Karyotypic diversity and chromosome evolution in the armored catfishes Callichthyinae (Siluriformes, Callichthyidae)

Abstract

The Callichthyinae subfamily is composed of five genera with a small number of described species. Molecular cytogenetics studies show the scarcity of records for this subfamily. The aim of the present study was to employ cytogenetic parameters in the analysis of three species belonging to the subfamily Callichthyinae sampled from the Paraná River (Brazil). Callichthys callichthys had 2n = 56 chromosomes (26 m-sm + 30 st-a); Lepthoplosternum pectorale had 2n = 64 chromosomes (8 m-sm + 56 st-a); and Hoplosternum littorale had 2n = 60 chromosomes (8 m-sm + 52 st-a). Regarding the location of the nucleolar organizer regions (NORs) (Ag-staining and 18S rDNA-FISH), different situations were found: single NORs in H. littorale and C. callichthys; multiple NORs in L. pectorale, with intra-individual and inter-individual variation. Heterochromatin was observed in the centromeric region in the chromosomes of the three species. Equilocal, interstitial bands were also found in H. littorale. Physical mapping of 5S ribosomal genes by FISH shows eight 5S rDNA sites in C. callichthys; four 5S rDNA sites in H. littorale and six 5S rDNA sites in L. pectorale. Using cytogenetic markers (diploid number, chromosome formula, NORs, heterochromatin distribution pattern and 5S and 18S rDNA sites), the chromosomal evolution in Callichthyinae is presented: Callichthys shows mostly basal chromosomal conditions, with mostly derived chromosomal conditions verified for the Hoplosternum-Dianema clade and Megalechis-Lepthoplosternum clade.

An uncommon co-localization of rDNA 5S with major rDNA clusters in Callichthyidae (Siluriformes): a report case in Corydoras carlae Nijssen & Isbrücker, 1983

“…However, syntenic localization of the major rDNA clusters and the 5S sites were observed for the first time in the genus Corydoras Lacepède, 1803 (present study) and Callichthys callichthys (Linnaeus, 1758) (Konerat et al 2014), the other integrant of the family Callichthyidae. In Loricariidae, Kronichthys lacerta (Nichols, 1919), Isbrueckerichthys duseni (Miranda Ribeiro, 1907), Parotocinclus maculicauda (Steindachner, 1877) and Trichomycterus sp.…”

“…Interestingly, all the possible syntenic conditions have been found in fishes, both sets of genes in distinct and disjoint chromosomal regions, as observed in Parodon nasus Kner, 1859 cited as Parodon tortuosus (Vicente et al 2001) and Astyanax paranae Eigenmann, 1914 cited as Astyanax scabripinnis (Mantovani et al 2005), or in adjacent regions, as in Triportheus nematurus (Kner, 1858) (Diniz et al 2009), Mugil incilis Hancock, 1830 (Hett et al 2011), Kronichthys lacerta , Isbrueckerichthys duseni , Parotocinclus maculicauda , Trichomycterus sp. (Ziemniczak et al 2012) and Callichthys callichthys (Konerat et al 2014), or the 5S rDNA interspersed along the clusters of 45S rDNA (co-localization), as in Astyanax altiparanae Garutti & Britski, 2000, Astyanax lacustris (Lütken, 1875), Astyanax fasciatus (Cuvier, 1819), Astyanax schubarti Britski, 1964 and Astyanax paranae cited as Astyanax scabripinnis (Almeida-Toledo et al 2002), Solea senegalensis Kaup, 1858 (Cross et al 2006), Bryconamericus cf. iheringii (Piscor et al 2013) and Corydoras carlae (present study).…”

Cytogenetic studies in the redtail catfish, Phractocephalus hemioliopterus (Bloch & Schneider, 1801) (Siluriformes, Pimelodidae) a giant fish from Amazon basin

“…In general, the 18S and 5S rDNA sites are not syntenic but located on different chromosome pairs, this feature being the most frequent patter in several Pimelodidae species (Carvalho et al 2010, Swarça et al 2008, 2009). However, recently syntenic localization of the major rDNA clusters and the 5S sites were reported in other species (Ziemniczak et al 2012, Konerat et al 2014, da Rocha et al 2016). So far, both patterns of rDNA and 5S rDNA localization, syntenic and not syntenic, have been described in Pimelodidae.…”