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Understanding the adaptative behaviors of dominant desert-steppe species under varying levels of grazing-related environmental degradation is an important step in elucidating the survival strategies and environmental response mechanisms of desert plants. In this study, the Xilamuren desert steppe in Northwest China was used as a case study location to systematically investigate the adaptative traits of three dominant plant species (Stipa breviflora, Cleistogenes squarrosa, and Convolvulus ammannii) from the perspectives of plant morphology, leaf structure, and photosynthesis. As degradation intensified, the adaptive changes in the three dominant plant species manifested in the following ways: 1) adjustment of substance allocation strategy, such that biomass was preferentially concentrated in the leaves and roots for photosynthesis and resource acquisition; 2) miniaturization, including reduced plant height, reduced leaf size, and leaf narrowing; 3) thickening of the leaves, epidermis, and cuticle to increase water storage and resist illumination and temperature elevation and thickening of the midrib veins to increase water and nutrient transportation; and 4) increased water-use efficiency in Stipa breviflora, which showed a stronger capacity to adjust to water stress than Cleistogenes squarrosa and Convolvulus ammannii. The results suggested that the morphological, structural, and functional adjustments of desert plants were related to the development of drought-resistance mechanisms through water-use strategies, including increased water absorption and water-use efficiency and decreased water consumption. These results enrich the existing knowledge of the environmental adaptation mechanisms of dominant plants in desert steppes, providing a scientific basis for the restoration of desert steppe ecologies and the formulation of suitable grazing policies.

Precipitation phase has a profound influence on the hydrological processes in the Naqu River basin, eastern Tibetan plateau. However, there are only six meteorological stations with precipitation phase (rainfall/snowfall/sleet) before 1979 within and around the basin. In order to separate snowfall from precipitation, a new separation scheme with S-shaped curve of snowfall proportion as an exponential function of daily mean temperature was developed. The determinations of critical temperatures in the single/two temperature threshold (STT/TTT2) methods were explored accordingly, and the temperature corresponding to the 50 % snowfall proportion (SP50 temperature) is an efficiently critical temperature for the STT, and two critical temperatures in TTT2 can be determined based on the exponential function and SP50 temperature. Then, different separation schemes were evaluated in separating snowfall from precipitation in the Naqu River basin. The results show that the S-shaped curve methods outperform other separation schemes. Although the STT and TTT2 slightly underestimate and overestimate the snowfall when the temperature is higher and colder than SP50 temperature respectively, the monthly and annual separation snowfalls are generally consistent with the observed snowfalls. On the whole, S-shaped curve methods, STT, and TTT2 perform well in separating snowfall from precipitation with the Pearson correlation coefficient of annual separation snowfall above 0.8 and provide possible approaches to separate the snowfall from precipitation for hydrological modelling.

The Tibetan Plateau (TP) is the roof of the world and water towers of Asia. However, research on hydrological processes is restricted by the sparse gauge network in the TP. The distributed hydrological model is an efficient tool to explore hydrological processes. Meanwhile, the spatial distribution of precipitation directly affects the precision of distributed hydrological modelling. The latest TRMM 3B42 (V7) precipitation was evaluated compared with gauge precipitation at station and basin scales in the Naqu River Basin of the TP. The results show that Tropical Rainfall Measuring Mission (TRMM) precipitation overestimated the precipitation with BIAS of 0.2; the intensity distributions of daily precipitation are consistent in the two precipitation data. TRMM precipitation was then corrected by the good linear relation between monthly areal TRMM precipitation and gauge precipitation, and applied into the Water and Energy Process model. The results indicate that the simulated streamflow using both precipitation data produce a good fit with observed streamflow, especially at monthly scale. Furthermore, the better relations between average slopes and runoff coefficients of sub-basins from the corrected TRMM precipitation-based model implies that the spatial distribution of TRMM precipitation is closer to the spatial distribution of actual precipitation, and has an advantage in driving distributed hydrological models.

