Nuclear DNA content in 20 species of Siluriformes (Teleostei: Ostariophysi) from the Neotropical region

Abstract

In the present study, 20 species of Siluriformes fish were analyzed in order to determine their nuclear DNA content and compare these data with their diploid number. In addition, the extension and importance of the changes that occurred during the process of diversification in the group of Neotropical freshwater catfish were investigated. The only species studied of the family Doradidae, Rhinodoras d'orbignyi (2n = 58), presented 3.46 ± 0.13 pg of DNA. Among the species of the family Heptapteridae, the values of nuclear DNA content and the diploid numbers ranged from 1.13 ± 0.09 pg of DNA in Pimelodella sp. (2n = 46) to 2.38 ± 0.07 pg of DNA in Imparfinis mirini (2n = 58). The family Loricariidae showed the widest variation in diploid number and nuclear DNA content values, ranging from 2n = 52 and 3.96 ± 0.22 pg of DNA in Liposarcus anisitsi to 2n = 76 and 4.90 ± 0.12 pg of DNA in Hypostomus sp. 4. In this group, two local samples of Pimelodus maculatus (Pimelodidae) were analyzed, and both exhibited 2n = 56, but different nuclear DNA content values (2.68 ± 0.22 pg and 2.82 ± 0.20 pg, respectively). Among the Pseudopimelodidae species analyzed, Pseudopimelodus mangurus (2n = 54) showed 2.23 ± 0.15 pg and Microglanis cottoides (2n = 54) exhibited 2.50 ± 0.18 pg of DNA. Two species of Trichomycterus (Trichomycteridae) also presented the same diploid number, 2n = 54 chromosomes, but, while the species from the Quinta stream presented a DNA content of 2.62 ± 0.19 pg, in the sample from the Capivara river this value was 2.30 ± 0.23 pg. In the analyzed species, the results showed that the changes in DNA content were frequently not followed by changes in the diploid number. This fact permits to suggest that, in addition to structural chromosome rearrangements, other mechanisms, including deletions, duplications and polyploidy, could be involved in the process of species differentiation in the representatives of the fish order Siluriformes.

Genetics of neotropical fish: from chromosomes to populations

“…Analysis of the nuclear DNA content of species in the Loricariidae family conducted by Fenerich et al (2004) showed that the variation in diploid number does not seem to be directly related to the genome size. Thus, Hypostomus sp.…”

Karyotype and nuclear DNA content of Trichomycterus areolatus (Siluriformes, Trichomycteridae)

“…(average = 2.62 ± 0.19 pg/nucleus) and T. cf. iheringi (average = 2.3 ± 0.23 pg/nucleus) (Fenerich et al, 2004). These findings show that this cellular parameter varies widely in Trichomycterus.…”

“…Of note are the considerable variations in nuclear DNA contents of three species of the same genus, even though they possess the same diploid number (2n = 54). However, this is not atypical in fishes, given that this type of interspecific variation is often observed at the genus level (Carvalho et al, 1998;Fenerich et al, 2004), and can result from different processes, such as duplication and/or loss of chromosome segments, or differential accumulation of repeated DNA elements in the genome, as already well documented in higher vertebrates (Hartl, 2000). The nuclear DNA content Colihueque et al 281 values described for Trichomycterys so far (2.3-5.04 pg/nucleus) are higher than the average described for fishes (2 pg/nucleus; Hinegardner and Rosen, 1972), although they fall within the upper range described for various species of Siluriformes (1.04-8.75 pg/nucleus; Carvalho et al, 1998).…”

Comparative cytogenetics of nine species of Hypoptopomatinae (Teleostei: Siluriformes: Loricariidae): the importance of structural rearrangements in chromosome evolution

“…This fast chromosome evolution in Hypostomus may be followed by some event of polyploidy as suggested by Fenerich et al (2004). Interestingly, other loricariid group with extensive chromosome diversification is the genus Corydoras that also experience some events of polyploidy (Shimabukuro-Dias et al 2004).…”