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The World of Protozoa, Rotifera, Nematoda and Oligochaeta

Mesenchytraeus

Mesenchytraeus Eisen, 1878 (ref. ID; 1257, 3692, 5971)

Family Enchytraeidae (ref. ID; 1257, 1928, 5971, 7854)

ref. ID; 1923

Setae simple pointed and usually straight, spermathecae open between segments 4/5 or 3/4 and 4/5. Usually whitish in appearance and seldom more than 25 mm in length. Sigmoidal setae arranged in 4 bundles per segment. Esophagus gradually merging into intestine. Head pore generally at the apex of the prostomium, nephridia plurilobed; peneal bulb with muscular strands. (ref. ID; 1923)

ref. ID; 5971

Brinkhurst and Jamieson (1971) and Goodman (1971) have pointed out the confusion that exists over the proper name for what is otherwise a clearly definable genus. When Eisen established Mesenchytraeus he did not designate one of the three species he described as the type (Goodman 1971). Nielsen and Christensen (1959) subsequently listed the three species Eisen had described as species dubia. This effectively moves Analycus Levinson, 1883 into position of priority as the genus name (Brinkhurst and Jamieson 1971). In reviewing the descriptions of M. primaevus, M. mirabilis and M. falciformis (Eisen, 1878), we found the written text and drawings to be at least sufficient. The size and segment count are given, the setae and nephridia are described, information on the habitat is given, and, most importantly, the reproductive structures are described in detail. From this information, it is obvious that the specimens are members of the present day Mesenchytraeus (sensu Nielsen and Christensen). In addition, through the courteous assistance of Dr. Roy Olerod, we have examined preserved specimens of these three species which were housed in the Naturhistoriska Riksmuseet, Sektionen for Evertebrat-zoologi, Stockholm, Sweden. The type collection numbers are as follows: M. primaevus, Nos.50, 31, 112 and 116; M. mirabilis, Nos.39 and 67; and M. falciformis, No.113. These are all whole or fragmented specimens preserved in alcohol. Although they have deteriorated with time, we could observe the general size, segment number, and setal shape. Setae are clearly sigmoid nodulate, indicating that the specimens are mesenchytraeids. From the rule of page priority and the fact that it is the best described and illustrated and was collected over the widest area, we designate Mesenchytraeus primaevus Eisen, 1878 as the type species for the genus. The species described below conform to the generic definition of Nielsen and Christensen (1959). (ref. ID; 5971)

