| Other Abstract | Unique faunae have been found to exist in ancient lakes of Yunnan Province. However, little taxonomic work has been carried out previously on the oligochaetes in these lakes. The present paper embodies the results of a comprehensive investigation of aquatic oligochaetes in Yunnan lakes carried out in 2002-2005. Qualitative and quantitative samples were collected from Fuxian Lake, Xingyun Lake, Yangzonghai Lake, Erhai Lake, Chenghai Lake and Lugu Lake. As a part of the author’s work, Dero trifida from Xichuan of Henan Province is provisionally involved.
At the beginning of the paper, a systematic account of 51 species belonging to 5 families and 20 genera is presented (see the list). Among them, 8 species were described as new to science: Ilyodrilus mesoprostata n. sp., Aulodrilus apenis n. sp., Varichaetadrilus vestibulus n. sp., Potamothrix scleropenis n. sp., P. plicapenis n. sp., P. miniopenis n. sp., P. paramoldaviensis n. sp. and P. aductus n. sp.; the genus Varichaetadrilus Brinkhurst et Kathman, 1983 is recorded from China for the first time. Previously, the species of Potamothrix and Varichaetadrilus were recorded mainly from the Holarctic. The new species decribed herein are the lowest-latitude members hitherto known in the two genera.
The fauna of oligochaetes in Yunnan lakes as a whole is similar to that of the Holarctic. The oligochaetes are unexpectedly species-rich in Yunnan lakes. Besides the recorded ones, a lot of species remain unnamed and need further study. Moreover, there are rather diverse endemic taxa, especially in the deep lake, Fuxian Lake, where six endemic species mainly belonging to Potamothrix have been founded.
Standing crops of oligochaetes were quite different in the six lakes. In Yangzonghai Lake and Xingyun Lake, oligochaetes were 4228 ind/m2 and 1594 ind/m2 in density, 4.66 g/m2 and 7.23 g/m2 in biomass, but the sanding crops were much lower in other lakes, e.g. oligochaetes in Fuxian Lake were 86 ind/m2 and 0.12 g/m2. By correlating standing crops of oligochaetes with a series of environmental variables, it demonstrated that density and biomass of oligochaetes were significant correlated negatively with water depth and Secchi depth, and positively with total nitrogen, total phosphorous and chlorophyll a.
At the end of this summary, the author present diagnoses of the new species. Types are deposited in Institute of Hydrobiology, Chinese Academy of Sciences. (This thesis is not to be regarded as a publication in the sense of the International Code of Zoological Nomenclature, and new scientific names mentioned in it must not be cited in any form)
1. Ilyodrilus mesoprostata n. sp. (Fig. 4.2; Tab. 4.1)
Holotype: IHB YAN 20030405n, whole-mounted specimen.
Type locality: Xingyun Lake (24°18'01′′N, 102°47'58′′ E), eastern Yunnan Province, China; depth 5.0 m, bottom temperature 16.1℃, dissolved oxygen in bottom water 7.6 mg/L, total nitrogen in water 2.960 mg/L, total phosphorus in water 0.129 mg/L, fine silt; 7 April 2003, collected by Y. Cui.
Etymology: The specific name “mesoprostata” is Latin for “prostate gland in the middle”, and refers to the junctions of prostate glands on to atria moved to the middle.
Description: Specimen incomplete, length > 4.4 mm, diameter at XI about 0.65 mm, segments > 22. Prostomium rounded triangular. Clitellum inconspicuous.
