Karyotype Differentiation in Chromaphyosemion Killifishes (Cyprinodontiformes, Nothobranchiidae). I: Chromosome Banding Patterns of C. Alpha, C. Kouamense and C. Lugens

Abstract

The karyotypes of three recently described species of Chromaphyosemion, namely C. lugens, C. alpha and C. kouamense, were analysed using conventional Giemsa staining, C-banding and sequential banding (fluorescence banding with 4', 6-diamidino-2-phenylindole (DAPI) and Chromomycin A(3) (CMA(3)), C-banding, AgNO(3)-staining). Diploid chromosome numbers ranged from 2n = 36 in C. lugens to 2n = 38 in C. alpha and C. kouamense. The karyotype of C. lugens consisted of one pair of metacentric (m) and 17 pairs of telocentric (t) chromosomes, that of C. alpha was composed of one pair of submetacentric (sm), six pairs of subtelocentric (st) and 12 pairs of t chromosomes, and that of C. kouamense comprised five pairs of st and 14 pairs of t chromosomes. In addition to the differences in karyotype structures and/or chromosome numbers, the karyotypes of the examined species differed with respect to NOR phenotype and distribution and base composition of heterochromatin. No heteromorphic sex chromosomes were detected in any of the species. Our findings provide cytotaxonomic evidence for the species distinctness of C. alpha, C. kouamense and C. lugens whose descriptions were based primarily on external morphology.

Karyotype differentiation in <i>Chromaphyosemion</i> killifishes (Cyprinodontiformes, Nothobranchiidae). III: Extensive karyotypic variability associated with low mitochondrial haplotype differentiation in <i>C. bivittatum</i>

“…Second, the karyotypes of all C. bivittatum populations contained three cytologically distinguishable types of heterochromatin: (i) DAPI-positive, AT-rich heterochromatin, (ii) CMA 3 -positive, GC-rich heterochromatin and (iii) heterochromatin of heterogeneous base composition that was neither DAPI-nor CMA 3 -positive. Third, the lack of heteromorphic sex chromosomes in C. bivittatum agreed with the results obtained for all other Chromaphyosemion populations examined to date (Scheel, 1968(Scheel, , 1974(Scheel, , 1990Völker et al, 2005.…”

“…First, Ag-NORs were always associated with GC-rich heterochromatin and thus conformed to the pattern observed in most neoteleostean fishes (Ráb et al, 1999), including most Chromaphyosemion populations examined (Völker et al, 2005. Second, the karyotypes of all C. bivittatum populations contained three cytologically distinguishable types of heterochromatin: (i) DAPI-positive, AT-rich heterochromatin, (ii) CMA 3 -positive, GC-rich heterochromatin and (iii) heterochromatin of heterogeneous base composition that was neither DAPI-nor CMA 3 -positive.…”

“…Such elements appear to be fairly common in Chromaphyosemion (Völker et al, 2005. The origin of these chromosomes is unknown, but the high frequency of chromosomal fusions and the observed cases of intraspecific presence/absence polymorphisms in C. riggenbachi and C. bivittatum might indicate that such elements are by-products of chromosomal fusions that may be lost from the karyotype after some time.…”

Reproductive isolation in a nascent species pair is associated with aneuploidy in hybrid offspring

“…Chromosome suspensions from embryos were prepared following a previously published method [37] using early-eyed stage embryos (approx. 150 -180 degree-days, i.e.…”

Karyotype differentiation in <i>Chromaphyosemion</i> killifishes (Cyprinodontiformes, Nothobranchiidae). II: Cytogenetic and mitochondrial DNA analyses demonstrate karyotype differentiation and its evolutionary direction in <i>C. riggenbachi</i>

“…DAPI-positive AT-rich heterochromatin, CMA 3 -positive GC-rich heterochromatin and heterochromatin of heterogeneous base composition (neither DAPI-nor CMA 3 -positive). Among the three Chromaphyosemion species previously examined with appropriate chromosome banding techniques, only C. kouamense presented all three kinds of heterochromatin, while in C. alpha and C. lugens only GC-rich and heterogeneous heterochromatin was found (Völker et al, 2005). It has been suggested that AT-rich heterochromatin is a hot spot for recombination promoting chromosomal rearrangements (e.g.…”