Biodiversity of aquatic insect and physicochemical water quality parameters in Mae Tao

Biodiversity of aquatic insect and physicochemical water quality parameters in receiving water bodies in Kasetsart University, Kamphaeng Saen Campus, Nakhon Pathom Province, central Thailand were assessed during October 2010 to September 2011. Seven sampling stations, each 100 m long, were established. Three replicates of samplings by aquatic D-net were used at sampling sites. A total of 4,257 individual of aquatic insect were collected during one year. Six Orders and 12 families were recorded in this study. The family Hydropsychidae and Chironomidae were the most abundance of aquatic insects that found in receiving water bodies. The CCA revealed the family Mesoveliidae and Chironomidae were correlated with alkalinity in receiving water bodies, whereas dissolved oxygen was correlated with family Baetidae, Coenagrionidae, Hydrophilidae, and Helotrephidae. Signs of increasing water quality deterioration were evident in the result of the physicochemical analyses.

No abstract

The Tapee River is one of the most important rivers in southern Thailand. The river crisscrosses from Khao Luang National Park, Nakhon Si Thammarat province to Surat Thani province and flows to the Thai Gulf. To study the biodiversity and distribution of Trichoptera species along the Tapee River, insects were collected by light trapping every 3 months from April 2004−February 2005. The results show that 105 species were found in 35 genera of 15 families. The most abundant families of Trichoptera in the Tapee River were Hydropsychidae, Leptoceridae, and Ecnomidae. The more widespread Trichoptera species included Ecnomus atevalus Malicky & Chantaramongkol, Dipseudopsis knappi Schmid & Denning, D. robustior Ulmer, Aethaloptera sexpunctata (Kolenati), Amphipsyche meridiana Ulmer, Cheumatopsyche cognita (Ulmer), Macrostemum fenestratum (Albarda), Ceraclea idaia Malicky & Chaibu, Oecetis tripunctata (Fabricius), and Parasetodes respersellus (Rambur). The upper Tapee River Trichoptera species included Rhyacophila petersorum Schmid & Denning, R. tantichodoki Malicky & Chantaramongkol, Ugandatrichia kerdmuang Malicky & Chantaramongkol, Chimarra spp., Pseudoneureclipsis spp., Psychomyia spp., Cheumatopsyche charites Malicky & Chantaramongkol, Diplectrona spp., Hydropsyche spp., Hydromanicus inferior Chantaramongkol & Malicky, Goera spp., Ganonema fuscipenne (Albarda), Goerodes abruptum Banks, and Marilia spp. The lower Tapee River Trichoptera species included Ecnomus talenoi, E. paget, Polymorphanisus spp., and Oecetis bengalica. The number of Trichoptera species was higher upstream and lower downstream.

The distribution and diversity of aquatic insects and water quality variables were studied among three streams of the Mae Klong Watershed. In each stream, two sites were sampled. Aquatic insects and water quality variables were randomly sampled seven times in February, May, September, and December 2010 and in January, April, and May 2011. Overall, 11,153 individuals belonging to 64 families and nine orders were examined. Among the aquatic insects collected from the three streams, the order Trichoptera was most diverse in number of individuals, followed by Ephemeroptera, Hemiptera, Odonata, Coleoptera, Diptera, Plecoptera, Megaloptera, and Lepidoptera. The highest Shannon index of diversity of 2.934 and 3.2 was recorded in Huai Kayeng stream and the lowest was in Huai Pakkok stream (2.68 and 2.62). The high diversity of insect fauna in streams is an indication of larger microhabitat diversity and better water quality conditions prevailing in the streams. The evenness value was recorded as high in most sites. The high species diversity and evenness in almost all sites indicated good water quality.

Larvae of only 2 of the 13 species of Hydromanicus known from Thailand have been described previously. In this research, the "metamorphotype method" was used to associate yet-unidentifiable larvae and pupae with their identifiable adults: Pupal identifications were based on genitalic features in common with described adults, and larvae were associated with the pupae. Herein, the final larval instar of Hydromanicus malayanus, H. abiud and H. inferior are described and illustrated.

Aquatic insects can accumulate pollutants such as cadmium from stream sediments. This research aimed to monitor cadmium concentrations in both larvae and adult Hydropsychidae (Trichoptera, Insecta) in Mae Tao (MT1 to MT5) and Mae Ku (MK2 and MK8) watersheds in northern Thailand. Samples were collected twice a month from July 2011 to May 2012 at seven sampling sites. The cadmium concentrations in the stream sediments ranged from 0.12 to 21.5 mg kg-1 wet weight. The highest concentration was recorded from the MT3 sampling site (21.5 mg kg-1), which is also closest to a mining area. The lowest concentration was recorded from the MK2 sampling site (0.12 mg kg-1). Cadmium concentrations in both larvae and adult Hydropsychidae were not significantly different at all sampling sites. However, the cadmium concentrations in Hydropsychidae larvae that ranged from 0.07-1.70 mg kg-1 were higher than the detected cadmium in adult samples (average 0.020 mg kg-1). There was no significant correlation between cadmium concentrations in sediments, and in both larvae and adult Hydropsychidae. Concentrations of cadmium in adult Hydropsychidae in this study were low. Even though the contamination of heavy metals was low in adult Hydropsychidae, long-term exposure to heavy metals could seriously impact terrestrial animals such as birds and bats that consume these insects.

Morphological characters of the larvae of four species in the genus Hydropsyche (H. dolosa, H. brontes, H. napaea, and H. camillus) are described and figured for the first time. The most important diagnostic features are illustrated, and some information regarding their distribution, biology, and habitat are included.