Type species

Mesenchytraeus primaevus Eisen, 1878 (ref. ID; 5971)
  1. Mesenchytraeus altus Welch, 1917 (ref. ID; 5971)
  2. Mesenchytraeus armatus (Levinsen, 1884) (ref. ID; 1257) reported year? (ref. ID; 4491)
    Syn; Mesenchytraeus setosus Michaelsen, 1888 in Southern, 1909 (ref. ID; 1257)
  3. Mesenchytraeus arcticus Bell, 1962 (ref. ID; 6651)
  4. Mesenchytraeus argentatus Nurminen (ref. ID; 6567)
  5. Mesenchytraeus asiaticus Eisen, 1904 (ref. ID; 5971)
  6. Mesenchytraeus atriaphorus Al., 1936 (ref. ID; 6651)
  7. Mesenchytraeus beringensis E., 1904 (ref. ID; 6651)
  8. Mesenchytraeus beumeri (Michaelsen, 1886) (ref. ID; 1257) reported year? (ref. ID; 1928)
  9. Mesenchytraeus bungei Michaelsen, 1901 (ref. ID; 3692)
  10. Mesenchytraeus celticus Southern, 1909 (ref. ID; 1257, 1928 original paper)
  11. Mesenchytraeus chaunus Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)
  12. Mesenchytraeus chromophorus Al., 1936 (ref. ID; 6651)
  13. Mesenchytraeus crenobius Timm, 1994 (ref. ID; 6651, 7854)
  14. Mesenchytraeus diplobulbosus Bell, 1949 (ref. ID; 6651)
  15. Mesenchytraeus diverticulatus Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)
  16. Mesenchytraeus eastwoodi Eisen, 1904 (ref. ID; 6651)
  17. Mesenchytraeus fenestratus (Eisen) (ref. ID; 1928)
  18. Mesenchytraeus flavus (Levinsen, 1884) (ref. ID; 6653) reported year? (ref. ID; 1928)
  19. Mesenchytraeus fontinalis Eisen, 1904 (ref. ID; 6651)
  20. Mesenchytraeus franciscanus Eisen, 1904 (ref. ID; 6651)
  21. Mesenchytraeus fuscus Eisen, 1904 (ref. ID; 6651)
  22. Mesenchytraeus gelidus Welch, 1919 (ref. ID; 6651)
  23. Mesenchytraeus glandulosus (Levinsen, 1884) (ref. ID; 1257)
    Syn; Mesenchytraeus harperi in Stephenson, 1926 (ref. ID; 1257)
  24. Mesenchytraeus grandis Eisen, 1904 (ref. ID; 6651)
  25. Mesenchytraeus grebnitzkyi Michaelsen, 1901 (ref. ID; 3692)
  26. Mesenchytraeus harrimani Eisen, 1904 (ref. ID; 6651)
  27. Mesenchytraeus hydrius Welch, 1919 (ref. ID; 5971)
  28. Mesenchytraeus kincaidi Eisen, 1904 (ref. ID; 6651)
  29. Mesenchytraeus kontrimavichusi Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)
  30. Mesenchytraeus konyamensis Michaelsen, 1916 (ref. ID; 6651)
  31. Mesenchytraeus lustianicus Coll., Mar.-Ans. & Gi., 1993 (ref. ID; 6651)
  32. Mesenchytraeus macnabi Bell, 1942 (ref. ID; 6651)
  33. Mesenchytraeus maculatus Eisen, 1904 (ref. ID; 5971)
  34. Mesenchytraeus magnus Altman, 1936 (ref. ID; 5971)
  35. Mesenchytraeus minimus Altman, 1936 (ref. ID; 6651)
  36. Mesenchytraeus monothecatus Bell, 1945 (ref. ID; 6651)
  37. Mesenchytraeus nanus Eisen, 1904 (ref. ID; 6651)
  38. Mesenchytraeus obscurus Eisen, 1904 (ref. ID; 5971)
  39. Mesenchytraeus orcae Eisen, 1904 (ref. ID; 5971)
  40. Mesenchytraeus pedatus Eisen, 1904 (ref. ID; 6651)
  41. Mesenchytraeus pelicensis Issel, 1905 (ref. ID; 6653)
  42. Mesenchytraeus penicillus Eisen, 1904 (ref. ID; 6651)
  43. Mesenchytraeus sanguineus Nielsen & Christensen, 1959 (ref. ID; 1257)
  44. Mesenchytraeus setchelli Eisen, 1904 (ref. ID; 6651)
  45. Mesenchytraeus setosus Michaelsen (ref. ID; 1928)
  46. Mesenchytraeus solifugus (Emery, 1898) (ref. ID; 6651)
  47. Mesenchytraeus svetae Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)
  48. Mesenchytraeus tetrapodus (ref. ID; 5971)
  49. Mesenchytraeus tundrus Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)
  50. Mesenchytraeus unalaskae Eisen, 1904 (ref. ID; 6651)
  51. Mesenchytraeus vegae Eisen, 1904 (ref. ID; 6651)
  52. Mesenchytraeus vshikovae Timm, 1994 (ref. ID; 6651), vshivkovae Timm, 1994 (ref. ID; 7854)

Mesenchytraeus celticus Southern, 1909 (ref. ID; 1257, 1928 original paper)

Descriptions

These worms are very large and thick in proportion, and of very soft consistency. The anterior end is white, or faintly yellow, whilst the middle and posterior parts are much darker. Microscopical examination shows that this is due to the large number of small dark coelomic corpuscles, very few of which pass in front of the 6th segment. The length of the living worm varies very much according to the state of contraction. The same individual may vary from 12-25 mm. Preserved specimens are 10-15 mm long and 1 mm broad. The setae are very numerous and all of the same size. The anterior ventral bundles usually contain 10 or 11, occasionally 12 or 13 setae. The lateral bundles contain 5-7 setae. The head pore is situated at the tip of the prostomium. The latter is thickly covered with prominent papillae. The epidermis is very granular, and is covered with rows of irregular amoeba-shaped isolated glands. The clitellum is very prominent. In the Irish specimens it occupied segment 1/211-13, in the Scotch specimens segments 12-14. The dorsal vessel appears to be intraclitellar in origin, rising about the 13th segment. The coelomic corpuscles are very numerous. They are small, oval, and full of very dark granules. There are seven pairs of septal glands in segments 4-10. The brain is concave in front and behind, and its breadth considerably exceeds the length. The nephridia are of the characteristic generic structure, consisting of a short, slender anteseptal, and a large bilobed postseptal. The duct is long and slender, and appears to rise between the two lobes, or from the base of the larger one. The spermathecae consist of a short thick duct, in which the lumen is very narrow, and a large, thin-walled ampulla, about three times as long as the duct. From the base of the ampulla depends a single oval diverticulum. The sperm-funnel is about one and a half times as long as broad, with a prominent lip. The duct is fairly long, about eight times as long as the funnel. It terminates in a pear-shaped penial bulb, which is slightly smaller than the funnel. Close to the external opening of the penis, a number of separate prostates open into the duct. The ovisac extends back into the 15th segment. The structure of the spermathecae, and the uniform size of the setae, indicate a relationship with M. flavus (Lev.). It differs from the latter species in the number of setae, septal glands, shape of brain and nephridia, etc. In M. flavus the setae number 4-6 in a bundle, there are only three pairs of septal glands, the brain is as long as broad, and the anteseptal of the nephridium has a distinct neck. (ref. ID; 1928)