Dorsal chaetae 2-5 hairs and 2-4 bifids per bundle; hairs smoothly and slender, 250-350 µm long, 2.0 µm thick basally; bifids 100-125 µm long, 2.5-3.0 µm thick, upper prongs longer and thicker than lower. Ventral chaetae bifid, 2-4 per bundle, 100-120 µm long, 2.5-3.0 µm thick, upper prongs longer and thinner than lower. Dorsal chaetae absent in XI. Spermathecal chaetae unmodified in X. Penial chaetae absent in XI. Male pores paired in line with ventral chaetae in mid-XI. Spermathecal pores paired in line with ventral chaetae in mid-X.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens short and broad, 240-360 µm long, 36-46 µm wide, entering atrium apically. Atrium 280-320 µm long, 58-108 µm wide. Prostate glands large, attached to atrium close to middle by short stalk. Ejaculatory ducts curved, about 54 µm long, 25-36µm wide. Soft part of penis cylindrical, about 32µm long, 20 µm diameter, enclosed in copulatory sacs; penis surrounded by tin cuticularized, truncated-cone shaped sheath, 116 µm long, 40-80 µm wide, one side of the ectal opening arced. Copulatory sacs 64 µm long, 40-50 µm wide, with outer muscular layer 10-15 µm thick.
Spermathecal ducts 160-250 long, 35-58 µm wide; ampullae oval to round, 105-125 µm in diameter, with sperm masses in lumina.
Distribution and habitat: Known only from type locality, Yunnan, China. Freshwater lake, 5.7 m depth, water temperature 17.7 ºC, fine silt.
2. Aulodrilus apenis n. sp. (Fig. 4.3; Tab. 4.2)
Holotype: IHB YAN 20020813d, whole-mounted specimen.
Type locality: Estuary of Gehe River (24º22′58′′ N, 102º49′49′′ E) in Fuxian Lake, eastern Yunnan, China; depth 41 m, bottom temperature 17.6 ℃, dissolved oxygen in bottom water 8.2 mg/L, total nitrogen in water 0.299 mg/L, total phosphorus in water 0.023 mg/L, fine clay; 8 August 2002, collected by Y. Cui & X. Liu.
Etymology: The specific name “apenis” is Latin for “without penis”, and refers to the absence of penis in this species.
Description: Specimen incomplete, length > 12.8 mm, diameter at XI about 0.44 mm, segments > 80. Prostomium conspicuously triangular, longer than wide. Clitellum inconspicuous.
Dorsal chaetae 1-4 hairs and 2-4 bifids per bundle; hairs slender and long, without serration, 260-320 µm long anteriorly, and 180-220 µm long in postclitellar segments; bifids pectinate, 80-120 µm long, 2.0-3.0 µm thick, with 2-3 thin intermediate teeth; upper prongs slightly longer or as long as and thinner than lower prongs. Ventral chaetae bifid, 1-4 per bundle, 75-88 µm long, 3.0-3.2 µm thick, upper tooth conspicuously longer and slightly thinner than lower tooth. Ventral chaetae unmodified in X and absent in XI. Male pores paired in line with ventral chaetae, posterior to middle of XI. Spermathecal pores paired in line with ventral chaetae in mid-X.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens 86-110 µm long, 15-25 µm wide, entering atrium subapically. Atrium curved, transition between ampulla and duct inconspicuous. Atrial ampulla ovoid, 110-120 µm long, 35-68 µm wide. Solid prostate glands large, attached to atrium close to union with vas deferens. Atrial ducts 90-160 µm long, 20-35 µm wide. Penes absent.
Spermathecae small, oval or elongated, 50-75µm long, 35-45 µm wide, with very short, indistinct ducts, and without sperms in ampullae.
Distribution and habitat: know only from type locality, Yunnan, China. Freshwater lake, 40 m depth, water temperature about 17 ºC, fine clay.
3. Varichaetadrilus vestibulus n. sp. (Fig. 4.4, 4.5; Tab. 4.3)
Holotype: IHB YAN 20030201a, whole-mounted specimen.
Type locality: Northeast of Jianshan (24º36′03′′ N, 102º51′14′′ E) in Fuxian Lake, eastern Yunnan Province, China; depth 97 m, bottom temperature 13.5 ℃, dissolved oxygen in bottom water 5.6 mg/L, total nitrogen in water 0.193 mg/L, total phosphorus in water 0.018 mg/L, fine clay; 14 February 2003, collected by Y. Cui.
