Enrichment of Artemia metanauplii in phospholipids and essential fatty acids as a diet for common octopus (Octopus vulgaris) paralarvae

Highly unsaturated fatty acids (HUFA), like the eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids and polar lipids (essentially phospholipids, PL) have been identified as essential nutrients for common octopus (Octopus vulgaris) paralarvae. However, they are not available in sufficient amounts in live preys as Artemia, making necessary a supplementation of these nutrients previous use. A commercial emulsion, soya liposomes, and marine and soya lecithins were used to supply HUFA and PL to Artemia metanauplii, those being regarded as suitable size preys for octopus paralarvae. Our results prove that a simultaneous enrichment in HUFA and PL is possible using enrichment diets combining HUFA‐ and PL‐rich products in short‐term (4 h) incubations. Particularly interesting was the enrichment efficiency shown by the marine lecithin, which enabled the enhancement of the PL fraction of Artemia metanauplii and, importantly, also their HUFA with a remarkable 13% DHA of total fatty acids. Marine lecithin arises as a novel enrichment diet for Artemia and more effective than some commercial products currently used in hatcheries worldwide.     

Effect of temperature on energetic demands during the last stages of embryonic development and early life of Octopus vulgaris (Cuvier, 1797) paralarvae

This study describes the effect of seasonal average temperatures (14 and 18°C) in the Ría of Vigo, on the utilization of external yolk over the last five Naef stages of development (XV–XX) for Octopus vulgaris embryos. Also, the transference of the outer yolk to the inner yolk sac, and its use during embryonic development and early life by O. vulgaris paralarvae. Temperature had a marked effect on embryonic development, except during stages XV–XIX (until the second inversion) where development time was the same (14 days), regardless of temperature. There were no significant differences in outer yolk decrease between consecutive Naef stages at 14°C and 18°C. Contrary, significant differences at all Naef stages from XV to XIX (both, with or without outer yolk) were observed for inner yolk between temperatures. A higher accumulation of inner yolk in embryos at 14°C was observed, due to lower yolk consumption. Paralarvae incubated at both temperatures were maintained independently at starvation during 4 days. At 18°C, a reduced accumulation of inner yolk, especially during Naef stage XIX, was observed. In 24 h old paralarvae, there was already significant higher inner yolk content at 14°C than at 18°C. Unfed paralarvae at 18°C lost weight faster than those at 14°C, due to higher energetic requirements. Finally, from these results, we propose a paralarvae rearing protocol during the first days after hatching and during the last five Naef stage (XV–XX) at lower temperatures, since the energy requirements are lower during the initial maturation stage.     

Fatty acid composition of polar and neutral lipid fractions of Octopus vulgaris Cuvier, 1797 paralarvae reared with enriched on‐grown Artemia

Rearing of common octopus Octopus vulgaris is limited by the lack of success during the paralarval stage, with generalized mortalities occurring before the settlement of the juveniles. The use of on‐grown Artemia cultured with the microalga Isochrysis galbana and further enriched with Nannochloropsis sp. has led to a certain degree of success. The present work aims at studying the effects of this rearing protocol (Nanno) on the fatty acid composition of paralarvae, by comparison with a diet based on on‐grown Artemia further enriched with a high polyunsaturated fatty acid oil emulsion (M70). After 28 days, survival was estimated at 3% for M70 and 22.5% for Nanno, whereas the average dry weight was not significantly different (Nanno: 1.76± 0.28 mg; M70: 1.88±0.22 mg). Although apparently no clear association between the fatty acid composition of the enriched preys and that of the total lipids of paralarvae could be established, further fractionation and fatty acid analysis of the total lipids into polar and neutral classes, followed by principal components analysis, revealed that irrespective of the diet, both lipid fractions showed distinct fatty acid patterns. Besides, the fatty acid composition of the polar lipids was more conservative, whereas that of the neutral lipids was more influenced by the diet, showing more variation among dietary treatments.     

