Dietary Arachidonic Acid Alters Tissue Fatty Acid Profile, Whole Body Eicosanoid Production and Resistance to Hypersaline Challenge in Larvae of the Temperate Marine Fish, Striped Trumpeter (Latris lineata)

Abstract

We determined the effect of dietary arachidonic acid (20:4n-6, ARA) on tissue ratios of ARA/eicosapentaenoic acid (20:5n-3, EPA) and subsequent whole body production of the eicosanoids, prostaglandin F 2a (PGF 2a ) and E 2 (PGE 2 ) in the marine larvae of striped trumpeter, Latris lineata. Larvae were also subjected to a hypersaline challenge (55 ppt) with an aim to determine possible relationships between tissue fatty acid profiles, prostanoid production, and their tolerance to osmotic challenge. From 5 to 23 days post-hatch (dph) larvae were fed live food, rotifers (Brachionus plicatilis), that had been enriched with one of five experimental emulsions containing increasing concentrations of ARA and constant EPA and 22:6n-3 (docosahexaenoic acid, DHA). Final ARA concentrations in the rotifers were 1.33, 3.57, 6.21, 8.21 and 11.22 mg g )1 DM. Larval growth and survival was unaffected by dietary ARA. Tissue fatty acid concentrations generally corresponded with dietary fatty acids and final tissue ratios of ARA/EPA ranged from 0.9 to 4.9. At 18 and 23 dph whole body concentrations of PGF 2a and PGE 2 generally increased as more dietary ARA was provided in a dose-response manner, and a significant elevation in both PGF 2a and PGE 2 in larvae fed the highest dietary ARA concentration was recorded at 23 dph compared to larvae receiving the lowest concentration. At 18 dph, the highest cumulative inactivity following a hypersaline challenge occurred in larvae fed 8.21 or 11.22 mg ARA g )1 DM, which was significantly greater than those receiving 3.57 mg ARA g )1 DM. At 23 dph no relationship between inactivity of larvae subjected to a hypersaline challenge to dietary ARA was evident. In summary, dietary ARA altered tissue ARA/EPA ratios, prostanoid production and resistance to a hypersaline challenge in larval striped trumpeter. While increasing dietary ARA generally resulted in elevation of prostanoids as well as increasing the number of inactive larvae following a hypersaline challenge at 18 dph, similar trends between prostanoids and larval inactivity were not evident at 23 dph, suggesting the exact mechanisms and relationships between eicosanoids and larval osmoregulation warrants further investigation. Nevertheless the study provides preliminary data on the effect of dietary ARA on the prostaglandin production in marine fish larvae.

Visual field of cultured striped trumpeterLatris lineata(Teleostei) larvae feeding on rotifer prey

“…It was unlikely that these larvae required a larger prey type (e.g. Artemia), since current culture methods for striped trumpeter include rotifer feeding up to day 23 with good growth and survival (Bransden et al 2004) and introduction of Artemia at a much larger larval size ($7 mm SL, Bransden et al 2005). The low number of feeding sequences acquired in the first 60 min of filming of older striped trumpeter larvae may be a result of chance, satiation, or larval condition.…”

Growth and survival of Hippocampus erectus (Perry, 1810) juveniles fed on Artemia with different HUFA levels

“…ARA can be a precursor for the synthesis of eicosanoids through the COX and LOX enzymes. These enzymes also used EPA as substrate to produce other eicosanoids, therefore, if ARA levels are too low in comparison with those of EPA, the synthesis of certain prostaglandins may be inhibited and biased in favor of eicosanoids derived from EPA, with reduced biological activity (Bransden et al, 2004). In this experiment the highest EPA/ARA ratio occurred in EPAX and this may have been detrimental to their survival.…”

Using oocyte essential fatty acid composition to assess spawner reproductive potential under hypersaline conditions

“…Conversion of ARA to prosta glandin in gills and other tissues has been reported in several teleost fishes (Ogata et al 1978, Henderson et al 1985, Beckman & Mustafa 1992. Enhanced dietary intake of ARA thus increased prostaglandin production (Bransden et al 2004) and thereby the resistance to hyperosmotic stress in a variety of fish larvae (Willey et al 2001, Koven et al 2003. Further, the ratios of (n-3) to (n-6) PUFA in oocytes sampled from Djifer and Foundiougne during the dry season were numerically higher than at Joal and at Foundiougne during the wet season, albeit not significantly.…”

“…Elevated levels of ARA, DHA, EPA, and the DHA/EPA ratio in oocytes accounted for an increased hatching success in a variety of fish species (Leray et al 1985, Pickova & Dutta 1997, Lane & Kohler 2006, Patterson & Green 2014, Asil et al 2017). Additionally, EFA play an important role in larval osmoregulation (Bransden et al 2004). ARA and EPA are substrates for the synthesis of hormone-like compounds called eicosanoids (Bell et al 1994, Tocher 2003, which are involved in reproduction, hormone release, cardiovascular function, neural function, and osmoregulation in a variety of organisms (Mustafa & Srivastava 1989).…”

“…In synergy with hormones, the subfamily prostaglandin modulates the ion and electrolyte balance in the kidney and gills of fishes (Horseman & Meier 1978, Brown & Bucknall 1986, Beckman & Mustafa 1992. Enhanced dietary intake of ARA thus increases prostaglandin production (Bransden et al 2004) and thereby the resistance to hyperosmotic stress in a variety of fish larvae (Willey et al 2003, Koven et al 2003. Also, the ratio of (n-3) to (n-6) PUFA in the gill lipids of European eels Anguilla anguilla (Linnaeus, 1758) reared in sea water was 3-fold higher than in individuals reared in freshwater, enhancing their ability to maintain osmotic equilibrium in waters of different salinities at different temperatures (Thomson et al 1977, March 1993.…”