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13 pages, 3 tables, 8 figures, The common octopus Octopus vulgaris is a highly valuable species worldwide, but to understand its population dynamics and requirements under culture conditions, it is crucial to improve our knowledge about its planktonic stages. Previous studies validating daily beak growth increments in these stages allowed age estimation and comparison of wild and cultured paralarvae. We aimed to improve age estimations in captivity, addressing the effect of temperature and diet, to obtain an accurate estimation of age in wild specimens collected from the coast to the open ocean off NW Spain and Morocco. We analysed the beak growth increments of reared paralarvae at 14 and 21°C with 2 different crustacean prey taxa (Artemia and spider crab Maja brachydactyla zoeae) over 30 d. Daily increment deposition at 21°C was confirmed, whereas, This study was funded by Spanish Government under Projects OCTOWELF (Ref. AGL2013- 49101-C2) and CAIBEX (CTM2007-66408-C02).

The present research describes the complete life cycle in captivity, including spawning, larval culture and fattening of juveniles until commercial size. Additionally, size, weight and age at each moulting stage were recorded, as well as zoeas biochemical composition. The most significant results obtained were as follows. Embryonic development lasted for 33 days. Each female had between three and five spawns, separated by 4–5 days each. Larval culture lasted for 20 days at 14–17°C. The zoeas turn to megalopa at ~11 days after hatch/DAH), and from megalopa to juvenile at ~20 DAH. Average survival was ~13%. Juvenile growth rate was higher during the first 8 months (0.22%–0.46% bw/day), and then gradually decreased when changing from live to frozen diets. Survival during the fattening phase was 63%. The final moult occurs at 450 DAH, when males and females have a carapace total length of 12.38 + 1.23 and 13.57 + 1.23 cm, respectively, and 541.56 + 104.26 and 670.68 + 162.6 g in total weight respectively. Biochemical composition of cultured zoeas showed a high amount of phospholipids and long‐chain fatty acids, docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA). Low survival rates in larval culture and especially after passing to the benthic life style are the main problems regarding spider crab culture, and need to be improved.

Survival and growth of juvenile octopi vary considerably. The objective of this research was to determine variations in weight, total lipids (TL), and total protein (TP) of newly hatched Octopus vulgaris paralarvae (0 days old) over the course of the spawning period. Newly hatched paralarvae dry weight from three females decreased throughout the spawning period. Similarly, newly hatched paralarvae TL percent decreased consistently (p < 0.05) in two of them and remained similar (p > 0.05) for the third female. Contrary, TP% did not vary regardless of the female or the time of hatching throughout paralarvae spawning. In conclusion, we believe that paralarvae used in O. vulgaris culture should be collected during the first 10 days of spawning, as they are larger and have higher lipid content; this increases the chances of a successful paralarvae culture, which is the major bottleneck in the culture of this species., 0,0000

The common octopus (Octopus vulgaris) is a promising species for aquaculture diversification, but massive mortality during the first life-cycle stages (paralarvae) is the main bottleneck for its commercial production in captivity. The aim of this study was to assess stress and nutritional condition biomarkers (HSP70, ROS enzymes and lipid peroxidation) (RNA/DNA, RNA/protein, protein/DNA and protein) in O. vulgaris paralarvae from different geographical origins and fed with Artemia enriched with marine phospholipids or microalgae (control group). To this end paralarvae were cultured for 30 days, in three different centres in Spain (Tarragona-Mediterranean area, Tenerife-Central Atlantic area and Vigo-North Atlantic area), under the same protocol, and fed on Artemia enriched with marine phospholipids (LC60) (Marine Lecithin LC 60®, PhosphoTech Laboratoires) or microalgae (control group). Dry weight and most biomarkers analysed in hatchlings showed significant differences related to their origin (centre). Fifteen day old paralarvae presented significant differences in specific growth rate (SGR) associated with their dietary regime, and also showed differences in biomarkers associated both with their geographical origin and dietary regime. The results suggest that the SGR of paralarvae were positively influenced by LC60, promoting growth and in agreement with the results of nutritional condition biomarkers (nucleic acids ratios). The antioxidant defences against oxidative damage were also boosted in the LC60 paralarvae group, possibly as a result of the elevated content in highly polyunsaturated fatty acids. In addition, the partial correlations found between biomarkers varied according to diet. However, no positive effect of LC60 on survival was observed. The high variability found among geographical origins, despite the use of the same rearing protocol, highlights the need to clarify the sources of such variability., This survey was funded by the Ministerio de Ciencia e Innovación (Spanish Government) under Project OCTOPHYS (AGL2010-22120-CO3), and by PROMETEO II/2014/085 (Generalitat Valenciana). D. Garrido was financed by a Ph.D. grant by Spanish Institute of Oceanography (MINECO, Spanish Government) (BOE 3rd November 2011). Most of the authors of this paper participate in the COST network, Action FA1301 (CephsInAction) focussing on Cephalopod welfare.

