Deformity or variation? Phenotypic diversity in the zebrafish vertebral column

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Comparative Anatomy

Background:

• Vertebral bodies comprise centra and arches, acting as developmental modules.
• A one-to-one relationship between centra and arches is typical in teleosts, except in the caudal fin.
• Deviations from this relationship are common in vertebrates, involving changes in centra or arch numbers.

Purpose of the Study:

• To investigate deviations from the one-to-one centra-arch relationship in zebrafish.
• To characterize vertebral column phenotypes in wild-type zebrafish.
• To explore the evolutionary and pathological implications of observed vertebral variations.

Main Methods:

• Phenotypic analysis of wild-type zebrafish.
• Whole-mount staining, histological analysis.
• Synchrotron radiation X-ray tomographic microscopy for 3D reconstructions.

Main Results:

• Identified three deviant centra phenotypes: fused centra, hemivertebrae, and reduced-length centra.
• Observed bilateral and unilateral variations in neural and haemal arches and spines.
• These variations resemble phenotypes in basal actinopterygians, other gnathostomes, and pathological conditions.

Conclusions:

• Zebrafish exhibit diverse vertebral column variations, primarily in the caudal region.
• These variations provide models for studying evolutionary changes and developmental pathologies.
• Distinguishing between natural variations, pathological alterations, and ancestral conditions requires further comparative analysis.