Paratypes: IHB YAN 20030205a-b, two specimens from east of Lichang (24º32′04′′ N, 102º51′43′′ E) in Fuxian Lake, eastern Yunnan Province, China; depth 113 m, bottom temperature 13.5 ℃, dissolved oxygen in bottom water 5.2 mg/L, total nitrogen in water 0.195 mg/L, total phosphorus in water 0.024 mg/L, fine clay; 14 February 2003, collected by Y. Cui.
Etymology: The specific name “vestibulus” is Latin for “vestibule”, and refers to the pear-shaped vestibule in the spermatheca duct.
Description: Length 11.3-30 mm (Holotype: 30 mm), with 58-140 segments (Holotype: 140 mm), width at XII about 0.58 mm. Prostomium rounded triangular, shorter than wide. Clitellum inconspicuous.
Dorsal chaetae of II-VII bifid only, 3-5 per bundle, 115-140 µm long, 2.5-3.0 µm thick, with upper prongs, twice as long as, and thicker than lower prongs, nodulus distal. Dorsals of VIII-X comprise 5(3) hairs and 5-6 bifids per bundle; hairs smoothly and slender, 250-300 µm long, 2.0 µm thick basally; bifids 110-135 µm long, 2.0-2.5 µm thick, prongs almost parallel, the upper prongs slightly longer or as long as than the lower. Dorsals of XI and XII bifid only, 5-6 per bundle, shorter and thicker than those of dorsals in II-VII, with upper prongs slightly longer than usually curved lower prongs. From XIII onwards, dorsals comprise 2-5 hairs and 3-6 bifids per bundle, shorter and thinner than those of VIII-X, hairs about 200-240 µm long, dorsal bifids about 100-115µm long, prongs of bifids similar to those of VIII-X, simple-pointed chaetae sometimes present. Ventral chaetae bifid, 6-8 per bundle anteriorly, 100-140 µm long, 2.0-3.0 µm thick, with prongs similar to those of dorsals in II-VII, 3-5 per bundle posteriorly, 90-110 µm long, 1.8-2.0 µm thick, upper prongs longer and thinner than the lower. Ventral chaetae absent from IX. Spermathecal chaetae one per bundle in middle X, entally embedded in muscular sacs, about 127 µm long, 4.0 µm thick, ental part curved, with ectal parts grooved. Penial chaeta one per bundle in posteriorly XI, 75-82 µm long, 2.8 µm thick, with upper prongs slightly longer and thinner than lower prongs. Male pores paired in line with ventral chaetae, posteriorly to middle of XI. Spermathecal pores paired in line with ventral chaetae in mid-X, immediately anterior to spermathecal chaetae.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens up to about 35 µm wide, not observed in its whole length but shorter than atrium, entering apical end of atrium. Atrium extend to XII, longer than vas deferens, about 1220 µm long, 40-85 µm wide, tubular and rather homogeneous throughout, with thin outer muscular layer and thick inner epithelium, ental and ectal parts strongly curved, and middle parts folded. Prostate glands small, attached to atrium close to union with vas deferens by short stalk. Soft part of penis cylindrical, about 75 µm long, 65 µm in diameter, enclosed in copulatory sacs; penis surrounded by thin cuticularized, somewhat thimble-shaped sheath, 80 µm long, 68 µm wide, with 5µm thick walls. Copulatory sacs 95 µm long, 80-100 µm wide, with muscular layer 10-20 µm thick.
Spermathecae in X-XIII, ampullae up to 600 µm long, maximally 390 µm wide, ducts totally about 950 µm long; latter complex, tripartite, each consisting of: (1) long ectalmost thin part, about 475 µm long, 50-75 µm wide, (2) middle vestibular part (Fig. 2A, sdv), pear-shaped, about 250 µm long, maximally 120 µm wide, (3) short entalmost part, 200 µm long, 63-112 µm wide, with thick inner epithelium. Spermatozeugmata 5-10 in each ampullae, about 500-900 µm long, but one or two spermatozeugmata in each duct, wide head in middle vestibular part, and narrow tail in ectalmost part, extending to spermathecal pores.
Distribution and habitat: Known only from Fuxian Lake, Yunnan Province, China. Freshwater lake, 97-113 m depth, < 14 ºC, fine clay.