?Etymology

First taken near Montpelier, Co. Dublin, under stones, in moss, etc., December 1907, when it was quite mature. In February, 1908, mature specimens were sent to me by Mr. W. Evans, from a roadside near Edinburgh. (ref. ID; 1928)

Mesenchytraeus chaunus Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)

Descriptions

A medium size species of approximately 12 mm adult length. Mean segment number is 59 for adults (n=40, SD 3.4). (Throughout this paper the mean segment number is followed in parentheses by the sample size (n) and by the standard deviation (SD).) General body color is pale white semitransparent, with gut contents visible and with intense white patches due to the aggregation of lymphocytes within the body cavity. Clitellum extends over XII-XIII; the clitellar glands are irregularly arranged and not a prominent feature. Setae are sigmoid nodulated. The dorsal setae in VI-X are reduced to 1,2, or 3 in number and are twice the size of setae throughout the rest of the body even in immature specimens. Setae within a bundle are not arranged in fanlike pattern, and are all of equal length. Setal pattern 1,2,3,4,5-2,3,4: 3,4,5,6,7,8-2,3,4,5,6. The brain is deeply incised on the posterior margin, with lateral margins parallel. There are two pairs of primary and three pairs of secondary septal glands; the primaries are closely appressed to the anterior septal wall, as is typical in this genus. The last pair of secondaries are often many lobed and extend into segment VIII. Chloragogen cells are light brown and begin in V. Cutaneous glands are irregularly arranged and indistinct. Dorsal vessel originates distinctly in one of XV, XVI, XVII, or XVIII. Lymphocytes are of the nucleate type only, ellipsoid in shape; they have distinct nuclei and are packed with refractile particles which appear black in transmitted light. Blood is colorless. Nephridia are bifurcate. There are esophageal diverticula, no sudden expansion between esophagus and intestine; no intestinal diverticula. The sperm funnels are 1/3 to 1 times as long as the body width at the clitellum, and 2 to 3 times as long as wide. The collar has two to three flaps which are variable in shape in moving specimens. An atrium is present with 4-6 attached atrial glands opening into the atrium proper. No penial or accessory glands are apparent. Seminal vesicles and egg sacs are present. Spermathecae are free from the esophagus. No glands are present at the ectal opening. The ectal portion appears muscular up to the point of internal diverticulum, the remainder nonmuscular. Distinct ampulla depending on the amount of sperm present; it extends back into segments V-X, depending upon the amount of coiling. Mediolateral ectal opening on V. (ref. ID; 5971)

Remarks

Of the large group of Mesenchytraeus having free spermathecae extending through several segments, only M. sanguineus Nielsen and Christensen, 1959 and M. orcae Eisen, 1904 have small internal diverticula as pictured for this species. Mesenchytraeus sanguineus has a sperm funnel unlike the one here and the ectal duct of the spermatheca is much longer. In addition M. sanguineus has distinctly red blood and no enlarged setae. Mesenchytraeus orcae has a spermatheca indistinguishable from that in Fig.3, but M. orcae is much smaller (33 segments). Eisen did not specifically state that there were no enlarged setae in M. orcae; however, he does give the number of setae found in dorsal and ventral bundles for the first 22 segments. We assumed that had enlarged setae been present, he would reported it. We have examined three cotypes borrowed from the Smithsonian Institution (USNM32919). We could not find enlarged setae but the material has suffered over time. (ref. ID; 5971)

