On the anatomic relation of choroid plexus to brain: a comparative study

Area of Science:

• Comparative anatomy
• Neuroscience
• Vertebrate evolution

Background:

• Choroid plexus and cerebral ventricle size varies widely across vertebrates.
• The functional significance of this variability, particularly in relation to air breathing transition, remains underexplored.
• Herrick's hypothesis suggested large choroid plexuses aid oxygen delivery during aquatic-to-terrestrial transition.

Purpose of the Study:

• To investigate the relationship between choroid plexus size, ventricular volume, and brain size in diverse vertebrate species.
• To explore the adaptive significance of variations in choroid plexus and ventricular size, especially concerning air breathing.

Main Methods:

• Comparative analysis of choroid plexus weight and brain weight.
• Measurement of ventricular volume relative to brain volume.
• Examination of 40 species across nine vertebrate groups.

Main Results:

• Choroid plexus weight and ventricular volume showed no correlation with brain size.
• Choroid plexus weight ranged from 0% to 5.2% of brain weight.
• Ventricular volume ranged from 0.9% to 132% of brain volume.
• Dipnoans, chondrosteans, holosteans, amphibians, and crossopterygians consistently exhibited large choroid plexuses.

Conclusions:

• Choroid plexus and ventricular size are not directly proportional to brain size in vertebrates.
• The adaptive significance of large choroid plexuses may be linked to homeostatic mechanisms and responses to increased PCO2 during air breathing.
• Specific vertebrate groups show a uniform pattern of large choroid plexuses, suggesting specialized roles.