B.K. Sharma 1 & Sumita Sharma 2
1,2 Freshwater Biology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong, Meghalaya 793022, India
1 firstname.lastname@example.org (corresponding author), 2 email@example.com
Editor: Rajashekhar K Patil, Mangalore University, Mangalore, India. Date of publication: 26 March 2015 (online & print)
Manuscript details: Ms # o4044 | Received 26 May 2014 | Final received 20 February 2014 | Finally accepted 27 February 2015
Citation: Sharma, B.K. & S. Sharma (2015). New records of rotifers (Rotifera: Eurotatoria) from Deepor Beel - a Ramsar site of India with an update on its rich rotifer diversity. Journal of Threatened Taxa 7(3): 7011–7016; http://dx.doi.org/10.11609/JoTT.o4044.7011-6
Copyright: © Sharma & Sharma 2015. Creative Commons Attribution 4.0 International License. JoTT allows unrestricted use of this article in any medium, reproduction and distribution by providing adequate credit to the authors and the source of publication.
Funding: Ministry of Environment & Forests (Govt. of India) sponsored project No. 22018-09/2010-CS (Tax).
Competing Interest: The authors declare no competing interests.
Acknowledgements: The samples for this study are collected with the support of the Ministry of Environment & Forests (Govt. of India) sponsored project No. 22018-09/2010-CS (Tax). The senior author is thankful to the Head, Department of Zoology, North-Eastern Hill University, Shillong for necessary facilities. The senior author is thankful to Messer’s M.K. Hatimuria and K. Sounii Pou for help in field collections. We thank our anonymous reviewers for useful comments.
Abstract: Plankton samples collected from Deepor Beel (a Ramsar site), during July 2011 to June 2013, revealed 155 species of Rotifera, belonging to 35 genera and 20 families. Of these, 16 species belonging to eight genera and seven families are new records to the rotifer fauna of this wetland of northeast India. Our observations raise the total richness of the phylum known till date from this important floodplain lake (beel) of the Brahmaputra river basin to 171 species and thus highlight its biodiversity value as one of the globally rich Rotifera habitats. The updated list is interesting for following meta-analyses of rotifer occurrence in this only well sampled freshwater ecosystem of the Indian sub-region.
Keywords: Meta-analyses, new records, rich habitat, tropical wetland.
Deepor Beel, the sole well sampled floodplain lake (beel) and Ramsar site of India, was identified as an interesting ecosystem of Asia for Rotifera diversity (Sharma & Sharma 2012). Our recent limnological survey (July 2011–June 2013) of this wetland revealed 155 rotifer species thus added 16 new species records and further affirmed the biodiversity value of this important beel of the Brahmaputra River basin of Assam vis-a-vis the role of sampling. The present study comments on various new records with a note on update on Rotifera diversity of Deepor Beel. We provide an inventory of 171 species known till date from this Ramsar site for following meta-analyses of occurrence of the taxon.
Materials and Methods
The present study is based on plankton samples collected, between July 2011 and June 2013, from Deepor Beel (91035’–91043’E & 260 05’–26011’N; area: 40km2; altitude: 42m) located in Kamrup district of Assam State of northeastern India (Fig. 1 A–B). This floodplain lake is covered with several aquatic macrophytes namely Hydrilla verticillata, Eichhornia crassipes, Vallisneria spiralis, Utricularia flexuosa, Trapa bispinosa, Euryale ferox, Najas indica, Monochoria hastaefolia, Ipomea fistulosa, Hygrorhyza aristata, Polygonum hydropiper and Limnophila sp. Qualitative plankton samples were collected monthly by towing nylobolt plankton net (# 50µm) from six sampling stations and were preserved in 5% formalin. On each sampling occasion, aquatic vegetation was disturbed before towing plankton net to facilitate collection of planktonic and semi-planktonic rotifers. All samples were screened; the rotifer taxa were isolated, mounted in polyvinyl alcohol-lactophenol mixture and were observed with a Leica DM 1000 image analyzer. Rotifer species were identified following Koste (1978), Segers (1995), Sharma (1998) and Sharma & Sharma (1999, 2000, 2008, 2013). The reference collections were deposited in the holdings of Freshwater Biology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong.
