Pseudoromicia brunnea (Thomas, 1880)

Volleth, Marianne, Mayer, Frieder, Heller, Klaus-Gerhard, Müller, Stefan & Fahr, Jakob, 2023, Karyotype comparison of five African Vespertilionini species with comments on phylogenetic relationships and proposal of a new subtribe, Acta Chiropterologica 25 (1), pp. 35-52 : 41-42

Pseudoromicia brunnea (Thomas, 1880)

The karyotype of this species consisted of 2n = 36 chromosomes with FNa = 50 ( Fig. 4 ), including seven large to medium meta- to submetacentric, one small submetacentric, and nine small acrocentric autosomal pairs. The X chromosome was a medium-sized submetacentric and the Y chromosome a small bi-armed chromosome. The bi-armed autosomal elements showed the following combination of chromosomal arms: 1/2, 3/4, 5/6 and 16/17 as in the vespertilionid basic karyotype, as well as derived associations 7/11, 8/9, 10/12, and 14/18. Two autosomal pairs showed derived conditions due to intrachromosomal rearrangements. The bi-armed element 3/4, which is metacentric in the basic karyotype, was submetacentric in P. brunnea . The formerly proximal part of arm 3, bearing homologous sequences to Eulemur chromosome EMA8, was shown to be situated in the proximal part of the long arm of P. brunnea chromosome 3/4 ( Fig. 5 ). This rearranged chromosome resulted either from a centromere repositioning or a pericentric inversion. Another presumed centromere repositioning in the formerly metacentric element 16/17 resulted in a submetacentric chromosome with a slightly enlarged arm 17.

The single NOR was found at the SC close to the centromere of arm 15. The mean number of active NORs per cell was 1.95 (20 cell scored from the male specimen). C-banding revealed only weak centromeric staining on the bi-armed elements but clear C-bands at the centromeres of the acrocentric elements, especially pronounced on chromosome 24. P. brunnea chromosome 5/6 showed a large heterochromatin block in arm 5 close to the centromere, resulting in a clearly enlarged size of arm 5 ( Fig. 6A ). A small intercalary heterochromatic band was found in the rearranged chromosome 3/4 on the long arm, approximately at the former location of the centromere. The small bi-armed Y chromosome consisted largely of C-positive heterochromatic material.

The G-banding pattern of the submetacentric X chromosome differed from that of state II in the basic karyotype. In P. brunnea , presumably due to a small pericentric inversion or centromere repositioning, the short arm and the proximal part of the long arm of the ancestral X, state II, constituted the long arm, whereas the distal part of the formerly long arm now built up the short arm ( Fig. 7 ).

The chromosomes 1/2, 11, 12, and 15 were present in state II. Therefore, P. brunnea is clearly a member of the tribe Vespertilionini sensu Volleth and Heller (1994) .

Figures

FIG. 4. G-banded karyotype of a male P. brunnea, 2n = 36. At the X, a horizontal line indicates the position of the centromere in the X chromosome of the basic karyotype, state II. Asterisks indicate interstitial heterochromatic segments

FIG. 5. Rearranged bi-armed pair 3/4 of P. brunnea depicted from left to right after G-banding, C-banding, FISH with E. macaco painting probe EMA8 and T. belangeri probe TBE6. The extant centromere is indicated by a dash, the ancestral centromere position by an asterisk. In the basic karyotype, EMA8 homologous sequences were located in the proximal region of the MMY3 homologous chromosomal arms, whereas here they are found in the long arm of P. brunnea chromosome 3/4 (TBE6, homologous to parts of MMY4, was used to delimit the proximal and distal regions of the MMY4 homologous segment in P. brunnea chromosome 3/4)

FIG. 6. C-banded metaphase spreads of (A) P. brunnea, (B) N. happoldorum, and (C) N. schlieffenii. X and Y chromosomes and heterochromatic segments of interest are indicated, numbers refer to MMY homologies. In (B), arrows point to those heterochromatic segments which showed differences between the homologs and arrowheads point to C-positive segments on pairs NHA11 and NHA13. For further explanation see main text

FIG. 7. Examples of G-banded X chromosomes: The banding patterns of the X chromosomes from L. kirinyaga (LKI) and N. schlieffeni (NSC) were similar to that of state II of the basic vespertilionid karyotype. The N. guineensis (NGU) X was the product of an X-autosome translocation and the X chromosomes from P. brunnea (PBR) and N. happoldorum (NHA) showed unique derived G-banding patterns