Simulium kiewmaepanense

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

Simulium kiewmaepanense

The banding patterns of all seven chromosomally prepared larvae (three females and four males) were fully analyzed, including one female and two males infected with an unidentified, probably new, species of microsporidium ( Fig. 1 ) characterized by individual spores 3.5–4.0 times longer than wide in clusters of eight. Chromosomal homologs were 98–100% paired along their lengths. The centromere regions were expanded and the nucleolar organizer was in the standard subgeneric position in IIIL. The chromosomal banding sequence differed from that of the Simulium subgeneric standard by three novel fixed inversions— IIS-1, IIS-2, and IIS-3 —plus IIIL-1 ( Fig. 2 ) of Adler and Kachvorian (2001). One hypothesis for resolution of IIS relative to the subgeneric standard is shown in Fig. 2 . Alternative hypotheses involve the choice of breakpoints for IIS-2 and IIS-3. For instance, breakpoints for IIS-3, although shown as c/e and d/g, could also be given as h/f (subsequent to inversion of IIS-2) and g/d. The correct interpretation could be resolved by discovery of an intermediate condition, i.e., a related species that has one or two of the IIS inversions. Sex chromosomes were cytologically undifferentiated (X 0 Y 0) and autosomal polymorphisms were lacking.

Figures

Fig. 1. Phase-contrast images of probable new species of microsporidium from fat body of female larva of Simulium kiewmaepanense, Doi Inthanon, Thailand. (A) Individual spores. (B) Developmental stages.

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.