Etymology

The name is derived from the type location at Chaun Bay, site of the tundra research station oerated by the Institute of Biological Problems of the North. (ref. ID; 5971)

Habitat and distribution

A terrestrial species found only Chaun Bay in the mesic heath, tussock tundra, and mountain sites. (ref. ID; 5971)

Type locality

Chaun Bay, U.S.S.R., 68 degrees 44'N, 170 degrees 36'E, from the mesic health study site, approximately 75 m inland from the research station. (ref. ID; 5971)

Examined materials

  • Holotype: USNM62087. (ref. ID; 5971)
  • Paratypes: USNM62088-62090. (ref. ID; 5971)

    Mesenchytraeus diverticulatus Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)

    Descriptions

    A small species; adult individuals are 7-10 mm long, with a mean number of segments of 50 (n=22, SD 2.3). The body is pale white and semitrasparent with gut contents visible. The clitellum extends over XII-XIII and is not a prominent feature. The clitellar glands are irregularly arranged. Seatae are sigmoid nodulated, of equal length within the bundles, with no abnormally large setae in any segment. Setal pattern 2,3,4-2,3,4: 2,3,4,5-2,3,4,5. The brain is usually deeply incised on the posterior margin but variable, the lateral margins parallel. There are two pairs of primary and two pairs of secondary septal glands, the primaries closely appressed the anterior septal wall. Chloragogen cells are light brown and begin to occur in V. Cutaneous glands are irregularly arranged and indistinct. Dorsal vessel originates in XIV-XV. Blood is colorless. The lymphocytes contain scattered refractile particles which appear black in transmitted light, with the matin portion of the lymphocyte clear. Lymphocytes are of the nucleate type only, ellipsoid in shape. Nephridia are bifurcate. There are no esophageal diverticula present. There is a sudden expansion of the esophagus into the intestine proper in VIII. Four intestinal diverticula are located in VIII; often, each one appears to have a more or less distinct lumen in its anterior portion. The lumen walls appear. Sperm funnels are 3/4 to 1+1/2 times as long as the body width at the clitellum and 2 to 3 times as long as wide. Collar is distinct with mature sperm in the prominent opening. Sperm duct is long and loosely coiled. Atrium present just ental to the penial opening, without atrial glands. A rosette of glands appressed to the inside of the body wall surrounds the sperm duct ectal to the atrium and immediately ental to the penial opening. Seminal vesicles and egg sacs are present. Spermathecae are short, normally confined to V but occasionally reaching to VI, and free from the esophagus. There are no glands present at the ectal opening and no diverticula along the ectal duct. Distinct club-shaped ampulla is present in fully mature individuals. Mediolateral ectal opening on V. (ref. ID; 5971)

    Remarks

    This is only species known to combine all the standard Mesenchytraeus features with a sudden gut expansion and intestinal diverticula, features that are normally associated with the genus Henlea. While there can be no doubt that this species belongs within the genus Mesenchytraeus, we can offer no explanation for this combination of characters. An understanding of the function of the expansion and diverticula would shed light on this question. (ref. ID; 5971)

    Etymology

    The name is derived from the distinguishing gut expansion and diverticula in VIII. (ref. ID; 5971)

    Habitat and distribution

    A terrestrial species found at Magadan in the bog, lowland larch, upland pine, and riparian birch sites. (ref. ID; 5971)

    Type locality

    Magadan (Snow Valley), U.S.S.R., 59 degrees 30'N, 151 degrees 50'E, from the upland pine study site. (ref. ID; 5971)

    Examined materials

  • Holotype: USNM62091. (ref. ID; 5971)
  • Paratypes: USNM62092. (ref. ID; 5971)

    Mesenchytraeus kontrimavichusi Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)