4. Potamothrix scleropenis n. sp. (Fig. 4.7-4.9; Tab. 4.4)
Holotype: IHB YNA 2002018a, whole-mounted specimen.
Type locality: East of Gushan Island (24′2405′′ N, 1025245′′ E) in Fuxian Lake, eastern Yunnan Province, China, 74 m depth, 13.7 ℃ bottom temperature, 5.8 mg/L dissolved oxygen of bottom water, 0.115mg/L total nitrogen of water, 0.015mg/L total phosphorus of water, fine clay; 8 Oct 2002, coll. Y. Cui & X. Liu.
Etymology: The specific name ‘scleropenis’ is Greek for ‘hard penis’, and refers to the cuticularized penis sheaths.
Description: Anterior part of specimen remaining, length > 7.2 mm, diameter at XI about 0.9 mm, segments > 22. Clitellum inconspicuous.
Dorsal chaetae of II-V bifid only, 6-9 per bundle, 120-140 µm long, 3.0-4.0 µm thick, with upper prongs blunt, twice as long as, and thicker than truncated, usually secondarily branched lower prongs. From VI onwards, dorsals 3-8 hairs and 3-7 bifids per bundle; hairs feathered, 200-360 µm long, 3.0-4.0 µm thick basally; bifids pectinate, 110-124 µm long, 3.2-3.6 µm thick, with (0) 1-2 thin (sometimes thick) intermediate teeth; upper prongs, occasionally somewhat bifurcated, slightly longer and conspicuously thinner than usually bifurcated lower prongs, or equally long. Ventral chaetae bifid, 6-9 per bundle anteriorly, 2-4 (5) per bundle in postclitellar segments, 100-140 µm long, 3.0-4.0 µm thick, with prongs similar to those of dorsals in II-V. Dorsal chaetae absent from XI. Spermathecal chaetae one per ventral bundle in X, entally embedded in muscular sacs, about 90 µm long, 3.6 µm thick; shafts strongly curved, with distal ends bifurcated and ectal parts grooved. Penial chaetae unmodified, 2-3 per bundle in XI, 76-80 µm long, 2.5-3.0 µm thick, with upper prongs longer and thinner than unbranched lower prongs. Male pores paired in line with ventral chaetae, posterior to middle of XI, immediately anterior to penial chaetae. Spermathecal pores paired in line with ventral chaetae in mid-X, immediately anterior to spermathecal chaetae.
Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens 300-320 µm long, 24-36 µm wide, entering atrium apically. Atrium 880-920 µm long, 60-110 µm wide, tubular and rather homogeneous throughout (right one somewhat folded in middle), with thin outer muscular layer and thick inner epithelium, and without prostate gland. Soft part of penis cylindrical and tapering ectally, about 140 µm long, basally 70 µm wide, ectally 24 µm wide, enclosed in copulatory sac; penis surrounded by cuticularized, somewhat thimble-shaped, sheath, 130 µm long, 30-100 µm wide, with 12-18 µm thick walls, and with edge of ectal opening irregular. Copulatory sac 160 µm long, 80-140 µm wide, with outer muscular layer 8-14 µm thick.
Spermathecal ducts 280-320 µm long, 70-140 µm wide, with outer muscular layers 3-4 µm thick; ampullae pear-shaped, 520-600 µm long, 200-480 µm wide. Spermatozeugmata 15-20 in each lumen, about 400-800 µm long.
Distribution and habitat: Known only from type locality, Yunnan, China. Freshwater lake, 74 m, <15 ℃, fine clay.
5. Potamothrix plicapenis n. sp. (Fig. 4.10; Tab. 4.4)
Holotype: IHB YAN 20030405l, whole-mounted specimen.
Type locality: Xingyun Lake (24°18'01′′ N, 102°47'58′′ E), eastern Yunnan, China; depth 5.0 m, bottom temperature 16.1℃, dissolved oxygen in bottom water 7.6 mg/L, total nitrogen in water 2.960 mg/L, total phosphorus in water 0.129 mg/L, fine silt; 7 April 2003, collected by Y. D. Cui.
