13 research outputs found
Molecular Cytogenetic Analysis of the European Hake Merluccius merluccius (Merlucciidae, Gadiformes): U1 and U2 snRNA Gene Clusters Map to the Same Location
The European hake (Merluccius merluccius) is a highly valuable and intensely fished species
in which a long-term alive stock has been established in captivity for aquaculture purposes.
Due to their huge economic importance, genetic studies on hakes were mostly
focused on phylogenetic and phylogeographic aspects; however chromosome numbers
are still not described for any of the fifteen species in the genus Merluccius. In this work we
report a chromosome number of 2n = 42 and a karyotype composed of three meta/submetacentric
and 18 subtelo/telocentric chromosome pairs. Telomeric sequences appear
exclusively at both ends of every single chromosome. Concerning rRNA genes, this species
show a single 45S rDNA cluster at an intercalary location on the long arm of subtelocentric
chromosome pair 12; the single 5S rDNA cluster is also intercalary to the long arm of chromosome
pair 4. While U2 snRNA gene clusters map to a single subcentromeric position on
chromosome pair 13, U1 snRNA gene clusters seem to appear on almost all chromosome
pairs, but showing bigger clusters on pairs 5, 13, 16, 17 and 19. The brightest signals on
pair 13 are coincident with the single U2 snRNA gene cluster signals. Therefore, the use of
these probes allows the unequivocal identification of at least 7 of the chromosome pairs that
compose the karyotype of Merluccius merluccius thus opening the way to integrate molecular
genetics and cytological data on the study of the genome of this important species.VersiĂłn del editor4,411
Genomic organization of repetitive DNAs highlights chromosomal evolution in the genus Clarias (Clariidae, Siluriformes)
Seasonal Changes in Upper Thermal Tolerances of Freshwater Thai Fishes
Seasonal change inferred to climate change inevitably influences Critical thermal maximum (CTmax) of riverine fishes. In this study, we investigated CTmax as thermal tolerance for four common riverine fishes, i.e., Danio regina, Channa gachua, Rasbora caudimaculata and Mystacoleucus chilopterus, in the Kwae Noi river system in western Thailand. The acute thermal tolerance was lower in the wet season (mean river temperature âŒ25 °C) and higher in the dry season (mean river temperature âŒ23 °C) with medians of wet season-CTmax for those four fishes of 35.3 ± 0.4, 36.2 ± 0.5, 37.3 ± 0.5 and 37.5 ± 0.6 °C, respectively, and high values of dry season-CTmax of 37.4 ± 0.5, 38.3 ± 0.5, 38.7 ± 0.7 and 39.1 ± 0.5 °C, respectively. The variations of CTmax for all of the four species in this study, throughout the wet and dry seasons, attribute to their seasonal plasticity in response to the dynamics of thermal stress. Under climate variability and climate change with increasing the higher temperatures of air and river, and altering the habitat, R. caudimaculata and M. chilopterus had higher capacities to tolerate the acute heat stress across wet and dry seasons