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Limnologica 33,280-292 (2003) © Urban & FischerVerlag http://www.urbanfischer.de/journals/limno LIMNOLOGICA

Sub-Recent Ostracoda from Qilian Mountains (NW China) and their ecological significance

S. Mischke *,1, U. Herzschuh 1, H. K[irschner 2, D. Fuchs ~, Zhang Jiawu 3, Meng Fei 3 & Sun Zhencheng 4

1Freie Universit~t Berlin, Interdisciplinary Centre for Ecosystem Dynamics in Central Asia, Germany 2Freie Universit/it Berlin, Institute of Biology, Systematic Botany and Plant Geography, Germany 3Lanzhou University, Centre for Arid Environment and Paleoclimate Research (CAEP), China 4 University of Petroleum, Department of Earth Science, Beijing, China

Received February 19, 2002 • Revised October 29, 2003 • Accepted November 5, 2003

Abstract

23 ostracod species have been recorded from surface and short core samples from the Qilian Mountains, NW China. Brooks and rivers, small shallow meadow and oxbow pools and a lake were sampled at an altitude ranging from 2900 m to 3570 m asl. Brooks were dominated by Candona rawsoni, lIyocypris cf. bradyi and/or Ilyocypris lacustris and Limnocythere inopinata. In river habitats Candona candida and Eucypris sp. were most abundant. Meadow pools with peaty, dystrophic waters mainly contained valves of Ilyocypris cf. bradyi and/or Ilyocypris lacustris and Eucypris sp. whereas the latter was replaced by Heterocypris incongruens in a shallow oxbow pool. Candona rawsoni, Cyclocypris ovum and Ilyocypris echinata were the most frequent species in the freshwater Lake Luanhaizi. The recorded taxa are mainly distributed in the holarctic realm but Fabaeformiscandona danielopoli and llyocypris echinata appear to be restricted to the cold mountainous region in China.

Key words: Freshwater Ostracoda - sub-Recent - ecology - Qilian Mountains -NW China

Introduction The Recent and sub-Recent ostracod faunas of certain regions of NW China such as the Qilian Mountains remain poorly known. A lot of work has been carried out in the large intermontane Qaidam Basin in the south of the mountain range, although studies have tended to focus on fossil Mesozoic and Cenozoic ostracods (SuN et al. 1995, 1997, 1999; YAN~ et al. 1995, 1997). Reports on Holocene or Late Pleistocene ostracods from the northern foreland of the Qilian Mountains were provided by CrmN (2000), PENG et al. (1998), W121NNEMANN et al. (1998) and ZHANG et al. (1998). Further studies on

Holocene ostracods from lakes and lake deposits in the north and northwest of the Qilian Mountains were carried out by M~SCrIKE and co-authors (MISCHKE 2001; MISCHKE & HOFMANN 1998; MISCHKE & SCHUDACK 2001; HOFMANN et al. 2002).

However, information on Recent or sub-Recent ostracods from the area in between, the Qilian Mountains, is still lacking. In an attempt to improve the situation, this paper reports on ostracods collected from different types of habitats in the central Qilian Mountains.

In addition, information on molluscs found in the samples is given in the "Appendix".

*Corresponding author: Dr. Steffen Mischke, Institute of Geological Sciences, Branch Palaeontology, Freie Universit~t Berlin, Malteserstr. 74-100, Flaus D, D- 12249 Berlin, Germany; e-mail: [email protected]

0075-9511/03/33/04-280 $15.00/0 Limnologica (2003) 33, 280-292

2. Study area and material

Sampling was carried out in the valleys of the Datong and Babao rivers which are enclosed by NW-SE aligned mountain chains (Fig. 1, Table 1). The altitude of sampling sites is in the range of 2900 m to 3570 m above sea-level (asl). The mean annual temperature of Babaosi station (2787 m asl) close to the town of Qilian (Fig. 1) is 0.7 °C (Observatory 1963). Mean January and July temperatures of the station are-13.6 °C and 13.4 °C re- spectively. The mean annual precipitation is recorded at the Datong River gauge station Gadatan near Menyuan (Fig. 1) amounting to 510.3 mm whereas the mean annual potential evaporation is as high as 1290 mm (Water conservation 1974).

32 samples of surface mud and short cores were taken from several water bodies. The substrate-water interface of slow flowing sections of brooks and rivers was sampled as well as meadow pools with peaty, dystrophic waters, an oxbow pool and Lake Luanhaizi (Table 1). The latter is one of very few lakes in the Qilian Mountains, it is a small (1.5 km2), open freshwater lake at an altitude of 3200 m asl northwest of the town Menyuan (Fig. 1). The lake has an outlet to the Datong River and a salinity of about 0.5 g/1 was determined for September 2001. Luanhaizi is partly surrounded by shallow peat bogs at

Sub-Recent Ostracoda from Qilian Mountains 281

the northern, western and southern margin. The catchment area of the lake is comparatively small and com- prises about 30 km 2.

Luanhaizi and a swampy brook near the main channel of the Babao River (samples 3-10, Fig. 1) were sampled not only by surface samples but also by short cores. In Luanhaizi, two cores were drilled in the littoral zone of the lake down to a depth of 1.6 m. The brook samples 3 to 10 were taken from two further short cores (length 0.40 and 0.63 m).

