Chromosomes of Asian cyprinid fishes: cytogenetic analysis of two representatives of small paleotetraploid tribe Probarbini

Abstract

BackgroundPolyploidy, although still poorly explored, represents an important evolutionary event in several cyprinid clades. Herein, Catlocarpio siamensis and Probarbus jullieni - representatives of the paleotetraploid tribe Probarbini, were characterized both by conventional and molecular cytogenetic methods.ResultsAlike most other paleotetraploid cyprinids (with 2n = 100), both species studied here shared 2n = 98 but differed in karyotypes: C. siamensis displayed 18m + 34sm + 46st/a; NF = 150, while P. jullieni exhibited 26m + 14sm + 58st/a; NF = 138. Fluorescence in situ hybridization (FISH) with rDNA probes revealed two (5S) and eight (18S) signals in C. siamensis, respectively, and six signals for both probes in P. jullieni. FISH with microsatellite motifs evidenced substantial genomic divergence between both species. The almost doubled size of the chromosome pairs #1 in C. siamensis and #14 in P. jullieni compared to the rest of corresponding karyotypes indicated chromosomal fusions.ConclusionBased on our findings, together with likely the same reduced 2n = 98 karyotypes in the remainder Probarbini species, we hypothesize that the karyotype 2n = 98 might represent a derived character, shared by all members of the Probarbini clade. Besides, we also witnessed considerable changes in the amount and distribution of certain repetitive DNA classes, suggesting complex post-polyploidization processes in this small paleotetraploid tribe.

A Cytogenetic Analysis of <i>Enteromius parablabes</i> (Daget, 1957) from Aho Stream, Ile-Ife, Nigeria

“…In addition, karyotyped diploid cyprinids have been found to be mostly made up of small-sized chromosomes and this makes identifying their morphological orientations difficult [16]. Another challenge in karyotyping cyprinid species is chromosome arm contraction due to temporal and dose colchicine treatment (eg variations from 0.02 ml of colchicine per gram wet weight) [17].…”

Taxonomic Diversity Not Associated with Gross Karyotype Differentiation: The Case of Bighead Carps, Genus Hypophthalmichthys (Teleostei, Cypriniformes, Xenocyprididae)

“…The karyotype structures in H. molitrix and H. nobilis, however, differed markedly among various studies. The reason for these discrepancies might be linked with the following facts; (i) chromosomes of cypriniform fishes generally exhibit very small size when compared to other teleosts (see, e.g., in [45,[54][55][56]); (ii) furthermore, cyprinoid chromosomes also exhibit a gradual decrease in size, with the centromere positions ranging stepwise from median to nearly terminal, making it difficult to assess the chromosomal categories with accuracy; and (iii) inspection of published chromosome pictures showed that previous reports were based on highly condensed chromosomes which also made it impossible to describe the karyotype accurately. However, careful analysis of a number of metaphase cells with less condensed chromosomes demonstrated that karyotypes of all three species of bighead carps at the level of conventionally Giemsa-stained chromosomes are in fact identical.…”

“…Among Cypriniformes, many studies have been conducted on polyploid species and especially on those of high aquacultural importance, such as genera Cyprinus and Carassius (see, e.g., in [55,74,86,87]) or on unisexually reproducing taxa such as Squalius, Cobitis, and Misgurnus and on species closely related to them [45,77,79,[88][89][90][91][92]. Some reports revealed amplified number of either 5S or 18S rDNA signals [45,55], different types of inter-individual/inter-populational polymorphisms in number and location of rDNAs [70,[88][89][90][91]93] or high interspecific variability in this character [91,92,94], while still other studies found rather standard patterns, with just one locus of one or both rDNA classes per haploid genome [45,77,95] or only a slight elevation in number of sites [56,95,96]. Among two Hypophthalmichthys species analyzed herein, a single pair of 5S rDNA loci occupied apparently homeologous chromosomes and were found adjacent to one of the multiple 18S rDNA clusters.…”

First chromosome analysis of Thai pufferfish Pao cochinchinensis (Steindachner, 1866)

“…gachua (Cioffi et al 2015), Cl. gariepinus (Maneechot et al 2016) and two cyprinid fishes, Catlocarpio siamensis and Probarbus jullieni (Saenjundaeng et al 2018). These fishes have the patterns of d(CA)15 repeats which distributed throughout the chromosome without strong accumulations in specific regions in all chromosomes.…”

“…However, this kind of study is scarcely applied in Thai freshwater fish. Exceptions are studies in Bagrid catfishes (Supiwong et al 2013(Supiwong et al , 2014a, Channids (Cioffi et al 2015), three Clarias species (Maneechot et al 2016), Toxotes chatareus (Hamilton, 1822) (Supiwong et al 2017), two cyprinid fishes (Saenjundaeng et al 2018), Asian swamp eel, Monopterus albus (Zuiew, 1793) (Supiwong et al 2019) and silulid catfishes (Ditcharoen et al 2019). The present study is the first report on chromosomal characteristics in P. cochinchinensis using conventional staining, Ag-NOR banding, and FISH technique, being the basis for further study by advanced genetics and for future comparative approaches concerning systematics and evolutionary relationships of buffer-fishes.…”