Paratypes: IHB YAN 20030405b, e, k, three specimens from type locality.
Other materials: IHB YAN 20030405a, c-d, f-j, m, o-s, 14 specimens from type locality.
Etymology: The specific name “plicapenis” is Latin for “folded penis”, and refers to penis surface folded, plici-formed.
Description: Thirteen complete specimens 4.0-8.7 mm long (Holotype: 4.2 mm), 24-46 segments (Holotype: 24). Diameter at XI 0.48-0.59 mm (Holotype: 0.52 mm). Prostomium conical. Clitellum inconspicuous.
Dorsal chaetae (0)1-4 hairs and 2-4 bifids per bundle, hairs slender and long, without serration, 320-380 µm long in anterior segments, and 280-325 µm long in posterior segments; bifids 50-62 µm long, 2.0-2.5 µm thick, upper prongs slightly longer and thinner than the lower, or equally long, usually pectinated, with 2-3 thin intermediate teeth. Ventral chaetae 3-7 per bundle anteriorly, 70-80 µm long, 2.0-2.5 µm thick, upper prongs conspicuously longer and thinner than the lower, 2-3 per bundle in posterior segments, 60-65 µm long, 1.8-2.2 µm thick. Spermathecal chaetae one per bundle in middle X, entally embedded in muscular sacs, 70-96 µm long, 2.5 µm thick, ental part curved, ectal parts grooved. Penial chaetae absent. Male pores paired in line with ventral chaetae, posterior to middle of XI. Spermathecal pores paired in line with ventral chaetae in mid-X, immediately anterior to spermathecal chaetae.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens very short, 25-40 µm long, 12-24 µm wide, entering atrium subapically. Atrium 580-730 µm long, 40-80 µm wide, tubular and bipartite, proximal part (2/5 of the total atria) with densely granular inner layer, and sparsely granular distal part. Prostate gland absent. Penis cylindrical and tapering ectally, surface folded, plici-formed, 76-150 µm long, basally 56-100 µm wide, ectally 26-58 µm wide, enclosed in copulatory sacs. Copulatory sac 100-150 µm long, 58-86 µm wide, with muscular layer 7-17 µm thick.
Spermathecae broken, numerous spermatozeugmata in coelom.
Distribution and habitat: Known only from type locality, Yunnan, China. Freshwater lake, 5 m depth, water temperature about 18 ºC, fine silt.
6. Potamothrix miniopenis n. sp. (Fig. 4.11; Tab. 4.4)
Holotype: IHB YAN 20021205b, whole-mounted specimen.
Type locality: East of Lichang (24º32′04′′ N, 102º51′43′′ E) in Fuxian Lake, eastern Yunnan Province, China; depth 113 m, bottom temperature 13.5 ℃, dissolved oxygen in bottom water 5.2 mg/L, total nitrogen in water 0.164 mg/L, total phosphorus in water 0.037 mg/L, fine clay; 11 December 2002, collected by Y. Cui & X. Liu.
Etymology: The specific name “miniopenis” is Latin for “small penis”, and refers to the small penis in this species.
Description: One complete specimen 7.6 mm long, 0.8 mm wide at XI, 27 segments. Prostomium conical. Clitellum inconspicuous.
