JoTT SHORT COMMUNI C ATION 3(6): 1856–1861 Distribution of aquatic insects in phumdis (floating island) of Loktak Lake, Manipur, northeastern India Kiranbala Takhelmayum 1 & Susmita Gupta 2 1,2 Department of Ecology & Environmental Science, Assam University, Silchar, Assam 788011, India Email: 1 [email protected], 2 [email protected] (corresponding author) Abstract: A study was made on the temporal fluctuations of Loktak Lake, a Ramsar site, (93046’–93055’E & distribution of aquatic insects around Phumdi Live (PL), Phumdi 0 0 Mixed (PM) and Phumdi Dry (PD) areas of Loktak Lake. Phumdis 24 25’–24 42’N) is the largest fresh water lake (26km are a heterogeneous mass of soil, vegetation and organic matter. long and 13km wide with 980km2 catchment area) in The study revealed the presence of predators, and the absence of herbivores and detritivores in both PL and PM, the PD area was the Manipur State of northeastern India (Fig. 1). The totally devoid of insects. Although both the habitats supported unique feature of the lake is the floating island called the same predator groups hemiptera and odonata, diversity phumdis which form the Kaibul Lamjao National Park and density in terms of family and species were higher in PL than in PM. Temporal fluctuations revealed that the Shannon- (the only home of Rucervus eldii eldii). Phumdis, are Weiner’s Diversity Index values were highest in June for both a heterogeneous mass of soil, vegetation and organic PL (0.726) and PM (0.47). In both the sites the highest density was recorded in February. The relative abundance of hemiptera matter at various stages of decomposition (Image was higher than that of odonata in most of the months in PL. 1). They float on lake water with about one-fifth of Phumdi Mixed was represented by one species of hemiptera only, in the month of February and dominated by odonates thickness above and four-fifths under the water surface otherwise. Community composition of odonata larvae did not appearing in three distinct vertical zones, lying one show any difference between the two habitats. Although the study revealed low diversity and density of insects in both sites, above the other. The uppermost root zone is generally the PL community provided a better habitat to aquatic insects 0–15 cm thick followed by the next mat zone of 25– than that of PM. These are of value as fish food and in turn for fish production. 65 cm and the lowermost peat zone 0–25 cm. Free- floating plants, such as water hyacinth and partly Keywords: Phumdis, hemiptera, odonata, Loktak Lake, insect, decomposed roots and rhizomes contribute greatly to its diversity, density. development. There are three types of phumdis. They are Phumdi Live (PL) mostly consisting of paragrass like Brachairia mutica, Alternathara phitoxiroides and plants like Salvinia calcullata, Cyperus difformis Date of publication (online): 26 June 2011 and Heydichium spicatum etc; Phumdi Mixed (PM) Date of publication (print): 26 June 2011 comprising both live and dry paragrass and plants, and ISSN 0974-7907 (online) | 0974-7893 (print) Phumdi Dry (PD) comprising dead, dry paragrass and Editor: R. Ramanibai plants (Singh et al. 2003). Phumdis provide a biological Manuscript details: sink to the key nutrients and govern the water quality Ms # o2526 Received 26 July 2010 and nutrient dynamics of the lake by absorbing most Final revised received 04 January 2011 Finally accepted 18 May 2011 of the nutrients and accumulating them in their tissues (WISA & LDA 2002). Citation: Takhelmayum, K. & S. Gupta (2011). Distribution of aquatic insects in phumdis (floating island) of Loktak Lake, Manipur, northeastern Faunal distribution and their assemblage is India. Journal of Threatened Taxa 3(6): 1856–1861. strongly dependent on the composition and structure Copyright: © Kiranbala Takhelmayum & Susmita Gupta 2011. Creative of vegetation (Korkeamaki & Suhonen 2002) and Commons Attribution 3.0 Unported License. JoTT allows unrestricted use of this article in any medium for non-profit purposes, reproduction and invertebrates are recognized as an essential food distribution by providing adequate credit to the authors and the source of publication. source for nesting and juvenile water fowl, fish, and amphibians in wetland systems (Swanson et al. Acknowledgements: The authors wish to thank Prof. Rajmuhon Singh, Department of Chemistry, Manipur University, Manipur, India, for his help 1979; Batzer et al. 1999). There are several studies and cooperation during the field and laboratory studies. Sincere thanks go to Dr. Animesh Bal, Zoological Survey of India, Kolkata for his help in on invertebrates, mainly aquatic insects in different hemipteran insect identification. fresh water systems or aquatic insects associated with OPEN ACCESS | FREE DOWNLOAD individual plant species or with the plant community 1856 Journal of Threatened Taxa | www.threatenedtaxa.org | June 2011 | 3(6): 1856–1861 Aquatic insects in phumdis of Loktak Lake K. Takhelmayum & S. Gupta Imphal West District Bishnupur District Senapati District Image 1. Phumdis (floating mat) of Loktak Lake Thoubal Chura-chandpur Microscope with the help of standard keys (Kumar District District 1973a,b; Bal & Basu 1994a,b; Westfall & Tennessen 1996; ZSI 2004). A number of identified insects were confirmed in the entomological laboratory of the Zoological Survey of India. Diversity indices were worked out using the package Biodiversity Professional Version 2. Figure 1. Loktak map, Manipur (source - Envis Centre in Results and Discussion Biogeochemistry, J.N.U, New Delhi) PL and PM areas were represented by two orders of insects, Hemiptera and Odonata; the PD area was devoid of insects. Seven species belonging to four (Wellborn & Robinson 1987; Parsons & Malthews families were recorded around PL. They were Ranatra 1995; Das & Gupta 2010; Hazarika & Goswami varipes and Laccotrephes ruber (Nepidae), Gerris sp. 2010). No study on the insects of Loktak Lake is on (Gerridae), Diplonychus rusticus (Belostomatidae) record. In this study we attempt to find the temporal belonging to the suborder Heteroptera, order Hemiptera fluctuations of distribution of aquatic insects around and Tramea sp., Leucorrhinia sp., Sympetrum sp. different types of phumdis of Loktak Lake in terms of belonging to the family Libellulidae of the suborder diversity and density. Extrapolation of this data might Anisoptera, order Odonata (Images 2 a–g). Around PM be of help to the planners in chalking out fish culture only four species belonging to two families, and two and lake management programmes. subfamilies were recorded. They were Diplonychus rusticus belonging to the family Belostomatidae and Materials and Methods all three Odonata species recorded in PL. Among the Aquatic insects were collected from the south- families, Libellulidae was the most prominent, being western region of the lake through an extensive survey present throughout in both sites (Table 1). around the PL, PM and PD habitats during February The Shannon-Weiner’s Diversity Index values to July, 2008 whereby the vegetation was disturbed around PL were relatively higher in most of the months and a circular net (mesh size 60µm) was dragged than that of PM. In both sites, Shannon H’ were highest around the vegetation for one minute (Subramanian & in June, 0.726 for PL and 0.47 for PM. Around PL, the Sivaramakrishnan 2007). Three such drags constituted highest evenness was recorded in March and the lowest a sample. Collected insects were immediately sorted in July, while the Berger Parker Dominance index was and preserved in 70% ethyl alcohol. They were later just the reverse. In contrast, around PM the highest identified using a Dewinter advance stereozoom evenness was recorded in June and the lowest in April Journal of Threatened Taxa | www.threatenedtaxa.org | June 2011 | 3(6): 1856–1861 1857 Aquatic insects in phumdis of Loktak Lake K. Takhelmayum & S. Gupta Table 1. Distribution of aquatic insects around Phumdi Table 2. Temporal variation of Shannon Weiner diversity Live (PL) and Phumdi Mixed (PM) area of Loktak Lake. index (H’ ), Evenness index (J) and Berger Parker index of dominance (d) around Phumdi Live (PL) and Phumdi Mixed Family / Order Species PL PM (PM) habitat of Loktak Lake subfamily Nepidae Diversity Ranatra varipes + - Habitat Feb Mar Apr May Jun Jul Ranantrinae index H' 0.714 0.598 0.657 0.292 0.726 0.353 Nepinae Laccotrephes ruber + - J' 0.918 0.993 0.94 0.971 0.933 0.739 Hemiptera Gerridae Gerris sp. + - Gerrinae PL d 0.313 0.286 0.319 0.6 0.308 0.688 Belostomatidae Diplonychus + + 1/d 3.2 3.5 3.133 1.667 3.25 1.455 Belostomatinae rusticus H' 0.423 0.292 0.398 0.426 0.47 0 Libellulidae Tramea sp. + + Trameinae J' 0.886 0.971 0.834 0.893 0.985 0 PM Odonata Leucorrhininae Leucorrhinia sp. + + d 0.48 0.6 0.545 0.556 0.375 0 1/d 2.083 1.667 1.833 1.8 2.667 0 Sympetrinae Sympetrum sp. + + Image 2a. Ranatra varipes Image 2d. Leucorrhinia sp. Image 2c. Laccotrephes ruber Image 2b. Gerris sp. Image 2g. Diplonychus rusticus Image 2f. Sympetrum sp. Image 2e. Tramea sp. 1858 Journal of Threatened Taxa | www.threatenedtaxa.org | June 2011 | 3(6): 1856–1861 Aquatic insects in phumdis of Loktak Lake K. Takhelmayum & S. Gupta 40 oxygen (Rooke 1984) it could be said that the PD area 35 Hemiptera Odonata comprising of dead and dry plants could not meet 30 25 their requirements for survival. Higher diversity and 20 density of aquatic insects in PL than in PM could be 15 attributed to the luxuriant vegetation of the PL area 10 5 which might have attracted more insects that looked for 0 refuge, oviposition site and food, as their assemblage Feb Mar Apr May Jun Jul Feb Mar Apr May Jun Jul is strongly dependent on the composition, structure PL PM Figure 2.