The fatty acid (FA) profile of wild Octopus vulgaris paralarvae of estimated age was individually analyzed for the very first time in order to establish a reference for comparison in rearing and nutritional studies. Age of each paralarvae was estimated by analysing daily increments on lateral hood surface of beaks. Wild paralarvae age ranged between 6 and 8 days and their FA composition resembled that from hatchlings produced under culture conditions. However, when compared with the FA composition of up to 20 days old cultured paralarvae described in the bibliography, some striking differences were found. Results showed higher levels of docosahexaenoic acid (22:6n − 3, DHA), lower contents of 18:1n − 9, 18:1n − 7 and 18:2n − 6 and negligible levels of 18:3n − 3 in wild paralarvae, when collated to reared one. These results seem to indicate that preys/diets supplied to cultured paralarvae fail to resemble paralarval natural composition and as a result do not fulfil their FA requirement. The individual applied technique developed in this study will allow to refine the study of wild paralarvae along its development, as well as to compare wild and cultured paralarvae of similar age. Statement of relevance Artemia does not fulfil paralarval fatty acid requirements., This study was funded by Spanish Government under Projects OCTOPHYS (Ref. AGL2010-22120-C03), OCTOWELF (Ref. AGL2013-49101-C2-1-R) and LARECO (CTM2011-25929). Most of the authors of this paper participate to the COST network, Action FA1301 (CephsInAction) focussing on Cephalopod welfare. D. Garrido was financed by a Ph.D. grant by Spanish Institute of Oceanography (BOE 3rd November 2011).

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.

This study analyzes the effect of low salinity on survival and daily food ingestion of octopus subjected to three different water salinities (20, 25, and 30 psu) for 3 days. During the 3-day experiment, octopuses at 20 psu immediately stopped eating, and all died during the first day; at 25 and 30 psu, the octopuses gradually reduced their feed intake and stopped eating after 2 days, but all survived, and when normal salinity conditions were reestablished (34–35 psu), they ingested 30–40 (~27.5% of the initial food intake) and 70–90 g of food/day (~63% of the initial food intake) respectively over the 5-day recovery period. Water salinity of 30 psu could be considered as the recommended lower limit below which actions, such as transferring the commercial floating cages to another location or submerging them, should be taken in order to prevent the negative effects of low salinities on farmed octopuses., 0,0000

Different assays related to the first feeding of Octopus vulgaris Cuvier, 1797 are compiled in this paper. They include: age at initial feeding age, prey size selection and optimal density, attack timing after feeding, and effect of dose number on the number of captures. Prey capture and ingestion processes were also analysed. Food supplied was cultured Artemia sp. Each assay lasted 15 min. Although paralarvae already start to feed on the hatching day (day 0), it is during day 2 when a greater number of attacks is recorded (81.7 ± 14.7% paralarvae attack). They mainly prefer (significance level α = 0.05) large Artemia , 1.4 ± 0.4 mm (77.0 ± 5.6% of the total attacks) than small Artemia , 0.8 ± 0.1 mm (23.0 ± 5.6%). There is also a slight predilection for the lowest Artemia concentration (33.3 ±12.6% paralarvae attack in a 0.1 Artemia ml − 1 density, opposite 16.7 ± 7.6 and 18.3 ± 7.6% in densities of 0.5 and 1 Artemia ml − 1 respectively). The greatest predatory activity is recorded during the first 5 min after food is supplied (72.2 ± 25.5%). An increase in the predatory activity was also observed when food was distributed in several doses instead of a single dose (75.0 ± 10.0% and 46.7 ± 17.6% respectively). It was proved for the first time that paralarvae completely ingest their preys (including their exoskeletons), in this case Artemia . Time needed for their total ingestion ranges between 4 and 10 min.

The effect of the adherence of the lipid droplet in the yolk-sac on the growth and survival of the European hake (Merluccius merluccius) larvae was studied under starved and feeding conditions. Recently hatched hake larvae with adhered and non-adhered lipid droplet (ALD and non-ALD) were maintained during 8 days under starvation conditions. The adherence of the lipid droplet positively affected larval survival during starvation. At the end of the yolk consumption period (7–8 days after hatching), 90% of the surviving larvae had an ALD, while 10% of the survivors had a non-ALD and showed a higher mortality rate. In a month feeding experiment, results show that the presence of non-ALD in newly hatched hake larvae negatively affected their growth and survival. Dry weight and length (TL) of 20-days-old larvae with ALD were significantly higher than those with non-ALD. Furthermore, lifespan of those larvae with non-adhered lipid droplet was shorter, with most of them dying during the first 15–20 days of culture. As conclusion, the percentage of the lipid droplet adherence at hatching could be used as an indicator of ‘quality’ for European hake larvae: the greater the number of larvae with adhered lipid droplet, the better larval growth and survival., 1,2030

