Pimelodus ortmanni, Haseman, 1911

Girardi, Simone C., Pavanelli, Carla S. & Margarido, Vladimir P., 2018, Contributions to the systematic of Pimelodidae (Osteichthyes, Siluriformes): basic and molecular cytogenetics on seven species of Pimelodus from three Brazilian hydrographic systems, Neotropical Ichthyology 16 (2), pp. 1-16 : 10

Pimelodus ortmanni . The diploid number was also 56 chromosomes (24 m + 18 sm + 8 st + 6 a) ( Fig. 1f ). Among one to four B chromosomes (micro-chromosomes and acrocentric) ( Fig. 1f ) were observed in all specimens, with intra- and inter-individual variation ( Tab. 4 ). The AgNORs were located in the terminal region of the long arm of a pair of subtelocentric chromosomes 24 ( Fig. 1f , box). C-banding revealed the existence of pale heterochromatin in the region of the telomeres and centromeres of some chromosomes, with more conspicuous heterochromatin being found in the telomeric region of short arm (pair 16) and long arm (pairs 10, 24 and 27), in both telomere (pair 5) and in the pericentromeric region of the long arm (pairs 17 and 18), while the B chromosomes are entirely heterochromatic ( Figs. 2f , 4 ). The 18S rDNA was located on the subtelocentric chromosome pair (24), which corresponds to the AgNORs, while the 5S rDNA was found in the pericentromeric region of the long arm of pair 18 ( Fig. 3f ).

Figures

Fig. 1. Karyotypesarranged fromGiemsa-stained chromosomes.a. Pimelodusabsconditus; b. Pimelodusbritskii; c. Pimelodus maculatus; d. Pimelodus microstoma; e. Pimelodus mysteriosus; f. Pimelodus ortmanni; g. Pimelodus paranaensis. Pairs of the AgNORs and B chromosomes are in the boxes. Scales bar = 10 μm.

Fig.2. Karyotypesarranged from C-banded chromosomes.a. Pimelodusabsconditus; b. Pimelodus britskii; c. Pimelodus maculatus; d. Pimelodus microstoma; e. Pimelodus mysteriosus; f. Pimelodus ortmanni; g. Pimelodus paranaensis. B chromosomes in the boxes. Scales bar = 10 μm.

Fig. 4. C-banded metaphase of Pimelodus ortmanni. Arrows indicate the heterochromatic B chromosomes. Scales bar = 10 μm.

Fig. 3. Karyotypes after FISH with 5S rDNA probes (red) and 18S rDNA probe (green). a. Pimelodus absconditus; b. Pimelodus britskii; c. Pimelodus maculatus; d. Pimelodus microstoma; e. Pimelodus mysteriosus; f. Pimelodus ortmanni; g. Pimelodus paranaensis. Scales bar = 10 μm.