Testudinellidae, H.K.Harring, 1913

Sharma, B. K. & Sharma, Sumita, 2011, Faunal diversity of rotifers (Rotifera: Eurotatoria) of Nokrek Biosphere Reserve, Meghalaya, India, Journal of Threatened Taxa 3 (2), pp. 1535-1541 : 1537-1540

Testudinellidae

65. Testudinella emarginula (Stenroos, 1898)

66. T. parva (Ternetz, 1892)

67. T. patina (Hermann, 1783)

Digononta

Bdelloidea

Philodinidae

68. Philodina citrina Ehrenberg, 1832 *

69. Rotaria macroceros (Gosse, 1851) *

70. R. neptunia (Ehrenberg, 1830)

* New records from Meghalaya

Discussion

This pioneering study on aquatic biodiversity of the Nokrek Biosphere Reserve records 70 species of Rotifera. Eight species namely Brachionus mirabilis , Tripleuchlanis plicata , Lecane arcula , L. blachei , Sinantherina socialis , S. spinosa , Philodina citrina and Rotaria macroceros are new records from the state of Meghalaya. The present report raises the number of rotifer species known from Meghalaya (vide Sharma & Sharma 1999) to 138 species. In addition, a couple of new species await description. The richness, in turn, comprises 31.7% of the species known from northeastern India and 50.7% of the rotifer fauna of the state of Meghalaya. Amongst 22 families and 43 genera of phylum Rotifera recorded from northeastern India (B.K. Sharma unpublished), 15 families and 24 genera are represented in our collections. Although the examined samples reflect a low rotifer diversity of Nokrek Biosphere Reserve, the fauna appears to be fairly speciose when compared with overall rotifer richness known from northeastern India in general and the state of Meghalaya in particular. The documented species, however, present a significant contrast to only 27 species belonging to nine families and 12 genera identified by one of the authors (S. Sharma unpublished) from this biosphere reserve based on limited samples deposited in the holdings of NERC, ZSI, Shillong.

Incomplete Rotifera inventories from the conservation areas of India may not permit meaningful comparisons with our report; this generalization is affirmed by only 14 species reported from the Nilgiri Biosphere Reserve ( Patil 2001). The diversity in Nokrek Biosphere Reserve is marginally higher than 64 species noticed in summer rotifer communities of 12 floodplain lakes of the Pobitora Wildlife Sanctuary, Assam ( Sharma 2006) while it broadly concurs with 74 species examined from some floodplain lakes of Kaziranga National Park ( Sharma & Sharma 2008) of Assam. On the other hand, the richness is distinctly lower than the reports of 110 ( Sharma & Sharma 2005b) and 120 ( Sharma 2009) species known from two Ramsar sites of India namely Deepor Beel (Assam) and Loktak Lake (Manipur), respectively as well as the 207 species from floodplain lakes in River Niger Delta, Nigeria, Africa ( Segers et al. 1993), 106 taxa from Thale-Noi Lake, a Ramsar site in Thailand, Asia (Segers & Pholpunthin 1997) and 114 species from the wetlands of the Rio Pilcomayo National Park, Ramsar site of Argentina, South America (Jose de Paggi 2001). However, we caution against overemphasizing the importance of the stated comparisons without considering sampling intensity and the nature of different ecosystems, particularly the floodplains of Assam and Manipur and elsewhere.

Biogeographically interesting elements include the Oriental endemic Lecane blachei ( Image 1). This lecanid was described from Cambodia (Berzins 1973) and thereafter recorded from Thailand ( Sanoamuang 1998) and India ( Sharma 2004) while it is recently re-recorded (Seanghun & Sanoamuang 2010) from Cambodia from the Mekong River basin. L. blachei exhibits a disjunct occurrence in India with records from Assam and West Bengal ( Sharma & Sharma 2008). Lecane unguitata ( Image 2 ), another palaeotropical species ( Segers 1996) as well as eastern hemispheric element (Savatenalinton & Segers 2005), shows a relatively wider distribution in India but is rare in the collections from the Nokrek Biosphere Reserve. Besides, Brachionus mirabilis ( Image 3 ), Lophocharis salpina ( Image4 ), Mytilina bisulcata ( Image5), Lecane haliclysta ( Image 6 ), L. furcata ( Image 7), L. stenroosi ( Image 8 ), Tripleuchlanis propatula , Testudinella parva ( Image 9 ) and T. emarginula ( Image 10 ) are examples of regional distributional interest. Lecane nitida is presently retained as a distinct species in L. curvicornis group following Segers & Sanoamuang (2007).

Lecanidae ,one of the largest families of monogonont rotifers ( Segers 1995), shows a distinct quantitative importance (34.3%); Brachionidae > Lepadellidae > Notommatidae form notable components (15.7, 10 and 7.1% respectively) of the rotifer fauna of the Nokrek Biosphere Reserve. Amongst different genera, the ‘tropic-centered’ Lecane shows high richness (24 species) while our collections are characterized by a relative paucity of species of another ‘tropic-centered’ genus, Brachionus ; the latter is attributed to the lack of typical limnetic habitats in the sampled area. Cosmopolitan species (71.2%) distinctly dominate the rotifer fauna, tropicopolitan species (16.5 %) are well represented while pantropical (5.6%) elements are relatively fewer. In general, the rotifer taxocoenosis of the Nokrek Biosphere Reserve reflects a ‘tropical character’. This generalization is in conformity with identical reports from other tropical faunas ( Green 1972; Fernando 1980; Dussart et al. 1984; Segers 1996, 2001, 2008; Sharma 1998a; Sharma & Sharma 2008). On the other hand, our results differ by lacking the quantitative dominance of Brachionidae , depending on ecological conditions, reported in quite a few of the listed works.

Our collections exhibit interesting variations in Rotifera richness in individual samples (2-23, 11 ± 5 species). Further, the rotifer communities are characterized by more littoral-periphytonic species and a paucity of planktonic elements. The present study shows the common occurrence of Plationus patulus , Euchlanis dilatata , Lecane bulla , L. leontina , L. luna , L. quadridentata and Testudinella patina while Brachionus bidentatus , B. calyciflorus , B. falcatus , Cephalodella forficula , C. gibba , C. mucronata , Sinantherina socialis , S. spinosa and Testudinella parva are rare species. Monogonont rotifers comprise the bulk of the recorded diversity (67 species) and in turn, show a higher richness of the members of order Ploima while the Bdelloidea include only three species.

To sum up, the Rotifera fauna of the Nokrek Biosphere Reserve reveals 70 species belonging to 24 genera and 15 families including eight new records from the state of Meghalaya, It is characterized by the occurrence of certain biographically interesting species, quantitative importance of tropic-centered’ Lecane , paucity of Brachionus spp. , richness of cosmopolitan species, general ‘tropical’ character and dominance of littoral-periphytonic species. The present species inventory, however, still requires updating based on more extensive collections as well as specific sampling of benthic and bdelloid rotifers. Nevertheless, this study is an important contribution to aquatic biodiversity of the biosphere reserves or conservation areas of India.

Figures

Image 2. Lecane unguitata (Fadeev), ventral view

Image 3. Brachionus mirabilis Daday, ventral view

Image 4. Lophocharis salpina (Ehrenberg), lateral view

Image 6. Lecane haliclysta Harring & Myers, dorsal view

Image 8. Lecane stenroosi (Meissner), dorsal view

Image 9. Testudinella parva (Ternetz), ventral view

Image 10. Testudinella emarginula (Stenroos), ventral view