3. Ostracods found in surface and subsurface samples from the Qilian Mountains

23 taxa were recorded in surface samples from different habitats and in short cores from Lake Luanhaizi and the Babao River (order according to MEISCH 2000). These taxa are figured in Plates 1 and 2.

Candona candida (O.E M10LLER, 1776) Candona weltneri HARTWIG, 1899 Candona rawsoni TRESSLER, 1957 Fabaeformiscandona caudata (KAUFMANN, 1900) Fabaeformiscandona danielopoli YIN & MARTENS,

1997

Fig. 1. Study area and sam- piing sites in the Qilian Moun- tains. Grey-shaded box in inset shows general location.

Limnologica (2003) 33, 280-292

282 S. Mischke et al.

Pseudocandona compressa (KocH, 1838) Pseudocandona cf. eremita (VEJDOVSKY, 1882) Cyclocypris ovum (JURINE, 1820) llyocypris cf. bradyi SARS, 1890 llyocypris lacustris KAUFMANN, 1900 Ilyoeypris echinata HUANG, 1979 Cypris pubera O.F. M~LLER, 1776 Eucypris dulcifons DIEBEL & PIETRZENIUK, 1969 Eucypris sp. Tonnacypris (?) sp. Psychrodromus aft. olivaceus (BRADY & NORMAN,

1889) Heterocypris incongruens (RAMDOHR, 1808) Heterocypris salina (BRADY, 1868) Scottia pseudobrowniana KEMPF, 1971 Cypridopsis vidua (O.E M~LLER, 1776) Sarscypridopsis aculeata (COSTA, 1847) Limnocythere inopinata (BAIRD, 1843) Paralimnocythere psammophila (FL0SSNER, 1965)

Ilyocypris cf. bradyi and Ilyocypris lacustris were identified on the base of the marginal ripplets on the posteroventral part of the inner lamella of the left valve rather than shape and size of the valves (VAN HARTEN 1979; JANZ 1994; MISCHKE 2001). A SEM was used for the investigation of the pattern of the marginal ripplets (Plate 1). However, L cf. bradyi and L lacustris were n o t

distinguished for each sample due to their similar ap-

pearance seen under the binocular microscope (Table 2). The marginal ripplets of Ilyocypris cf. bradyi from the

Qilian Mountains slightly differ from those described for L bradyi by JANZ (1994). Thus specimens were identified with reservation.

Valves of male ostracods were recognised only in case of taxa which display a distinct sexual dimorphism (Table 2).

3.1. Brooks and rivers

Samples from running water habitats were either dominated by valves of Candona rawsoni, Limnocythere inopinata, Ilyocypris cf. bradyi and/or I. lacustris or by Candona candida and Eucypris sp. The former assem- blage was typically found in samples from a slowly flowing swampy brook with a dense cover of semi- aquatic plants (Tables 1 and 2). In addition, species of Heterocypris (H. incongruens and H. salina) were found in surface and subsurface samples rather frequently whereas Pseudocandona compressa, Eucypris dulcifons and Sarscypridopsis aculeata occurred sporadically and at low densities only. A single fragment of a large taxon was recorded in one of these samples, most likely be- longing to a species of Tonnacypris (Plate 2).

The samples from the Babao River itself or from an inflowing brook yielded abundant valves and carapaces of Candona candida and Eucypris sp. (Table 2). Ily-

Table 1. Description of sample sites.

No Site description Plant cover Altitude

Samples from running waters 3", 4", 5 small swampy brook near main river (Babao

River), carbonate-rich alluvial loess 6"-9", 10 small swampy brook near main river (Babao

River), carbonate-rich alluvial loess 11 small bed of Babao River, slowly flowing 13 bed of Babao River, slowly flowing 15 small bed of Babao River, slowly flowing 16 quiet areas of the Babao River and inflowing brook

Samples from pools 1 swampy meadow pools in Babao catchment 2 swampy meadow pools in Babao catchment

12 swampy meadow pools in Datong catchment 14 shallow oxbow pool near Babao He

Samples from Lake Luanhaizi 17"-20", 21 littoral zone near outflow area at western

margin, floating fen layer below water level 22 littoral zone of Luanhaizi at northern margin 23*-32* littoral zone of Luanhaizi at eastern margin

dense Cyperaceae cover on swampy surface 3200 m

dense Cyperaceae cover on swampy surface 3200 m

vegetation almost lacking 2900 m algae abundant, higher plants lacking 3080 m dense cover of charophytes and other plants 3080 m higher plants abundant 3540 m

moderate plant cover 3540 m moderate plant cover 3570 m moderate plant cover 3540 m moderate plant cover 3080 m

dense cover of littoral macrophytes (Hippuris)

dense cover of littoral macrophytes (Hippuris) dense cover of littoral macrophytes (Hippuris)

3200 m

3200 m 3200 m

* Subsurface samples from short cores (< 1.6 m).

Limnologica (2003) 33,280-292

Sub-Recent Ostracoda from Qilian Mountains

Table 2. Distribution of ostracods in samples 1 to 32 from Qilian Mountains.