    Descriptions

    A medium size species, adult individuals approximately 12 mm long with a mean number of segments of 53 (n=44, SD 3.2). General body color is pale white semitransparent with gut contents visible. The clitellum extends over XII-XIII; the clitellar glands are irregularly arranged and not prominent. Setae are sigmoid nodulated. The ventral setae in V-IX are reduced to 2 or 3 in number and are twice the size of setae throughout the rest of the body. Setae within a bundle are all of equal length. Setal pattern 2,3,4,5-1,2,3,4: 1,2,3,4,5,6-2,3,4,5,6. The brain is not incised on the posterior margin; lateral margins are parallel. There are two pairs of primary and three pairs of secondary septal glands; the last pair of secondaries are often many lobed and extend into VIII. Chloragogen cells are light brown and begin to occur in V. Cutaneous glands are irregularly arranged and not prominent. Dorsal vessel originates distinctly in one of XV-XVIII. Blood is colorless. Lymphocytes are nucleate only, elongate ellipsoid in shape. They are indistinctly colored and finely granular in texture. Nephridia are bifurcate. There are no esophageal or intestinal diverticula, and no sudden expansion between esophagus and intestine. Sperm funnels are 1/3 as long as body width at the clitellum, and 2 times as long as wide. The walls of the sperm funnels are thick and no collar is apparent. The funnel opening is prominent and filled with mature sperm. Sperm duct is short and 1/3 as wide as the widest part of the body of the funnel. No atrial or penial structures were observed. Seminal vesicles and egg sacs are present. Spermathecae are normally free from the esophagus but occasionally a thin strand of connective tissue was observed running from the end of the ampulla to the gut wall. No glands are present at the ectal opening. The ectal portion appears muscular up to the point of the diverticulum; the remainder is nonmuscular, normally coiled in segment V, but sometimes reaching to VII. The internal diverticulum and surrounding muscular wall is distinctly and cosistently set apart from the rest of the spermatheca. The ampulla is distinctly club-shaped in fully mature individuals. Mediolateral ectal opening on V. (ref. ID; 5971)

    Remarks

    This species is similar to M. orcae and M. sanguineus but differs from them as discussed for M. chaunus above. It is similar to M. chaunus except the spermathecae of M. kontrimavichusi do not extend beyond VII and are constricted between the point the diverticulum and the ampulla. In addition, M. kontrimavichusi has the unique enlarged ventral setae in V-IX. Timm and Popcenko (1978) described an aquatic species, M. tetrapodus, having enlarged ventral setae in VI and VII, but it is in the group of Mesenchytraeus having attached spermathecae with two large diverticula. S.F. MacLean and E.A. Morgan (unpublished data) described a mesenchytraeid worm from Barrow, Alaska, which also has the enlarged ventral setae, but which has a simple club-shaped spermathecae. (ref. ID; 5971)

    Etymology

    Named in honor of Dr. Vytus Leonovich Kontrimavichus, corresponding member of the Academy of Sciences, U.S.S.R., Director of the Institute of Biological Problems of the North (I.B.P.N.), gracious host and friend. (ref. ID; 5971)

    Habitat and distribution

    A terrestrial species found at Chaun Bay in the tussock tundra and mountain sites. (ref. ID; 5971)

    Type locality

    Chaun Bay, U.S.S.R., 68 degrees 44'N, 170 degrees 36'E, from the mountain site aproximately 20 km inland along the Chaun River. (ref. ID; 5971)

    Examined materials

  • Holotype: USNM62093. (ref. ID; 5971)
  • Paratypes: USNM62094-62095. (ref. ID; 5971)

    Mesenchytraeus svetae Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)

    Descriptions

    A small species, adult individuals 7-10 mm long, with a mean number of segments of 42 (n=29, SD 2.9). General body color is pale white, semitransparent, with gut content visible. The clitellum extends over XII-XIII; the clitellar glands are irregularly arranged and not a prominent feature. Setae are sigmoid nodulated, of equal length within the bundles, with no abnormally large setae in any segment. Setal pattern 1,2,3-1,2,3: 2,3,4,5-1,2,3,4. The brain is not incised posteriorly and lateral margins are parallel. Two pairs of primary and two pairs of secondary septal glands are present; the last pair of secondaries are often many lobed and extend into VII. Chloragogen cells are light brown and begin to occur in V. Cutaneous glands are irregularly arranged and are not a prominent feature. Dorsal vessel originates in XIV-XV. Blood is colorless, Lymphocytes with a few scattered granules, most of the lymphocyte clear. Lymphocytes are of the nucleate type only, ellipsoid in shape. Nephridia are bifurcate on the postseptale. There are no esophageal or intestinal diverticula, or sudden expansion of the gut. Sperm funnels are 1/2 to 1 times as long as the body width at the clitellum, and 2 to 3 times as long as wide. They bear a prominent, V-notched opening with mature sperm present. Atrium and penial bulb are present but no glands were observed. Spermathecae are free from the intestine. No glands are present at the ectal opening. There is one prominent diverticulum on the ectal duct. Spermathecae reach back to IX or X. Mediolateral ectal opening on V. Ampulla distinct. (ref. ID; 5971)

