Different responses of incidence-weighted and abundance-weighted multiple facets of macroinvertebrate beta diversity to urbanization in a subtropical river system

Urbanization is one of the major drivers of biotic homogenization (i.e., decrease in beta diversity) in freshwater systems. However, only a few studies have simultaneously examined how urbanization affects multiple facets (i. e., taxonomic, functional and phylogenetic) of beta diversity and its underlying ecological drivers in urban river macroinvertebrates. Here, we distinguished the patterns and ecological mechanisms of multiple facets of macroinvertebrate beta diversity weighted by incidence and abundance data in a subtropical river system with a distinct urbanization gradient. We also investigated how total beta diversity patterns stem from replacement versus richness difference among sites. Our results showed that taxonomic and phylogenetic beta diversities weighted by incidence data were primarily driven by replacement of taxa, whereas the richness difference contributed more to multiple facets of beta diversity based on abundance data. Furthermore, multiple facets of beta diversity decreased with urbanization for both incidence-weighted and abundance-weighted data, but the former showed more substantial decreases. Both replacement and richness difference components contributed roughly equally to the decline of incidence-weighted beta diversity. In contrast, the losses of abundanceweighted beta diversity were mainly associated with replacement of taxa. Variation partitioning results revealed that all beta diversity measures based on incidence data were governed primarily by local and land-use variables, whereas spatial variables were more relevant in driving beta diversity weighted by abundance data. Overall, by comparing different facets and components of beta diversity weighted by incidence versus abundance data, we suggest that incidence-weighted data may be more sensitive in portraying the impacts of urbanization on macroinvertebrate diversity. This likely resulted from the fact that incidence-weighted data shows the importance of rare taxa in shaping homogenization induced by urbanization.Peer reviewe

Different responses of incidence-weighted and abundance-weighted multiple facets of macroinvertebrate beta diversity to urbanization in a subtropical river system

Urbanization is one of the major drivers of biotic homogenization (i.e., decrease in beta diversity) in freshwater systems. However, only a few studies have simultaneously examined how urbanization affects multiple facets (i. e., taxonomic, functional and phylogenetic) of beta diversity and its underlying ecological drivers in urban river macroinvertebrates. Here, we distinguished the patterns and ecological mechanisms of multiple facets of macroinvertebrate beta diversity weighted by incidence and abundance data in a subtropical river system with a distinct urbanization gradient. We also investigated how total beta diversity patterns stem from replacement versus richness difference among sites. Our results showed that taxonomic and phylogenetic beta diversities weighted by incidence data were primarily driven by replacement of taxa, whereas the richness difference contributed more to multiple facets of beta diversity based on abundance data. Furthermore, multiple facets of beta diversity decreased with urbanization for both incidence-weighted and abundance-weighted data, but the former showed more substantial decreases. Both replacement and richness difference components contributed roughly equally to the decline of incidence-weighted beta diversity. In contrast, the losses of abundanceweighted beta diversity were mainly associated with replacement of taxa. Variation partitioning results revealed that all beta diversity measures based on incidence data were governed primarily by local and land-use variables, whereas spatial variables were more relevant in driving beta diversity weighted by abundance data. Overall, by comparing different facets and components of beta diversity weighted by incidence versus abundance data, we suggest that incidence-weighted data may be more sensitive in portraying the impacts of urbanization on macroinvertebrate diversity. This likely resulted from the fact that incidence-weighted data shows the importance of rare taxa in shaping homogenization induced by urbanization.Peer reviewe

Limnodrilus simplex sp nov (Oligochaeta: Naididae: Tubificinae) from Changjiang River, China

Limnodrilus simplex sp. nov. (Oligochaeta: Naididae: Tubificinae) is described based on a single specimen from the mainstream of the Changjiang River near Anqing City, Anhui Province, China. The new species is assigned to Limnodrilus by the presence of long vasa deferentia, spindle-shaped atria with long ejaculatory ducts, large prostate glands, and thick cylindrical penial sheaths. It differs from its congeners in having simple-pointed chaetae and cuticularized penial sheaths without hoods. Limnodrilus simplex is closer to L. paramblysetus and L. amblysetus in possessing penial sheaths with relatively low length/maximum width ratio

