Opusc. Zool. Budapest, 2016, 47(2): 123–130 Interesting rotifers (Rotifera: Eurotatoria) from floodplain lakes of lower Brahmaputra river basin of Assam, northeast India B.K. SHARMA1 & S.I. KHAN Bhushan Kumar Sharma & Shaikhul Islam Khan, Freshwater Biology Laboratory, Department of Zoology, North-Eastern Hill University, Shillong 793 022, Meghalaya, India. E-mail: [email protected] (1corresponding author) Abstract. The plankton and semi-plankton samples collected from four floodplain lakes (beels) of Barpeta district of lower Brahmaputra river basin, Assam state, northeastern India (NEI) revealed eighteen rotifer species of biodiversity and biogeographic interest belonging to five families and six genera. One species is new to the Indian Rotifera and one species is new to Assam. Our collections are characterized by two Australasian elements, five Oriental endemics, seven paleotropical species, and one cosmo (sub) tropical species. Nine species, restricted to date to NEI, are examples of regional distribution importance in India while six species depicted disjunct distribution in the country. Interestingly, seven species are categorized as Eastern hemisphere elements. All the taxa are illustrated to warrant validation as an increasing magnitude of ‘unverifiable records’ is a serious impediment for the progress of rotifer biodiversity in India. Keywords. Biodiversity, distribution, interesting taxa, lower Assam, tropical floodplains. INTRODUCTION MATERIALS AND METHODS T ropical and subtropical floodplain lakes are This study is a part of limnological reconnais- hypothesized to be Rotifera rich habitats sance undertaken in four floodplain lakes (beels) (Segers et al. 1993). The rotifer assemblages of of Barpeta district of Assam (Table 1) during these ecotones are poorly documented in India in August 2011 – July 2013. These beels are ‘ma- general except for the floodplain lakes (beels) of naged’ locally to harvest their fishery potential. the Brahmaputra river basin of Assam state which Plankton and semi-plankton samples were collect- are known for their rich and interesting rotifer ed from various beels by towing a nylobolt plank- diversity (Sharma & Sharma 2005, 2008, 2013, ton net (# 50 µm) and were preserved in 5% for- 2014a, 2014b, 2014c, 2015a) in the Indian sub- malin. Individual collections were screened with a region. The present limnological reconnaissance Wild stereoscopic binocular microscope; the roti- is undertaken to further explore the biodiversity fer taxa were isolated and mounted in Polyvinyl importance of ‘managed beels’ (for fisheries) of alcohol–lactophenol, and were observed with Lei- Barpeta district of lower Assam. During the ca (DM 1000) stereoscopic phase contrast micros- course of the study, we observed eighteen Roti- cope fitted with an image analyzer. The different fera species of biodiversity and biogeographic rotifers were identified following the works of value. The recorded species are listed and com- Koste (1978), Segers (1995), Sharma (1983, 1987, ments are made on their status, occurrence, and 1998), Sharma & Sharma (1997, 1999, 2000, distribution. All the taxa are illustrated to warrant 2008, 2013, 2015a, 2015b, 2015c). The reference validation as the Indian literature is flooded with materials are in the holdings of Freshwater Bio- ‘ad-hoc unverifiable’ reports lacking validations logy laboratory, Department of Zoology, North- (BKS, unpublished). Eastern Hill University, Shillong. _______________________________________________________________________________________________________ urn:lsid:zoobank.org:pub:7E12D075-D769-437C-BCB2-84CF43E2FE19 HU ISSN 2063-1588 (online), HU ISSN 0237-5419 (print) http://dx.doi.org/10.18348/opzool.2016.2.123 Sharma & Khan: Interesting rotifers from floodplain lakes of lower Brahmaputra river basin of Assam, India Table 1. List of the sampled beels. Sl. No. Beel