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Proceedings of the 7th IMT-GT UNINET and The 3rd International PSU-UNS Conferences on Bioscience Temporal variation of adult Ephemeroptera, Plecoptera and Trichoptera collected in Tupah river, Kedah, northern peninsular Malaysia Suhaila, A.H*. and Che Salmah, M.R. School of Biological Sciences, Universiti Sains Malaysia, 11800 Penang. MALAYSIA. *Corresponding author: e-mail: [email protected], phone:+6012-4629064 Introduction The adults of aquatic insects are important food to numerous species of fish and birds. According to Enders and Wagner (1996), provision of suitable habitat for adult aquatic insects is an important consideration as the adult stage can be critical in regulating population numbers of aquatic immatures. Collection of the adult EPT at this site would provide a rapid view of local river health and provide a list to guide identification of the immature stages found in samples. The aims of this study were to document the adult EPT fauna selected at the Tupah River and to evaluate factors that could influence the temporal distribution of adults. Materials and methods This study was carried out in the Tupah River, Merbok in the Gunung Jerai Forest Reserve, Kedah. This second order river is located at N5⁰ 45.008’ E100⁰ 26.526’ in Kuala Muda district. Adults EPT were collected for 12 months (January to December 2008) at 1900-2300 hrs (about 4 hours by night) using a light trap made of a mercury light bulb (250 watt) powered by a EM650Z portable generator and a white sheet. Two sheets (1.7 m long x 1 m wide) were hung side by side forming an angle and were placed 5 m from the river edge. The light was provided between the sheets. The adults EPT that landed on the sheets were collected and placed in a jar. They were preserved in universal bottles filled with 75% ETOH. In the laboratory, the insects were identified following keys of Johnson and Triplehorn (2005) and Wang and McCafferty (2004). Results and discussion Sixteen families of adults EPT have been identified from 1689 individuals collected from the area. Trichoptera was the most prevalent order, representing 60.5% of the total EPT. The other two orders much fewer [Ephemeroptera (22.1%) and Plecoptera (17.5%]. The adults’ populations were high in May and June. The Kruskal-Wallis test revealed a significant difference in adult EPT abundance between months of study (X2 = 23.716, P<0.05). Higher number of Trichoptera especially Hydropsychidae, leading to high numbers of adults probably associated with algal biomass (Quinn et al., 1997). Furthermore, this net-making species always inhabit the side of rock facing water flows and they feed on the materials caught in their nets (Johnson and Triplehorn, 2005). Their females appear to be selective for particular substrates to lay their eggs (Badcock ,1953). In Tupah River, oviposition habitats were readily available because sub-optimally embedded rocks were plentiful in the river. Meanwhile, the peak of EPT abundance in May and June coincided with low precipitation during that month thus conducive for emergence. Moreover, warmer temperatures usually increase metabolism that lead to earlier emergence (Voshell and Reese, 2002). On contrary, more diverse Ephemeroptera were observed in the wet season, which probably related to fewer predators such as birds, bats and amphibians during this season. According to Baxter et al. (2005), the riparian predators have influenced on emergent adults of aquatic insects distribution and population biology. The population of Plecoptera was very low in Tupah River. Many Plecoptera emerge on land and because of this, they are prone to Carabidae 114 Proceedings of the 7th IMT-GT UNINET and The 3rd International PSU-UNS Conferences on Bioscience predation (Coleoptera) (Collier and Scarsbrook, 2000). Furthermore, Plecoptera was less diverse and normally represented by lower number of individuals (Yule and Yong, 2004). Conclusion Collection of the adult EPT at this river indicated that Tupah River provided suitable habitats for both adults and immature EPTs. Among the three orders, Trichoptera was the most diverse and represented by higher abundance. It seems probable that substrate type, water depth and rainfall involved in emergence success that determined the abundance and diversity of EPT. References Badcock, R.M. (1953). Observation of oviposition under water of the aerial insect Hydropsyche angustipennis (Curtis) (Trichoptera). Hydrobiologia 5(102), 222-225. Baxter, C.V., Fausch, K.D. and Sauders, W.C. (2005). Tangled webs: reciprocal flows of invertebrate prey link streams and riparian zones. Freshwater Biology 50, 201-220. Collier, K.J. and Scarsbrook, M.R. (2000). Use of riparian and hyporheic habitats. In Collier, K.J. and Winterbourn, M.J. (eds.). New Zealand stream invertebrates: ecology and implications for management. New Zealand Limnological Society, Christchurch, New Zealand. 415 pp. Enders, G. and Wagner, R. (1996). Mortality of Apatania fimbriata (Insecta: Trichoptera) during embryonic, larval and adult life stages. Freshwater Biology 36, 93–104. Quinn, J.M., Cooper A.B., Davies-Colley, R.J., Rutherford, J.C. and Williamson, R.B. (1997). Land-use effects on habitat, water quality, periphyton and benthic invertebrates in Waikato, New Zealand, hill country streams. New Zealand Journal of Marine and Freshwater Research. 31, 579-597. Johnson, N.F. and Triplehorn, C.A. (2005). Study of Insect. Thompson Brooks. United States of America. 863 pp. Voshell, J.R. and Reese, J. (2002). A Guide to Freshwater Invertebrates of North America. Mc Donald and Woodward Publishing Co. Blacksburg,Virginia. 450 pp. Wang, T.Q. and McCafferty, W.P. (2004). Heptageniidae (Ephemeroptera) of the World. Part 1: Phylogenetic Higher Classification. Transactions of the American Entomological Society 130(1), 11-45. Yule, C.M. and Yong, H.S. (2004). Freshwater invertebrates of the Malaysian Region. Academy of Science Malaysia. Kuala Lumpur. 861 pp. 115