283

Taxa Running waters Pools

3* 4* 5 6* 7* 8* 9* 10 11 13 15 16 1 2 12 14

Candona candida r a ° Candona weltnefi r Candona rawsoni a ° a ° a ° a ° a ° a ° a ° r ° juven i leCandoninae a a a a a a a r r a Fabaeformiscandona caudata Fabaeformiscandona danbiopofi Pseudocandona compressa a r r Pseudocandona cf. eremita Cydocypris ovum r Ilyocypris cf. brady/& L/acustris a a a a a a a a a /yocypris echinata Cypris pubera Eucypris du/cffons r r r Eucypris sp. a a a Tonnacypris (?) sp. r Psychrodromus aft. olivaceus Heterocypris incongruens a a a a r a Heterocypris salina a a 5cottia pseudobrowniana dypridopsis vidua Sarscypfidopsis aculeata r r Limnocythere bopinata a a a a a a a a Paralimnocythere psammophila

a

a r r

r a

a r a

Taxa Lake Luanhaizi

17" 18" 19" 20* 21 22 23* 24* 25* 26* 27* 28* 29* 30* 31" 32*

Candona candida r r a a a a Candona weltneri Candona rawsoni a a ° a ° a ° a ° a ° a ° juveni le Candoninae a a a a a a a Fabaeformiscandona caudata r a ° a ° a ° Fabaeformiscandona danielopofi a ° a ° a ° a ° a ° Pseudocandona compressa r a a r r a Pseudocandona cf. eremita r Cyclocypris ovum a a a a a a a ilyocypris cf, brady/& i. lacustris r Ilyocypris echinata a a a a a a a (ypris pubera r Eucypris dulcifons r Eucypris sp. Tonnacypris (?) sp. Psychrodromus aft. olivaceus r Heterocypris incongruens Heterocypris salina 5cottia pseudobrowniana r Cypridopsis vidua r r Sarscypridopsis acu/eata Limnocythere inopinata a a a a r r Paralimnocythere psammophila

a a a a r r r a r

a ° a a ° a ° a ° a ° a a ° a °

a a a a a a a a a

a ° a ° r a ° a o

r r a

a a a a a a a a a

r r r r a a a a a a a a a

r r

a a a

r r

a a a a a

* Subsurface samples from short (< 1.6 m) cores; a - abundant (> 10 valves per sample); r - rare (< 10 valves per sample); o _ valves of males in addit ion to those of females.

Limnologica (2003) 33,280-292


Plate 1

Limnologica (2003) 33, 280-292

ocypris cf. bradyi and/or I. lacustris, Heterocypris incongruens, Cyclocypris ovum and Candona weltneri were clearly minor taxa. Notably, sample 15 is the only one containing valves of male specimens of Candona candida (Plate 1).

3.2. Pools Surface samples from swampy meadow pools which re- ceive a considerable humic input from organic detritus were collected at sites with a comparatively high elevation (Table 2). Pools were generally very shallow (depth < 0.2 m). The first two sites in the uppermost reaches of the Babao River (samples 1 and 2) yielded only few valves of Ilyocypris cf. bradyi and/or L lacustris, Eucypris sp. and juvenile Candoninae.

A third site of meadow pools (sample 12) was sampled at a similar elevation in the Datong catchment area (Fig. 1). Contrastingly, valves of llyocypris cf. bradyi and/or L lacustris and Eucypris sp. were abundant there and few valves of Cypridopsis vidua, ParaIimnocythere psammophila and juvenile Candoninae were found in addition.

The sampling of a shallow oxbow pool close to the Babao River (sample 14) yielded abundant valves and carapaces of Heterocypris incongruens and Ilyocypris cf. bradyi and/or L Iacustris. No other taxa were present there.

3.3. Lake Luanhaizi

The surface samples from the northern and western littoral zone of Lake Luanhaizi (samples 21 and 22) contained valves of Candona candida, Candona rawsoni, Fabaeformiscandona caudata, Fabaeformiscandona danielopoli, Pseudocandona compressa, Cyclocypris ovum and Ilyocypris echinata at higher quantities. Valves of Pseudocandona cf. eremita, Cypris pubera, Psychrodromus aft. olivaceus, Scottia pseudobrowniana, Cypridopsis vidua and Limnocythere inopinata were recorded at low densities only.

The subsurface samples from Lake Luanhaizi mainly revealed less diverse ostracod assemblages probably re-


sulting from the smaller size of core samples. However, in contrast to surface samples Limnocythere inopinata displayed a high abundance in subsurface samples. Fur- thermore, valves of Eucypris dulcifons, Ilyocypris cf. bradyi and/or L lacustris and Heterocypris salina were exclusively recorded in subsurface samples from Lake Luanhaizi although they are present occasionally and in low densities only.

The most striking feature of the ostracod fauna of Lake Luanhaizi is the general abundance of Candona rawsoni, CycIocypris ovum and Ilyocypris echinata in all surface and subsurface samples (Table 2).

Interestingly, males of Fabaeformiscandona caudata were recorded from the lake in the Qilian Mountains which have been found otherwise only in Canada so far (MHSCH 2000).

