PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 125(1):000–000. 2012. Two new species of Potamothrix (Oligochaeta: Tubificinae) from plateau lakes of Yunnan Province, southwest China
Yongde Cui and Hongzhu Wang* (YDC, HZW) State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China, e-mail: [email protected]
Abstract.—Two new species of Potamothrix (Oligochaeta: Tubificinae), P. rhytipeniatus, new species and P. aductus, new species, are described from Fuxian Lake and Xingyun Lake of Yunnan Province, southwest China. Potamothrix rhytipeniatus differs from congeners by its wrinkled penis surface and vasa deferentia entering the atrium subapically. Potamothrix aductus is distinguishable from all congeners by lacking a spermathecal duct. Hitherto, 31 species of freshwater oligochaetes have been recorded from Yunnan Province, including seven endemic species from plateau lakes.
Keywords: endemic species, oligochaete morphology, plateau lakes, Tubificinae
The existence of unique fauna in common palaeolake in the early Holo- ancient lakes of Yunnan Province, south- cene. They were isolated in the middle west China has been recognized through Holocene Epoch, but a water course, several studies (Wang 1988, Yang & Chen Gehe River, remains, through which 1995, Sket 2000). However, our knowl- Fuxian Lake receives water from Xin- edge of freshwater oligochaetes in these gyun Lake (Nanjing Institute of Geogra- lakes is poor; only an aberrant bran- phy & Limnology 1990). For the main chiobdellidan species was reported from physico-chemical parameters of the two Erhai Lake (Liang 1963). During the lakes, refer to our three previous accounts limnological investigation of lakes in this (Cui et al. 2008, Cui & Wang 2008, 2009). province in 2002–2003, a number of Lake sediment samples were collected oligochaete samples were collected. In with a weighted Petersen grab (16 cm2)and four previous accounts (Cui & Wang processed through a 250 mm sieve. Large 2005, 2008, 2009, Cui et al. 2008), 29 worms were sorted manually in a white species, belonging to 2 families and 14 porcelain dish, and small ones were sorted genera, were reported on the basis of the under a dissecting microscope. Specimens collected material. As a serial study, the werepreservedin10% formalin. present paper gives the description of two Preserved specimens were examined first new species of Potamothrix (Oligochaeta: in temporary glycerine mounts, then Tubificinae) from two plateau lakes. stained with borax carmine, dehydrated in an alcohol series, cleared in xylene, and Materials and Methods mounted in Canada balsam. Measure- ments of body and chaetae were made Located in the Yunnan-Guizhou Pla- from glycerine mounts. Other observations teau in southwest China, Fuxian Lake were made on the permanent mounts. and Xingyun Lake originated from a Drawings were made using a camera lucida. Types and other specimens are * Corresponding author. deposited in the Institute of Hydrobiology
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Fig. 1. Potamothrix rhytipeniatus. A, dorsal pectinated chaeta from VIII; B, dorsal bifid from VI; C, ventral chaeta from IV; D, spermathecal chaeta; E, lateral view of male ducts in segments X–XI; F, G, penes of two paratypes.
