Are Pericentric Inversions Reorganizing Wedge Shell Genomes?

Area of Science:

• Marine Biology
• Cytogenetics
• Evolutionary Biology

Background:

• Wedge shells (Donacidae family) are dominant bivalves globally, often exhibiting sympatric species distribution across different coastal zones.
• Understanding the genetic basis of divergence in closely related species is crucial for evolutionary studies.

Purpose of the Study:

• To perform a molecular cytogenetic analysis of two sympatric wedge shell species, Donax trunculus and Donax vittatus.
• To investigate the role of chromosomal rearrangements in karyotype divergence between these closely related species.

Main Methods:

• Molecular cytogenetics, including karyotype analysis and gene mapping.
• Comparison of chromosome structure, heterochromatic bands, and ribosomal RNA (rRNA) and histone gene cluster locations.

Main Results:

• Distinct karyotypes were observed: D. trunculus predominantly featured metacentric and submetacentric chromosomes, while D. vittatus had 10-11 telocentric pairs out of 19.
• Both species possessed GC-rich heterochromatic bands and conserved chromosomal locations for 45S rRNA, 5S rRNA, and H3 histone gene clusters.
• D. trunculus exhibited an additional 45S rDNA cluster, and intraspecific pericentric inversions were detected in both species.

Conclusions:

• Pericentric inversions are significant contributors to karyotype divergence in wedge shells.
• The high conservation of gene clusters and heterochromatic bands suggests close genetic relatedness despite chromosomal differences.
• This study provides insights into the mechanisms of speciation and chromosomal evolution in marine bivalves.