Latitude Longitude Elevation (m) 1 Fingua N26o17’08.7” E91o02’00.2” 37.9 2 Baria N 26o21’35.9” E 91o02’43.1” 43.7 3 Sorbhog N26o30’22.2” E90o53’20.6” 48.3 4 Balaisuti N26o21’19.7” E90o52’12.8” 54.6 A B Figure 1. A = Map showing Northeast India (NEI), B = Map of Assam indicating Barpeta district (the sampling area marked by an arrow) RESULTS Family Lepadellidae 7. Lepadella discoidea Segers, 1993 A total of eighteen interesting rotifer species 8. L. vandenbrandei Gillard, 1952 belonging to five Eurotatoria families and six genera are reported in the systematic list given Family Lecanidae below: Phylum Rotifera 9. Lecane blachei Berzins, 1973 10. L. bulla diabolica (Hauer, 1936) Class Eurotatoria 11. L. lateralis Sharma, 1978 Subclass Monogononta 12. L. niwati Segers, Kothetip & Sanoamuang, Order Ploima 2004 Family Brachionidae 13. L. simonneae Segers, 1993 1. Brachionus bennini Leissling, 1924 ** Family Testudinellidae 2. B. dichotomus reductus Koste & Shiel, 1980 3. B. durgae Dhanapathi, 1974 14. Testudinella amphora Hauer, 1938 4. B. kostei Shiel, 1983 15. T. brevicaudata Yamamoto, 1951 5. Keratella edmondsoni Ahlstrom, 1943 16. T. dendradena de Beauchamp, 1955* 6. K. javana Hauer, 1937 17. T. greeni Koste, 1981 124 Sharma & Khan: Interesting rotifers from floodplain lakes of lower Brahmaputra river basin of Assam, India Family Trochosphaeridae last to the Indian sub-region. B. bennini is report- ed from the Afrotropical, Australasian, Neotro- 18. Filinia camasecla Myers, 1938 pical, Oriental, and Palaearctic regions (Segers * New record for India; **new record for Assam state 2007). This brachionid is examined from NEI from Mizoram (Sharma 1987, Sharma & Sharma Testudinella dendradena de Beauchamp (Fig. 2014d, 2015c) and is also observed from Madhya 2) is a new record for India and Brachionus Pradesh in central India (Sharma & Naik 1996); bennini Leissling (Fig. 3) is new record from As- the present report extended its distribution within sam state. B. dichotomus reductus Koste & Shiel NEI. (Fig. 4) and B. kostei Shiel (Fig. 5) are Austral- asian elements; Keratella edmondsoni Ahlstrom The biogeographically interesting elements in- (Fig. 6), Lecane blachei Berzins (Fig. 7), Lecane cluded: (i) the Australasian Brachionus dichoto- bulla diabolica (Hauer) (Fig. 8), L. niwati Segers, mus reductus and B. kostei; (ii) five Oriental Kothetip & Sanoamuang (Fig. 9) and Filinia endemics namely Keratella edmondsoni, Lecane camasecla Myers (Fig. 10) are Oriental endemics. blachei, Lecane bulla diabolica, L. niwati and Brachionus durgae Dhanapathi (Fig. 11), Kera- Filinia camasecla; and (iii) the paleotropical tella javana Hauer (Fig. 12), Lepadella discoidea Keratella javana, Lepadella discoidea, L. vanden- Segers (Fig. 13), L. vandenbrandei Gillard (Fig. brandei, Lecane lateralis, L. simonneae, Testu- 14), Lecane lateralis Sharma (Fig. 15), L. dinella brevicaudata and T. greeni. Besides, simonneae Segers (Fig. 16), Testudinella ampho- Brachionus durgae, Testudinella amphora and T. ra (Fig. 17), T. brevicaudata Yamamoto (Fig. 18), dendradena merit distribution interest. and T. greeni Koste (Fig. 19) are other species with interesting distributions. Referring to the first category, Segers (2001) remarked on occurrence of reductus vicariant of B. dichotomus outside Australia, hinted at a pos- DISCUSSION sible Australian origin of this taxon and hypo- thesized its recent expansion to Southeast Asia. Our collections from the sampled beels of The disjunct populations of this brachionid known lower Assam, NEI revealed eighteen interesting from India only from NEI (Meghalaya, Tripura species of Rotifera spread over five eurotatorian and Assam) are hypothesized (Sharma & Sharma families and six genera. Testudinella dendradena 2014a, 2014c, 2014d, 2015b, 2015c) to their is a new record to the Indian Rotifera and Brachi- possible recent expansions to the Indian