Effects of feeding with different live preys on the lipid composition,growth and survival of Octopus vulgaris paralarvae

To move forward in the farming of Octopus vulgaris paralarvae, it is necessary to search for a live prey easy to obtain and maintain in the laboratory that meets the nutritional requirements of the octopus paralarvae and adapts to its predatory behaviour. Grapsus adscensionis zoeae (Crustacea, Decapoda) seems to fulfil most of these targets, and it was herein used to deepen knowledge of paralarvae lipid requirements and composition, growth and survival. To this purpose, the effects of feeding with Grapsus zoeae as sole prey were compared with Artemia at two different stages (nauplii and juveniles), which also differed in their lipid profiles. After 15 days of feeding, the best growth and survival of paralarvae was obtained in the Grapsus group, and no differences were observed between both Artemia groups. Triacylglycerides storage in paralarvae seemed to be co‐related with a lower growth and survival, but not with its prey levels. Contrarily, sterol ester levels were higher in paralarvae fed Grapsus, reflecting its content in the prey. The best paralarval viability was related to higher levels of 22:6n‐3 (DHA) and 20:4n‐6 (ARA), also reflecting its higher content in the prey. On the other hand, neither the 20:5n‐3 (EPA) levels in the prey nor in paralarvae were related to growth or survival. The implications of these results are discussed considering the lipid requirements of O. vulgaris paralarvae.     

Utilization of diets with different fish oil content in common octopus (Octopus vulgaris Cuvier, 1797) and resulting changes in its biochemical composition

The aim of the present work was to obtain the lipid utilization of Octopus vulgaris supplying formulated semi‐moist diets with different contents in cod oil (reduced from water content): 0 g kg^?1 (A0, 138 g kg^?1 lipids DW; N = 4), 100 g kg^?1 (A100, 286 g kg^?1 lipids DW; N = 6) and 200 g kg^?1 (A200, 388 g kg^?1 lipids DW; N = 6). The rest of the ingredients were constant in the three diets: 200 g kg^?1 gelatin, 100 g kg^?1 egg yolk powder, 150 g kg^?1 freeze‐dried Todarodes sagittatus and 50 g kg^?1 freeze‐dried Sardinella aurita). Survival was 100% with the three diets. The highest absolute feeding (15.8 ± 1.2 g day^?1), growth (9.6 ± 1.4 g day^?1; 0.91% BW day^?1) and feed efficiency rates (60.3%) were obtained with diet A0. This diet also showed greater retention of lipid and protein than A100 and A200. Protein digestibility was above 95% in all of the diets. Only diet A0 led to a high lipid digestibility coefficient (81.25%), which fell drastically to 12.3% in A200. It was notable the high polar lipid digestibility rates (83–89%) respect to neutral lipids (2–87%) in all diets. The best results were obtained with lipid feeding rates of around 1 g day^?1 and a suitable lipid content on 130–140 g kg^?1 DW in formulated diets for O. vulgaris.     

High feeding and growth rates in common octopus (Octopus vulgaris) fed formulated feeds with an improved amino acid profile and mixture of binders

Four semi‐moist formulated feeds were supplied to Octopus vulgaris subadults (664 ± 70 g; 18.4 ± 0.7°C) in two different experiments. In the experiment #1, two diets were prepared with a new mixture of binders (gelatine 150 g kg^?1, starch 100 g kg^?1 and gum 50 g kg^?1). The GEL15‐Squid and GEL15‐Hake feeds included 100 g kg^?1 freeze‐dried squid (Todarodes sagittatus) or hake (Merluccius sp.) respectively. Both feeds showed low water disintegration rates at 24 h (13.6–15.0% dry weight). The specific feeding rate was higher in animals fed GEL15‐Hake (2.7%BW day^?1), but the growth and feed efficiency were significantly better in animals fed GEL15‐Squid (1.4%BW day^?1 and 61.2% respectively; P < 0.05). The proximate composition of the digestive gland, carcass and whole animals was similar. In the experiment #2, the GEL15‐Squid amino acid profile was improved by replacing 50 g kg^?1 gelatine by 50 g kg^?1 freeze‐dried squid (GEL10‐Squid) or freeze‐dried fish (GEL10‐Fish). These feeds showed higher water disintegration rates (31.7–36.3% dry weight). The feeding rates (2.2–2.3%BW day^?1), growth (1.5%BW day^?1) and feed efficiency were similar for both diets. Total lipids were higher in the digestive gland and whole animals fed GEL10‐Fish diet (P < 0.05). Future effort could be directed towards alternative binders that allow improve amino acid balance with a minimum gelatine content or even supplementation trials including essential amino acids.     