Dorsal chaetae of II-IV bifid only, 7-10 per bundle, 135-148 µm long, 3.0-3.5 µm thick, upper prongs longer and thinner than occasionally bifurcated lower prongs. Dorsals 5-8 hairs and 5-7 bifids per bundle in V-X; hairs feathered, 240-420 µm long, 2.6-3.2 µm thick basally; bifids pectinate, 120-140 µm long, 2.8-3.2 µm thick, with 1-2 intermediate teeth, upper prongs slightly longer and thinner than usually bifurcated lower prongs, or equally long. Dorsals 1-4 hairs and 2-6 bifids per bundle in posterior segments, shorter and thinner than those of anterior segments, hairs 280-320 µm long, bifids 90-110 µm long, 2.6-2.8 µm thick. Ventral chaetae bifid, 6-8 per bundle anteriorly, 140-150 µm long, 3.0-3.5 µm thick; 2-4 (5) per bundle in postclitellar segments, 80-110µm long, 2.4-3.2 µm thick, with prongs similar to those of dorsals in II-IV. Spermathecal chaetae one per bundle in middle to posterior part of X, entally embedded in muscular sacs, about 145-160 µm long, 4.0 µm thick, with ectal parts grooved. Penial chaetae absent. Male pores paired in line with ventral chaetae, anterior to middle of XI. Spermathecal pores paired in line with ventral chaetae, posterior to middle of X, immediately anterior to spermathecal chaetae.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens 38-65 µm long, 16-22 µm wide, entering atrium apically. Atrium 690 µm long, 28-80 µm wide, tubular and rather homogenous, with thin outer muscular layer and thick inner epithelium. Prostate gland small, attached to ental part of atrium. Penis small, cylindrical, 38-54 µm long, 22-44 µm wide, enclosed in copulatory sacs. Copulatory sac 65-80 µm long, 54-802 µm wide, with muscular layer 3-4 µm thick.
Spermathecae extended to XII, ducts 470-490 µm long, 38-65 µm wide, ampullae elongated, 520-540 µm long, maximally 300-315 µm wide. Spermatozeugmata 5-8 in each ampulla, about 300-460 µm long.
Distribution and habitat: Known only from type locality, Yunnan, China. Freshwater lake, 113 m depth, < 14 ºC, fine clay.
7. Potamothrix paramoldaviensis n. sp. (Fig. 12; Tab. 4.4)
Holotype: IHB YAN 20020812i, whole-mounted specimen.
Type locality: Opposite to Gushan Island (24°24'05′′N, 102°52'45′′E) in Fuxian Lake, eastern Yunnan Province, China; depth 78 m, bottom temperature 15.9℃, dissolved oxygen in bottom water 9.6 mg/L, total nitrogen in water 0.155 mg/L, total phosphorus in water 0.0234 mg/L, fine clay; 8 August 2002, collected by Y. Cui & X. Liu.
Etymology: Named “paramoldaviensis” for the resemblance with Potamothrix moldaviensis Vejdovský & Mrázek, 1902 in terms of male genitalia.
Description: Specimen incomleted, length > 4.4 mm, diameter at XI about 0.68 mm, segments > 13. Prostomium rounded triangular. Clitellum inconspicuous.
Chaetae all bifid, 4-6 per bundle dorsally, 3-6 per bundle ventrally, 80-120 µm long, 2.0-2.6 µm thick, upper prongs longer and thinner than lower prongs. Spermathecal chaetae one per bundle posterior to middle of X, entally embedded in muscular sacs, 145-160 µm long, 4.0-4.5 µm thick, ental part curved, ectal part grooved. Penial chaetae modified, 1-2 per bundle in posterior part of XI, 70-74 µm long, 2.0-2.4 µm thick, upper prong as long as and thicker than lower. Male pores paired in line with ventral chaetae in posterior part of XI, immediately anterior to penial chaetae. Spermathecal pores paired in line with ventral chaetae in posterior to middle of X, immediately anterior to spermathecal chaetae.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens very short, 27-38 µm long, 16-20 µm wide, entering atrium apically. Atrium 1050-1130 µm long, 38-90 µm wide, tubular and rather homogenous, with thin outer muscular layer and thick inner epithelium. Prostate gland small, attached to ental part of atrium. Penes absent.
Spermathecal ducts 345-360 µm long, 38-70 µm wide, ampullae pear-shaped, 420-430 µm long, maximally 230-250 µm wide. Spermatozeugmata 6-9 in each ampulla, 300-640 µm long.
Distribution and habitat: Known only from type locality, Yunnan, China. Freshwater lake, 78 m depth, < 16 ºC, fine clay.
8. Potamothrix aductus n. sp. (Fig. 13; Tab. 4.4)
Holotype: IHB YAN 20020812a, whole-mounted specimen.