sub- onus bennini is a new addition to the rotifer fauna region. This taxon is reported from the Oriental of Assam. The former is treated as a distinct region from Vietnam (Zhdanova 2011) and from species following Segers (2007) though Jersabek Thailand (Athibai et al. 2013, Sa-Ardrit et al. & Leitner (2013) considered it as T. patina dend- 2013). Brachionus kostei, described from radena. We also followed analogies of resurrect- Australia, is known from Papua Guinea and Thai- tion of Lecane nitida; Mytilina michelangellii and land while Segers (2007) considered its un- M. brevispina vide Segers & Savatenalinton published report from northeast China as a (2010), Pourriot (1996) and Luo & Segers (2014), possible example of introduction. This species is respectively for the said treatment. T. dendradena known from India exclusively from Assam state is diagnosed by its characteristic vitellarium and it of NEI (Sharma 2004, 2014, Sharma & Sharma co-occurred with T. patina in some collections. 2008, 2014d, 2015b, Sharma et al. 2015). Never- Further, these two species differed in size and theless, these two Australasian elements affirmed habitat; the former being distinctly larger and affinity of Rotifera assemblage of Assam state as preferred the littoral-periphytonic regions. T. den- well as of NEI with the faunas of Southeast Asia dradena is known from the Afrotropical, Neo- and Australia, and thus supported remarks of tropical and Oriental regions (Segers 2007); the Sharma (2005) and Sharma and Sharma (2005, present report extended its distribution within the 2008, 2013, 2014a, 2014c, 2014d). 125 Sharma & Khan: Interesting rotifers from floodplain lakes of lower Brahmaputra river basin of Assam, India Our collections are characterized by five Ori- Orissa, Tamil Nadu, Tripura, West Bengal) indi- ental endemics namely Keratella edmondsoni, cated disjunct but relatively wider occurrence. Lecane blachei, Lecane bulla diabolica, L. niwati Besides, the cosmo (sub) tropical Brachionus and Filinia camasecla and thus affirmed affinity durgae (Andhra Pradesh, Assam, Goa, Kerala, of Assam Rotifera with the Oriental fauna. The Maharashtra, Orissa, Tamil Nadu) and Testudi- first species was described from Tamil Nadu nella amphora (Assam) are examples of regional (Ahlstrom 1943) as K. quadrata var. edmondsoni distribution of interest. The latter is known from while Nayar (1965) raised it to the status of a the Australian, Neotropical and Oriental regions distinct species. This brachionid indicated disjunct (Segers, 2007); it is examined from the last region occurrence in India with reports from Assam from Thailand (Sa-Ardrit et al. 2013) and (NEI), Rajasthan, Orissa, and Tamil Nadu. It is Vietnam (Trinh Dang et al. 2013), and Sharma et reported in the Oriental region from Thailand (Sa- al. (2015) extended its distribution to the Indian Ardrit et al. 2013) and Cambodia (Meas & sub-region based on collections from the Majuli Sanoamuang 2010, Sor et al. 2015). L. blachei, River Island, upper Assam while Sharma & described from Cambodia is also known from Sharma (2015c) recorded it from Mizoram state Thailand, while its Indian reports are restricted till of NEI. The present report further extends its date to Assam (NEI) and West Bengal (Sharma & occurrence to lower Assam. Sharma 2014b). L. bulla diabolica, originally described from Tamil Nadu (Hauer 1936), was Keratella javana, Lecane lateralis, L. simon- known globally by its sole non-illustrated Oriental neae, L. unguitata, Lepadella discoidea, L. van- record from Thailand (Segers & Savatenalinton denbrandei, and Testudinella greeni are catego- 2010) till Sharma & Sharma (2014b) extended its rized as Eastern hemisphere elements vide Segers distribution within India to NEI (Assam, Mani- (2001). In addition, three other members of this pur); the current second Indian report from Assam category: Brachionus