A new record of Brachionus from China(Rotifera:Monogononta:Brachiondae)

JIN Liwen, WU Bo, LUO Yongting, WANG Quanxi

(College of Life and Environment Sciences,Shanghai Normal University,Shanghai 200234,China)

A:dorsal view. B:ventral view;fu:fulcrum,man:manubria,ra:rami,un:unciFigure 1 Brachionus kostei A:lorica dorsal.B:lorica ventralC:specimen under the LM.D:specimen with egg

Description:Brachionuskosteidorsal lorica with six pointed occipital spines and two slightly convoluted foot-opening spines(Shiel 1983,Segers 2007).The anterior lateral and the median spines are relatively long,while the anterior submedian spines are hardly evident(Fig.1 A-D).The dorsal lorica is patterned with several facets,one triangular frontal panel below median spines,two unpaired pentagonal facets in the middle of lorica and two lateral quadrangular panels(Fig.1A).Two blunt spines exist at the ventral anterior margin forming a medial U-shaped sinus which leads two cuticular ridges with granular borders(Fig.1B,D).The ridges extends slightly into the middle of lorica,ending in a panel enclosed by two lateral convex and three small concave arches(Fig.1B).

The trophi[1]ofBrachionuskosteibelongs to the malleate type(Fig.2 A,B).It is symmetrical and composed of paired manubria,rami and unci,and an unpaired fulcrum.The manubrium is close to triangular.Fulcrum is short,rod-shaped and quite thick in the lateral view.Rami very broad,triangular,inner margin smooth without teeth.Unci broad,with 5 striaes,and there are molars-like ossiculums at the proximal side.

Figure 2 Trophi of Brachionus kostei(under SEM)

Measurement:Lorica length 102.2±12.71 μm(n=15),lorica width 77.63±11 μm(n=15)(Tab.1).

Table 1 measurement of lorica

n:number of specimen,AVG:Average,S:Standard Deviation

Ecology:The samples were collected from several places in Shanghai in temperate zone.It is found in Suzhou River,Jinweicheng River and a puddle in Shanghai Normal University.The pH value of the sampling sites is 7.4-8.0,and temperature of water is 9-28℃.Being found in both spring and summer,the assemblage withBrachionuskosteiincluded:Anuraeopsisfissa,Asplanchnabrightwelli,Brachionusangularis,B.budapestinensis,B.calyciflorus,B.caudatus,B.falcatus,B.forficula,B.havanaensis,B.quadridentatus,Lecanebulla,L.luna,Trichocercasimilis,Polyarthrasp..

Discussion:This species is new recorded amongBrachionusin China,and is detected from several samples indifferent habitats in both spring and summer.There’re some differentiae in comparing with the original description[2].This species is smaller in the measurement,lorica length 102.2±12.71 μm(n=15),width 77.63±11 μm(n=15),while Shiel′s recordis lorica length 108-140 μm,lorica width 110-115 μm.Foot-opening spines convoluted but is not remarkable as Shiel′s description.This may becaused by the environmental aspects.

Brachionuskosteiwas considered as endemic to Australia[3],but it was also found in northern and northeast Thailand[4-5].The distribution ofBrachionuskosteiranges from tropical region of south Asia and Australia to temperate region of east Asia,which shows evidence of the relation between the rotifer faunas of Australian,Oriental and Palaearctic.

参考文献:

[1] DE SMET W H.Preparation of rotifer trophi for light and scanning electron microscopy[J].Hydrobiologia,1998,387/388:117-121.

[2] SHIEL R J.The genusBrachionus(Rotifera:Brachionidae) in Australia,with a description of a new species[J].Proc R Soc Vict,1983,95(1):33-37.

[3] SEGERS H.Annotated checklist of the rotifers(Phylum Rotifera),with notes on nomenclature,taxonomy and distribution[J].Zootaxa,2007,1564:3-14.

[4] SEGERS H,Wirawan K& La-orsri S.Biodiversity of freshwater microfauna in the floodplain of the River Mun,Northeast Thailand:the Rotiferamonogononta[J].Hydrobiologia,2004,515:1-9.

[5] LA-ORSRI S.Rotifera of some freshwater habitats in the floodplain of theRiver Nan,northern Thailand[J].Hydrobiologia,1998,387/388:27-33.