Another species of Fabaeformiscandona has been identified from Lake Luanhaizi that was described from Lake Erhai close to Qinghai Lake only (Y~q & MARTENS 1997; Fig. 1). Valves of both females and males of F. danieIopoli were found in the surface samples and some of the subsurface samples from Lake Luanhaizi. This finding proves that E danielopoli is not restricted to the ancient basin of Qinghai Lake as was expected earlier by YIN ~; MARTENS (1997).

4. Ecological significance of ostracods from the Qilian Mountains

Autecological data of the taxa recorded from the Qilian Mountains derive from a number of papers and the ex- tensive summarising work of MEISCH (2000). Most of the original references reviewed and cited by MHSCH (2000) and used here were not given due to space limita- tions. Refer to the reference list in MEISCH (2000) for quotation of original papers.

Candona candida C. candida inhabits a great variety of subaquatic environments ranging from the littoral and profundal zones

Fig. 1. Candona candida, ~. LV int., length 1080 IJm (SM617). Fig. 2. C. candida, Cf LV int., length 1110 IJm (SM622). Fig. 3. Candona welt- neff, RV ext., length 1130 IJm (SM599). Fig. 4. Candona rawsoni, ~. RV int., length 1040 pm (SM618). Fig. 5. C. rawsoni, C~ RV ext., length 1190 IJm (5M549). Fig. 6. Fabaeformiscandona caudata, ~. LV int., length 1190 !Jm (SM624). Fig. 7. F. caudata, C~ RV ext., length 1010 tim (SM548). Fig. 8. Fabaeformiscandona danielopoli, ~. RV ext., length 1290 pm (SM547). Fig. 9. F. danielopoli, C~ LV int., length 1200 tim (SM572). Fig. 10. Pseudocandona compressa, RV ext., length 834 pm (SM586). Fig. 11. Pseudocandona cf. eremita, juvenile LV ext., length 775 IJm (SM554). Fig. 12. Cyclocypris ovum, LV ext., length 475 ym (SM557). Fig. 13. Ilyocyprisc[ bradyi, LV int., length 997 tim (SM645). Fig. 14. Marginal ripplets of/. cf. bradyi, enlargement of posteroventral area of specimen of Fig. 13, width of cutting 490 tJm. Fig. 15. Ily- ocypris lacustris, LV int., length 840 !Jm (SM603). Fig. 16. Marginal ripplets of I. lacustris, enlargement of posteroventral area of specimen of Fig. 15, width of cutting 450 IJm. Fig. 17. Ilyocypris echinata, LV ext., length 1250 IJm (SM583). Fig. 18. I. echinata, carapace in dorsal view, length 1170 tim (SM607). Fig. 19. I, echinata, LV int., length 1210 IJm (SM 581). Fig. 20. Marginal ripplets of I. echinata, enlargement of posteroventral area of specimen of Fig. 19, width of cutting 615 !]m. Fig. 21. Cypris pubera, juvenile LV int., length 1290 !]m (SM 558). (All specimens housed in the Interdisciplinary Centre for Ecosystem Dynamics in Central Asia of the Freie Universit~t Berlin, Germany.)

Limnologica (2003) 33,280-292


Plate 2

Limnologica (2003) 33,280-292

of lakes to springs, swamps and subterranean habitats. The species is typically found in shallow water bodies but a maximum depth of 311 m was recorded in Lago Maggiore (Italy, MEISCI4 2000). The burrowing animals prefer permanent water bodies with a fine, organic-rich bottom, although juveniles are reported to be desiccation resistant (ibid.). Very abundant in Pleistocene cold-climate deposits, C. candida is clearly related to cold waters (CARBONEL et al. 1988). Males of C. Candida were found occasionally only and almost always in low numbers (MEISCH 2000). Holarctic distribution. Material from the QUian Mountains: The occurrence of Candona candida in samples from running waters and Lake Luanhaizi (Table 2) confirms the characteriza- tion of the species as rheoeuryplastic and oligothermophilic (NOCHTERLEIN 1969; MEISCH 2000). The preference of permanent water bodies is emphasised by the absence of the species from pools and the small swampy brook (Tables 1 and 2). Valves of male specimens have been collected from quiet areas of a densely vegetated fiver bed.

Candona weltneri This coldstenothermal and oligohalophilic species preferentially inhabits small seasonal or permanent water bodies such as swamps and peaty ditches although it is found in lakes as well (HmLER 1972; PmTRZEX~UK 1977; MEISCH 2000). There, C. weltneri occurs more frequently in the littoral zone than the profundal. Palaearctic distribution. Material from the Qilian Mountains: One valve of C. welmeri was recorded in a sample from the substrate- water interface of a slowly flowing river.

Candona rawsoni C. rawsoni is often present in cold and fresh to saline waters of temporary or permanent ponds (DELORME 1969). The animals tolerate comparatively high salini-


ties (up to 45%0 recorded; CURRY 1995) and low oxygen levels (as low as 2.5 mg/1; HAMMER 1986). In China the species is often recorded as C. swaini STAPHN, 1963 or C. arcina LmP~N, 1963 which are regarded as junior syn- onyms of C. rawsoni (DreXEL & PIETRZENIUK 1975). Ho- larctic distribution. Material from the Qilian Mountains: C. rawsoni is very abundant in samples from a densely vegetated brook and from Lake Luanhaizi. The species is absent from river habitats as was reported likewise by DELORME for North America (1969). It was further not found in the peaty, dystrophic waters of pools possibly due to calcite undersaturation which is not tolerated by C. rawsoni (CURRY 1995).

