The diploid number decrease in cardinalfishes (Apogonidae, Kurtiformes): chromosomal rearrangements and related biological features

• Published in: Nucleus (Calcutta) 2024-08, Vol.67 (2), p.419-430
• Main Authors: dos Santos, Éricka Wannescka, de Bello Cioffi, Marcelo, da Costa, Gideão Wagner Werneck Félix, Amorim, Karlla Danielle Jorge, Oliveira, Vanessa Cristina Sales, Bertollo, Luiz Antônio Carlos, Molina, Wagner Franco
• Format: Article
• Language: English
• Subjects: Bioluminescence; Biomedical and Life Sciences; Cell Biology; Chromosome rearrangements; Chromosomes; Cytogenetics; Diploids; Genetic structure; Heterochromatin; Karyotypes; Life Sciences; Microsatellites; Nucleotide sequence; Original Article; Phaeoptyx pigmentaria; Phylogeny; Species; Sphaeramia nematoptera; Synteny
• ISSN: 0029-568X; 0976-7975
• DOI: 10.1007/s13237-023-00438-2

Cardinalfishes are a diverse family of small fish found in reef habitats. Some species exhibit bioluminescence and unusual characteristics of buccal egg incubation. Cytogenetic data on the family are confined to Pacific species but reveal remarkable karyotype diversity, as highlighted by low diploid values (2n = 34–46), which likely resulted from centric fusions. Therefore, chromosomal investigations, including samples from different marine regions and with a broader phylogenetic range, are required to elucidate the karyotype history of this group. In this study, we analyzed species from the Atlantic Ocean ( Apogon americanus and Phaeoptyx pigmentaria ) and the Indo-Pacific region ( Sphaeramia nematoptera and Pterapogon kauderni ) using conventional (Giemsa staining, Ag-NORs, and C-banding) and molecular (in situ mapping of rDNAs, retrotransposons, and microsatellites) cytogenetic methods. A noticeable karyotype reduction (2n = 46 in S. nematoptera and Pte. kauderni , 2n = 38 in P. pigmentaria , and 2n = 36 in A. americanus ) was detected, as well as a decrease in C-positive heterochromatin content (limited to telomeric and centromeric areas). In Indo-Pacific Ocean species, 18S rDNA and 5S rDNA are situated on distinct chromosomes, whereas in Atlantic Ocean species, they are syntenic. Interstitial telomeric sequences were found in S. nematoptera , A. americanus, and P. pigmentaria , indicating that in tandem fusions played a role in the chromosomal decrease in this group. Cardinal fish karyotype variability is remarkable, given the conservative diploid number that characterizes other Percomorpha species. It is probable that biological traits, such as buccal incubation and a brief pelagic larval stage, influence their genetic structure and the rapid rate of chromosomal differentiation. Graphical abstract