Effects of co‐supply ratios of swimming crab Portunus trituberculatus zoeae and Artemia on survival and growth of East Asian common octopus Octopus sinensis paralarvae under an upwelling culture system

Despite recent advances in culture technology for East Asian common octopus Octopus sinensis paralarvae using upwelling systems, securing suitable feed for the paralarvae is an unresolved issue. The zoea of the swimming crab Portunus trituberculatus is a good candidate for paralarval feed because of the high fecundity of the adult females. To investigate the effects of supplying P. trituberculatus zoeae and their feeding method on paralarvae, we cultured paralarvae with supplying different combination ratios of zoeae and Artemia (10:0, 7:3, 5:5, 3:7 and 0:10), and with or without supplementing rotifers using small‐scale (3‐L) upwelling systems. Paralarval survival rate and growth were improved when zoeae were supplied as the main feed, but reduced when the proportion of Artemia exceeded half the whole preys. Supplementing rotifers did not affect the paralarval survival and growth. Subsequently, paralarvae were cultured by supplying zoeae (partially augmented by Artemia) using three large (1‐kl) upwelling systems to assess their feeding effectiveness in juvenile octopus production. Paralarvae could be cultured at high survival rates of 77.1 ± 5.1% to reach benthic juveniles at 23 days after hatching. In conclusion, supplying P. trituberculatus zoeae augmented with Artemia under an upwelling culture system has great potential for juvenile octopus production.     

Effective use of glucose rather than starch in formulated semimoist diets of common octopus (Octopus vulgaris)

The aim of the present work was to test the capacity of O. vulgaris to use carbohydrates supplied in three diets: a diet without added carbohydrates (diet C0: 500 g kg^?1 water, 200 g kg^?1 gelatine, 100 g kg^?1 egg yolk powder, 50 g kg^?1 freeze‐dried Sardinella aurita and 150 g kg^?1 freeze‐dried Todarodes sagittatus), and two obtained by substituting 50 g kg^?1 of T. sagittatus by glucose (diet GLU50) or by starch (diet STA50). The most stable and best accepted diet was STA50 (SFR 1.26%BW day^?1), although there were no significant differences in the growth rates obtained with the three diets: 10.1 g day^?1, 9.4 g day^?1 and 11.2 g day^?1 for C0, GLU50 and STA50, respectively (P > 0.05). The feed efficiency indices were better for GLU50, of particular note being the protein productive value of 72% and a feed conversion ratio lower than 1. Protein and lipid digestibility were similar in all three diets (96–98% for proteins and 85–94% for lipids), whereas carbohydrate digestibility was higher in GLU50 (98%) than in C0 (84%) and STA50 (0.33%). The content of carbohydrates increased in muscle and the digestive gland as a consequence of the increased carbohydrates intake.     

Effective use of glucose rather than starch in formulated semimoist diets of common octopus (Octopus vulgaris)

The aim of the present work was to test the capacity of Octopus vulgaris to use carbohydrates supplied in three diets: a diet without added carbohydrates (diet C0: 500 g kg^?1 water, 200 g kg^?1 gelatine, 100 g kg^?1 egg yolk powder, 50 g kg^?1 freeze‐dried Sardinella aurita and 150 g kg^?1 freeze‐dried Todarodes sagittatus) and two obtained by substituting 50 g kg^?1 of T. sagittatus by glucose (diet GLU50) or by starch (diet STA50). The most stable and best‐accepted diet was STA50 (SFR 1.26%BW day^?1) although there were no significant differences in the growth rates obtained with the three diets: 10.12 g day^?1, 9.37 g day^?1 and 11.22 g day^?1 for C0, GLU50 and STA50, respectively (P > 0.05). The feed efficiency indices were better for GLU50, of particular note being the protein productive value of 71.88% and a feed conversion ratio lower than 1. Protein and lipid digestibility were similar in all the three diets (96–98% for proteins and 85–94% for lipids), whereas carbohydrate digestibility was higher in GLU50 (98%) than in C0 (84%) and STA50 (0.33%). The content of carbohydrates increased in muscle and the digestive gland as a consequence of the increased carbohydrates intake.     

Growth and feed efficiency of Octopus vulgaris fed on dry pelleted

The purpose of this study was to evaluate the effect of two dry extruded diets on growth and nutritional composition of digestive gland (DG) and muscle of Octopus vulgaris. Both artificial diets (FMK and 3FMK) were composed of gelatin, maltodextrin, yolk, fish and krill meal. The 3FMK diet contained more fishmeal (3×) than the FMK diet. These diets were compared with a control frozen diet consisting of golden grey mullet (Liza aurata) and crab (Liocarcinus depurator). The 3FMK diet promoted higher intakes and feed efficiency than FMK diet, resulting in larger growths (296 respect to 158 g in 42 days; 0.81% vs. 0.78% body weight/day). There was significantly lower moisture, protein and ash content in digestive glands of animals fed pellets (P < 0.05). No significant differences were observed on nutritional composition of muscle among the three groups. Even though the results were still below those of the control group (increase of 1258 g), the good performance in terms of acceptance and growth showed that this extruded diet can be the starting point to develop a commercial feed for this species.     

