Three-dimensional reconstruction of postovulatory follicles from histological sections
The postovulatory follicle (POF) resorption process is classified in daily phases by examination of their 2-D histomorphological structure and characteristics to indicate the elapsed time since spawning. These characteristics were used to investigate the associated reduction in volume by 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 POFs were analysed to collect the sequence of profiles to generate a 3-D model. The volume of POFs determined from 3-D reconstruction was also compared to results following Cavalieri and Geometrical Best-Fitting methods. The data of POF volumes obtained were shown to be typical characteristic of four and three 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 determined by the three methods listed above, and therefore, the volume of POFs may, be used to validate the reliability of 2-D histomorphological staging to age POFs.