Our collections revealed 155 rotifer species including 16 new records and raised the tally of our earlier list vide Sharma & Sharma (2012) to 171 species; a systematic list of the updated species inventory of Deepor Rotifera is presented in Appendix 1. Brachionus kostei (Image 1), Colurella adriatica, C. colurus, Euchlanis meneta (Image 2), Lecane bifurca (Image 3), L. rhenana (Image 4), L. rhytida (Image 5), L. undulata (Image 6), Lepadella lindaui (Image 7), L. quinquecostata (Image 8), L. triba (Image 9), L. vandenbrandei (Image 10), Mytilina michelangellii (Image 11), Trichocerca scipio (Image 12), T. weberi (Image 13) and Wolga spinifera (Image 14) are new additions to the rotifer fauna of this Ramsar site. Sixteen species, including those of three sessile genera of the Flosculariidae, listed earlier from this floodplain lake, are not observed in our current collections. Brachionus caudatus var. personatus is allocated to B. ahlstromi following Giri & De Paggi (2006).
One-hundred-and-fifty-five species, belonging to 35 genera and 20 Eurotatorien families, observed presently from Deepor Beel reveal speciose Rotifera assemblage and reiterate our hypothesis (Sharma & Sharma 2012) on habitat diversity and environmental heterogeneity of this Ramsar site. This report adds 16 species, belonging to seven families and eight genera, as new records to our earlier list (Sharma & Sharma 2012), thereby, raising the richness of the Phylum known from Deepor Beel to 171 species. Total richness comprises ~71.0 % and ~42.0% of the rotifer species known till date from northeastern India (NEI) (Sharma & Sharma 2014a) and India (B.K. Sharma unpublished), respectively and, hence, indicate biodiversity value of this Ramsar site as one of the globally rich freshwater ecosystems for diversity of Rotifera notwithstanding an estimate of occurrence of +210 species of the taxon in the tropical lakes (Dumont & Segers 1996). The latter estimate, based mainly on certain data from Africa, Brazil and Australia, needs re-consideration on tropical lakes in Asia and Southeast Asia particularly in light of the relatively well studied Indian and Thai Rotifer faunas. The rich rotifer diversity of this Ramsar site supports hypothesis of Segers et al. (1993) indicating (sub) tropical floodplains to be the world’s rotifer rich habitats. In general, high richness of Rotifera in Deepor beel is attributed primarily to the rotiferologist effect (Fontaneto et al. 2012) though our earlier (Sharma & Sharma 2005b, 2011) and present new additions are partly the result of the extensive sampling.
Of the new additions, Brachionus kostei, Mytilina michelangellii and Lecane rhenana are biogeographically interesting elements. The report of the Australasian B. kostei merits special mention; it is now known to occur beyond its classical distribution limits in north-east China (Segers 2007) as a possible example of introduction. This brachionid is observed so far from the floodplains of the Brahmaputra River basin (Sharma 2004, 2014; Sharma & Sharma 2014a,c). M. michelangellii was originally described from Brazil (Reid & Turner 1988) as subspecies of M. ventralis; it is presently retained as a distinct species following its resurrection by Pourriot (1996). This species is characterized by lack of any postero-dorsal spine and restricted global distribution than the cosmopolitan M. ventralis. Segers (2007) indicated distribution of M. michelangellii limited to Afrotropical and Neotropical region while Sa-Ardrit et al. (2013) listed it from Thailand based on the sole report by Jithland & Wongrat (2006). Sharma & Sharma (2014c) recently extended its distribution to the Indian sub-region. This species is so far examined only from Deepor Beel with possibility of extension of its distribution elsewhere in NEI (B.K. Sharma pers. comm.).