(IHB), Chinese Academy of Sciences 5 m, bottom temperature 16.1uC, dis- (CAS), Wuhan, China. Abbreviations used solved oxygen at bottom 7.6 mg/L, total in the figures are: Roman numerals 5 nitrogen in water 2.960 mg/L, total segment number; at 5 atrium; mu 5 phosphorus in water 0.129 mg/L, fine silt; muscle; pe 5 penis; pr 5 prostate gland; 7 Apr 2003, coll. Y. Cui. ps 5 penial sac; sa 5 spermathecal Paratypes.—IHB YAN 20030405b, e, k, ampulla; sc 5 spermathecal chaeta; scs 5 mature specimens mounted in Canada spermathecal chaeta sac; sf 5 sperm funnel; balsam, stained with borax carmine, three sz 5 spermatozeugmata; vd 5 vas deferens. specimens from type locality. Other materials.—IHB YAN 20030405a, Systematics c, d, f–j, m, o–s, mature specimens mounted in Canada balsam, stained with borax Class Clitellata carmine, 14 specimens from type locality. Family Naididae Etymology.—The specific name ‘‘rhyti- Subfamily Tubificinae peniatus’’ is Greek for ‘‘rhytis penis’’ and Genus Potamothrix Vejdovsky´ & Mra´zek refers to penes with wrinkly surface. (1902) Description.—Thirteen complete speci- Potamothrix rhytipeniatus, new species mens 4.0–8.7 mm in length (Holotype: Fig. 1 4.2 mm), 24–46 segments (Holotype: 24). Holotype.—IHB YAN 20030405l, ma- Diameter at XI 0.5–0.6 mm (Holotype: ture specimen mounted in Canada bal- 0.5 mm). Prostomium conical. Clitellum sam, stained with borax carmine. inconspicuous. Type locality.—Xingyun Lake (24u189010N, Dorsal chaetae (0)1–4 hairs and 2–4 102u479580E), eastern Yunnan, China; depth bifids per bundle, hairs slender, without
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serration, 320–380 mm long anteriorly, whereas that in most penes-possessing and 280–325 mm long posteriorly; bifids congeners is smooth. Secondly, its vasa (Fig. 1A, B) usually pectinated, 50–62 mm deferentia enter the atria subapically, long, 2.0–2.5 mm thick, with 2–3 fine whereas those of other species join the intermediate teeth, upper prong slightly atria apically. Potamothrix rhytipeniatus longer and thinner than lower or equally appears closely related to P. cekanovska- long. Ventral chaetae (Fig. 1C) anteriorly jae Finogenova 1972 and P. manus 3–7 per bundle, 70–80 mm long, 2.0– Finogenova 1976 from the Caspian Sea 2.5 mm thick, upper prongs conspicuously (Finogenova & Poddubnaja 1990) in the longer and thinner than lower, posteriorly respect that all of them have bipartite 2–3 per bundle, 60–65 mm long, 1.8– atria without prostate glands. However, 2.2 mm thick. Spermathecal chaetae the atria of the new species is conspicu- (Fig. 1D) one per bundle in mid-X, ously short, only one-fifth to one-quarter entally embedded in glandular sac, 70– the length of atria of the other two 96 mm long, 2.5 mm thick, ental part species. In addition, the new species has curved and ectal part grooved. Penial hairs and pectinate chaetae, whereas its chaeta absent. Male pores paired in line two allies have dorsal bifids only. With with ventral chaetae, posterior to middle regard to the relatively short atria, the of XI. Spermathecal pores paired in line new species shows some affinity to P. with ventral chaetae in mid-X, immedi- bavaricus (O¨ schmann 1913) and P. scler- ately anterior to spermathecal chaetae. openis Cui & Wang 2005. However, the Pharyngeal glands in II–III. Chlorago- ratio of vasa deferentia to atria and the gen cells from VI onwards. No coelomo- shapes of the atria are different among cytes. Male genitalia (Fig. 1E) paired. them. Specifically, the ratio of measure- Vasa deferentia (Fig. 1E, vd) very short, ments of the vasa deferentia to atrium are 25–40 mm long and 12–24 mm wide, 1:18 to 1:23 and bipartite for P. rhytipe- entering