Tubifex tubifex tubifex (Muller 1774

<i>Tubifex tubifex</i> (Müller, 1774) <p>(Figs 9–10, table 1)</p> <p> <i>Lumbricus tubifex</i> Müller, 1774: 27.</p> <p> <i>Tubifex tubifex</i> Müller: Liang 1962: 20 –22; Brinkhurst 1965: 123 –124; Brinkhurst 1966: 145; Brinkhurst & Jamieson 1971: 453 –456; Brinkhurst & Marchese 1987: 3154 –3155; Holmquist 1983: 189 –192; Timm 2006: 32 –37; Marotta <i>et al.</i> 2009: 181 –187.</p> <p>For further synonymies and citations of the name see Brinkhurst & Jamieson (1971).</p> <p> <b>New material.</b> IHB XZ 20130630 m–r, 6 mature specimens, whole-mounted in Canada balsam. 1 mature specimen, processed for Scanning Electron Microscopy. Collected from one river in Cuomujiri Mountain (29°45'54" N, 94°24′25″ E) of southern Tibet, China., ca. 3,537 m asl. Substrate type silt, hydrophytes abundant. Water depth 30–100 cm, water temperature 11.1°C, pH 7.0, dissolved oxygen 9.0 mg/L, conductivity 16.5 µs/cm. Collected on 30 June 2013 by the authors.</p> <p> <b>Description.</b> Length 14–21 mm, width at genital segments X–XI 1.0– 1.2 mm. Segments 76–84. Prostomium obtuse (Fig. 9A). Clitellum inconspicuous. No coelomocytes. Dorsal chaetae 1–2 hairs and 2–3 bifids per bundle. Hairs slightly hirsute, 250–550 µm long, 2–4 µm thick (Fig. 9C). Dorsal bifids pectinate, 100–150 µm long, 2–4 µm thick, two short outer teeth nearly equal, 7.5 µm long, with 1–4 fine intermediate teeth, nodulus distal (Fig. 9D). Ventral chaetae bifid, anteriorly 3–5 per bundle, posteriorly 2–3 per bundle, 55–150 µm long, 3–5 µm thick, anterior upper tooth slightly thinner than and nearly 2 times as long as lower (10 µm/6 µm), posterior upper tooth as long as lower (7 µm/6 µm), with (0) 1–3 fine intermediate teeth, nodulus distal (Fig. 9E–F). Ventral chaetae in X and XI present, unmodified. Spermathecal pores paired in line with lateral line, in anterior of X (Figs. 9B: spp). Male pores paired in line with ventral chaetae, middle to posterior of XI (Fig. 9B: mp).</p> <p>Chloragogen cells beginning in VI onwards. Male genitalia generally paired in X–XI, in one specimen shifted to VI–VII. Sperm funnel cup-shaped. Vas deferens long and irregularly coiled, anteriorly 30 µm wide, posteriorly 50 µm wide, ciliated throughout and entering atrium subapically (Fig. 10B: vd). Atrium comma-shaped, 500–600 µm long, maximally 120–125 µm wide, with long ejaculatory duct gradually becoming narrower toward the ectal end, and enlarged into a characteristic subspherical widening at the base of penis (Fig. 10B: at). Large compact prostate gland with stalk-like attachment connected to ental atrium subapically near the vas deferens, 150–200 µm long, 200–250 µm wide (Fig. 10B: pr). Penis cylindrical (Fig. 10B: pe), 150–175 µm long, covered with a short, tub-shaped, flexible (= non-chitinous), cuticle ring. Testes paired in X, immediately behind septum 9/10. Ovaries paired in XI, immediately behind septum 10/11. Spermathecae generally paired in X (One specimen shifted to VI), with ampullae partially pressed into XI, 500–625 µm long, 250–330 µm wide; duct 150–225 µm long; sperm not observed in lumina (Fig. 10A: spa).</p> <p> <b>Remarks.</b> <i>T. tubifex</i> is one of the most widely distributed species in the world, and has been redescribed over and over again (Liang 1962; Brinkhurst & Jamieson 1971; Brinkhurst & Marchese 1987; Hrabě 1981; Holmquist 1983; Timm 2006; Marotta <i>et al.