Stomatorhinus walkeri

Ozouf-Costaz, Catherine, Coutanceau, Jean-Pierre, Bonillo, Céline, Belkadi, Laurent, Fermon, Yves, Agnese, Jean-François, Guidi-Rontani, Chantal & Paugy, Didier, 2015, First insights into karyotype evolution within the family Mormyridae, Cybium 39 (3), pp. 227-236 : 232

Stomatorhinus walkeri

The karyotype is composed of 2n = 50 (2sm + 48a), FN = 52. C-bands are found in the centromeric regions of all chromosomes and many in the interstitial, pericentromeric or telomeric regions of acrocentric pairs. In particular, the first pair of acrocentrics is strongly heteromorphic due to a pericentromeric constriction of unequal size within this pair ( Fig. 3 ). The 18S rDNA genes are heteromorphic in size, DAPI-negative, and located in the long arms of an acrocentric chromosome pair ( Fig. 5E, F ). This chromosome pair probably corresponds to the first acrocentric pair in the karyotype, as shown in figure 3. With the FISH protocol used for the other mormyrid species, the telomeric probe produced almost no signals in the telomeres ( Fig. 5G ). We tested two different batches of telomeric probe at several concentrations (up to 50 ng /µl) and less stringent post-hybridization washes (not detailed in the method) without obtaining any further hybridization spots. The microsatellite (GAA) 10 is, on the contrary, the most abundant among species examined ( Fig. 5H ).

Figures

Figure 3. - Karyotypes of G. petersii, GNPE, M. moorii, MAMO, I. opdenboschi, IVOP, Brienomyrus sp., BR SP, S. walkeri, STWA, and P. microphthalmus, PEMI, after conventional Giemsa staining and C-banding. Scale bar = 10 µm.

Figure 5. - Metaphase plates of Brienomyrus sp. (A, B, C, D), S. walkeri (E, F, G, H) and P. microphthalmus (I, J, K, L), showing FISH patterns of the 18S rDNA probe, indirectly DIG-labelled, detected with rhodamine; DAPI counterstaining on the same metaphase plate; patterns of the Atto 488 labelled (TTAGGG)7 probe; patterns of the Cy3 labelled (GAA)10 satellite probe. Scale bars = 10 µm.