Abstract The tilapia Oreochromis mossambicus shows a series of short ovarian cycles throughout the
year. The present study examined the impact of low intensity ambient natural light (ANL) in indoor
environment on the follicular developmental status and the spawning cycle of O. mossambicus. The
stripped fish (eggs removed manually, day 1) held outdoors in direct natural light (DNL) successfully
spawned between 24 and 28 days, whereas those reared inANLfailed to spawn despite the presence of
a significantly higher number of stage V (vitellogenic) follicles in the ovary compared to that of DNL
during the prespawning phase (day 23). These fish did not spawn even up to day 50. The profile of
serum levels of cortisol did not show a significant difference between the two experimental conditions.
On the other hand, the serum levels of estradiol (E2) were significantly higher during vitellogenic phase
(day 18) compared to previtellogenic phase (day 12) in both experimental fish. In fish exposed to DNL,
the serum levels of E2 decreased prior to spawning, but remained significantly higher in fish exposed to
ANL, suggesting the possible absence of a steroidogenic shift prior to spawning. The results reveal
that lack of a critical environmental cue such as the light signal might affect the spawning cycle by
causing alterations in the ovarian steroidogenic activity, for the first time in a continuously breeding
fish such as O. mossambicus.
2015 The Egyptian German Society for Zoology. Production and hosting by Elsevier B.V. This is an
open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Abstract The tilapia Oreochromis mossambicus shows a series of short ovarian cycles throughout theyear. The present study examined the impact of low intensity ambient natural light (ANL) in indoorenvironment on the follicular developmental status and the spawning cycle of O. mossambicus. Thestripped fish (eggs removed manually, day 1) held outdoors in direct natural light (DNL) successfullyspawned between 24 and 28 days, whereas those reared inANLfailed to spawn despite the presence ofa significantly higher number of stage V (vitellogenic) follicles in the ovary compared to that of DNLduring the prespawning phase (day 23). These fish did not spawn even up to day 50. The profile ofserum levels of cortisol did not show a significant difference between the two experimental conditions.On the other hand, the serum levels of estradiol (E2) were significantly higher during vitellogenic phase(day 18) compared to previtellogenic phase (day 12) in both experimental fish. In fish exposed to DNL,the serum levels of E2 decreased prior to spawning, but remained significantly higher in fish exposed toANL, suggesting the possible absence of a steroidogenic shift prior to spawning. The results revealthat lack of a critical environmental cue such as the light signal might affect the spawning cycle bycausing alterations in the ovarian steroidogenic activity, for the first time in a continuously breedingfish such as O. mossambicus. 2015 The Egyptian German Society for Zoology. Production and hosting by Elsevier B.V. This is anopen access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
การแปล กรุณารอสักครู่..