Fabaeformiscandona caudata This species is rarely found in the littoral zone of lakes although it was recorded from ponds and streams also. E caudata is much more typical for the sublittoral and profundal of lakes (ME~sCt4 2000). Therefore it is not often recorded and ecological information remain somewhat uncertain. Males of F. caudata are very rare and reported with certainty only from Canada so far (ibid.). Holarctic distribution. Material from the Qilian Mountains: Valves of males and females were recorded from the surface and some of the subsurface samples of Lake Luanhaizi exclusively.

Fabaeformiscandona danielopoli F. danielopoli was recorded from a single site (Lake Erhai) near Qinghai Lake up to now (Y~N & MARTENS 1997, Fig. 1). In Lake Erhai (salinity 1.05 g/l), animals were collected amongst abundant macrophytes and on sediment rich in organic detritus (ibid.). The species was only collected close to the inflowing river and thus might be rheophilic (ibid.). The lake is rather small (5 km2), shallow (mean water depth 3.9 m) and covered by ice for 100 to 129 days per year. Water temperature at the

Fig. 1. Eucypris dulcifons, RV ext., length 1100 lJm (SM630). Fig. 2. Eucypris sp., LV int., length 1270 IJm (SM621). Fig. 3. Eucypris sp., RV i nt., length 1310 tim (SM620). Fig. 4. Tonnacypris(?) sp., fragment, int., length 1250 pm (SM598). Fig. 5. Psychrodrornusaff. olivaceus, LV int., length 1490 IJm (SM609). Fig. 6. Heterocypris incongruens, LV int., length 1680 pm (SM610). Fig. 7. Heterocypris salina, RV int., length 1020 pm (SM628). Fig. 8.5cottia pseudobrowniana, juvenile RV ext., length 542 IJm (SM546). Fig. 9. Cypridopsis vidua, LV int., length 685 lJm (SM619). Fig. 10.5arscypridopsisaeuleata, LV ext., length 560 IJm (SM608). Fig. 11. Limnocythere inopinata, LV ext., non-noded form, length 548 IJm (SM597). Fig. 12. L. inopinata, LV ext., noded form, length 543 tim (SM615). Fig. 13. Paralimnocytherepsammophila, C~ LV ext., length 544 ym (SM600). Fig. 14. P. psammophila, 9. RV ext., length 563 tim (SM601). Figs. 15-23: Molluscs from the Qilian Mountains Fig. 1S. Gyraulus cf. eugyne, shell apical, max. diameter 4.83 mm, 4.25 whorls, (M 13). Fig. 16. Same specimen as in Fig. 15, umbilical. Fig. 17. Gyraulus cf. eugyne, apertural, max. height 1.28 mm, (R24). Fig. 18. Gyraulus cf. eugyne, protoconch, (R24). Fig. 19. Radix cf. peregra, height 9.8 mm, width 6.5 ram, (M6). Fig. 20. Valvata sp., juvenile shell, height 1.07 mm, width 0.93 mm, (R36). Fig. 21. Pisidium sp., RV, lenght 2.6 ram, height 2.4 mm, (R27). Fig. 22. Pisidium sp., hinge of LV, (R29). Fig. 23. Pisidium sp., hinge of RV, (R30). (All specimens housed in the interdisciplinary Centre for Ecosystem Dynamics in Central Asia of the Freie Universit~t Berlin, Germany.)

Limnologica (2003) 33,280-292


time of collection was 0-1 °C, pH was 8.1 (ibid.). The authors speculate that F. danielopoli might be endemic to the ancient Qinghai basin. Material from the Qilian Mountains: The species was also recorded from Lake Luanhaizi in the course of our study. As Lake Erhai, Lake Luanhaizi is a small, freshwater lake located at a comparable altitude (3200 m). E danielopoli was not present in any samples from running waters or pools and thus might be regarded as a typical lake dweller occurring in waters of low salinity. The species is obviously not restricted to the ancient Qinghai basin although it may have originated from the basin as was suggested by Y~y & MARTENS (1997).

Pseudocandona compressa Animals are found at shallow depth in permanent and temporary water bodies. P. compressa is a mesothermophilic and oligorheophilic species (MEISCH 2000). It has not been found deeper than 8 m and inhabits fresh and slightly saline lakes and coastal waters (ibid., BHA- TIA & SINGH 1971). Up to now recorded from Europe, Turkey, Iran, Siberia and probably N America (MEISCH 2000). Material from the Qilian Mountains: P. compressa has been found sporadically in samples from a small swampy brook and more frequently in samples from Lake Luanhaizi.

Pseudocandona eremita (VEJDOVSKY, 1882) P eremita is clearly related to underground waters, it is frequently found in wells or caves or in similar epigean habitats such as springs (MEISCH 2000). Animals found in surface waters are regarded as transported by outflow- ing underground waters. Records of the species come from eastern and southeastern Europe and Asia Minor (ibid.). Material from the Qilian Mountains: There was only one juvenile valve in surface sediments of Lake Luan- haizi sampled from a floating fen layer below the water level. Due to the lack of adult valves the specimen was identified as P. cf. eremita.

