Cahu, C.

Kjørsvik, E.

Mazurais, D.

Politis, Sebastian Nikitas

Tomkiewicz, Jonna

World, P.A.

Zambonino‐Infante, J.

Online Research Database In Technology

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Downloaded from orbit.dtu.dk on: Dec 20, 2017Biochemical, histological and molecular study of digestive tract development inEuropean eel larvae (Anguilla anguilla) prior to exogenous feedingMazurais, D.; Kjørsvik, E.; World, P.A.; Politis, Sebastian Nikitas; Cahu, C.; Tomkiewicz, Jonna;ZamboninoInfante, J.Publication date:2013Document VersionPublisher's PDF, also known as Version of recordLink back to DTU OrbitCitation (APA):Mazurais, D., Kjørsvik, E., World, P. A., Politis, S. N., Cahu, C., Tomkiewicz, J., & ZamboninoInfante, J. (2013).Biochemical, histological and molecular study of digestive tract development in European eel larvae (Anguillaanguilla) prior to exogenous feeding. Poster session presented at Aquaculture Europe 13, Trondheim, Norway.Biochemical, histological and molecular study of digestive tract development in European eel larvae (Anguilla anguilla) prior to exogenous feedingD. Mazurais1, E. Kjørsvik2, P.A. Wold2, S. Politis3, C. Cahu1, J. Tomkiewicz3, J. Zambonino‐Infante11 Ifremer, Unit of Functional Physiology of Marine organism, BP 10070, 29280 Plouzané, France. 2 The Norwegian University of Science and Technology, Department of Biology, N‐7491 Trondheim, Norway3 Technical University of Denmark, National Institute of Aquatic Resources, Jaegersborg Allé 1, 2920 Charlottenlund, Denmark.INTRODUCTIONReferences: [1] Ohta et al. (1997) Fish Physiology and Biochemistry  ; [2] Tomkiewicz (2012) DTU Aqua Report No 249 ; [3] Zambonino Infante J.L. and C.L. Cahu. 2001. Comp Biochem Physiol C . MATERIALS & METHODSSampling: 100‐150 larvae sampled from 3 to 14 DPHand preserved:• ‐80°C (enzyme studies)• RNAlater (gene expression studies)• Glutaraldehyde/formalin fixative (for histology)Specific primers were designed using data from EEL GENOME project: http://www.zfgenomics.org/sub/eelRESULTS & DISCUSSIONx400Figure 2Figure 1Figure 3x12Figure 5x340Figure 4Enzymatic study 2The activity of the studied enzymes paralleled the increase in expression of their corresponding coding gene (Fig. 2, 3, 4, 5 for lipase, amylase, trypsin and aminopeptidase N respectively).This result suggests that eel larvae have functional capabilities for digestive enzyme synthesis as early as the first days of their life. In addition, we have noted that the gene expression of allthe enzymes considered in this study highly increased from day 7 to day 14, suggesting that this date is close to the settlement of the eel digestive functions, just after mouth opening andbeginning of the exogenous feeding.Histological studyOne day after hatching, the digestive tract waspoorly developed and was only observed in theanterior part of the larvae, close to the yolk oildroplet. At D6 (Fig.6), the digestive tract (DT)appeared as a straight tube with a tight lumen. Asolid yolk syncytium layer was present (Sy).At D12 (Fig. 7 and 8), immature liver (L), pancreas(P) tissue, and the gall bladder (GB) were observed.Numerous cilia in the intestinal tract were observedanterior to the liver (*), and villi structures with adense microvilli layer (Mv) was observed in thedigestive tract posterior to the liver.This study indicates that the developmental pattern of digestive enzymes in eel larvae differs from that of other marine fish larvae. In particular, it evidences an importantenzymatic potential for lipid hydrolysis. Data suggest that eel larvae have an elevated nutritional requirement for lipids, an information that opens the way to develop newstrategies for feeding eel larvae.CONCLUSIONThis research was part of the PRO‐EEL project: “Reproduction of European Eel: Towards a self‐sustained Aquaculture (Grant no. 245257)” funded by the European Commission through the FP7 Programme. P. Lauesen, C. Graver and M. Krüger‐Johnsen participated in the reproduction experiments providing larvae for the study.ACKNOWLEDGMENTSEuropean eel natural stocks have declined dramatically these last decades mainly due to intensive fisheries. In order to reduce the fishing pressure, a sustainable aquacultureindustry needs to be developed and to be self‐sustaining with fry.Controlled reproduction and larval development of eel constitute two major bottlenecks for the aquaculture development of this species. In the PRO‐EEL project, thecapability to produce viable eggs and larvae of European eel, Anguilla anguilla, has increased. However, survival rate reduces to zero during the first feeding stage, due todifficulties to feed the larvae. Hence identifying development of their digestive system and adequate feed is a main focus.Experiments were performed at the DTU eel facility, DK, aspart of PRO‐EEL, using standard procedures [1,2].• Wild female broodstock and farmed male broodstock• Gamete production through hormonal induction• Incubation of embryos at 20°C in 36ppt seawater• Prior to hatch (45 HPF) transfer to 20 l containers and• addition of 40ppm penicillin and 65ppm streptomycinEnzymatic study 1Very high activities in lipase‐like enzymes (Fig. 1) were detectedimmediately after hatching, and the activities continued to increase inthe developing larvae.Such enzymatic pattern is hardly detected at early developmental stagesin other marine fish species [3] suggesting a specific and importantnutritional need in neutral lipids for eel larvae.OBJECTIVESThis study aimed at:• examining the developmental pattern of thedigestive tract in eel larvae• comparing results to what is known for othermarine fish species in order to define appropriatefeeding strategies for A. anguillaA. anguilla 14 DPHFigure 6. D6 – anterior digestivetract (DT) and yolk syncytium(Sy). Scale bar 50µm.Figure 7. D12 – liver (L), pancreas (P), gall bladder (GB), anterior digestivetract (DT).  Scale bar 50µm.Figure 8. D12 – posterior digestive tractwith microvilli (Mv). Scale bar 50µm. Position of liver/pancreasScan to view video of active larvae in feeding stage

Biochemical, histological and molecular study of digestive tract development in European eel larvae (Anguilla anguilla) prior to exogenous feeding

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Biochemical, histological and molecular study of digestive tract development in European eel larvae (Anguilla anguilla) prior to exogenous feeding

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