Commercial culture of octopus has not yet been achieved due to the high mortality recorded during the first weeks of life. Several researchers have pointed out nutrition as the key factor of influence on paralarval mortality in culture (Iglesias, Sanchez, Bersano, Carrasco, Dhont, Fuentes, Linares, Munoz, Okumura, Roo, van der Meeren, Vidal & Villanueva 2007; Villanueva, Escudero, Deulofeu, Bozzano & Casoliva 2009; Seixas, Rey-Mendez, Valente & Otero 2010; Seixas, Otero, Valente, Dias & Rey-Mendez 2010; Fuentes, Sanchez, Lago, Iglesias, Pazos and Linares 2011). Nevertheless, several other factors, such as culture volume, can influence the success in paralarvae rearing. The lack of a standardized culture technique has meant that some authors have reared paralarvae in relatively large tank volumes: from 20 000 L used by Hamazaki, Fukunaga, Yoshida and Maruyama (1991), 9000 L (Moxica, Linares, Otero, Iglesias & Sanchez 2002), 6000 L (De Wolf, Lenzi & Lenzi 2011) and 1000 L (Iglesias, Otero, Moxica, Fuentes & Sanchez 2004), whereas others have worked with smaller volumes: Villanueva, Koueta, Riba and BoucaudCamou (2002) used 25 L tanks, Carrasco, Arronte & Rodriguez 2006; 30 L and Seixas (2009) 50 L. This study analyses tank volume effect on growth and survival of octopus paralarvae in their first month of life, using enriched artemia as live diet. Protein and lipid composition of paralarvae were also analysed to have an approach to paralarvae condition. Materials and methods

The larval development of reared European hake, Merluccius merluccius (Linnaeus, 1758), during the lecithotrophic phase, from hatching until 5 days post-hatching (dph), and throughout the endo-exotrophic feeding phase (6-10 dph) was studied by histology and histochemistry. Many crucial morphological, cellular and tissular changes were observed during both feeding phases, mostly those related to digestive and visual ontogenetic events, such as differentiation of buccopharyngeal cavity and eye development (at hatching); pigmentation and differentiation of cone-photoreceptors (4 dph); opening of the mouth and anus, appearance of intestinal valves (5-6 dph); presence of buccopharyngo-esophageal (5-6 dph) and intestinal (9 dph) mucous cells; folding of intestinal mucosa (6 dph); development of regional specific digestive musculature (6 dph); typical structure and functionality of the liver (sinusoids, biliary and pancreatic ducts, glycogen, protein and lipid reserves) (4-6 dph); and characteristic acinar distribution pattern of eosinophilic zymogen granules of the exocrine pancreas (6 dph). Between 9 and 10 dph, the hake larvae showed evident signs of lipid absorption within enterocytes of the anterior intestinal region and a remarkable process of pynocitosis and intracellular digestion was detected in the posterior intestine (supranuclear inclusions or acidophilic protein vesicles). In hake larvae at 10 dph, a proliferation of renal tubules, spleen differentiation and gill development, as well as the presence of the first thyroid follicle, were clearly distinguished. At this time, stomach gastric gland differentiation was not detected and endocrine pancreas and gill lamellae were not evidenced. However, and interestingly, swim bladder and eyes (developing rods) were well differentiated in larval development from 9 dph onwards. In summary, in European hake larval development during the endo-exogenous feeding phase and especially at 9 to 10 dph, most systems, organs and tissues were well differentiated. Particularly, digestive and visual systems were developed and physiologically functional some days before the start of the exogenous feeding phase., 1

For the first time, a spontaneous spawning of hake was recorded in Spain in April 2009. The spawn was obtained from broodstock kept in captivity for two years at the facilities of the Spanish Institute of Oceanography in Vigo (NW Spain). Eggs were transparent, spherical and had an average diameter of 1.067 ± 0.024 mm; yolk occupied the majority of egg volume. The oil droplet had a diameter of 0.27 ± 0.03 mm. The incubation period of the eggs lasted for 4 days at 14°C and the duration from hatching to the total absorption of the yolk sac was between 5–7 days after hatching, at the same temperature. Newly hatched larvae had an average total length of 3.20 ± 0.13 mm and began feeding 6 days after hatching; a daily growth rate of 0.158 mm day-1 was observed from hatching to yolk sac consumption. This paper describes the daily evolution of biometric and morphological characteristics of the different stages of embryos and larvae of European hake up to the age of 19 days.