</i> 2009). The morphological accounts of this cosmopolitan species show some differences, mainly in the hair chaetae, the penial sheath and the spermatheca (Table 1). Some of these differences, however, may be due to different observation techniques or modes of interpretation: Under SEM-observation, the hair chaetae of <i>T. tubifex</i> from Tibet are slightly hirsute. Other authors, using light-microscopy, could not determine whether the hair chaetae of <i>T. tubifex</i> from other areas were serrate or not (Liang 1962; Brinkhurst & Jamieson 1971; Brinkhurst & Marchese 1987; Hrabě 1981). Furthermore, we identified a cuticle ring around the penis of <i>T. tubifex</i> from Tibet, whereas other authors, referring to the same structure, describe a penial sheath (Brinkhurst 1965; Brinkhurst & Jamieson 1971; Brinkhurst & Marchese 1987; Hrabě 1981). The cuticle ring in specimens from Tibet is flexible and non-chitinous—we observed contractions in living specimens—and it shows clearly in vivo but is difficult to see or seemingly absent in material that has been stained with borax carmine and mounted whole in Canada balsam. We therefore agree with Holmquist (1983) and Timm (2006) that <i>T. tubifex</i> has no penial sheaths proper.</p> <p> sheath <i>al</i>. 2009 Italy serrate muscular description no <i>et</i> Marotta</p> <p>Netherlands smooth cuticle ring present absent or with spermatozeugmata Timm 2006 Denmark serrate</p> <p>not</p> <p>or cuticle ring present absent or with spermatozeugmata Holmquist 1983 areas</p> <p>Slovakia serrate sheath penial or present absent with spermatozeugmata Hrabě 1981 other and</p> <p>Tibet North</p> <p>America not serrate or penial sheath or present absent with spermatozeugmata Brinkhurst & 1971 Jamieson</p> <p>from southern, China River serrate description without present Sungari no spermatozeugmata 1962 Liang</p> <p> <i>tubifex</i></p> <p> of <i>Tubifex</i> China Tibet, slightly hirsute cuticle ring present without spermatozeugmata research present</p> <p>Comparison</p> <p> cuticle <b>1</b>. Area Hair Penial Spermatheca Reference <b>Table</b></p> <p> <b>Table 2</b>. Comparison of <i>Tubifex</i> species with funnel-shaped penial sheaths</p> <p> Species <i>Tubifex laxus</i> <b>n. sp.</b> <i>Tubifex gracilentus</i> <b>n. sp.</b> <i>Tubifex montanus</i> <i>Tubifex conicus</i> He, Cui & <i>Tubifex newfei</i> Pickavance Kowalewski, 1919 Wang, 2012 & Cook, 1971 In the material of <i>T. tubifex</i> from Tibet, spermathecae are generally paired in X with no sperm observed in lumina, which is different from <i>T. tubifex</i> from other areas that usually have paired spermathecae with spermatozeugmata, or only one spermatheca with spermatozeugmata, or no spermatheca at all (Brinkhurst & Jamieson 1971; Hrabě 1981; Holmquist 1983; Timm 2006).</p> <p> <b>Distribution and habitat.</b> Cosmopolitan. Freshwater.</p>Published as part of <i>Cui, Yongde, 2017, Four species of Tubifex Lamarck (Annelida: Oligochaeta: Naididae) from Tibet, China, pp. 366-378 in Zootaxa 4320 (2)</i> on pages 373-377, DOI: 10.11646/zootaxa.4320.2.10, <a href="http://zenodo.org/record/891958">http://zenodo.org/record/891958</a&gt