    Remarks

    This species is unique because of its spemathecae. The only similar species is M. asiaticus Eisen, 1904 which has a very long ectal duct on the spermatheca before the point where the diverticulum is located. Mesenchytraeus asiaticus is longer, with 54 segments. The sperm funnel of M. asiaticus appears to have a broad opening and variable shape. Mesenchytraeus svetae has a sperm funnel with a well defined opening and constant shape. In the very wettest sites specimens of this worm were found which were shorter in length (5-7 mm) but not segment number, had distinctly pink blood, and lymphocytes with black refractile particles. Though small, these differences were consistent. Until further study we choose to place these two supposed ecotypes under one name. (ref. ID; 5971)

    Etymology

    Named as a token of respect for Dr. Svetlana Bondarenko, whose interest in Enchytraeidae as intermediate hosts for cestodes of the family Hynenolepididae led to this research opportunity. (ref. ID; 5971)

    Habitat and distribution

    A terrestrial species found at Chaun Bay in the tussock tundra, tussock trough, and mountain sites. (ref. ID; 5971)

    Type locality

    Chaun Bay, U.S.S.R., 68 degress 44'N, 170 degrees 36'E, from the tussock tundra site. (ref. ID; 5971)

    Examined materials

  • Holotype: USNM62096. (ref. ID; 5971)
  • Paratypes: USNM62097-62098. (ref. ID; 5971)

    Mesenchytraeus tundrus Piper, MacLean & Christensen, 1982 (ref. ID; 5971 original paper)

    Descriptions

    Small species, 7-10 mm long with adult individuals having a mean segment number of 45 (n=28, SD 3.8). General body color is pale white or with a slight pink tint due to the color of the blood. The clitellum extends over XII-XIII; the clitellar glands are irregularly arranged and not a prominent feature. Setae are sigmoid nodulated, of equal length within the bundles, with no enlarged setae in any segment. Setal pattern 2,3,4,5-1,2,3,4,5: 3,4,5,6,7-1,2,3,4,5,6. The brain is deeply incised posteriorly, with lateral margins mostly parallel. There are two pairs of primary and two pairs of secondary septal glands; the last pair of secondaries are often many lobed and extend into VII. Chloragogen cells are light brown and begin to occur in V. Cutaneous glands are irregularly arranged and range from indistinctly colored to orange-brown, especially near the head. The dorsal vessel originates distinctly in one of XIV-XVI. Blood is a distinct pink with yellow tinge. Lymphocytes are a distinct brown-yellow in transmitted light, packed with many fine granules, and occur in large numbers througout the body. Nucleate lymphocytes only, ellipsoid to elongate ellipsoid in shape. Nephridia are bifurcate. There are no esophageal diverticula, no intestinal diverticula and no sudden expansion of the gut. Sperm funnels are 1/2 to 2/3 times as long as the body width at the clitellum; accessory glands are present surrounding the penial opening. Seminal vesicles and egg sacs are present. Spermathecae are free and club shaped; coiled in segment V, frequently extending back to IX/X. There are no glands at the ectal opening and no diverticula. (ref. ID; 5971)

    Remarks

    The accessory glands at the penial opening of M. tundrus are small and difficult to see unless carefully dissected. In living specimens the body wall is contracted around the penial opening forming a penial slit and what appears to be a penial bulb and atrium; however, these are not true structures. This species, together with M. diverticulatus, belongs to a small group having simple club-shaped spermathecae. Mesenchytraeus altus Welch, 1917, described from the Colorado Rocky Mountains, is similar to M. tundrus, but larger (58-73 segments) and has a distinctly different sperm funnel (five times longer than wide). Mesenchytraeus magnus Altman, 1936 has a similar spermatheca, but is one of the very large species of the genus (60-111 segments). (ref. ID; 5971)

    Etymology

    The name is derived from the occurrence of this species in tundra. (ref. ID; 5971)

    Habitat and distribution

    A terrestrial species found at Chaun Bay in mesic heath, tussock tundra, and tussock trough sites. (ref. ID; 5971)

    Type locality

    Chaun Bay, U.S.S.R., 68 degrees 44'N, 170 degrees 36'E, from the tussock trough site. (ref. ID; 5971)

    Examined materials

  • Holotype: USNM62099. (ref. ID; 5971)
  • Paratypes: USNM62100. (ref. ID; 5971)