diversicornis, B. forficula re-affirmed its distribution in NEI. L. niwati is an and L. unguitata, though not listed in this report, interesting lecanid described from Thailand (Se- are observed in our lower Assam samples (BKS, gers et al. 2004). Sharma (2014) and Sharma & unpublished).The report of the stated taxa imparts Sharma (2014b) recently extended its distribution yet another interesting character to the rotifer to NEI based on specimens from the Majuli River fauna of Assam and NEI. Island of upper Assam and Loktak Lake (a Ram- sar site), Manipur, respectively while the present We categorize all the documented species into study further extended its distribution to lower three groups: (a) Restricted to NEI: Brachionus Brahmaputra river basin. The Oriental F. cama- dichotomus reductus, B. kostei, Keratella javana, secla indicated disjunct occurrence in India with Lepadella vandenbrandei, Lecane blachei, L. ni- reports from Assam, Manipur and Tripura states wati, Testudinella amphora, T. brevicaudata, T. of NEI and Kerala (South India). dendradena and T. greeni; (b) Disjunct and rest- ricted distribution in India: Brachionus bennini, Amongst the palaeotropical elements, Kera- Keratella edmondsoni, Lecane bulla diabolica, L. tella javana (Assam, Meghalaya, Tripura), Lepa- simonneae and Filinia camasecla; (c) Disjunct della vandenbrandei (Assam, Mizoram), Testudi- with relatively wide distribution in India: Brachi- nella brevicaudata (Assam, Manipur, Tripura) onus durgae, Lecane lateralis, Lepadella disco- and T. greeni (Assam) merit regional biogeog- idea. raphical interest with their reports so far only from NEI. Lecane simonneae (Assam, Kerala, To sum up, the reports of new records, species Manipur, Tripura) exhibited disjunct yet restricted of global and regional distribution importance and distribution in India while Lepadella discoidea Eastern Hemisphere elements merit biodiversity (Assam, Delhi, Kerala, Manipur, Meghalaya) and and biogeographic interest. The Australasian and Lecane lateralis (Assam, Kerala, Meghalaya, Oriental species impart special affinity of Assam 126 Sharma & Khan: Interesting rotifers from floodplain lakes of lower Brahmaputra river basin of Assam, India Rotifera with Southeast Asia as well as Australia. SA-ARDRIT, P., PHOLPUNTHIN, P. & SEGERS, H. The study highlights interesting elements of NEI (2013): A checklist of the freshwater rotifer fauna rotifers as compared with other regions of India. of Thailand (Rotifera, Monogononta, Bdelloidea). 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Symposium on River Biodiversity: Ganges–Brah- Inland Water Biology, 4(4): 425–434. maputra–Meghna River System, Ecosystems for doi: 10.1134/ S1995082911030205 128 Sharma & Khan: Interesting rotifers from floodplain lakes of lower Brahmaputra river basin of Assam, India 2 3 4 6 5 7 8 9 10 11 Figures 2-11. 2 = Testudinella dendradena de Beauchamp (ventral view); 3 = Brachionus bennini Leissling (dorsal view); 4 = Brachionus dichotomus reductus Koste & Shiel (ventral view); 5 = Brachionus kostei Shiel (dorsal view); 6 = Keratella edmondsoni Ahlstrom (dorsal view); 7 = Lecane blachei Berzins (ventral view); 8 = Lecane bulla diabolica (Hauer) (lateral view); 9 = Lecane niwati Segers, Kothetip & Sanoamuang (dorsal view); 10 = Filinia camasecla Myers (dorsal view);11 = Brachionus durgae Dhanapathi (ventral view). 129 Sharma & Khan: Interesting rotifers from floodplain lakes of lower Brahmaputra river basin of Assam, India Figures 12-19. 12 = Keratella javana Hauer (ventral view); 13 = Lepadella discoidea Segers (ventral view); 14 = Lepadella vandenbrandei Gillard (ventral view); 15 = Lecane lateralis Sharma (dorsal view); 16 = Lecane simonneae Segers (dorsal view); 17 = Testudinella amphora Hauer (dorsal view); 18 = Testudinella brevicaudata Yamamoto (ventral view); 19 = Testudinella greeni Koste (dorsal view). 130