COPEPODS OR ROTIFERS? EVALUATING THE USE OF DIFFERENT FEEDING PROTOCOLS FOR LARVAE OF ATLANTIC BLUEFIN TUNA (Thunnus thynnus. L)
Betancor, M.B.,Ortega-García, Aurelio,de-la-Gándara, Fernando,Tocher, D.R.,Mourente, Gabriel,Varela, José Luis
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Abstract
There are still many issues that require to be solved in larval rearing of Atlantic bluefin tuna (Thunnus thynnus; ABT) to prevent “mass-mortality” during this developmental stage. Initial data related to the feeding sequence of ABT larvae suggested that mortality observed during the first stages of life could be due partly to nutritional deficiencies. Previous studies demonstrated that copepods appeared to be a superior live prey compared to rotifers during the first two weeks of life. Our overarching aim was to evaluate different feeding strategies during first feeding of ABT larvae from a performance, compositional and molecular perspective. In order to do so, two groups of ABT larvae were fed with either copepod (Acartia tonsa; C) nauplii or rotifers (Brachionus rotundiformis; R) enriched with Algamac 3050® from mouth opening to 13 days after hatching (dah). After this, the group C-larvae was fed either Artemia enriched with Algamac 3050® (CA), Acartia nauplii and copepodites (CC) or sea bream (Sparus aurata) yolk-sac larvae (CY), while the R group passed on to being fed on Artermia enriched with Algamac 3050® (RA) up to 18 dah. After 13 dah, larvae fed C grew more than those fed R although there were no differences in survival. ABT larvae fed R accumulated highest eicosapentaenoate (EPA) but lowest docosahexaenoate (DHA) and total n-3 long-chain polyunsaturated fatty acids (LC-PUFA) than C-fed larvae, reflecting dietary contents. Indeed, there was no activation in the expression of the enzymes involved in LC-PUFA biosynthesis. However, the different live prey elicited regulation of transcription factor, digestive enzyme, lipid metabolism and oxidative stress genes. At 18 dah larvae fed CY and CA were the largest size with larvae fed RA displaying the lowest growth with no differences in survival among the dietary treatments. The highest DHA contents were found in ABT larvae fed CC and CY, whereas the lowest contents were found in RA-fed larvae. Indeed, RA-fed larvae showed the highest level of the intermediate product n-3 docosapentaenoate, which could be reflecting up-regulation in the biosynthetic pathway although this was not supported by gene expression data.
Full text
-.. 'l u". __: :: ~ ~ ~ ~ 18 "' International Symposium on Fi sh Nutrition and F eed ing 40 Ye ars of Research In Fish Nutrition Las Palmas de Gran Canaria , Spain June 3rd -7th, 2018 COPEPODS OR ROTIF E RS? EVALUATING T HE USE OF DIFF E RENT FE EDING PRO T OCOLS FOR LARVAE OF ATLANTIC BLU E FIN TUNA (Thunnus thynnus. L) Dr . Mon ic a Betancor University of Stirling Dr . Aure li o Ortega lnstltuto Espoflol de Oceonograffa Dr . Fe rna n do de la Ga nda ra Institute Espanol de Oceanografia Pr of. Doug las Toch er (1) Pr of . Ga brie l Mo ur ente Universidad de Cadiz Dr. Jo se Lui s Varela Departamenta de Bio/ogia, Facultad de Ciencias de/ Mar y Ambientales, Universidad de Cadiz, 11510 Puerta Real, Cadiz, Spain There are still many issues t hat require to be so lved in larval reari ng of At lantic bluefin tuna (Thunnus thynnus; ABT ) to prevent "mass-mortali ty" during this developmental stage. Initial data related to the feeding sequence of ABT larvae suggested that morta li ty observed during the fi r st stages of life co uld be due partly to nutr it i ona l defici enc i es. Previo us studies demonstrated that copepods appeared to be a superior live prey co mpared to rotifers during the first two weeks of li fe. Our overarching aim was to eva luate different feeding strategies dur ing first feeding of ABT larvae fr om a performan ce, compositional and molecular perspecti ve . In or der to do so, two groups of ABT larvae were fed with either copepod (Acartia tonsa; C) nauplii or rot ifers (Brac hionus rotundiformis; R) enriched with Algam ac 3050• from mouth opening to 13 days after hatching (dah). After thi s, the group Clarvae was fed either Artemia enriched with A lga mac 3050• ( CA), Acartla nauplii and copepodites ( CC) or sea bream (Sparus au rat a) yolksac larvae (CV), wh ile the R group passed on to being fed on Artermia enriched w it h A lga mac 3050* (RA) up to 18 dah. After 13 dah, larvae fed C grew more than th ose fed R although there were no d iff erences In survival. ABT larvae fed R accumulated highest eicosapentaenoate (EP A) but lowest docosahexaenoate (DHA) an d total n-3 long-chain polyunsaturated fatty acids ( LC - PUFA) than C-fed larvae, re fl ecting dietary contents. Indeed, there was no activation in the expression of the enzymes involved in LC-PUF A biosynthesis. However, the di ff erent live prey elicited regulation of transcription factor, digestive enzyme, li pid metaboli sm and oxidative st r ess genes. At 18 dah larvae fed CV and CA were the largest size with larvae f ed RA displaying the lowest growth with no differences in su rvival among the dietary treatments. T he highest DHA contents were found in ABT larvae f ed CC and CY, whereas the lowest contents were found in RA-fed larvae. Indeed, RA-fed larvae showed the highest l eve l of the Intermediate product n-3 docosapentaenoate, which could be reflecting up-regu lat ion in the biosynthetic pathway although this was not supported by gene expression data.