Download Temporal variation of adult Ephemeroptera, Plecoptera and

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
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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.
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