Type locality: Opposite to Gushan Island (24°24'05′′N, 102°52'45′′E) in Fuxian Lake, eastern Yunnan Province, China; depth 78 m, bottom temperature 15.9℃, dissolved oxygen in bottom water 9.6 mg/L, total nitrogen in water 0.155 mg/L, total phosphorus in water 0.0234 mg/L, fine clay; 8 August 2002, collected by Y. Cui & X. Liu.
Paratypes: IHB YAN 20020812n; one specimen from type locality, IHB YAN 20020808b, one specimen from southeast of Niumo (24°28'40′′N, 102°52'31′′E) in Fuxian Lake, eastern Yunnan, China; depth 108 m, bottom temperature 14.0℃, dissolved oxygen in bottom water 6.6 mg/L, total nitrogen in water 0.184 mg/L, total phosphorus in water 0.0234 mg/L, fine clay; 8 August 2002, collected by Y. Cui & X. Liu.
Other materials: IHB YAN 20020812c, one specimen from the same locality with paratypes, IHB YAN 20030209b, one specimen from northeast of Dashazui (24º22′58′′N, 102º49′49′′E) in Fuxian Lake, eastern Yunnan, China; depth 87 m, bottom temperature 13.7 ℃, dissolved oxygen in bottom water 5.8 mg/L, total nitrogen in water 0.229 mg/L, total phosphorus in water 0.022 mg/L, fine clay; 14 February 2002, collected by Y. Cui.
Etymology: The specific name “aductus” is Latin for “no ducts”, and refers to the absence of spermathecal duct.
Description: Two complete specimens 9.2-11.8 mm long (Holotype: 9.2 mm), 0.80-0.96 mm wide at XI (Holotype: 0.96 mm), 49-68 segments (Holotype: 49 segments). Prostomium conical. Clitellum inconspicuous.
Dorsal chaetae of II-VI bifid only, 7-8 per bundle, 100-144 µm long, 3.0-4.0 µm thick, upper prongs obviously longer and thicker than the lower. Dorsals 1-6 hairs and 3-6 bifids per bundle from VII onwards, hairs feathered, 340-420 µm long, 2.8-3.2 µm thick basally; bifids pectinate, 108-140 µm long, 3.0-4.0 µm thick, with 0-2 intermediate teeth, upper prong slightly longer or as long as, and thinner than lower. Ventral chaetae bifid, 6-8 per bundle anteriorly, 140-150 µm long, 3.0-3.5 µm thick; 2-4 (5) per bundle in postclitellar segments, 80-110µm long, 2.4-3.2 µm thick, with prongs similar to those of dorsals in II-VI. Spermathecal chaetae one per bundle in middle to posterior part of X, entally embedded in muscular sacs, about 180-220 µm long, 4.0 µm thick, with ectal parts grooved and contorted. Penial chaetae absent. Male pores paired in line with ventral chaetae of middle XI. Spermathecal pores paired in line with ventral chaetae, posterior to middle of X, immediately anterior to spermathecal chaetae.
Pharyngeal glands in II-III. Chloragogen cells from VI onwards. No coelomocytes. Male genitalia paired. Vas deferens short, 40-50 µm long, 13-22 µm wide, entering atrium apically. Atrium 580-640 µm long, 30-75 µm wide, tubular and rather homogenous, with thin outer muscular layer and thick inner epithelium. Prostate gland small, 90-110 µm long, max 62-75 µm wide, attached to ental part of atrium. Penis small, cylindrical and tapering ectally, 62-80 µm long, basally 66-75 µm wide, ectally 26-44 µm wide, enclosed in copulatory sac. Copulatory sac 90-110 µm long, 54-84 µm wide, with muscular layer 4-6 µm thick.
Spermathecal ducts absent, oval ampullae 440-490 µm long, maximally 250-280 µm wide. Spermatozeugmata 2-4 in each ampulla, about 460-710 µm long.
Distribution and habitat: Known only from Fuxian Lake, Yunnan, China. Freshwater lake, 70-110 m depth, < 16 ºC, fine clay. |