Tubifex conicus He, Wang & Cui 2012

<i>Tubifex conicus</i> He, Wang & Cui, 2012 <p>(Figs 7–8)</p> <p> <i>Tubifex conicus</i> He, Wang & Cui, 2012: 160 –162, Fig. 1.</p> <p> <b>New material.</b> IHB XZ20150602 a–e, 5 mature specimens, whole-mounted in Canada balsam, from Gyaring Co, preserved in IHB, CAS. Gyaring Co (30°58' 43″N, 88°28′04″E), a lake located in northern Tibet of China, ca. 4,648–4,659 m asl. Water depth 11–37 m, water temperature 6.3–8.9°C, pH 6.3–8.9, dissolved oxygen 7.3–7.7 mg / L, conductivity 323–329 µs/cm. Collected by Yongde Cui and Baoqiang Wang on 2 June 2015.</p> <p> <b>Description.</b> Length 6.1–11.6 mm, width at genital segments X–XI 0.28–0.42 mm. Segments 38–65. Prostomium obtuse. Clitellum inconspicuous. No coelomocytes. Dorsal chaetae (0) 1 hair and 1–4 bifids per bundle. Hairs serrate, posteriorly generally absent (Fig. 7A, B). Dorsal bifids pectinate, upper and lower tooth subequal, with 2–3 fine intermediate teeth (Fig. 7A). Ventral chaetae bifid, 3–4 per bundle anteriorly, 2 per bundle posteriorly, upper tooth slightly longer than lower, with (0) 1–2 fine intermediate teeth (Fig. 7C, D). Ventral chaetae in X present, unmodified. Ventral chaetae in XI absent. Male pores paired in line with ventral chaetae, middle to posterior of XI.</p> <p>Chloragogen cells from VI onwards. Male genitalia paired in X–XI. Sperm funnel cup-shaped, 20 µm long, 40 µm wide (Fig. 8A,B: sf). Vas deferens 400–560 µm long, 12–15 µm wide, nearly 3–4 times as long as atrium, ciliated throughout and entering atrium apically (Fig. 8A, B: vd). Atrium spindle-shaped, 120–160 µm long, maximally 32–40 µm wide (Fig. 8A, B: at). Ejaculatory duct present. Prostate gland solid, 80–84 µm long, 60–64 µm wide, attached to ental portion of atrium (Fig. 8A, B: pr). Penis inconspicuous, surrounded by cuticular, symmetrical and funnel-shaped penial sheath. Penial sheath 36–40 µm long, 48–56 µm wide at ental end (Fig. 8A, B, C: ps). Testes paired in X, immediately behind septum 9/10. Ovaries paired in XI, immediately behind septum 10/11. Spermathecae absent.</p> <p> <b>Remarks.</b> The main difference of our redescription from <i>T. conicus</i> as originally described (He <i>et al.</i> 2012) is the absence of spermathecae. However, after our reinvestigation of the type series (holotype and paratypes), we are sure that the testes of <i>T. conicus</i> were mistaken for spermathecae in the original description. Further slight differences between the descriptions concern thickness of atrial epithelium (thicker in the redescription) and penial sheaths (thicker in the original description). They may relate to the stage of maturity or to different modes of interpretation of observations. The size and shape of atria in the original observation and this research are about the same. Penial sheaths appear to have a thick cuticle laterally in the holotype, but when comparing type series and our material, we found no significant differences in penial sheath thickness.</p> <p> <b>Distribution and habitat.</b> Known from Yamdrok Yumco (Lake Yamzho Yumco), Gyaring Co, Chargut Co, Uruni Co, Chikui Co, Amdo Tsonak Co, Tibet, China. All these lakes are located at above 4,000 m asl in Tibet. Gyaring Co, the locality of present redescribed materials, is about 300 km from the holotype locality of <i>T. conicus</i>, Yamdrok Yumco. Freshwater and brackish water.</p>Published as part of <i>Cui, Yongde, 2017, Four species of Tubifex Lamarck (Annelida: Oligochaeta: Naididae) from Tibet, China, pp. 366-378 in Zootaxa 4320 (2)</i> on pages 371-372, DOI: 10.11646/zootaxa.4320.2.10, <a href="http://zenodo.org/record/891958">http://zenodo.org/record/891958</a&gt

Tubifex laxus Cui, 2017, n. sp.