Development of an in vitro model to assess protein bioavailability in diets for common octopus (Octopus vulgaris)

An in vitro model designed to assess protein bioavailability in diets for growing Octopus was developed. The model required a previous assessment of some functional features of protein digestion in this species like the main producing organs, optimum pH for activity and total production per g tissue. The main producing organs identified were the salivary glands and the hepatopancreas (HP), being optimum pH for protease activity quite different in both organs (mostly alkaline in the posterior salivary glands and acid in the HP). In spite of the high‐specific protease activity measured in the salivary glands, a major role of the HP in protein hydrolysis is suggested due to the much bigger size of this viscera. All this information was used as a basis to develop an in vitro two‐step hydrolysis process, which simulated protein hydrolysis performed by these two organs using the Octopus enzymes. The assay was used to evaluate differences in amino acid bioavailability from several protein sources (casein, gelatin, fish meal, squid meal and krill meal) that could be used as feed ingredients for this species. As significant differences were detected both in total amount and in rate of release of the amino acids from such proteins, the model is proposed as a complementary tool in the selection and nutritional evaluation of protein ingredients to be used in diets for Octopus.     

Performance of formulated diets with different level of lipids and glutamate supplementation in Octopus vulgaris

Growth, feed efficiency and proximate and lipid class composition of subadults Octopus vulgaris (788 ± 133 g; 18.5°C) fed formulated diets of low lipid (LL: 8 g kg^?1) and high lipid levels (HL: 84 g kg^?1) and each one of these with three different levels of glutamate supplementation (0, 5 and 20 g kg^?1) were compared. All the animals accepted the diets with a survival of 100%. The addition of glutamate did not stimulate feeding rates in any of the assays (2.48–2.64 and 1.86–2.01%Body weight day^?1 for LL and HL, respectively; P > 0.05). The best growth, feed efficiency and protein productive value were observed in the groups fed 5 or 20 g kg^?1 glutamate supplementation at both lipid levels, with significant differences for LL diet (P < 0.05). A better feed efficiency was achieved with the HL diet (14.6–27.5% vs. 2.5–19.2% for LL diet). There were no significant differences in the proximate composition of carcass (animal excluding the digestive gland). However, a substantial amount of lipids accumulated in the digestive gland, mainly triglycerides, was detected as a consequence of higher lipid ingestion or glutamate supplementation. It was notable the lower percentages of phosphatidylethanolamine and phosphatidylcholine in the digestive gland of animals with best growth.     

Nucleic acids and fatty acids of the common octopus, Octopus vulgaris, in relation to the growth rate

The aim of this study was to investigate changes in the ribonucleic acid (RNA)/deoxyribonucleic acid (DNA) ratio and the fatty acid composition of cultured Octopus vulgaris (50–750 g) in relation to recent (last 30 days) specific growth rate (SGR). Wild animals (80–500 g), collected in the field throughout the year (Aegean Sea, Mediterranean), were also examined for the aforementioned biochemical parameters. Octopuses were reared in a closed seawater system at three different temperatures (15, 20 and 25 °C). The octopuses were fed on squid (Loligo vulgaris). The cultured animals showed a high n‐3 (33–52.9%) and n‐6 (3.3–13.7%) polyunsaturated fatty acid content, but with a high variation for 22:6n‐3 [docosahexaenoic acid (DHA)], 20:5n‐3 [eicosapentaenoic acid (EPA)] and 20:4n‐6 [arachidonic acid (AA)]. The proportion of these fatty acids (% total fatty acids) and the RNA/DNA ratio were linearly (P<0.0001) related to SGR. Specifically, RNA/DNA (0.5–1.9) and AA (2.7–10.7%) increased, while EPA (10.4–19.7%) and DHA (20.8–31.9%) decreased, with increasing SGR (0.4–1.7% day⁻¹). The highest levels of SGR, RNA/DNA and AA were detected in small (50–150 g) octopuses reared at 20 and 25 °C and in large (500–750 g) animals reared at 15 °C. Similar RNA/DNA levels and fatty acid percentages were found in wild octopuses. It is concluded that RNA/DNA, DHA, EPA and AA could be used as biochemical indices for predicting the growth rate of O. vulgaris.     

