Pimelodus microstoma, Steindachner, 1877

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 : 6

Pimelodus microstoma . The diploid number was also 56 chromosomes (24 m + 18 sm + 8 st + 6 a) ( Fig. 1d ). The AgNORs were located in the terminal region of the long arm of a pair of subtelocentric chromosomes 24 ( Fig. 1d , box). C-banding highlighted pale heterochromatin in the region of the centromere in the most of chromosomes, with more conspicuous heterochromatin being found in the telomeric region of the short arm (4) and long arm (pairs 16 and 24), in both telomeres (pair 8) and in the pericentromeric region of the long arm in pair 18 ( Fig. 2d ). 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. 3d ). Pimelodus mysteriosus . The diploid number was also 56 chromosomes (28 m + 10 sm + 2 st + 16 a) ( Fig. 1e ). The AgNORs were located in the terminal region of the long arm of a pair of subtelocentric chromosomes 20 ( Fig. 1e , box). C-banding highlighted pale heterochromatin in the region of the centromere in the most of chromosomes, with more conspicuous heterochromatin being found in the telomeric region of the short arm (pair 20) and long arm (pairs 5, 17, 20, 21, 22, 23, 24, 26, 27 and 28), in interstitial region (pairs 21 and 23) and in the pericentromeric region of the long arm of pairs 21 and 22 ( Fig. 2e ). The 18S rDNA was located on the subtelocentric chromosome pair (20), which corresponds to the AgNORs, while the 5S rDNA was found at multiple sites, located in the interstitial region of the long arm of pair 1 and pericentromeric region of the long arm of pairs 21 and 22 ( Fig. 3e ).

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. 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.