Grassland ecosystems play an important role in maintaining biodiversity, global carbon balance. Aiming at the desert steppe with an extremely fragile ecological environment, the spatiotemporal relation between vegetation fractional coverage (VFC) and climate was explored in this study in a pixel-scale analysis method. There was an overall increasing trend in the VFC of the study area. The coefficient of correlation between average precipitation from 2000 to 2013 and VFC was 0.81, and during the growing season, the coefficient of correlation between average temperature and VFC was −0.76. The two dominant factors of VFC in the study area, precipitation and temperature, were used as indicators to establish an ecological suitability index (ESI) for desert steppe to reflect the hydrothermal conditions for vegetation growth. The ESI of the study area varied from 0.03 to 0.94 with its average being 0.39, and the coefficient of correlation between ESI and VFC was 0.84. On the basis of ESI, an optimized layout adjustment was made for existing farmland in the study area so as to take advantage of natural conditions to the greatest extent and reduce impacts of human activities. The optimized layout of farmlands would adapt better to the natural climatic characteristics of the desert steppe regions, meanwhile, bring about ecological and environment benefits to the original agro–pastoral ecotone of the desert grasslands areas. Results from this study further our understanding of the desert steppe, and provide some reference for ecological restoration and new cycle of returning farmland to grassland policy.

Fridericia paroniana Issel, 1904 Fridericia paroniana Issel, 1904. Issel 1905; Nielsen & Christensen 1959; Rota & Healy 1994; Rota 1994; Rota 1995; Xie et al., 1999a; Schmelz 2003; Schmelz & Collado 2010. Fridericia nielseni Dash, 1972. Fridericia maculata Issel ssp. macroglandulosa D��zsa-Farkas, 1989. For further synonymies see Schmelz (2003). Examined materia l. XZO201610001, XZ201610002, XZO20161003, ThREE FUllY maTURE SPEcimENS, FiXEd, STaiNEd, WhOlE mOUNT. MORE ThaN 10 SPEcimENS PRESERVEd iN 70% EThaNOl. Descriptions. Small SiZE. BOdY lENgTh 4���5 mm (4���9 mm iN ViVO). BOdY WidTh 200���250 ��m aT V, 270���330 ��m aT XII. SEgmENT NUmbER 40���45. ChaETaE STOUT, USUallY 2 PER bUNdlE. EPidERmal glaNd cEllS cONSPicUOUS, 2���3 ROWS PER SEgmENT. CliTEllUm aT XII���1 /2XIII, giRdlE-ShaPEd, gRaNUlOcYTES mORE NUmEROUS ThaN hYalOcYTES. BRaiN WEaklY cOVEX aNTERiORlY, ROUNd OR TRUNcaTE POSTERiORlY, 140���170 ��m lONg, 80���100 ��m WidE. OESOPhagEal aPPENdagES STOUT, UNbRaNchEd. ThREE PaiRS OF PhaRYNgEal glaNdS iN IV���VI, ThE FiRST PaiR WiTh dORSal cONNEcTiON. FiVE PaiRS OF PREcliTEllaR NEPhRidia FROm VI/VII���X/XI, aNTESEPTalE 43���48 ��m lONg, 20���26 ��m WidE, POSTSEPTalE 80���94 ��m lONg, 30���47 ��m WidE, EFFERENT dUcT aRiSiNg FROm ThE middlE OF ThE POSTSEPTalE. COElEmO-mUcOcYTES NUmEROUS, 22���36 ��m iN diamETER, lENTicYTES 8���12 ��m iN diamETER. ChYlUS cEllS iN XIV���XVI. DORSal blOOd VESSEl aRiSiNg FROm XVIII. BlOOd cOlORlESS. SPERm FUNNEl Small, cYliNdRical, 95���114 ��m lONg, 40���50 ��m WidE, cOllaR aS WidE aS OR SlighTlY NaRROWER ThaN FUNNEl bOdY, 40���45 ��m WidE. HEadS OF SPERmaTOZOa 45���55 ��m iN lENgTh. VaS dEFERENS 7���9 ��m WidE, iRREgUlaR WOUNd iN lOOP iN XII. BURSal SliT lONgiTUdiNal, SOmETimES ���T-ShaPE���. NO SUbNEURal glaNdS. SPERmaThEca