and identified it as R. sinicus (Chen). In 1976, Sokol'skaja described, from the Chukchi Peninsula, R. leonidi devoid of any pseudopenes, with small intermediate teeth in ventral crotchets. Rhyacodrilus sp. from Kunashir Island (Sokol'skaja 1969) was also attributed to R. leonidi by Sokol'skaja (1976). Later on, apparently confused by the variability of Rhyacodrilus on the Kamchatka Peninsula where many speciemens with multiplied or shifted reproductive organs (once described as R. riabuschinskii by Michaelsen 1929), and some others with protruded pseudopenes were found, Sokol'skaja (1964, 1983) lumped her Amur River material as well as R. leonidi together with R. coccineus. Meanwhlie Semernoj (1971) redescribed the Amur worms found by Sokol'skaja (1958) as a separate species, R. sokolskajae. He pointed out their differences from R. sinicus: smaller size but larger segment number, the presence of intermediate teeth in dorsal chaetae and the lack of penial sacs (replaced by special musculature of pseudopenes). All these differences, apart from size and the segment number, can also be subjective. Semernoj did not noted the character of vasa deferentia which are rather long in both cases but bipartite in Chen's material and uniform in the Amur worms. In the Amur River, R. sokolskajae apparently takes the place of the typical R. coccineus. In some Transbaikalian lakes, Semernoj (1971) described another species, R. sibiricus (erroneous spelling: sibirica), sympatric with R. coccineus, R. sibiricus has club-shaped atria with invariably protruding psedopenes. Still more confusion arose when Brinkhurst (1965) and Brinkhurst and Jamieson (1971) followed some others (e.g. Qi and Erseus 1985), tried to synonymize R. sinicus with the poorly definied R. sodalis (Eisen). No external penial structure was described in the American R. sodalis either by Eisen (1879, 1885) or by Brinkhurst (1965). Figures 8B-C in Ohtaka (1995) demonstrate that R. sodalis has atria with an oval ampulla and a short ejaculatory duct, as well as a simple invaginated male pore and pectinate chaetae with very long, thin teeth. Liang (1987), finding a single specimen of Rhyacodrilus, but with a forward shift of the reproductive system, in the Yangtze River, defined it as R. riabuschinskii. R. hiemalis (Ohtaka, 1995) from several Japanese lakes has pectinate chaetae in both anterior dorsal and vental bundles like R. leonidi, pectinate penial chaetae and club-shaped atria that can form pseudopenes. Large masses of glandular cells around male pores, as well as thin-walled spermathecal ducts distinguish this species clearly from R. coccineus and its other closest relatives. Thus, there exists a cluster of morphologically close species (and/or infraspecific units?) of the genus Rhyacodrilus in the Far East. R. coccineus s. s. is the only common Palaearctic species (with some introductions to North America and some localities in the Southern Hemisphere?). The other have more limited distribution ranges. Among them, R. hiemalis has several distinct characters (see above). R. sibiricus is also well defined by its club-shaped atria and regularly protruding pseudopenes. My R. coccineus (?) from Ul'conok has similar atria but pseudopenes are not always protruding. Facultatively protruding pseudopenes are also described in R. sokolskajae and in some Kamchatkan worms identified by Sokol'skaja (1983) as R. coccineus s. l. R. sinicus is distinguished first by a bipartite vas deferens, while the penis described by Chen (1940) can be interpreted more correctly as a pseudopenis. The unusually large size given for R. sinicus, 80-150 mm, is probably a misprint unnoticed by Chen, since te segment number 42-56 would rather fit to a body length of 8-15 mm. The presence of intermediate teeth in the ventral chaetae of R. leonidi as well as their alleged lack in the dorsal pectinates of R. sinicus can be a matter of different microscopic techniques. Particularly long and thin teeth in dorsal needles are charateristic of R. hiemalis and of R. coccineus (?) from Ul'conok, but can occur also in other populations of R. coccineus as an individual variation. Evidently, the latter character gave Brinkhurst (1965) the idea of the possible identity of some Asian Rhyacodrilus with the North American R. sodalis. However, no external pseudopenes are described in the American R. sodalis so far. The whole assemblage badly needs a revision. (ref. ID; 7854)

    Examined materials

    168 specimens from 21 samples, collected from different watercourses. Eight mature individuals studied on serial sectios, the rest as whole mounts. (ref. ID; 7854)