Assessment of diet and temperature on the overall performance of Patagonian red octopus (Enteroctopus megalocyathus,Gould) paralarvae

The limitation to sustain the Patagonian red octopus Enteroctopus megalocyathus aquaculture is the lack of an efficient diet to obtain high survival during the paralarvae stage. This work has studied the performance of paralarvae under different combinations of feeds and temperatures using a factorial design. The diets were based on various Artemia enrichments: (a) Nannochloropsis sp, (b) Ori‐gold (Skretting) and (c) LC60 (Phosphotek). The temperatures chosen were in accordance with those found in their environment: 10°C (winter), 12°C (spring–autumn) and 14°C (summer), by triplicate. The factorial combinations were tested in two experiments with paralarvae of different age: Exp 1, from newly hatched to 14 days after hatching (DAH), and Exp 2, from that point to 42 DAH. It was concluded that temperature was the primary variable affecting mortality, feed intake, relative weight condition index, morphometric variables and trypsin activity. The enriched Artemia diets had the main impact on the leucine‐aminopeptidase activity, and on the fatty acid contents, mainly 20:5n‐3 (EPA) and 22:6n‐3 (DHA). Paralarval growth was increased by temperature with only one diet and at a certain age. Nutritional requirements varied between early and late paralarvae, and the possibility of changing the diets according to the development age is discussed.     

Growth,survival rate and fatty acid composition of sterlet (Acipenser ruthenus) larvae fed fatty acid‐enriched Artemia nauplii

We evaluated the growth and survival rate of sterlet (Acipenser ruthenus) larvae fed Artemia nauplii enriched with Olioω3 or Red Pepper commercial emulsions (BernAqua NV, Belgium). Sterlet larvae, 0.022 ± 0.002 g body weight, were randomly assigned to one of three feeding regimes with two different feeding durations. After administering live feed for 7 or 14 days, larvae were weaned onto commercial food and reared to 36 days posthatching (28 days of feeding). There were no significant differences in body weight among groups at the end of the trial. A significantly higher survival rate (p < 0.05) was observed in larvae fed Artemia enriched with Red Pepper for 14 days compared to other feeding regimes. Based on the analysis of growth parameters, we can conclude that 7 days of live feeding to be sufficient for efficient rearing of sterlet larvae. And longer duration of live feeding with use of special enrichment can be recommended for a higher survival rate.     

Effect of two extruded diets with different fish and squid meal ratio on growth,digestibility and body composition of Octopus vulgaris (Cuvier, 1797)

The present work studies the growth and body composition of 18 Octopus vulgaris (6 per treatment) fed two extruded diets, namely FMS and 3FMS, based on different fish and squid meal ratios (1:1, and 3:1 respectively). The diets are compared with a control diet based on crab (Carcinus mediterraneus) and bogue (Boops boops). The growing tests were conducted on animals placed in individual 300 L rectangular fibreglass tanks in an open seawater system, containing PVC tubes as shelters, resulting in 100% survival rate. The control group exhibited the highest specific growth rates (SGR = 2.14%BW day^?1), while values of around 0.69%BW day^?1 were achieved by octopuses fed the extruded diets. Even though the three groups of animals showed similar digestive gland indexes, the two extruded diets promoted significant differences in the muscle composition and fatness of the digestive gland. Digestibility of dry matter was not affected by the type of extruded diet, obtaining ADC values of around 88%. The results suggest that squid and fish meal can be both used in dry pelleted extruded diets, with moderate acceptance by the octopus, even though the formulation must be optimized with the aim of improving acceptability and achieve growths in the range of natural diets.     

Growth,food intake,protein retention and fatty acid profile in Octopus vulgaris (Cuvier, 1797) fed agglutinated moist diets containing fresh and dry raw materials based on aquaculture by‐products

The lack of specific compound diets for cephalopods is limiting the industrial development of some species. In this study, four agglutinated moist diets were tested in individually reared Octopus vulgaris (979 ± 151 g) for 8 weeks. All diets were based on bogue Boops boops, accidentally reared in fish farms (aquaculture by‐product), and agglutinated with alginate and calcium. One diet was based exclusively on bogue fillets, two on bogue fillets complemented with meat from two crab species (Portunus pelagicus, Grapsus grapsus) and the last one on bogue and G. grapsus meals. As a control diet, bogue and P. pelagicus were supplied fresh on alternate days. All diets induced similar feed intake (2.1–2.6% day^?1). However, the meal‐based diet induced negative growth in comparison with the control and the other agglutinated diets (0.80–0.85% day^?1). Higher lipid content in agglutinated diets (28–30% dw) in comparison with the control diet (16% dw) led to higher protein retention in muscle. These results underline the inadequacy of traditional meals in diets for cephalopods and that the inclusion of crab meat did not increase feeding rates and growth in O. vulgaris. The dietary fatty acid, with high levels of oleic and linoleic acid and low levels of ARA, clearly reflected in digestive gland, while only decreasing ARA and increasing EPA levels were observed in muscle, with no apparent negative effect on growth.