laRgE, WiTh 1���2 laRgE, FlOPPY EcTal glaNdS. AmPUlla ShaPE VaRiOUS, WiTh 2 Sac-likE diVERTicUla, EcTal dUcT lONg, 155��� 173 ��m lONg, 10���13 ��m WidE. ENTal dUcTS cONNEcT SEPaRaTElY TO ThE OESOPhagUS. USUallY 1 OR 2 maTURE Egg aT a TimE. Differential diagnosis. OUR SPEcimENS cONFORm WEll TO ThE dEScRiPTiON OF F. paroniana giVEN bY SchmElZ (2003) aNd XiE et al. (1999a). ThiS SPEciES iS WidESPREad iNclUdiNg GERmaNY, DENmaRk, NEThERlaNdS, IRElaNd, AUSTRia, HUNgaRY, SPaiN, ITalY, AlgERia, TURkEY, NORTh AmERica aNd MOROccO. IN ChiNa, iT WaS FOUNd iN SichUaN, HUbEi, aNd JiliN PROViNcES aNd TibET., Published as part of Lu, Yajing, Xie, Zhicai & Zhang, Junqian, 2018, Preliminary taxonomical investigation of soil enchytraeids (Clitellata, Enchytraeidae) from south region of Tibet, China, pp. 395-410 in Zootaxa 4496 (1) on pages 402-403, DOI: 10.11646/zootaxa.4496.1.29, http://zenodo.org/record/1446917, {"references":["Issel, R. (1904) Due nuove Fridericia. Atti della Societa Ligustica di Scienze Naturali e Geografiche, Genova, 15, 31 - 39.","Issel, R. (1905) Materiali per una fauna dell'Arcipelago Toscano. Isola d'Elba. III. Enchitreidi dell'Isola d'Elba. Annali Del Museo Civico Di Storia Naturale Di Genova, Series 3, 2, 5 - 8.","Nielsen, C. O. & Christensen, B. (1959) The Enchytraeidae, critical revision and taxonomy of European species, Natura Jutlandica, 8 - 9, 1 - 160.","Rota, E. & Healy, B. (1994) The enchytraeid fauna of North Africa Hydrobiologia, 278, 53 - 66. https: // doi. org / 10.1007 / BF 00142311","Rota, E. (1995) Italian Enchytraeidae (Oligochaeta). I. Italian Journal of Zoology 62, 183 - 231. https: // doi. org / 10.1080 / 11250009509356067","Xie, Z. C., Liang, Y. L. & Wang, H. Z. (1999 a) Taxonomical studies on Fridericia (Enchytraeidae, Oligochaeta) along the Changjiang (Yangtze) Basin. Acta Hydrobiologica Sinica, 23 (Supplement), 158 - 163.","Schmelz, R. M. (2003) Taxonomy of Fridericia (Oligochaeta, Enchytraeidae). Revision of species with morphological and biochemical methods. Abhandlungen des Naturwissenschaftlichen Vereins in Hamburg, Neue Folge, 38, 1 - 415.","Schmelz, R. M. & Collado, R. (2010) A guide to European terrestrial and freshwater species of Enchytraeidae (Oligochaeta). Soil Organisms, 82, 1 - 176.","Dash, M. C. (1972). New Enchytraeidae (Oligochaeta) from the Penny Forest soil of British Columbia, Canada. Annales Zoologici Fennici, 9, 15 - 16.","Dozsa-Farkas, K. (1989) Fridericia Arten aus Marokko (Oligochaeta: Enchytraeidae). Acta Zoologica Hungarica, 35, 29 - 39."]}

Henlea perpusilla Friend, 1911 (FigURE 4G���J) Henlea perpusilla Friend, 1911. Černosvitov 1937; Nielsen & Christensen 1959; Chalupsk�� 1986; Kasprzak 1986; Rota & Healy 1994; Rota 1995; Rota et al. 1998; Wang et al. 1999; Schmelz & Collado 2010. Henlea brucei Stephenson, 1922. Henlea balcanica Černosvitov, 1930. Examined material. XZO201604001, XZO201604002, XZO201604003, ThREE adUlTS, FiXEd, STaiNEd aNd WhOlEmOUNTEd SPEcimENS. Description. BOdY lENgTh 5���6.4 mm (5���10 mm iN ViVO). SEgmENT NUmbER 30���38. BOdY WidTh 158���210 ��m aT V aNd 175���290 ��m aT XII (256���280 ��m aNd 340���460 ��m iN ViVO). ChaETaE FORmUla (2)3-5 ��� 3-5: 3-6,(7,8) ��� 2- 5,(7,8), STRaighT diSTallY, SlighTlY bENT PROXimallY. PREcliTEllaR EPidERmal glaNd cEllS cONSPicUOUS, abOUT 3 TRaNSVERSE ROWS PER SEgmENT. BRaiN iN II, WEaklY cONcaVE aNTERiORlY, SlighTlY iNciSEd OR TRUNcaTE POSTERiORlY, 