Check List 10(2): 292–298, 2014 © 2014 Check List and Authors Chec List ISSN 1809-127X (available at www.checklist.org.br) Journal of species lists and distribution Rotifers (Rotifera: Eurotatoria) from wetlands of Majuli PECIES S – the largest river island, the Brahmaputra river basin of OF upper Assam, northeast India ISTS L B. K. Sharma North-East ern Hill University, Department of Zoology, Freshwater Biology Laboratory, Permanent Campus, Umshing, Shillong - 793 022, Meghalaya, India. E-mail: [email protected] Abstract: Plankton samples collected from the floodplain lakes (beels) and small wetlands (dobas or dubies) of Majuli, sixthe Palaeotropicallargest river island and one of theHolarctic world speciesand a unique are biogeographically fluvial landform interesting of the Brahmaputra elements; oneriver species basin ofis anortheast new record India, to Indiareveal while 131 Rotiferaseveral speciesspecies arebelonging of regional to 33 interest. genera Theand rotifer17 families. fauna Two is predominantly Australasian (Australiantropical indicating & Asian), high four richness Oriental, of cosmopolitan species and important contribution of tropicopolitan and pantropical species. Lecanidae > Lepadellidae are the most diverse families; Lecane Lepadella Bory de St. Vincent > Trichocerca Lamarck are species-rich genera. The and rare occurrence of species of Nitzsch Brachionus > Pallas, Keratella Bory de St. Vincent, Filinia Bory de St. Vincent, Asplanchna Gosserotifers and communities Polyarthra areEhrenberg characterized in particular. by several small-sized littoral-periphytic taxa, paucity of the Brachionidae in general Introduction small wetlands (dobas or dubies) of Majuli River Island Majuli, commonly called ‘Majoli’ (land in the middle of (Long.: 93°–95° E, Lat.: 25°–27° N), upper Assam (Figure two parallel rivers) is the largest river island of the world, 1). Sampled beels are indicated in Table 1. situated in the upper reaches of the river Brahmaputra in The collections were made by towing plankton net (# Upper Assam region of northeast India. It is an interesting 50 µm) and were preserved in 5% formalin. All the samples were screened, rotifers were isolated and mounted in arose from the Brahmaputra basin after a catastrophic polyvinyl alcohol-lactophenol mixture, and observed with region made up purely of fluvial geomorphology which Leica (DM 1000) stereoscopic phase contrast microscope level alluvial plain. It is, therefore, a unique geographical occurrenceflood in 1750 and and a result in course of the ofdynamics time turned of this into vast a riverflat- fitted with an image analyzer. The different taxa were cultural heritage site is alarmingly shrinking due to erosion, identified based on Koste (1978), Segers (1995) and withsystem. about This 33% hotspot of its for landmass flora and eroded fauna in and the an latter important half of Sharma and Sharma (1999, 2000, 2008). The reference 20th century; if this trend continues this island may cease Freshwatercollections (NEHU/BKS/Assam-Majuli:Biology Laboratory, Department 1 - NEHU/BKS/ of Zoology, to exist on the world map. Majuli is dotted with wetlands North-EasternAssam-Majuli: Hill180) University, are deposited Shillong. in the holdings of ranging from small dobas or dubies lakes (beels) which contribute notably to its socio-economy Results to several floodplain One hundred and eighty samples collected from Majuli The present study, a part of our pioneering limnological River Island reveal a total of 131 species, belonging to 33 surveythrough oftheir the significant Majuli River fishery Island, potential. documents faunal genera and 17 families (Table 2). Lepadella vandenbrandei diversity of planktonic and littoral-periphytic Rotifera. Gillard (Figure 2 A) is a new record from India. Brachionus This study merits special biodiversity value in light of the dichotomus reductus B. kostei Shiel (Figure 2 C) are Australasian species, while Keratella river basin to be one of the globally rich habitats for edmondsoni AhlstromKoste (Figure & Shiel 2 D) (Figure, Lecane 2 blacheiB) and hypothesis on the floodplain lakes of the Brahmaputra (Figure 2 E), L. niwati We present here a list of rotifer species examined from (Figure 2 F), and Filinia camasecla Myers (Figure 2Berzins G) are planktonRotifera (Sharma samples 2005; collected Sharma from and severalSharma 2008,wetlands 2012). of Oriental endemics. In addition,Segers, KotethipLecane rhytida& Sanoamuang Harring Majuli. Comments are made on nature and composition L. undulata Hauer (Figure 2 I) of the fauna, occurrence of interesting elements and are recent new additions to Indian Rotifera (Sharma and distribution of different species. Sharma& Myers in (Figure 2014b). 