The ovarian follicular development
In both experimental groups, the ovary contained stage I–III
(previtellogenic) follicles with some degenerating stage IV
(vitellogenic) follicles during mouthbrooding phase (on day
1, Fig. 2A). While the remnant stage IV follicles reabsorbed
by follicular cells were found at the end of previtellogenic
phase (on day 12, Fig. 2B), a new batch of stage IV follicles
was observed again at the end of the vitellogenic phase (on
day 18, Fig. 2C). Some stage V (vitellogenic) follicles were seen
on day 18 in fish kept at ANL condition in contrast to absence
of these follicles in fish exposed to DNL. However, fully
ripened stage V follicles with larger yolk granules were found
in the prespawning phase in both experimental fish (day 23,
Fig. 2D and E).
The mean number of stage I follicles showed a significant
(P < 0.001) progressive increase through previtellogenic (day
12) and vitellogenic (day 18) phases compared to day 1, but
decreased significantly (P < 0.001) later during the prespawning
phase (day 23, Fig. 3A) in fish exposed to DNL. A similar
trend was found in fish exposed to ANL except for a significant
(P < 0.001) decrease during the previtellogenic phase
compared to that of DNL.