120 ��m iN lENgTh aNd 94 ��m iN WidTh. ThREE PaiRS OF PhaRYNgEal glaNdS iN IV���VI, all WiThOUT dORSal cONNEcTiON. OESOPhagEal aPPENdagES PRESENT iN VI, WiThOUT bRaNchES. INTESTiNal diVERTicUla abSENT. GUT WidENiNg cONSPicUOUSlY aT VII/VIII (Fig. 4G, J). CliTEllUm ElEVaTEd cONSPicUOUSlY, aT XII���XIII, cEllS iN RETicUlaTE PaTTERN, hYalOcYTES iSOlaTEd (Fig. 4H). DORSal blOOd VESSEl FROm VIII. FiVE PaiRS OF PREcliTEllaR NEPhRidia iN VI/VII���X/XI. COElOmOcYTES abUNdaNT, ROUNd OR OVal, 22���26 ��m iN SiZE (Fig. 4G). SPERm FUNNEl Small, cYliNdRical, cOllaR NaRROWER ThaN FUNNEl bOdY, lENgTh 1.5��� 2 TimES aS lONg aS WidTh, 50���86 ��m iN lENgTh aNd 36���57 ��m iN WidTh (Fig. 4I). VaS dEFERENS lONg, WOUNd iN iRREgUlaR lOOPS iN XII. SEmiNal VESiclE WEll-dEVElOPEd, OccUPYiNg iN XI, SOmETimES EXTENdiNg FORWaRdS iNTO X. HEadS OF SPERmaTOZOa 25���30 ��m. SPERmaThEca iN V. NO EcTal glaNdS. EcTal dUcT 68���81 ��m lONg aNd 9���12 ��m WidE. AmPUlla WiThOUT diVERTicUla, SlighTlY WidER ThaN EcTal dUcT, 25���30 ��m lONg aNd 15 ��m WidE. ENTal dUcT 84���96 ��m iN lENgTh aNd 7���11 ��m iN WidTh, UNiTEd PROXimallY aNd cONNEcTiNg JOiNTlY WiTh OESOPhagUS dORSallY iN VI. USUallY 1 OR 2 maTURE EggS aT a TimE. Differential diagnosis. OUR SPEcimENS cONFORm WEll TO ThE dEScRiPTiON OF Henlea perpusilla (ROTa 1995, SchmElZ & COlladO 2010). ThiS SPEciES iS WidESPREad iNclUdiNg iN AmERica, EUROPE aNd ThE ANTaRcTic. IN ChiNa, ThE WORmS WERE FOUNd iN GUiZhOU, HUNaN, JiliN PROViNcES aNd TibET., Published as part of Lu, Yajing, Xie, Zhicai & Zhang, Junqian, 2018, Preliminary taxonomical investigation of soil enchytraeids (Clitellata, Enchytraeidae) from south region of Tibet, China, pp. 395-410 in Zootaxa 4496 (1) on pages 403-405, DOI: 10.11646/zootaxa.4496.1.29, http://zenodo.org/record/1446917, {"references":["Friend, H. (1911) New British Henleas. The Zoologist, Series 4, 15, 464 - 468.","Cernosvitov, L. (1937) Zur Kenntnis der Enchytraeiden. III. Revision der Friendschen Enchytraeidentypen. Zoologischer Anzeiger, 117, 191 - 205.","Nielsen, C. O. & Christensen, B. (1959) The Enchytraeidae, critical revision and taxonomy of European species, Natura Jutlandica, 8 - 9, 1 - 160.","Chalupsky, J. (1986) Czechoslovak enchytraeids (Oligochaeta, Enchytraeidae) I. Enchytraeids from an apple orchard by Bavorov in South Bohemia. Vestnik Ceskoslovenske spolecnosti zoologicke, 50, 13 - 21.","Kasprzak, K. (1986) Skaposzczety wodne i glebowe, II. Rodzina: Wazonkowce (Enchytraeidae). Polska Akademia Nauk Instytut Zoologii, Warszawa, 366 pp.","Rota, E. & Healy, B. (1994) The enchytraeid fauna of North Africa Hydrobiologia, 278, 53 - 66. https: // doi. org / 10.1007 / BF 00142311","Rota, E. (1995) Italian Enchytraeidae (Oligochaeta). I. Italian Journal of Zoology 62, 183 - 231. https: // doi. org / 10.1080 / 11250009509356067","Rota, E., Healy, B. & Erseus, C. (1998) Biogeography and taxonomy of terrestrial Enchytraeidae (Oligochaeta) in Northern Sweden, with comparative remarks on the genus Henlea. Zoologischer Anzeiger, 237, 155 - 169.","Schmelz, R. M. & Collado, R. (2010) A guide to European terrestrial and freshwater species of Enchytraeidae (Oligochaeta). Soil Organisms, 82, 1 - 176.","Stephenson, J. (1922) The Oligochaeta of the Oxford University Spitsbergen expedition. Proceedings of the Zoological Society of London, 74, 1109 - 1138. https: // doi. org / 10.1111 / j. 1469 - 7998.1922. tb 07096. x","Cernosvitov, L. (1930) Zur Kenntnis der Oligochatenfauna des Balkans. I. Uber die Oligochaten aus Bosnien. Zoologischer Anzeiger, 86, 319 - 333."]}