<i>Tubifex laxus</i> n. sp. <p>(Figs 1–3)</p> <p> <b>Holotype.</b> IHB XZ20130630 j, mature specimen, stained and whole-mounted in Canada balsam.</p> <p> <b>Type locality.</b> Wetland in Cuomujiri Mountain (29°47′46″N, 94°24′53″E), southeast Tibet of China, ca. 3,990 m asl. Sediment silt, with abundant hydrophytes. Water depth 15–20 cm, water temperature 11.5 °C, pH 6.2, dissolved oxygen 9.1 mg /L, and conductivity 19.3 µs/cm. Collected on 30 June 2013 by the authors.</p> <p> <b>Paratype.</b> IHB XZ20130630 k, 1 mature specimen whole mounted in Canada balsam, from the type locality.</p> <p> <b>Other material</b>. 1 specimen for SEM, from the type locality.</p> <p> <b>Etymology.</b> The epithet “ <i>laxus</i> ” is Latin for “wide”, and refers to the relatively wide atrium of the species.</p> <p> <b>Description.</b> Length 6.8–7.2 mm (holotype: 6.8 mm), width at genital segments X–XI 0.4–0.5 mm (holotype: 0.5 mm). Segments 41–46 (holotype: 46). Prostomium obtuse or conical (Figs. 1A, 2A, 3A: pro). Clitellum inconspicuous, in X–XI. No coelomocytes. Dorsal chaetae (1) 2–3 hairs and 2–5 bifids per bundle. Hairs slightly hirsute, 110–300 µm long, 2–4 µm thick (Fig. 1B, C). Dorsal bifids palmate, 40–90 µm long, 2–4 µm thick, upper and lower tooth subequal, 6–8 µm long, with 6–10 fine intermediate teeth, nodulus distal (Figs. 1C, D, 3D). Ventral chaetae bifid, (3) 4–5 per bundle anteriorly, 2–3 per bundle posteriorly, 60–100 µm long, 2–4 µm thick, upper tooth slightly thinner and longer than lower (4–5 µm/3–5 µm), with (0) 1–2 fine intermediate teeth, nodulus distal (Figs. 1E, F, 3B, C). Ventral chaetae in X–XI present, unmodified. Male pores paired in line with ventral chaetae, in middle to posterior of XI.</p> <p>Pharynx in III–IV, 180–200 µm long, 120–150 µm wide (Figs. 2A, 3A: ph). Chloragogen cells from VI onwards. Male genitalia paired in X–XI. Sperm funnel cup-shaped, 20–30 µm long, 55–75 µm wide (Figs. 2C, 3F: sf). Vas deferens 500–600 µm long, about 3 times as long as atrium, uniformly 15 µm wide, internally ciliated along the whole length and entering atrium apically (Figs. 2C, 3F: vd). Atrium ovoid placed vertically in XI, 140– 160 µm long, maximally 85–100 µm wide; no ejaculatory duct (Figs. 2B, C, 3F: at). Prostate gland solid, attached to ental portion of atrium by short stalk, 25–35 µm long, 70–85 µm wide (Figs. 2C, 3F: pr). Penis inconspicuous, surrounded by cuticular, symmetrical and funnel-shaped penial sheath. Penial sheath 30–40 µm long, 35–40 µm wide at ental end, length to width ratio nearly 1.0 (Fig. 2D, 3E, F: ps). Testes paired in X, small, immediately behind septum 9/10 (Fig. 2A: t). Seminal vesicles in X–XI, with little developing sperm. Ovaries paired in XI, immediately behind septum 10/11 (Fig. 2A: o). Egg present in XI. Spermathecae absent.</p> <p> <b>Remarks.</b> The new species could be placed in the genera <i>Tasserkidrilus</i> Holmquist, 1985 or <i>Tubifex</i> (<i>sensu stricto</i>) based on: vas deferens at least two times longer than atrium, ejaculatory duct lacking, solid prostate gland attached to ental portion of atrium, and conical penial sheath (Brinkhurst & Jamieson 1971; Holmquist 1983, 1985; Timm 1989). However, in species of <i>Tasserkidrilus</i> the ventral chaetae in XI are lacking in mature specimens, the atrium consists of two or three portions of different thickness, and the penial sheath is asymmetrical (Timm 1989).</p> <p> These characters are inconsistent with those of the new material. Therefore, we discard <i>Tasserkidrilus</i> as a possible genus for the new species. Although its vasa deferentia are not bipartite, the new material agrees with the generic diagnosis of <i>Tubifex</i> in the following characters: long vas deferens entering atrium apically, ovoid atrium placed vertically in XI with no ejaculatory duct, solid prostate gland attached to ental atrium by a short stalk, and symmetrically funnel-shaped penial sheath (Brinkhurst & Jamieson 1971; He <i>et al.</i> 2012). The new species is easily distinguished from allied species by its relatively wide atrium (Brinkhurst & Jamieson 1971; Pickavance & Cook 1971; Hrabě 1981; He <i>et al.</i> 2012; Peng <i>et al.</i> 2014) (Table 2).</p> <p> <b>Distribution and habitat.</b> Known only from the type locality, Cuomujiri Mountain, southeast Tibet of China. Freshwater.</p>Published as part of <i>Cui, Yongde, 2017, Four species of Tubifex Lamarck (Annelida: Oligochaeta: Naididae) from Tibet, China, pp. 366-378 in Zootaxa 4320 (2)</i> on pages 367-369, DOI: 10.11646/zootaxa.4320.2.10, <a href="http://zenodo.org/record/891958">http://zenodo.org/record/891958</a&gt

