Springer 2005
Fish Physiology and Biochemistry (2004) 30: 129–136 DOI 10.1007/s10695-005-3417-9
Dynamics of total body fatty acids during early ontogeny of pikeperch (Sander lucioperca) larvae S.-M.E.-A. Abi-Ayad1, Z. Boutiba1, C. Me´lard2 and P. Kestemont3,* 1
Laboratoire de Biologie et Pollution Marines, De´partement de Biologie, Faculte´ des Sciences, The University Es-Se´nia of Oran, Oran, Algeria; 2Centre de Formation et de Recherche en Aquaculture (CEFRA), University of Lie`ge, 10, Chemin de la Justice, B-4500 Tihange, Belgium; 3Unite´ de Recherches en Biologie des Organismes (URBO), The University of Namur, 61, rue de Bruxelles, B-5000 Namur, Belgium; *Author for correspondence (E-mail:
[email protected]) Accepted: March 8, 2005
Key words: feeding, fish, larval development, lipids, PUFA metabolism
Abstract The fatty acid composition of pikeperch (Sander lucioperca) was determined according to their physiological status, during starvation (10 days) and feeding (28 days). In starved larvae, polyunsaturated, monounsaturated and saturated fatty acids were utilized as metabolic substrates until day 9. At day 10, all fatty acid levels remained stable or, at least, increased in larval body. Among fatty acids, docosahexaenoic acid 22:6 n-3 was used preferentially (20.3% from total fatty acids utilized) followed by palmitoleic acid 16:1 n-7 (13.9%) and then by oleic 18:1 n-9 (12.3%), linoleic 18:2 n-6 (10.1%), linolenic 18:3 n-3 (9.7%) and eicosapentaenoic 20:5 n-3 (9.1%) acids. On the other hand, arachidonic acid 20:4 n-6 was utilized very lowly (0.3%). In fed larvae, no utilization of body fatty acids was observed during the experiment. It seems that energy requirements (and others) of fed larvae were satisfied by feed.
Introduction It is clearly established that composition of nutrients in eggs and larval bodies change during ontogeny of fishes (Tocher et al. 1985a, b; Dabrowski et al. 1991; Abi-ayad et al. 2000). At the larval stage utilization of fatty acids is different and selective among fish species and depends on yolk reserves transferred by breeders (Heming and Buddington 1988). Different approaches were used to determine to what extent different nutrients (amino acids, fatty acids and carbohydrates) were catabolized to provide energy during fish ontogeny. Lipids and fatty acids are the major energetic substrates in fishes (Paba 1988; Sargent 1995). Some highly unsaturated fatty acids (HUFA) such
as docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3), and arachidonic acid (ARA, 20:4n-6), constitute also structural components during organogenesis such as cell membranes (muscles, brain, retina) and precursors of high physiologically active molecules as eicosanoids (Bell and Tocher 1989; Goetz et al. 1989a, b; Bell et al. 1992; Navarro and Sargent 1992; Sargent 1995). During larval development of Eurasian perch (Perca fluviatilis), Abi-ayad et al. (2000) showed that saturated fatty acids were not catabolized neither by fed larvae nor by starved one. They also showed that DHA profile constituted the main difference between starved and fed larvae. In starved perch (Abi-ayad et al. 2000) and mahimahi
130 (Coryphaena hippurus) (Ako et al. 1991) larvae, DHA was spared on detriment of other fatty acids for formation of new cells. While, in fed larvae, the same fatty acid was intensively catabolized as energy source and particularly during the first week of feeding. Considering the importance of fatty acids and particularly of DHA in predatory fish species (Tocher et al. 1992), the aim of the present study was to characterize the dynamics of (n-3) polyunsaturated fatty acids, particularly of linolenic (LNA, 18:3n-3), EPA and DHA during the larval development of pikeperch (Sander lucioperca), a European percid species, and thus to determine if this preferential mobilization of DHA is a common metabolic process within the percid family.
Materials and methods Facilities and fish Eggs and larvae were obtained from wild pikeperch breeders originating from the River Meuse (Belgium). The breeders were caught in April, 3 weeks before the spawning period, selected and transferred to the experimental aquaculture station of the University of Lie`ge (Tihange, Belgium). Both sexes were stocked together into 1.6 m3–4.0 m2 spawning tanks under ambient temperature and photoperiod. The spawning tanks were checked daily to remove the eggs (E) obtained by spontaneous spawning and fertilization. The eggs collected were incubated in conical tanks at 15 C until hatching. Just after hatching, larvae were divided into two groups. The first group was starved (Sl) until 90% of the fish died. Samples (2 g) of starved larvae were stored at )30 C for total fatty acid analysis at days Sl-1, Sl-3, Sl-5, Sl-7, Sl-9 and Sl-10 corresponding to 1, 3, 5, 7, 9 and 10 days post hatching, respectively. The second group of larvae (Fl) was fed Artemia nauplii (San Francisco Bay Brand, USA) and dry feed (Nippaı¨ Shrimp Feed, Japan) over a period of 28 days (fatty acid composition of larval feed, see Table 1). Artemia nauplii were distributed alive five times daily by using a peristaltic pump. The dry feed was distributed automatically during 12 h (0900 h– 2100 h) at a frequency of 15 min per hour (h). Samples of fed larvae (2 g) was stored at )30 C for total fatty acid analysis at days Fl-1 (1 day post
Table 1. Major fatty acid composition (in % of total fatty acids) of live and dry feeds distributed to pikeperch larvae Fatty acids
Artemia nauplii small size (400 l)
Artemia nauplii ([400 l)
Dry food
16:0 18:0 16:1 18:1 18:2 20:4 18:3 20:5 22:6
12.9 4.2 14.4 26.0 2.7 3.0 1.8 12.3 3.1
10.3 4.6 3.5 24.4 6.0 1.0 27.6 2.6 0.6
7.8 3.1 2.8 47.2 1.6 0.2 0.9 8.6 4.9
n-7 n-9 n-6 n-6 n-3 n-3 n-3
hatching), Fl-7 (7 days post hatching), Fl-14 (14 days post hatching) and Fl-28 (28 days post hatching). All experiments were carried out in triplicate and the samples were taken from two different spawnings (n=3 · 2).
Total fatty acid analysis The fatty acids, from whole body larvae, were methylated and extracted according to procedures described by Kates (1975). They were separated in a Chrompack C.P.9001 chromatograph equipped with a BPX 70 column (50 m · 0.2 mm), using Hydrogen as carrier gas at a pressure of 100 kPa. The injection and detection temperatures were 250 C and 280 C, respectively. Peak identification and quantification were carried out using a calibrated plotter integrator and reference standards. Fatty acids are expressed in lg ind)1. (on a dry matter basis). Dried samples were obtained after freeze-drying at )40 C of fresh samples. Analysis of data All data are expressed as the mean ± S.D (n=3 · 2) and are statistically compared by oneway variance analysis (ANOVA) and PLSD Fisher test (for homogeneous variance) and by nonparametric variance analysis of Kruskal-Wallis and Mann–Withney U-test (for non homogeneous variance), after verification of variance homogeneity by Hartley test (d’Hainaut 1975a, b).
131 Results Starved larvae All fatty acids classes were utilized (P
