Effects of Dietary Arachidonic Acid on the Reproductive Physiology of Female Atlantic Cod (Gadus morhua L.).

Abstract

a b s t r a c tThe present study was designed to investigate potential effects of arachidonic acid (ARA) on the reproductive physiology of female Atlantic cod (Gadus morhua L.).Two-year old Atlantic cod of both sexes were equally distributed into eight sea cages after completion of their first spawning in May 2005. Four experimental groups were established and fed diets with different levels of ARA corresponding to 0.5, 1, 2 and 4% of total fatty acid. Ovarian growth and development was documented every month. Fatty acid composition was analysed in ovaries, liver and plasma at the beginning of the experiment, one month prior to spawning, and in spent fish, one month after spawning was completed. Plasma concentrations of estradiol-17b, testosterone and vitellogenin, and ovarian gene transcript levels of steroidogenic acute regulatory protein (star), P450aromatase (cyp19a1a) and 20b-hydroxy steroid dehydrogenase (20bhsd/cbr1) were monitored every month in fish fed the experimental diets and related to oocyte stage. Potential fecundity was calculated based on ovarian samples taken one month before onset of spawning.Ovarian and plasma ARA levels were highly correlated to dietary ARA levels. There was a net accumulation of ARA compared to other essential fatty acids in ovarian tissue that was reflected in a decrease in EPA:ARA ratio. Plasma concentrations of vitellogenin, estradiol-17b and testosterone and key gene transcript levels were affected by dietary ARA and stage of maturation. The results show that ARA has a significant influence on the reproductive physiology of female Atlantic cod.

Arachidonic acid matters

“…From these studies, the suggested optimal ARA doses in broodstock diets were varying substantially from as little as 0.6% d.w. (3.6% TFA) in Japanese flounder up to 1.6%–2.1% d.w. (13.2%–16.3% TFA) in blue gourami. A dose‐dependent response of dietary ARA inclusion was also observed in some species, such as Japanese flounder 135 and Atlantic cod 141 . In pikeperch ( Sander lucioperca ), an ARA dietary level of only 3.0% TFA negatively impacted on the egg quality, 142 which was attributed by the authors to the altered ARA/EPA ratio.…”

“…A dose-dependent response of dietary ARA inclusion was also observed in some species, such as Japanese flounder 135 and Atlantic cod. 141 In pikeperch (Sander lucioperca), an ARA dietary level of only 3.0% TFA negatively impacted on the egg quality, 142 which was attributed by the authors to the altered ARA/EPA ratio.…”

“…161 In Atlantic cod females, plasma concentrations of vitellogenin, estradiol-17β and testosterone, and transcript levels of key genes, P450aromatase (cyp19a1a) and 20bhydroxy steroid dehydrogenase (20bhsd/cbr1), were affected by dietary ARA (0.5%-4.0% TFA), and interestingly, these effects were also dependent on gonadal development stage. 141 Importantly, dietary ARA has been reported to exert significant effects on reproduction-related gene expression not only in gonads and liver, but also in the brain. A study on male tongue sole brains showed that the PKC-ARRB-ERK-ATF3 pathway was possibly involved in the stimulation of gonadotrophin-releasing hormone by dietary ARA (9.63% TFA), whereas the PI3K/Akt and TLR/NF-κB pathways was apparently not directly involved in this process.…”

“…This was consistent with a decrease of ARA content in ovaries during sexual development, 125 which was also observed in other species, such as silver pomfret ( Pampus argenteus ), 123 Limbaugh's damselfish ( Chromis limbaughi ) 160 and bluefin tuna ( Thunnus thynnus thynnus ) 161 . In Atlantic cod females, plasma concentrations of vitellogenin, estradiol‐17β and testosterone, and transcript levels of key genes, P450aromatase ( cyp19a1a ) and 20bhydroxy steroid dehydrogenase ( 20bhsd/cbr1 ), were affected by dietary ARA (0.5%–4.0% TFA), and interestingly, these effects were also dependent on gonadal development stage 141 …”

Possible involvement of PKC/MAPK pathway in the regulation of GnRH by dietary arachidonic acid in the brain of male tongue sole Cynoglossus semilaevis

“…The importance of arachidonic acid (ARA) in fish reproduction has been widely demonstrated in several species such as European sea bass Dicentrarchus labrax (Bruce et al, ), Japanese flounder Paralichthys olivaceus (Furuita, Yamamoto, Shima, Suzuki, & Takeuchi, ), Atlantic halibut Hippoglossus hippoglossus (Mazorra et al, ), rice field eel Monopterus albus (Zhou, Wu, Zhu, & Yan, ), Senegalese sole Solea senegalensis (Norambuena, Estévez, Carazo, & Duncan, ; Norambuena, Estévez, et al, ; Norambuena, Morais, et al, ) and Atlantic cod Gadus morhua (Norberg et al, ). ARA in broodstock diets has been reported to affect the spawning performance, egg quality, gonadal steroidogenesis and offspring quality.…”