# Histological and Macromolecular Characterization of Folliculogenesis in Loggerhead Sea Turtles (Caretta caretta): Novel Insights into the Onset of Puberty

## TL;DR

This study explores the reproductive development of loggerhead sea turtles in the Adriatic Sea, revealing earlier puberty onset than previously thought using advanced imaging techniques.

## Contribution

The integration of histological and FTIR imaging methods provides novel insights into folliculogenesis and puberty onset in loggerhead sea turtles.

## Key findings

- Logistic regression estimated the size at which 50% of females are sexually mature at 58.54 cm Curved Carapace Length (CCL).
- FTIR imaging revealed biochemical distributions of proteins, lipids, and nucleic acids in ovarian compartments.
- Sub-adult females showed earlier puberty onset than previously inferred from macroscopic criteria.

## Abstract

The Adriatic Sea is a critical neritic habitat for juvenile and adult female loggerhead sea turtles (Caretta caretta), where intense anthropogenic pressures and environmental stressors may influence their reproductive biology. Knowledge on the onset of puberty in this population is limited by scarce information on the sub-adult stage, a transitional phase in which reproductive competence is acquired. This study integrated histological analysis and Fourier-transform infrared (FTIR) imaging spectroscopy to provide both structural and biochemical characterization of folliculogenesis, with emphasis on vitellogenesis, in C. caretta from the north-central Adriatic Sea. Histological analysis determined the progression of follicle development, while FTIR imaging, a label-free and spatially resolved technique, mapped the distribution of proteins, lipids, and nucleic acids across ovarian compartments. Logistic regression estimated the size at which 50% of females are sexually mature (L50) at 58.54 cm Curved Carapace Length (CCL). Based on this value, 60% of sub-adult females were already mature, indicating earlier puberty than previously inferred from macroscopic criteria. These preliminary results, along with reports of sporadic nesting in the Adriatic, raise the question of whether this basin may host further nesting events in the future. FTIR imaging proved to be a powerful tool for reproductive biology in non-model marine vertebrates.