Tubifex gracilentus Cui, 2017, n. sp.

<i>Tubifex gracilentus</i> n. sp. <p>(Figs. 4–6)</p> <p> <b>Holotype.</b> IHB XZ20150511 a, mature specimen, stained and whole-mounted in Canada balsam.</p> <p> <b>Type locality.</b> Juemu River (29°39'23″N, 94°17′12″E), southeast Tibet of China, ca. 3,290 m asl. Sediment silt. Water depth 40–60 cm, water temperature 6.4°C, pH 6.2, dissolved oxygen 8.8 mg /L, and conductivity 12.3 µs/cm. Collected on 11 May 2015 by the authors.</p> <p> <b>Paratype.</b> IHB XZ20150511 b, 1 mature specimen, stained and whole-mounted in Canada balsam, from the type locality.</p> <p> <b>Other material</b>. 1 specimen for SEM, from the type locality; 1 mature specimen whole-mounted in Canada balsam, from Trigu Co (Co means lake in Tibet).</p> <p> <b>Etymology.</b> The epithet “ <i>gracilentus</i> ” is Latin for “slender and thin”, and refers to the thin and long penial sheath of this species.</p> <p> <b>Description.</b> Length 6.4–6.7 mm (Holotype: 6.7 mm), width at genital segments X–XI 0.5–0.6 mm (holotype: 0.6 mm). Segments 32–34 (holotype: 32). Prostomium obtuse or conical (Fig. 4A). Clitellum inconspicuous. No coelomocytes.</p> <p>Dorsal chaetae (0) 1–2 hairs and 1–4 bifids per bundle. Hairs smooth anteriorly (Fig. 4B), serrate posteriorly (Fig. 4C), 120–300 µm long, 2–3 µm thick. Dorsal bifids pectinate, 50–100 µm long, 1.5–2.5 µm thick, upper and lower tooth subequal, 6–8 µm long, with 2–3 (4) fine intermediate teeth, nodulus distal (Figs. 4D, 5D). Ventral chaetae bifid, (2) 4–6 per bundle anteriorly, 2–3 per bundle posteriorly, 60–160 µm long, 2–3 µm thick, upper tooth twice as long as lower (4 µm/2 µm), with (0) 1–2 fine intermediate teeth, nodulus distal (Figs. 4E,F, 5A–C). Ventral chaetae in X–XI present, unmodified. Male pores (Figs. 5G, 6C: mp) paired in line with ventral chaetae in anterior of X. Spermathecal pores (Fig. 5E: spp) paired in line with ventral chaetae, middle to posterior of XI.</p> <p>Chloragogen cells from VI onwards. Male genitalia paired in X–XII. Sperm funnel cup-shaped, 30–40 µm long, 40–60 µm wide (Fig. 5G, H: sf). Vas deferens long and irregularly coiled, 1800–2000 µm long, at least 3 times as long as atrium, anteriorly 14–16 µm wide, posteriorly 28 µm wide, ciliated throughout and entering atrium apically (Figs. 5G, H, 6A: vd). Atrium spindle-shaped, 560–640 µm long, maximally 80–100 µm wide (Figs. 5G, H, 6A: at). Ejaculatory duct 100–120 µm long, 20–32 µm wide, entering muscular bulb (Fig. 5G, H, 6A: ed; Fig. 5G: mb). Prostate gland large, attached to ental portion of atrium, 120–140 µm long, 80–100 µm wide (Fig. 5G, H, 6A: pr). Penis inconspicuous, surrounded by cuticular, symmetrical and funnel-shaped penial sheath. Penial sheath extremely thin, long and sinuous, 32–36 µm wide at ental end, 3–5 µm wide at thin and prolonged ectal portions, 520–540 µm long, length to width ratio nearly 15–16 (Figs. 5G, H, 6B: ps). Testes paired in X, immediately behind septum 9/10. Ovaries paired in XI, immediately behind septum 10/11. Spermathecae paired in X, ampullae oblong, 200–280 µm long, 140–250 µm wide; duct 100–120 µm long, 24–28 µm wide; sperm random in lumina, no spermatozeugmata (Figs. 5E, 6C: sp).</p> <p> <b>Remarks.</b> The main identification characteristics of long and winding vas deferens divided into thin and thick sections, long atrium gradually tapering towards distal portion, large prostate gland and elongate penial sheath suggest that the present species belongs to the genus <i>Tubifex</i> (Brinkhurst & Jamieson 1971; Holmquist 1985; Juget <i>et al.</i> 2006). <i>Tubifex tubifex</i> (Müller, 1774) resembles this species in pectinate dorsal chaetae, long and winding vas deferens divided into thin and thick sections, large prostates, and in atria with a long ejaculatory duct, but differs from it in a cylindrical penis covered with a short and tub-shaped cuticle ring. Furthermore, spermathecae are absent, or present with spermatozeugmata, or present with empty ampullae. <i>T</i>. <i>gracilentus</i> <b>n. sp.</b> is easily distinguished from its congeners by the extremely thin and long funnel-shaped penial sheath (Table 2).</p> <p> <b>Distribution and habitat.</b> Known from the type locality, Cuomujiri Lake and Trigu Co. Freshwater.</p>Published as part of <i>Cui, Yongde, 2017, Four species of Tubifex Lamarck (Annelida: Oligochaeta: Naididae) from Tibet, China, pp. 366-378 in Zootaxa 4320 (2)</i> on pages 369-371, DOI: 10.11646/zootaxa.4320.2.10, <a href="http://zenodo.org/record/891958">http://zenodo.org/record/891958</a&gt