Cyclocypris ovum C. ovum is a common species in almost all types of aquatic habitats. It is often found in the littoral zone of lakes, in springs, slightly saline (up to 6.4%~, MHSCH 2000) and temporary as well as in swampy waters. Cor- respondingly, the species tolerates low oxygen levels (MEZQUITA et al. 1999b). In the Alps, C. ovum was collected at 2500 m asl (GRAF 1938). Holarctic distribution. Material from the Qilian Mountains: Valves of C. ovum were found in all samples from Lake Luanhaizi at high densities. Surprisingly the species was not found in pools and with one exception not in running water habitats.

llyocypris bradyi I. bradyi prefers slowly flowing, cooler waters of springs and streams but is also found in ponds and swamps (VICTOR et al. 1981; CURRY 1999; MEZQUITA 1999b). Animals are poor swimmers and burrow or crawl among aquatic plants and organic debris (KOTLIA et al. 1998). They are able to tolerate low O2 concentra- tions of about 3 rag/1 (MEZQUITA 1999b). The animals recorded in lakes are usually reported as transported by rivers or from nearby springs. Holarctic distribution. Material from the Qilian Mountains: See L lacustris (below).

llyocypris lacustris There are only few records of I. lacustris from several prealpine lakes in Europe (LOFFLER 1975), from a site in Saxony-Anhalt (unpubl. data, R. FUHRMANN & H. JANZ), from a river in eastern Mongolia (SARS 1903) and from late Pleistocene permafrost deposits of the Bykovsky Peninsula (Laptev Sea) in Siberia (as/. cf. lacustris, unpubl. data L. SCHIRRMEISTER & S. WETTERICH). Records derive from lakes or lake deposits mainly. Living animals were found at 30 m depth in Lake Constance whereas valves and empty carapaces occurred within a depth range of about 5 to 145 m (LOFFLER 1969). Material from the Qilian Mountains: L cf. bradyi and I. Iacustris were not distinguished for each sample due to their similarities in shape and size although SEM analyses revealed the presence of both species on the base of the pattern of the marginal ripplets (see chapter 3). I. cf. bradyi and/or I. lacustris were often found in samples from brooks and rivers in high numbers. They are partly abundant in samples from pools but generally rare in samples of Lake Luanhaizi if present at all.

Ilyocypris echinata The species is recorded from the Qaidam Basin (SUN et al. 1995) in the south of the Qilian Mountains as well as from the Tibetan Plateau (HUANG 1985) and from deposits of freshwater or oligohaline environs of the ad- joining Zoige region (WANG & ZHU 1991). Material from the Qilian Mountains: There was no record of the species from any of the samples from running water or pool habitats. Instead, valves of L echinata were abundant in all surface and subsurface samples from Lake Luanhaizi. In contrast to species such as I. bradyi or I. gibba which are related to flowing waters (CURRY 1995; DELORME 1969; VICTOR et al. 1981) I. echinata may be regarded as a typical lake dweller.

Cypris pubera O.E MULLER, 1776 This animal clearly prefers temporary and permanent shallow water bodies such as ponds, pools, ditches, slow rivers and the littoral zone of lakes (MEISCH 2000). C. pubera was not recorded from the profundal zone of

Limnologica (2003) 33,280-292

lakes. Larvae develop to sexual mature adults within 4 to 6 weeks. In contrast to juvenile and adult animals, eggs are resistant to desiccation (ibid.). Holarctic distribution. Material from the Qilian Mountains: Two juvenile valves were recorded from surface sampling of the littoral zone of Lake Luanhaizi. The rareness of the species may result from the mesothermophilic to polythermophilic character of the species (NI~CHTERLEIN 1969; HILLER 1972; MEISCH 2000).

Eucypris dulcifons This species was found only fossil in Neogene to Qua- ternary deposits from Germany, Turkey, western Siberia and northwestern China up to now (FREELS 1980; MIS- CHKE 2001). In consideration of accompanying taxa, E. dulcifons inhabits lakes as well as small shallow water bodies (DmBEL & PIZTRZENIUK 1975). Material from the Qilian Mountains: Few valves of E. dulcifons were found in samples from a small swampy brook and in a single sample from Lake Luanhaizi.

Psychrodromus olivaceus (BRADY & NORMAN, 1889) The oligothermophilic species clearly prefers waters flowing from springs or ponds which are fed by springs (PIETRZENIUK 1985; MEISCH 2000). Animals found in ponds or lakes were attributed either to subaquatic springs or drift form nearby springs (MEISCH 2000). Records from Europe and Asia Minor so far (ibid.). Material from the Qilian Mountains: One valve of Psychrodromus aft. olivaceus was recorded from a surface sample of Lake Luanhaizi. The specimen from the Qilian Mountains differs from Psychrodromus olivaceus by a more rounded posteroventral margin (Plate 2).

