Farlowella cf. amazonum (Günther, 1864)

Marajó, Leandro, Viana, Patrik F., Ferreira, Milena, Rapp Py-Daniel, Lúcia H. & Feldberg, Eliana, 2018, Cytogenetics of two Farlowella species (Loricariidae: Loricariinae): implications on the taxonomic status of the species, Neotropical Ichthyology 16 (4), pp. 1-8 : 2

Farlowella cf. amazonum (Günther, 1864) . Farlowella cf. amazonum had diploid chromosome number 58 and karyotype composed of 14metacentric+30submetacentric+14subt elocentric, with fundamental number (FN) = 116 ( Fig. 1a ). No evidence was found of the presence of differentiated sex. The first chromosome pair had a secondary constriction on the long arm with a subtle difference between the two homologs. This region corresponded to the NOR ( Fig. 1c ) and the 18S rDNA sites ( Fig. 2c ).

C-bands are pale, distributed mainly in the centromeric position, although differing in amount among chromosomes. Additionally, some other conspicuous signals were also found, such as in the long arms of the 1 st pair and the short arms of the 20th pair that were completely heterochromatic, and in both telomeric regions of pairs No. 13, 21, 26, 27, and 28 ( Fig. 1b ).

Hybridization with the 5S rDNA probe revealed signals only on the short arms of sm pair No. 20, which was completely heterochromatic ( Fig. 2d ). The mapping of the telomeric sequences revealed signals in the terminal regions of all the chromosomes, in addition to an accumulation of these sequences in the terminal portion of the long arms of pairs No. 16, 19, 21, 22, 26 and 27, no Interstitial Telomeric Sequences (ITS) were observed ( Fig. 2a ).

Figures

Fig. 1. Karyotype of Farlowella cf. amazonum: (a) Giemsa staining, (b) C-banding, and (c) NORs (highlighted). Karyotype of Farlowella schreitmuelleri: (d) Giemsa staining, (e) C-banding, and (f) NORs (highlighted). Scale bar = 10 µm.

Fig. 2. Karyotype of Farlowella cf. amazonum: (a) telomeric sequences, (c) 18S rDNA, and (d) 5S rDNA. Karyotype of Farlowella schreitmuelleri: (b) telomeric sequences, (e) 18S rDNA, and (f) 5S rDNA. Scale bar = 10 µm.