FIGURE 1. Tubifex laxus n in Four species of Tubifex Lamarck (Annelida: Oligochaeta: Naididae) from Tibet, China

FIGURE 1. Tubifex laxus n. sp., SEM micrographs. A. Lateral view of anterior body. B. Hairs in IV. C. Hair chaeta and palmate chaeta in XII. D. Dorsal palmate chaetae in XII. E. Ventral chaetae in IV. F. Ventral chaetae in XIII. Scale bars: A. 500 µm; B, C. 10 µm; D – F. 20 µm

Three new species of Potamothrix (Oligochaeta, Naididae, Tubificinae) from Fuxian Lake, the deepest lake of Yunnan Province, Southwest China

Three new species of Potamothrix Vejdovský & Mrázek, 1902 (Oligochaeta: Tubificinae), P. praeprostatus sp. n., P. paramoldaviensis sp. n. and P. parabedoti sp. n., are reported from Fuxian Lake of Yunnan Province, Southwest China. P. praeprostatus differs from its allies by its prostate glands joining atria in its proximal to middle portion, and spermathecal chaetae. P. paramoldaviensis is distinguishable from its allies bypenial chaeta but no penes, and differs from P. moldaviensis by its homogenous atrium. P. parabedoti is distinctive in the position of its reproductive organs, and differs from P. bedoti by its homogenous atrium. Hitherto, 34 freshwater oligochaete species have been recorded in Yunnan Province, including nine endemic species from the plateau lakes