    Rhyacodrilus falciformis Bretscher, 1875 (ref. ID; 1257) or 1901 (ref. ID; 3692, 5939, 6585, 6618, 6651, 6653)

    Descriptions

    Small worms. Few bifid setae both dorsally and ventrally, upper teeth much longer than the lower. Penial setae greatly enlarged, one on each side of XI ventrally, with sickle-shaped ends. Atria elongate with diffuse prostate glands. (ref. ID; 5939)

    Rhyacodrilus hiemalis Ohtaka, 1995 (ref. ID; 6651, 7098, 7854) reported author and year? (ref. ID; 6648)

    Descriptions

    Dorsal hair chaetae usually distributed in anterior half of the body but sometimes found in more posterior segments; 4-8 per bundle anteriorly. Dorsal pectinates 5-9 per bundle anteriorly; the lateral teeth long and parallel, and the intermediate teeth many, long and distinct. Ventral chaetae 6-8 per bundle anteriorly, 2-5 posteriorly, invariably bearing intermediate teeth. Artia ovoid with diffused prostate cells. Pseudopenes protrusible. Mass of diffused gland cells set around male pores. (ref. ID; 7098)

    Remarks

    This species is compared with nearly cosmopolitan R. coccineus (Vejdovsky) and its unclear relatives, Far East Russian R. sokolskajae Semermoi and R. sibiricus Semermoi, Chinese R. sinicus Chen and North American R. sodalis (Eisen). However, the number of hair chaetae is greater and intermediate teeth are longer and more distinct in the present species than in above compared congeners. Moreover, the diffused gland cells around male pores have never been reported in the congeners. Ohtaka (1995) confirm by examination of the specimens that Rhyacodrilus sp. of Narita (1990; from Lake Biwa) and Takada et al. (1992; from Lake Suwa) are ascribed to the present species. According to ecological studies by Narita (1990) and Takada et al., (1992), this species breeds during cold season but aestivates in deeper sediments during summer. (ref. ID; 7098)

    Rhyacodrilus isossimovi Cekanovskaya, 1975 (ref. ID; 7201) reported author and year? (ref. ID; 6660)

    Descriptions

    The setae in this species are all bifid, with long upper teeth. There are two, sometimes three penial setae on each side of XI which bear very reduced teeth. (ref. ID; 7201)

    Notes

    It has all the characteristics of a Rhyacodrilus and is close to R. stephensoni Cern. with which it is compared by the describer. No mention is made of another ?Asiatic species R. levaninovae Sok, which also has all bifid setae, as do R. fultoni and R. bifidus from Australia, of which the former lacks prostates. (ref. ID; 7201)

    Type materials

    ZIAS (Zoological Institute, Academy of Sciences, Leningrad) 1/38360. No material by the author. (ref. ID; 7201)

    Rhyacodrilus korontneffi (Michaelsen, 1905) (ref. ID; 3692, 7201)

    Synonym

    Clitellio korotneffi Michaelsen, 1905 (ref. ID; 7201); Taupodrilus korotneffi Michaelsen, 1908 (ref. ID; 7201)

    Type materials

    ZMUH (Zoological Museum of the University of Hamburg) V6589, 6590 (2 and 20 specimens, respectively). (ref. ID; 7201)

    Rhyacodrilus multispinus Michaelsen, 1905 (ref. ID; 7201)

    Synonym

    Clitellio multispinus Michaelsen, 1905 (ref. ID; 7201); Taupodrilus multispinus Michaelsen, 1908 (ref. ID; 7201)

    Notes

    The large number of setae in anterior segments that rapidly declines to more usual numbers posteriorly is reminiscent of Isochaetides baicalensis, and may account for the confusion of material in the Hamburg collection. The description of R. korotneffi mentions the diffuse prostates on the atria, penial setae, and sperm masses in the spermathecae, all rhyacodriline characteristics, but not any other useful characters such as the presence of coelomocytes. The description of the second species lacks even mention of the few rhyacodriline characters described for the first, according to the account in Cekanovskaya (1962). (ref. ID; 7201)

    Type materials

    ZMUH (Zoological Museum of the University of Hamburg) V6588, two specimens examined in fluid. All three of the original specimens were immature, which is cofirmed for the two that survive. (ref. ID; 7201)