Fridericia bulboides Nielsen & Christensen, 1959 (FigURE 3A) Fridericia bulboides Nielsen & Christensen, 1959. Christensen 1961; Dash 1970; M��ller 1971; Kasprzak 1979; Chaluspk�� 1986; Kasprzak 1986; Rota 1994; Rota & Healy 1994; Rota 1995; Wang et al. 1999; Schmelz 2002, 2003; Schmelz & Collado 2010. Examined material. XZO201604007, XZO201604008, TWO FUllY maTURE SPEcimENS, WhOlE-mOUNTEd aNd STaiNEd. SiXTEEN FUll maTURE SPEcimENS iN 70% EThaNOl. Description. Small SPEciES. BOdY lENgTh 4���5 mm (6.4���9.2 mm iN ViVO). SEgmENT NUmbER 28���31. ChaETaE USUallY 2���4 PER bUNdlE. ChaETaE FORmUla: 2-4 ��� 2-4: 3,4 ��� 2-4. EPidERmal glaNd cEllS cONSPicUOUS iN PREcliTEllaR REgiON, ONE TRaNSVERSE ROW PER SEgmENT (Fig. 3A). CliTEllUm ElEVaTEd cONSPicUOUSlY, giRdlE-ShaPEd. BRaiN 152���160 ��m iN lENgTh, 75���98 ��m iN WidTh, SlighTlY cONcaVE aNTERiORlY, TRUNcaTE POSTERiORlY. OESOPhagEal aPPENdagES UNbRaNchEd, lONg, USUallY cOilEd iNTO a maSS iN IV/V, ThEN EXTENdiNg backWaRdS iNTO VI OR VII. ThREE PaiRS OF PhaRYNgEal glaNdS iN IV���VI; FiRST PaiR WiTh dORSal cONNEcTiON, SEcONd aNd ThiRd PaiR WiTh VENTRal lObES. FiVE PaiRS OF PREcliTEllaR NEPhRidia FROm VI/VII TO X/XI. ANTESEPTalE 26���31 ��m lONg, 16���18 ��m WidE, POSTSEPTalE 62���68 ��m lONg, 20���32 Um WidE, EFFERENT dUcT RiSiNg mEdiallY OR clOSE TO SEPTUm. MUcOcYTES WiThOUT REFRacTilE VESiclES, 30��� 37 ��m iN diamETER. LENTicYTES ScaRcE. ChYlUS cEllS iN XIII���XIV. DORSal blOOd VESSEl RiSiNg FROm XIV���XVII. BlOOd cOlORlESS. CliTEllUm aT XII���1 /2XIII, WEll-dEVElOPEd, giRdlE-ShaPEd. SPERm FUNNEl 2���3 TimES aS lONg aS WidE, 82���87 ��m iN lENgTh aNd 33���38 ��m iN WidTh. COllaR aS WidE aS FUNNEl bOdY, abOUT 30���35 ��m WidE. HEad OF SPERmaTOZOa abOUT 80 ��m lONg. VaS dEFERENS ThiN aNd lONg, 5���8 ��m WidE, WOUNd iN iRREgUlaR lOOPS iN XII. BURSal SliT lONgiTUdiNal. SUbNEURal glaNdS abSENT. SPERmaThEca iN V, WiTh a ball-ShaPEd EcTal glaNd, 15���19 ��m iN diamETER. EcTal dUcT 112���124 ��m lONg aNd 10���12 ��m WidE. AmPUlla ONiON-ShaPEd, WiThOUT diVERTicUla, diamETER 26���29 ��m, 2���3 TimES WidER ThaN EcTal dUcT. Differential diagnosis. ThE mORPhOlOgical chaRacTERS OF OUR SPEcimENS cORRESPONd WEll TO ThE dEScRiPTiON giVEN bY SchmElZ (2003), EXcEPT FOR ThE SiZE OF ThE FUNNEl cOllaR (aS WidE aS VS. NaRROWER ThaN FUNNEl bOdY). IN ChiNa, ThE WORmS WERE FOUNd iN HUbEi, YUNNaN, JiNliN PROViNcES aNd TibET., Published as part of Lu, Yajing, Xie, Zhicai & Zhang, Junqian, 2018, Preliminary taxonomical investigation of soil enchytraeids (Clitellata, Enchytraeidae) from south region of Tibet, China, pp. 395-410 in Zootaxa 4496 (1) on page 399, DOI: 10.11646/zootaxa.4496.1.29, http://zenodo.org/record/1446917, {"references":["Nielsen, C. O. & Christensen, B. (1959) The Enchytraeidae, critical revision and taxonomy of European species, Natura Jutlandica, 8 - 9, 1 - 160.","Christensen, B. (1961) Studies on cyto - taxonomy and reproduction in the Enchytraeidae. Hereditas, 47, 387 - 449. https: // doi. org / 10.1111 / j. 1601 - 5223.1961. tb 01782. x","Dash, M. C. (1970) A taxonomic study of Enchytraeidae (Oligochaeta) from Rocky Mountain forest soils of the Kananaskis region of Alberta, Canada. Canadian Journal of Zoology, 48, 1429 - 1435. https: // doi. org / 10.1139 / z 70 - 242","Moller, F. (1971) Systematische Untersuchungen an terricolen Enchytraeiden einiger Grunlandstandorte im Bezirk Potsdam. Mitteilungen aus dem Zoologischen Museum in Berlin, 47, 131 - 167. https: // doi. org / 10.1002 / mmnz. 19710470114","Kasprzak, K. (1979) Skaposzczety (Oligochaeta) Pienin. I. Wazonkowce (Enchytraeidae). Fragmenta faunistica, Warszawa, 24, 7 - 56. https: // doi. org / 10.3161 / 00159301 FF 1979.24.1.007","Kasprzak, K. (1986) Skaposzczety wodne i glebowe, II. Rodzina: Wazonkowce (Enchytraeidae). Polska Akademia Nauk Instytut Zoologii, Warszawa, 366 pp.","Rota, E. & Healy, B. (1994) The enchytraeid fauna of North Africa Hydrobiologia, 278, 53 - 66. https: // doi. org / 10.1007 / BF 00142311","Rota, E. (1995) Italian Enchytraeidae (Oligochaeta). I. Italian Journal of Zoology 62, 183 - 231. https: // doi. org / 10.1080 / 11250009509356067","Schmelz, R. M. (2002) Records and taxonomy of Fridericia species found in the Mols area. Natura Jutlandica Occasional Papers, 2, 75 - 85.","Schmelz, R. M. (2003) Taxonomy of Fridericia (Oligochaeta, Enchytraeidae). Revision of species with morphological and biochemical methods. Abhandlungen des Naturwissenschaftlichen Vereins in Hamburg, Neue Folge, 38, 1 - 415.","Schmelz, R. M. & Collado, R. (2010) A guide to European terrestrial and freshwater species of Enchytraeidae (Oligochaeta). Soil Organisms, 82, 1 - 176."]}

Mesenchytraeus spermatoglomeratus sp. nov. (Figures 1, 2, Tables 1, 3) Holotype. Fully mature, whole-mounted specimen, stained, JLO201412005. Type locality. Mt. Changbai, Jilin Province, hardwood forest, 42°180.607''N, 127°50.453''E, 1034 m asl, dark brown forest soil under Quercus mongolica, coll. Z. J. Piao, Dec. 2014. Paratypes. JLO201412003–JLO201412004, two whole mounted adult specimens from Korean pine broadleaved mixed forest, 42°20.150''N, 127°53.056''E, 1084 m asl, dark brown forest soil under Pinus koraiensis, 10 December 2014, coll. Z. J. Piao; JLO201412006, one whole mounted adult specimen from type locality, same data as holotype. JLO201503001–JLO201503002, two whole mounted specimens, fully mature, from secondary Betula platyphylla forest, 42°22.719''N, 128°01.020''E, 786 m asl, dark brown forest soil under Betula platyphylla, 2 April 2015, coll. Z. J. Piao. Etymology. Named after the shape of sperm bundles: "glomeratus" refers to "condensed into a ball". " spermatoglomeratus " refers to the sperm bundles of the new species, rolled into a round ball shape. Diagnosis. This new species is recognized by the following characters, diagnostic in combination: 1) enlarged ventral chaetae in segments V–VI and XI, 2 per bundle; 2) five pairs of preclitellar nephridia in VI/VII to X/XI; 3) sperm sacs asymmetrically paired from XI–XIV to XV–XXIV, containing curly ball-shaped sperm bundles; 4) spermathecae without diverticula, ental ducts connected with oesophagus in VI–VII; 5) atrium tubular, with 4–6 developed prostate glands, distinct from vas deferens; 6) vas deferens very long, extending backwards to XV– XXII. Description. Small worms, active, twisting when submerged in water, pale in vivo, body wall thin, transparent. Body length 6.5–11.5 mm (holotype 8.0 mm), 7.0– 12.5 mm in vivo; body width 270–355 µm at V (330–450 µm in vivo), 470–575 µm at clitellum (320–625 µm in vivo). Segments 28–46 (holotype 34). Head pore transverse slit near the apex of prostomium (Fig. 