Heterocypris incongruens Shallow seasonal pools and small permanent water bodies with clayey substrate lacking any macrophytes were preferentially inhabited by H. incongruens (HILLER 1972; MEISCH 2000). In addition, animals were frequently recorded from slowly flowing areas of brooks and rivers, from springs, rockpools and strongly eu- trophic ponds with low oxygen levels (ibid.). Animals and eggs of H. incongruens are desiccation resistant and the latter even tolerate freezing (MEIscI-I 2000). The highest recorded salinity of host water is 20%o (ibid.). The cosmopolitan species was found at an altitude of 2400 m asl in the Alps and at 2690 m asl in the Caucasus (ibid.). Material from the Qilian Mountains: Abundant valves of H. incongruens were recorded from some of the brook and river samples and from the shallow oxbow pool (Tables 1 and 2). In accordance with the affinity of the species to seasonal and small permanent water bodies there is no record from Lake Luanhaizi.


Heterocypris salina H. salina is a good swimmer and inhabits small, shallow water bodies (GOTTNER 1980). The species occurs in a wide range of salinities including pure freshwater habitats but an optimum salinity of 5-10%o is proposed (MEISCH 2000). According to GOTTNER (1980), the upper salinity limit for reproduction occurs at about 20-25%o, much lower than the highest recorded salinity at which specimens of H. salina have been found. Animals may occur even in pure freshwater habitats, then in low con- centrations (HAMMER 1986). Larvae reach sexual maturity within 40 days only (CARBONEL et al. 1988). Holarc- tic distribution. Material from the Qilian Mountains: Valves of H. salina were found in a few samples from the small swampy brook and Lake Luanhaizi as well. In the former the species occurred in higher densities but in Lake Luanhaizi only rare valves were recorded.

Scottia pseudobrowniana This species is often related to swampy or spring environments (MEISCH 2000). It inhabits the waters flowing from springs, ponds and peaty swamps. S. pseudobrowniana displays a distinct affinity to organic matter, it even occurs at semi-terrestrial sites in wet leaf litter and moss cushions (MEIsCH 2000). Probably holarctic distribution. Material from the Qilian Mountains: Only one juvenile valve and a juvenile carapace were found in a surface sample from Lake Luanhaizi. The occurrence of these valves within surface mud from a floating fen layer some centimetres below the water level of Lake Luan- haizi somewhat resembles the finding of the species from a ,floating fen soil' of a lake in Romania described by DANIELOPOL & VESPREMEANU (1964).

Cypridopsis vidua C. vidua is adapted to a wide variety of habitats, it prefers densely vegetated, shallow, permanent water bodies, such as the littoral zone of small and large lakes, ponds, springs and slow flowing rivers (BEYER & MEISCH 1996). Animals are rapid swimmers, eggs are desiccation resistant (GONTHER 1986; MEZQUITA et al. 1999a). Development of larvae starts in spring and is very fast, a second generation reaches sexual maturity already in September/October (MEISCH 2000). Cos- mopotitan distribution. Material from the Qilian Mountains: Rare valves of C. vidua were collected from a densely vegetated meadow pool and from some of the surface and subsurface samples from Lake Luanhaizi. Although abundant at lower altitudes in northwestern China (MISCHKE 2001; MTSCHKE & SCI4UDACK 2001), the development of the polythermophilic species (NUCHTERLEIN 1969; HILLER 1972) might be limited by the high elevation of the sampling sites in the Qilian Mountains.

Limnologica (2003) 33,280-292


Sarscypridopsis aculeata (COSTA, 1847) S. aculeata seems to prefer slightly saline water bodies of both inland and coastal type (HOLMES 1996). The species is rare in pure freshwater but very abundant in coastal rockpools (MEISCH 2000). Development of larvae is very rapid, sexual maturity is reached within about 30 days, 3 to 4 generations were produced within June and November in rockpools at the Baltic Sea coast. A salinity optimum of 17%o was recorded for these populations (GANNING 1971). Cosmopolitan distribution. Material from the Qilian Mountains: Only two valves of S. aculeata were found in a densely vegetated brook. The rareness of the species probably reflects its preference of meso- to polyhaline conditions.

Limnocythere inopinata L. inopinata occurs in a wide variety of habitats ranging from the shallow littoral zone of lakes to small ponds and from freshwater to highly alkaline water bodies (GEIGER 1994). Although mainly found in shallow water bodies, the species is also reported from the profundal zone. HILLER (1972) reported the occurrence of L. inopinata down to a depth of 64 m in the Baltic Sea. Inter- estingly, species of Limnocythere are among the few taxa which are reported from the open-water zone of lakes in America (HOLMES 1997; VANCE et al. 1997). L. inopinata tolerates high chloride levels and occurs in waters that are enriched in Na-HCO3-CO3, but depleted in Ca (HOLMES et al. 1999). A maximum abundance is reported for a salinity range of 3-9%o (KEMPF 1986, cit. in HOLMES et al. 1999). The species is unable to swim and prefers calm waters rich in macrophyte debris on the lake bottom (MHSCH 2000). Maximum abundance of adults is clearly restricted to the summer months (in Central Europe, HILLER 1972). L. inopinata is distributed in the holarctic realm and was probably introduced to S-Africa (MEISCH 2000). Material from the Qilian Mountains: Although regarded as polythermophilic (HILLER 1972; MEISCH 2000), valves of L. inopinata were frequently found in the brook samples and in samples from Lake Luanhaizi yielding valves in higher densities mainly. It was not found in samples from river habitats and also not present in pool samples. Valves from the Qilian Mountains are usually not noded but sample 19 contained noded forms also (Plate 2). However, the ecological significance of noding in L. inopinata is not known up to now.