atrium subapically. Atrium niatus; 1:8 to 1:9 and tripartite for P. (Fig. 1E, at) 580–730 mm long, 40–80 mm bavaricus (Timm 1970, Finogenova & wide, tubular and bipartite, proximal part Poddubnaja 1990), and 1:3 and homoge- (two-fifths of total atria) with densely nous for P. scleropenis (Cui & Wang granular inner layer, distal part sparsely 2005). granulated. Prostate gland absent. Penis (Fig. 1E–G, pe) cylindrical and tapering Potamothrix aductus, new species ectally, surface folded, plici-formed, 76– Fig. 2 150 mm long, 56–100 mm wide basally and Holotype.—IHB YAN 20020812a, whole- 26–58 mm wide ectally. Penial sac mounted specimen. (Fig. 1F, G, ps) 100–150 mm long, 58– Type locality.—East of Gushan Island 86 mm wide, with outer muscular layer (24u249050N, 102u529450E) in Fuxian Lake, 7–17 mm thick. eastern Yunnan Province, China; depth Spermathecae ampullae broken (all 78 m, bottom temperature 15.9uC, dis- collected specimens), with numerous sper- solved oxygen at bottom 9.6 mg/L, total matozeugmata in coelom. nitrogen in water 0.155 mg/L, total phos- Distribution and habitat.—Known only phorus in water 0.023 mg/L, fine clay; 8 from type locality, Yunnan Province, Aug 2002, coll. Y. Cui and X. Liu. China. Freshwater lake, 5 m deep, water Paratypes.—IHB YAN 20020812n; one temperature about 16uC, fine silt. specimen from type locality, IHB YAN Remarks.—This species has two distin- 20020808b, one specimen from southeast guishing characters. First, the penial of Niumo (24u289400N, 102u529310E) in surface of the new species is wrinkly, Fuxian Lake, eastern Yunnan, China;
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Fig. 2. Potamothrix aductus. A, hair; B, distal end of dorsal bifid from VI; C, distal end of dorsal pectinate chaeta from VIII; D, distal end of dorsal bifid from III; E, distal end of ventral chaeta from V; F, spermathecal chaeta; G, lateral view of male ducts in segments X–XII; H, spermatheca. depth 108 m, bottom temperature 14.0uC, segments). Prostomium conical. Clitellum dissolved oxygen at bottom 6.6 mg/L, inconspicuous. total nitrogen in water 0.184 mg/L, total Dorsal chaetae (Fig. 2C, D) of II–VI phosphorus in water 0.023 mg/L, fine bifid only, 7–8 per bundle, 100–144 mm clay; 8 Aug 2002, coll. Y. Cui and X. Liu. long, 3.0–4.0 mm thick, upper prong Other materials.—IHB YAN 20020812c, longer and thicker than lower. From VII one specimen from the same locality onwards, dorsals 1–6 hairs and 3–6 bifids with paratypes, IHB YAN 20030209b, per bundle; hairs (Fig. 2A) feathered, one specimen from northeast of Dashazui 340–420 mm long, 2.8–3.2 mm thick (24u229580N, 102u499490E) in Fuxian basally; bifids (Fig. 2B, C) pectinate, Lake, eastern Yunnan, China; depth 108–140 mm long, 3.0–4.0 mm thick, with 87 m, bottom temperature 13.7uC, dis- 0–2 intermediate teeth, upper prong solved oxygen at bottom 5.8 mg/L, total slightly longer or as long as, and thinner nitrogen in water 0.229 mg/L, total than lower. Ventral chaetae (Fig. 2E) phosphorus in water 0.022 mg/L, fine bifid, 6–8 per bundle anteriorly, 140– clay; 14 Feb 2003, coll. Y. Cui. 150 mm long, 3.0–3.5 mm thick; 2–4 (5) per Etymology.—The specific name ‘‘aduc- bundle in postclitellar segments, 80– tus’’ is Latin for ‘‘no ducts’’ and refers to 110 mm long, 2.4–3.2 mm thick, with the absence of a spermathecal duct. prongs similar to those of dorsals in II– Description.—Two complete specimens VI. Spermathecal chaetae (Fig. 2F, G, sc) 9.2–11.8 mm long (Holotype: 9.2 mm), one per bundle in middle to posterior part diameter at XI 0.80–0.96 mm (Holotype: of X, entally embedded in glandular sacs, 0.96 mm), 49–68 segments (Holotype: 49 about 180–220 mm long, 4.0 mm thick,