2A). Epidermal gland cells inconspicuous, almost absent. Chaetal formula: 2,3 - 3,4: 2–5(6) - 2–5(6), up to 6 per bundle in the last segments. Chaetae sigmoid, nodulated, distally thinner and single-pointed. Lateral chaetae 44–100 µm in length and 3.5–5 µm in maximal width, shortest in II (44–48 µm), gradually increasing in size from III backwards, maximal size in IX (80–100 µm) (Table 1). Ventral chaetae, except those in V, VI and XI, 63–120 µm in length and 4–7.5 µm in maximal width (Fig. 1A, D). Ventral chaetae in V, VI and XI reduced to 2 per bundle (occasionally 3) (Fig. 1B, C, E). Ventral chaetae in V and VI longer and stouter than the others even in immature specimens, 126–158 µm in length and 7.5–11 µm in maximal thickness (Fig. 1B, C). Ventral chaetae in XI shorter and thinner than in V and VI, but thicker than the ordinary ventral ones, 6–8.5 µm in maximal thickness (Fig. 1E). Chaetae of XII lacking in fully mature specimens. Clitellum extending from 1/ 2 XI to XIII, elevated conspicuously. Hyalocytes (12–24 µm in diameter) more abundant than granulocytes, irregularly arranged and in contact with each other. Granulocytes (13–22 µm in diameter) irregular in shape, having some connection with each other and forming a loose net (Fig. 2B, F). Male pores distinct in the ventral middle of XII. Spermathecal pores paired, in the lateral line at IV/V (Fig. 2K). Length of lateral chaetae (µm) 71–90 71–85 71–80 71–80 65–75 Width of lateral chaetae (µm) 3.5–5 3.5–5 3.5–5 3.5–5 3.5–4.5 Number per bundle 3 3 3 3,4 3 Length of ventral chaetae (µm) 110–120 105–120 90–105 85–102 75–85 Width of ventral chaetae (µm) 6–8.5 6–7.5 5–6 5–6 5–6 Number per bundle 2 2,3 4 4 5 Brain in I-II (Figs. 1J, 2E), trapezoidal, deeply concave anteriorly and slightly incised posteriorly, 137–170 µm long and 105–125 µm in maximal width. Blood colourless or slightly yellowish. Dorsal vessel arising from XIV– XVI. Two pairs of primary pharyngeal glands in IV and V, attached to septa of 4/5 and 5/6 respectively, and both not connected dorsally. Three pairs of secondary lobes ventrally in V–VII, largest in VI. No oesophageal appendages. Intestinal diverticula absent. Chloragogen cells developed, originating from VIII, 12–45 µm high, absent in clitellum. Coelomocytes abundant, disc-shaped with conspicuous nuclei, 7.5–15.0 µm in diameter, with uneven refractile granules (Fig. 2C). Five pairs of nephridia in preclitellar segments from VI/VII to X/XI. Anteseptale stalked, containing nephrostome only; postseptale bilobed and with fewer interstitial tissue. Efferent duct arising between the two lobes (Figs. 1F, 2G). Sperm funnels cylindrical, occupying 1/3–1/2 body cavity in XI, 390–440 µm in length and 122–200 µm in maximal width. Their ental openings much narrower than funnel body, 43–73 µm wide. The heads of spermatozoa 17–20 µm in length (Figs. 1I, 2I). Vasa deferentia with conspicuous cilia in the canal, wound in irregular spirals in coelom from XII and posteriorly into XV–XXII, 18–30 µm in width, lumen of vasa deferentia 14–24 µm wide (Fig. 2L). The transition between vas deferens and atrium gradual. Atria in XII–XIII, cylindrical, remarkably wider than vasa deferentia, 415–650 µm long and 65–85 µm in maximal width. No cilia observed in atrial canal. Each atrium possessing 4–6 tubular prostate-like glands (each 117–195 µm in length and 50–68 µm in width) (Figs. 1H, 2I,J). Each atrium divided