Publication Abstract

Three-dimensional reconstruction of postovulatory follicles from histological section.

Maria Kortaa, Hilario Muruaa, Iñaki Quincoces, Anders Thorsen, and Peter Robin Witthames*

During the degeneration process, the volume size of POF also suffers changes. This characteristic was used to investigate the volume diminishment process based on three-dimensional (3-D) reconstruction of POFs in ovary samples of European hake (Merluccius merluccius) and Atlantic cod (Gadus morhua). Ovaries were serially sectioned and the POFs were analysed to collect the sequence of profiles necessary to generate a 3-D model. The results of the process of volumechange in POFs were also compared to quantifications using other techniques, such as the Cavalieri method and Geometrical Best-Fitting methods. The data of POF volumes obtained agreed with 4 and 3 different POF histomorphological stages defined for hake and cod, respectively. In both species, POFs shrank sharply in the first hours, and then decreased more gradually until their complete resorption. There was no statistical difference in volume measurement of POFs between different methods. Therefore, the volume of POFs may, thus, be used to validate the reliability of POFs histomorphological staging to age POFs.

The incidence of postovulatory follicle (POF) stages is essential in fisheries studies. They are used to estimate fecundity parameters such as spawning fraction, which in conjunction with other parameters, is used in Daily egg production method (DEPM) to estimate population spawning stock biomass. The ovarian follicle becomes a POF after the egg has been released. The POF degenerates during the first few days after spawning, until to be completely resorpted from the ovary. The POF resorption process is classified in daily phases, each indicating the time elapsed since last spawning. Each daily degeneration phase is usually identified and staged by examination of their two dimensional (2-D) histomorphological structure and characteristics.