2 H) and Materials and Methods Discussion This study is based on plankton samples collected on The higher rotifer biodiversity (131 species) observed many occasions during 2010-2012, from the littoral and beels) and 30+ nature of Majuli Rotifera. These comprise ~34.0% and in the sampled floodplains indicates rich and diverse limnetic regions of 20+ floodplain lakes ( 292 Sharma | Rotifera from wetlands of Majuli, India ~55.0% of species of the Phylum known till date from from India, Assam state (Sharma 2004); this second Indian India and northeast India, respectively. The rotifer richness reported from this limited geographical area Orientalreport also endemics: affirms Keratellaits occurrence edmondsoni restricted Ahlstrom to northeast, Lecane India.blachei Besides, Majuli, L. niwati collections are characterized by four, andforms Sharma a significant 2014a) fractionand also (~60.0%) compares of well total with species 155 and Filinia camasecla Myers; the last two species are found recorded from floodplains of the state of Assam (Sharmapats) of in India Berzins only in its northeast Segers, region Kotethip while & K. Sanoamuang edmondsoni Manipur (Sharma 2009). The Paleotropical Lepadella and L. blachei exhibit disjunct distribution in this country vandenbrandeispecies reported is anfrom interesting the floodplain addition lakes to the( rotifer (Sharma and Sharma 2013). Of the members of these two categories, the reports of B. kostei and F. camasecla environmental heterogeneity of the sampled beels and beyond their classical distribution limits: i.e., north-east dobasfauna orof dubies India. The documented diversity reflects China and Panama, respectively are possible examples of lakes of northeast India as Rotifera rich habitats of the introduction (Segers 2007). Indian sub-region and (Sharma affirms the2005; hypothesis Sharma onand floodplain Sharma The occurrence of six Paleotropical species namely Dipleuchlanis ornata Segers, Lepadella discoidea Segers, Segers et al. (1993) on the rich rotifer diversity of (sub) L. vandenbrandei Gillard, Lecane lateralis Sharma, L. 2008, 2012). Our results also support the hypothesis of simonneae Segers and L. unguitata (Fadeev), and the Holarctic Lecane elongata Asian)tropical taxa floodplain namely lakes. Brachionus dichotomus reductus features of Majuli Rotifera. The tropical-latitude specimens The occurrenceB. kostei of Shiel, two aAustralasian noteworthy feature(Australian of this & Harring & Myers are notable study, supports our remarks (Sharma 2005; Sharma Koste and Brachionus diversicornis & Shiel and (Daday)of the latter, Lepadella may represent discoidea, glacial L. vandenbrandeirelicts as hypothesized, Lecane northeast India with those of Southeast Asia and Australia. bylateralis, Segers L. (1996).simonneae In andaddition, L. unguitata SegersSharma (2001) 2005, remarked2008, 2012) on theon occurrencethe affinity of of the Rotifera reductus of Eastern Hemisphere species following Savatenalinton and vicariant of B. dichotomus Segers (2005). are categorized as the recent expansion of these populations to Southeast Lecane niwati, L. rhytida and L. undulata are recent Asia with Australia as possible outside origin Australia, of this hypothesizing taxon. The additions to the Indian fauna based on the samples report of this vicariant from upper Assam region supports examined from Majuli River Island (Sharma and Sharma B. dichotomus reductus is known till 2014b). Besides, the collections from Majuli indicate date from India exclusively from the states of Assam and several species of regional distribution importance namely Segers′sTripura ofhypothesis. its northeast region. B. kostei Lophocharis oxysternon (Gosse), Mytilina acanthophora was first known Figure 1. District map of Assam state indicating location of Majuli River Island (insert Map of India indicating Assam state of northeast India). 293 Sharma | Rotifera from wetlands of Majuli, India Hauer, Macrochaetus longipes Myers, Lepadella benjamini (20 species) > Trichocerca (13 species) are species-rich Harring, L. costatoides Segers, L. dactyliseta (Stenroos), genera; these families and genera include about 51.0% L. elongata , L. quinquecostata (Lucks), Lecane doryssa Harring, L. elongata , L. paxiana respectively. Interestingly enough, the relative consistency Hauer, L. pusillaKoste Harring, L. monostyla (Daday), L. ofand the 58.0% importance of the ofrotifer three speciesperiphytic observed monogonont from generaMajuli, thienemanni Hauer, TrichocercaHarring abilioi & Myers and indicates the possibility of assemblage rules for the Testudinella tridentata Smirnov. Of these, Macrochaetus longipes, Lepadella benjamini, L. dactyliseta,Segers L. & elongata, Sarma L. quinquecostata, Lecane doryssa, L. elongata, L. pusilla and compositionperiphytic community