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with ectal parts grooved and contorted. moldaviensis Vejdovsky´ & Mra´zek 1902, Penial chaetae absent. Male pores paired in was revised by Holmquist (1985) and line with ventral chaetae of mid-XI. Sper- Finogenova & Poddubnaja (1990). Alto- mathecal pores paired in line with ventral gether, 18 species were previously known chaetae, posterior to middle of X, immedi- and mainly distributed in the Holarctic ately anterior to spermathecal chaetae. region (Brinkhurst & Jamieson 1971, Pharyngeal glands in II–III. Chlorago- Hrabe 1981, Brinkhurst & Wetzel 1984, gen cells from VI onwards. No coelomo- Finogenova & Poddubnaja 1990, Sˇporka cytes. Male genitalia (Fig. 2G) paired. 1994, Milbrink 1999, Milbrink & Timm Vasa deferentia (Fig. 2G, vd) short, 40– 2001). Through recent investigation of 50 mm long, 13–22 mm wide, entering plateau lakes, four species of Potamothrix atrium apically. Atrium (Fig. 2G, at) 580– (Oligochaeta: Tubificinae), P. rhytipenia- 640 mm long, 30–75 mm wide, tubular and tus, P. aductus, P. scleropenis Cui & Wang rather homogenous, with thin outer mus- 2005 and P. bedoti (Piguet 1913), are cular layer and thick inner epithelium. known from Fuxian Lake and Xingyun Prostate glands (Fig. 2G, pr) small, 90– Lake of Yunnan Province, southwest 110 mm long, maximum 62–75 mm wide, China. They are the lowest-latitude mem- attaching to ental atrium. Soft parts of bers of the genus hitherto known. More- penis (Fig. 2G, pe) small, 62–80 mm long, over, studies show that Potamothrix is 66–75 mm wide basally and 26–44 mmwide unexpectedly species-rich in plateau lakes ectally, cylindrical and tapering ectally, of Yunnan Province, especially in Fuxian enclosed in penial sacs. Penial sac Lake where three species were recorded, (Fig. 2G, ps) 90–110 mm long, 54–84 mm and the specific identities of another two wide, with muscular layer 4–6 mm thick. species of Potamothrix are still in doubt Spermathecae (Fig. 2H) without duct, and need further confirmation from more oval ampullae (Fig. 2H, sa) 440–490 mm specimens. With regard to the total long, maximally 250–280 mm wide. Sper- findings of oligochaetes from Yunnan, matozeugmata (Fig. 2H, sz) 2–4 in each we have reported 31 species, including ampulla, about 460–710 mm long. seven endemic forms. To increase our Distribution and habitat.—Known only faunistic knowledge about Chinese oligo- from Fuxian Lake, Yunnan Province, chaetes, more studies in plateau waters China. Freshwater lake, 70–110 m depth, should be carried out. water temperature less than 16uC, fine clay. Remarks.—This species is easily distin- Acknowledgments guishable from all congeners by lacking a spermathecal duct and the contorted ectal WeareindebtedtoDrs.XueqinLiu, parts of the spermathecal chaetae. Jianhui Qin and Sixin Li (Institute of With regard to the homogenous atria Hydrobiology, Chinese Academy of Sci- with prostate glands, the new species is ences) for their kind assistance with the similar to Potamothrix scleropenis Cui field work. Special thanks are due to Profs. &Wang2005fromYunnanProvince, Yanling Liang (Institute of Hydrobiology, China. However, P. scleropenis differs Chinese Academy of Sciences) and Tarmo from this new species by having a penial Timm (Centre for Limnology, Tartumaa, sheath and penial chaetae. Estonia) for their inspired comments on the manuscript. Financial support was Conclusions provided by National Natural Science Foundation of China (No. 30470205) and The genus Potamothrix, established by the Knowledge Innovation Program of the (Vejdovsky´ & Mra´zek 1902) for P. Chinese Academy of Sciences.
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