Karyotype differentiation in tellin shells (Bivalvia: Tellinidae)

Abstract

BackgroundAlthough Tellinidae is one of the largest and most diverse families of bivalves, its taxonomy is utterly chaotic. This is mainly due to the morphological diversity and homoplasy displayed by their shells and to the scarcity of the molecular phylogenetic studies performed on them. A molecular cytogenetic analysis of four tellin shell species, Bosemprella incarnata, Macomangulus tenuis, Moerella donacina and Serratina serrata, was performed. To molecularly characterize the analyzed specimens, the sequence of a fragment of the mitochondrial cytochrome c oxidase subunit I (COI) was also studied.ResultsThe karyotypes of the four species were composed of different amounts of bi-armed and telocentric chromosomes. The chromosomal mapping of 45S and 5S rDNA and H3 histone gene clusters by fluorescent in situ hybridization also revealed conspicuous differences on the distribution of these DNA sequences on their karyotypes. Vertebrate type telomeric sequences were located solely on both ends of each chromosome in all four tellin shells.ConclusionWe present clear evidence of the valuable information provided by FISH signals in both analyzing chromosome evolution in Tellinidae and as a further tool in identifying tellin shell specimens for molecular phylogenies.

Are Pericentric Inversions Reorganizing Wedge Shell Genomes?

“…The 2n = 38 diploid chromosome numbers of the two wedge shell species studied here coincide with previous reports for Donax variabilis [ 23 ] and D. trunculus [ 21 , 24 , 25 ]. This is also the usual diploid number found in most bivalve species belonging to the subclass Heterodonta [ 27 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 ].…”

“…In contrast, the karyotypes of the wedge shells studied here present some unusual characteristics for the subclass Heterodonta. Typically, those bivalve karyotypes are poor in telocentric chromosomes [ 41 , 44 ] and the presence of undetectable short arms in the telocentric pairs is uncommon. The best known examples are the dwarf surf clam Mulinia lateralis [ 45 ], three razor shell species [ 41 , 46 ], and one tellin shell species [ 44 ].…”

“…Typically, those bivalve karyotypes are poor in telocentric chromosomes [ 41 , 44 ] and the presence of undetectable short arms in the telocentric pairs is uncommon. The best known examples are the dwarf surf clam Mulinia lateralis [ 45 ], three razor shell species [ 41 , 46 ], and one tellin shell species [ 44 ]. This is also the case for D. vittatus karyotypes in which, of a total of 10 or 11 telocentric chromosome pairs, only the 45S rDNA-bearing chromosome pair 6 clearly presented detectable short arms.…”

“…Whether the relative abundance of repetitive sequences in wedge shells [ 17 , 18 , 20 , 21 , 22 ] is related to the high amount of pericentric inversions will need to be investigated further. In this sense, knowing the karyotypes of the other two species of European Donax , D. semistriatus , and D. variegatus [ 14 , 15 , 16 ] and, in a broader sense, performing comparative cytogenetic analyses of other bivalve groups also characterized by presenting some species rich in telocentric chromosomes and others lacking them, such as surf clams [ 44 ] and razor shells [ 40 , 45 ] could shed some more light on the question.…”

Cytogenetics in Arctica islandica (Bivalvia, Arctidae): the Longest Lived Non-Colonial Metazoan

“…Molecular cytogenetic analyses have been published for a total of 32 species of eight families of heterodont bivalves, Cardiidae [ 16 ], Donacidae [ 17 , 18 , 19 , 20 ], Mactridae [ 21 , 22 , 23 , 24 ], Pharidae [ 25 , 26 ], Psammobidae [ 27 ], Veneridae [ 21 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ], Solenidae [ 35 ] and Tellinidae [ 27 , 36 ]. Whilst in all of them diploid chromosome numbers were 2n = 38 and vertebrate type hexamere repeats (TTAGGG)n appeared just at telomeric locations, 45S rDNA, 5S rDNAs and H3 histone gene clusters showed differences in their distribution.…”