Abstract
Problem statement: Chironomidae have been recorded in rice fields throughout the world including in many countries such as India, Australia and the USA. Although some studies provide the key to genera level and note the difficulty of identifying the larvae to species level. Chironomid researches have been hindered because of difficulties in specimen preparation, identification, morphology and literature. Systematics, phylogenetics and taxonomic studies of insects developed quickly with emergence of molecular techniques. These techniques provide an effective tool toward more accurate identification of ambiguous chironomid species. Approach: Samples of chironomids larvae were collected from rice plots at Bukit Merah Agricultural Experimental Station (BMAES), Penang, Malaysia. A 710 bp fragment of mitochondrial gene Cytochrome Oxidase subunit I (COI) was amplified and sequenced. Results: Five species of Chironomidae; three species of subfamily Chironominae, Chironomus kiiensis, Polypedilum trigonus, Tanytarsus formosanus, two species of subfamily Tanypodinae, Clinotanypus sp and Tanypus punctipennis were morphologically identified. The phylogenetic relationship among these species was been investigated. High sequence divergence was observed between two individuals of the presumed C. kiiensis and it is suggested that more than one species may be present. However the intraspecific sequence divergence was lower between the other species of Tanypodinae subfamily. Interestingly, Tanytarsus formosanus showed close phylogenetic relationship to Tanypodinae species and this presumably reflect co-evolutionary traits of different subfamilies. Conclusion: The sequence of the mtDNA cytochrome oxidase subunit I gene has proven useful to investigate the phylogenetic relationship among the ambiguous species of chironomids.
Highlights
Chironomidae is considered a species-rich family of flies, with almost 15000 species described worldwide[1]
The larvae of five chironomid taxa belonging to subfamilies Chironominae and Tanypodinae were identified from the rice field at Bukit Merah Agricultural Experimental Station (BMAES) based on morphological characters
The species were identified as Chironomus kiiensis Tokunaga, Polypedilum trigonus Edwards, Tanytarsus formosanus Kieffer (Chironominae), Clinotanypus sp and Tanypus punctipennis Meigen (Tanypodinae)
Summary
Chironomidae is considered a species-rich family of flies, with almost 15000 species described worldwide[1]. As an important component of the aquatic insect community, Chironomidae has proven useful as biological indicators because of their sensitivity to chemical changes in aquatic ecosystems[2]. They are often included in most ecological and toxicological studies[3] and to assess the environment in many lentic environments[4]. In Malaysia, rice is the third most important economic crop covering an area of about 209300 h[5] They are considered a very important aquatic ecosystem as commercial resources and as a biotic resource especially as wetland habitats[6]. Tropical rice fields are diverse in insect fauna, which serve as an important food source for fishes[6,7]
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