Paralimnocythere psammophila The species occurs at sites in the littoral zone of lakes where higher vegetation is lacking (MEISCH 2000). Ani- mals were generally found at low numbers (ibid.). P. psammophila was recorded from Germany, France, Spain, Russia and the Ukraine so far (MARTENS 1992; MEISCH 2000).

Material from the Qilian Mountains: Valves of two female and one male specimens were recorded from a densely vegetated meadow pool as the only site among those investigated in the course of this study.

5. Conclusion Female and male valves of Fabaeformiscandona danieIopoli, so far only reported from Lake Erhai close to Qinghai Lake (YIN & MARTENS 1997), were found in samples from Lake Luanhaizi in the Qilian Mountains. The species was not found in samples from running water habitats or shallow pools and thus may be regarded as a typical lake-dwelling species. Likewise, Ily- ocypris echinata was not found in brook, river or pool samples but in samples from Lake Luanhaizi and seems to be restricted to lake environments also.

In accordance to its coldstenothermal characteristic, female and male valves of Candona rawsoni were very abundant in samples from brooks and Lake Luanhaizi. Al- though usually occurring in a variety of aquatic habitats, Cyclocypris ovum displayed a strong preference of lake environments in samples from the Qilian Mountains. As expected, Heterocypris incongruens was found in brook, river and pool samples but not in samples from Lake Lu- anhaizi. Few female and male valves of the rarely recorded species Paralimnocythere psammophila were collected from a shallow meadow pool. Notably, usually rare males of Candona candida were recorded from the substrate of a densely vegetated river. Furthermore, males of Fabae- formiscandona caudata which have been recorded with certainty from Canada so far were collected from Lake Luanhaizi in the course of this study. Apart from the frequent occurrence of male valves in populations of Can- dona rawsoni, Fabaeformiscandona caudata and F. danielopoli, female valves have been found exclusively probably reflecting the advantage of parthenogenetic populations to colonize new habitats rapidly and to sustain in water bodies of harsh and fickle environments.

The occurrence of Candona rawsoni, Fabaeformis- candona caudata, E danielopoli, IIyocypris echinata and I. Iacustris at high-altitude sites of the Qilian Mountains which may be characterised by a mean July air temperature of 13.4 °C (Babaosi station near Qilian town at about 2800 m asl, Observatory 1963, Fig. 1) and their absence from freshwater lakes of the Gobi desert (e.g., Lake Bosten, MISCHKE & SCHUDACK 2001) stresses the impor- tance of factors related to altitude such as summer temperature and duration of ice cover with respect to ostracod biogeography. Correspondingly, polythermophilic taxa such as Cyprideis torosa, Darwinula stevensoni, Herpetocypris chevreuxi and Ilyocypris salebrosa, all common at sites of the Gobi desert (e.g. MlSCHKE & SCHUDACK 2001; PENG et al. 1998; WONNEMANN et al. 1998) about 2000 m lower than those presented here,

Limnologica (2003) 33,280-292


were not found in water bodies of the Qilian Mountains. However, polythermophilic species such as Limno- cythere inopinata, Cypris pubera and Cypridopsis vidua (N~CHTERLEIN 1969; HILLER 1972; MEISCH 2000) were recorded from the high altitude, cold environment of the sampled region (2900 m to 3570 m asl). Thus, palaeocli- mate interpretation with respect to temperature based on the presence of polythermophilic ostracod species in fossil assemblages should be dealt with caution.

Appendix: Molluscs from the Qilian Shan Four mollusc taxa were recorded in the surface and snb- surface samples from the Qilian Mountains only (see Plate 2):

Gyraulus cf eugyne MEIER-BROOK 1983 Radix cf. peregra O.F. MI~ILLER 1774 Valvata sp. Pisidium sp.

Identification of molluscs is based mainly on GLOER & MEIER-BROOK (1998) and MEIER-BROOK (1983). The documented taxa are holarctic and with the exception of Val- vata sp. typical representatives of temporary water bodies. Valvata is usually preferring permanent water bodies.

The samples from the Qilian Mountains contained only few specimens of Valvata sp., occurring exclusively in some of the subsurface samples from Lake Luan- haizi and the small swampy brook (samples 3, 6, 7; Tablel). Fragments of GyrauIus were found at the latter position too (samples 4 and 7) whereas sediments of Lake Luanhaizi yielded shells of Gyraulus cf eugyne in high numbers. Shells of Radix cf. peregra were documented from various habitats including swampy meadow pools (sample 12), branches of the Babao River (samples 13 and 15), the shallow oxbow pool (sample 14) and Lake Luanhaizi (samples 17, 19, 21, 23, 25, 27). Finally, shells of Pisidium were recorded in all samples from Lake Luanhaizi and in addition in a sample from a small bed of the Babao River (sample 15).

Acknowledgements Burkhard Scharf made valuable suggestions that helped to improve our paper greatly. Funding was provided by the Deutsche Forschungsgemeinschaft (DFG, Grant No. KU 534/2-1) and the Deutscher Akademischer Austauschdienst (DAAD, Gradu- ate Fellowship to U.H., Grant No. D/01/01075). Both sources of funding are gratefully acknowledged.

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