Chromosomal evolution in large pelagic oceanic apex predators, the barracudas (Sphyraenidae, Percomorpha)

Area of Science:

• Cytogenetics
• Evolutionary Biology
• Ichthyology

Background:

• The Sphyraena genus (barracudas) comprises 27 species of large, pelagic predators found in tropical and subtropical oceans.
• Existing evolutionary and chromosomal data for barracudas are limited, hindering a comprehensive understanding of their diversification.
• Barracudas are of significant interest to commercial and sport fishing due to their size.

Purpose of the Study:

• To investigate the cytogenetic patterns of three Sphyraena species: S. guachancho, S. barracuda, and S. picudilla.
• To compare cytogenetic data with existing phylogenetic relationships within the Sphyraena genus.
• To identify conserved traits and evolutionary novelties in barracuda karyotypes.

Main Methods:

• Conventional cytogenetic techniques: Giemsa staining, C-banding, and Ag-NOR staining.
• Molecular cytogenetic techniques: CMA3 banding, and in situ hybridization with 18S rDNA, 5S rDNA, and telomeric probes.
• Analysis of karyotypic patterns in Sphyraena guachancho, S. barracuda, and S. picudilla.

Main Results:

• Karyotypic patterns were found to contrast with current phylogenetic proposals for the Sphyraena genus.
• Distinct karyotypes were observed among closely related species, while less related species exhibited similar patterns.
• Evidence suggests homoplasic characteristics, with similar karyotype patterns evolving independently at least twice.

Conclusions:

• The study reveals significant diversity and homoplasy in the karyotypic patterns of Sphyraena species.
• Cytogenetic data provide insights into ancient conserved traits and evolutionary novelties within the genus.
• Further cytogenetic investigation of more Sphyraenidae species and related families is crucial for understanding their evolutionary history.