The tropicopolitan Lecane rhenana is another recent addition (Sharma & Sharma 2014c) to the rotifer fauna of India. This lecanid is known from the African, Neotropical and Palaearctic regions (Segers 2007) while it is reported from the Oriental region from Thailand (Sa-Ardrit et al 2013) and Cambodia (Meas & Sanoamuang 2010). The lateral margins of dorsal plate of our specimens reach the head aperture margins and hence deviate from original description of the taxon thus supporting the remarks by Segers (1995) on “confused taxonomy” of this species. We agree with Segers (loc cit.) and Jersabek and Leitner (2013) on “unlikely synspecificity of L. sibina and L. rhenana” as proposed by Koste (1978).
Colurella adriatica, C. colurus, Lecane bifurca, L. rhytida, L. undulata, Lepadella lindaui, L. quinquecostata, L. triba, L. vandenbrandei, Trichocerca scipio, T. weberi and Wolga spinifera are other new additions to Deepor Rotifera. Interestingly majority of these species are characterized by their occurrence restricted to NEI. The paleotropical Lepadella vandenbrandei is recently added to the Indian Rotifera from the wetlands of Majuli River Island, upper Assam (Sharma 2014) while Lecane rhytida and L. undulata are also recent reports based on our collections from NEI (Sharma & Sharma 2014b). Lepadella lindaui and L. quinquecostata are known from the floodplains of Assam (Sharma 2004) while Trichocerca scipio is reported from Assam (Sharma & Sharma 2005a) as T. jenningsi which is a junior synonym of the former (Segers 2001). Euchlanis meneta and Wolga spinifera, two additions to NEI (Sharma & Sharma 2014a, 2014b), are examples of disjunct regional distribution in India. The former is so far known from the Kashmir Himalayas (Edmondson & Hutchinson 1934) and Andhra Pradesh (Dhanapathi, 1976), and its report from Gujarat (Dhuru et al. 2003) lacks validation. W. spinifera is, however, observed from the Yamuna River at Delhi (Sarma 1988) and Tamil Nadu (Sharma and Sharma 2009).
Following this biodiversity update, the most speciose Eurotatorien families Lecanidae > Lepadellidae = Brachionidae > Trichocercidae comprise ~70.0% of the rotifer richness known from this Ramsar site. Further, three littoral-periphytonic genera Lecane (47 species) > Lepadella (22 species) > Trichocerca (17 species), together, include ~50.3% species of Deepor Rotifera. The relative consistency of the importance of three periphytic monogonont genera in our present collections (~52.0%) as well as our earlier reports from this Ramsar site (~45.5% vide Sharma & Sharma 2005b; 50.6% vide Sharma & Sharma 2012) support hypothesis of Green (2003) on the possibility of assemblage rules for the periphytic community. Interestingly, the stated significance broadly concurs with their percentage composition in Rotifera from the floodplains of Niger delta (Segers et al. 1993), Broa reservoir, Brazil (Segers & Dumont 1996), River Nan, Thailand (Sanoamuang 1998), Bolivia (Segers et al. 1998) and Okavango Delta of South Africa (Green 2003). This generalization is also supported by our other reports from the floodplains of the states of Assam (Sharma 2005; Sharma & Sharma 2008) and Manipur (Sharma 2009a,b) of northeastern India.
To sum up, various new records support the importance of recent sampling of Deepor Beel, 155 species examined in our present collections reiterate the environmental heterogeneity of this interesting floodplain lake of India and our update on 171 species known till date from this Ramsar site impart it biodiversity value as one of the globally rich habitat for the taxon. Our plankton collections with bias towards planktonic and semi-planktonic taxa yet highlight lacunae on periphytic, sessile and benthic taxa vis-a-vis the rotifer associations with diverse aquatic macrophytes. We estimate occurrence of 220+ rotifer species from this interesting ecotone following specific sampling and analysis of the stated communities.
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