Characterizing postovulatory follicles of anchoveta Engraulis ringens in captivity

Abstract

The present study characterized the ages of POFs of anchoveta, by inducing spawning in captivity. This will allow the validation of the data obtained in the field, which in turn makes the estimates of spawning frequency of this species in the natural environment more reliable. Morphological characteristics of POFs of E. ringens were similar to those described for E. mordax. Day 0 POFs appeared as a long cord with numerous folds, with ordered and well-defined follicular cells, with little, if any, degree of degeneration, a thin theca, and a visible follicle lumen. Six hours after spawning, POFs present the first signs of degeneration, with the appearance of pyknotic nuclei in the granulosa and the follicle lumen, some lymphocytes and vacuoles in the granulosa cells. After 12 hours, follicles look very contracted and reduced, with very irregular granulosa cells, the theca is more attached to the granulosa, and there is a greater presence of pyknotic nuclei, therein, evidence that cellular degeneration is in progress. POFs of 24 hours are already degenerated, irregularly shaped, with cluttered granulosa cells and small lumen, with remains of eosinophilic granules. After 36 hours, POFs are very small and, at this level, can be confused with advanced atretic oocytes.