into two distinct parts, an ental part (length: 217–400 µm; width: 27.5–58 µm) with thin muscle layer and thick epithelium, and an ectal part (length: 200–350 µm; width: 25–44 µm) with a muscular duct connecting with the penial bulb. Penial bulb large, compact in ventral of XII, consisting of muscle strands and surrounded by masses of accessory glands of different size (Figs. 1H, 2J). A pair of sperm sacs large from XI–XIV in different size, and backwards extending to XV–XXIV, each containing numerous ball-shaped sperm bundles (diameter: 50–110 µm), a large number of spermatozoa coiled inside in vivo but much more loose in fixed condition (Fig. 2D,H). Egg sacs paired, large from XIV–XXII, continuing caudad to XVII–XXXIII, usually containing 2–11 mature eggs at a time. One pair of spermathecae in V–VII, without ectal glands. Ectal duct 215–385 µm long and 37–50 µm wide, projecting into ampulla. Ampulla spherical, 83–102 µm in diameter. No diverticula visible. Ampulla filled with spermatozoa in fully mature specimens. Ental ducts stout, 195–244 µm long and 62–67 µm wide, connecting to the dorsal side of oesophagus separately in the posterior of VI or anterior of VII (Figs. 1G, 2K). Differential diagnosis (Table 3). This new species is morphologically most similar to the co-occurring species M. gigachaetus Xie, 2012, M. anisodiverticulus Shen et al., 2012 and M. monodiverticulus Shen et al., 2012 and to a further terrestrial species, M. longiductus Christensen & Dózsa-Farkas, 2012, collected in Korea, which also have enlarged ventral chaetae in V–VI, and atria, egg sacs, and spermathecae attached to oesophagus. However, Mesenchytraeus spermatoglomeratus sp. nov. possesses enlarged ventral chaetae in XI and ball-shaped sperm bundles in the sperm sacs, two characteristics absent in the latter four species. Besides, M. gigachaetus differs from M. spermatoglomeratus by a higher number per bundle of enlarged ventral chaetae (3–4), no sperm sac visible and no atrial prostate gland. Mesenchytraeus anisodiverticulus is distinct from this new species by its absence of atrial prostate glands and the presence of two asymmetrical spermathecal diverticula. Mesenchytraeus monodiverticulus is different from M. spermatoglomeratus by its higher number per bundle of enlarged ventral chaetae (4 or 5), absence of atrial prostate glands, and spermatheca with one diverticulum. In Mesenchytraeus longiductus, atrial prostate glands are less numerous (only 2) and fewer accessory glands surround the penial bulb (only 4–5). Five other species (M. crenobius Timm, 1994, M. kontrimavichusi Piper et al., 1982, M. tetrapodus Timm, 1978, M. monochaetus Bretscher, 1900 and M. calyx Dózsa-Farkas et al., 2015) differ from M. spermatoglomeratus in terms of location and number of enlarged chaetae, chaetae formula, spermatheca, origin of dorsal vessel and habitat requirement. Unlike the new species, M. crenobius, M. tetrapodus and M. monochaetus are aquatic enchytraids. They also have 1–2 spermathecal diverticula. The terrestrial M. kontrimavichusi differs from this new species in: spermatheca with one diverticulum, not attached to oesophagus, atria absent, dorsal vessel arising from XV–XVIII. The other terrestrial member, M. calyx, is different from M. spermatoglomeratus by its larger body size (20–39 mm), the location of enlarged chaetae (VII–IX) and spermatheca with 7–9 pointed diverticula.