Cytogenetics of Simulium siamense Takaoka and Suzuki, 1984 (Diptera: Simuliidae) in northeastern Thailand

Abstract

We analysed salivary gland polytene chromosomes of 796 larvae from 17 populations of Simulium siamense in northeastern Thailand. Seventeen floating and two fixed chromosome inversions were recorded. Three cytoforms (A, F and G) were recognised and two of them are new (F and G). Cytoform F is distinguished by a fixed inversion on the long arm of chromosome II (IIL-8) and cytoform G by fixed inversions on the long arm of chromosome II (IIL-8) and short arm of chromosome III (IIIS-2). Significant departures from Hardy–Weinberg equilibrium due to heterozygote deficiency in geographically intermediate populations and absence of shared polymorphic inversions of the cytoforms indicate separation of the gene pool. Morphometric analysis of the larvae revealed significant differences in body length (F = 5.00, p =0.007) and head capsule width (F = 4.68, p = 0.010) among cytoforms.

Keywords:

• black fly
• chromosome inversion
• cytoform
• polytene chromosome
• Simulium

Acknowledgements

This work was financially supported by grant from Mahasarakham University (grant year 2010). We would like to thank Peter Adler (Clemson University, USA) and Adrian Plant (National Museum of Wales, UK) for valuable comments on the manuscript.