Simulium undecimum, Takaoka, Srisuka & Saeung, 2018

Adler, Peter H., Srisuka, Wichai, Low, Van Lun, Takaoka, Hiroyuki & Saeung, Atiporn, 2019, High-Elevation Chromosomal Diversity of Black Flies (Diptera: Simuliidae) in Thailand, Insect Systematics and Diversity 3 (2019), No. 1, pp. 1-10 : 2-3

Simulium undecimum

The banding patterns of all 54 chromosomally prepared larvae (28 females and 26 males) were fully analyzed, including two females infected with mermithid nematodes. The patterns corresponded precisely with the banding sequence of S. malayense cytoform B described by Thaijarern et al. (2018) as having the following fixed inversions: IIS-1, IIS-2, IIS-3, IIL-1, IIIL-3, IIIL-5, IIIL-6, and IIIL- 10. Among the nuclei in individual larvae, ectopic pairing was absent or expressed among any or all combinations of the thick, darkly staining centromere bands. Homologs were 98–100% paired along their lengths. We found a small, glassy band, not previously reported,

a Identification confirmed by association of gill histoblasts from one mature larva with two pupal exuviae.

b The larva of this species is undescribed; identification was made based on the gill histoblast of one mature larva. in section 66 of IIL in all larvae ( Fig. 2C ), possibly reflecting enhanced polytenization or nucleotide content. Sex chromosomes were microscopically undifferentiated (X 0 Y 0) and polymorphisms were absent.

Figures

Fig. 2. Species-specific chromosomal sequences of species from Doi Inthanon,Thailand. (A) IS base of Simulium tenebrosum cytospecies B (female larva), with bracket indicating limits of IS-33; C, centromere. (B) IIIL end of S. kiewmaepanense (male larva), showing IIIL-1 sequence (bracketed). (C) IIL distal half of S. undecimum (male larva) with bracket indicating limits of IIL-1 and enhanced, glassy band (+). (D) IIS of S. kiewmaepanense (male larva) showing IIS-1, IIS-2, IIS-3 sequence.The sequence involves two coincident breakpoints.Thus, for the hypothesis shown, inverting IIS-3 will create the e/g junction representing the IIS-1 break proximal to the centromere; when IIS-2 is then inverted, it creates the h/f junction representing the IIS-1 break distal to the centromere.The Simulium subgeneric standard sequence is, thus, obtained by alphabetically ordering the fragments indicated by the letters a–h; bu, bulge; C, centromere; RoB, ring of Balbiani.