Polytene Chromosomes of an Indian Himalayan black fly Simulium (Nevermannia) praelargum (Diptera: Simuliidae) Willie HENRY1, Subrata Kumar DEY2, Rakesh VARMA1, Sachin THAPA1, William S PROCUNIER3 1 2
P.G. Department of Zoology, Darjeeling Government College, Darjeeling, West Bengal 734101, India School of Biotechnology, West Bengal University of Technology,BF-142, Sector 1,Salt Lake City, Kolkata 700064, West Bengal, India
Consultant, North Bay, Ontario, P1B 5W6, Canada
Abstract High quality polytene chromosome maps (n=3) of a Himalayan Simuliid Simulium praelargum Datta, 1973 are presented and represent the first cytological description of a taxon found in the feuerborni group, subgenus Nevermannia. Polytene chromosomes one (I) and two (II) are metacentric, chromosome three (III) is submetacentric with the length of each chromosome occupying 37.25 %, 31.36 % and 31.34 % of the total complement length, respectively. Typical simuliid diagnostic intergeneric chromosomal markers are found within the polytene complement of this species. The nucleolar organizer (N.O.) is found at the base of the short arm of chromosome one (IS), the Ring of Balbiani (R.B.), double bubble (D.B.) and triad occur in the short arm of chromosome two (IIS), the Parabalbiani Ring (P.B.) and grey band (gb) occur in the long arm of chromosome two (IIL) and the Blister (B) and Capsule (Ca) occur in the short arm of chromosome three (IIIS).Terminal bands at the end of IIIS are heterochromatinized and present atypically with respect to other simuliid fauna. Populations studied so far are unique among the Simuliidae in that they exhibit chromosome structural monomorphism. These high resolution polytene chromosome maps will form the basis for future cytological characterization and phylogenetic comparisons amongst members of the feuerborni group [Current Zoology 56 (4): – 2010]. Key words Black fly, Feuerborni group, Simulium praelargum, Polytene chromosome maps, Monomorphism.
Black flies of the family Simuliidae represent a small group of insects in the order Diptera. Some of these taxa are established vectors of different parasitic diseases (Adler, 2005) including the new and old world tropical vector sibling complexes of human onchocerciasis (Procunier, 1989). Simuliid fauna of the Oriental region and the Indian sub –continent are less studied than fauna from other regions of the world (Adler and Crosskey, 2009) with cytotaxonomic studies on Indian Simuliids being rather scanty. Nevertheless, recent combined molecular and Received Jan. 20, 2010; accepted Feb. 08, 2010
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© 2010 Current Zoology
W. HENRY et al.: Polytene Chromosomes of S. (Nevermannia) praelargum cytological approaches have been encouraging to help resolve the biosystematics of a number of groups within S.E. Asia (Tangkawanit, et. al., 2009; Kuvangkadilok, et. al., 2008 ) including relationships based on molecular data for some members of the feuerborni group (Thanwisi, et al., 2006; Otsuka, et al., 2001). In this regard, the promise of DNA barcoding (Rivera and Currie, 2009), proteomic (Cupp and Cupp 1997; Cupp, et al., 1998) and genomic (Procunier WS, et al., 2005) approaches that target the functionally important salivary gland may also be instructive for understanding evolutionary biology and hierarchal classification of this family. Notwithstanding these integrated taxonomic approaches, cytotaxonomy still remains the gold standard for initially resolving species identity within closely related groups and can contribute significantly to resolving their genetic relationships through the establishment of stepwise paracentric sequential inversion phylogenies (Rothfels 1979, 1989) and in some cases can provide chromosomal biomarkers for supraspecific ranking (Procunier and Muro, 1994). More than 15 species of black...