Effects of supplementation of decapods zoea to Artemia basal diet on fatty acid composition and digestive gland histology in common octopus (Octopus vulgaris) paralarvae

The present study aimed to evaluate the effect of the supplementation of different crab zoeas to enriched Artemia basal diet for O. vulgaris paralarvae during the first month of life. Paralarvae were fed using: enriched Artemia nauplii alone and Artemia co-fed with either first zoea stages of Grapsus adscensionis or Plagusia depressa. The experiment was carried out over a period of 28 days, in 0.12 m3 tanks with a flow-through rearing system. Growth in dry weight as well as mantle length and width were assessed weekly. Additionally, prey and paralarvae fatty acid composition and digestive gland (DG) histology were evaluated. Addition of low amounts of crab zoeas (approx.100 indv. L-1 day-1) provided during critical life stages of O.vulgaris proved to be good enough to improve paralarvae growth and survival in comparison to those fed exclusively on enriched Artemia. These results were supported by the finding of a higher number of glycoprotein absorption vacuoles in the DG from paralarvae co-fed with crab zoeas, suggesting a higher feeding activity. In addition, the fatty acid analysis of crab zoea showed that these are good sources of dietary arachidonic and eicosapentaenoic acids during the octopus planktonic life stage, whereas the low docosahexaenoic (DHA) content, suggests the use of additional DHA sources or higher zoeas densities to meet paralarvae nutritional demand to carry out a successful metamorphosis to benthic life

Tuning branching in ceria nanocrystals

Branched nanocrystals (NCs) enable high atomic surface exposure within a crystalline network that provides avenues for charge transport. This combination of properties makes branched NCs particularly suitable for a range of applications where both interaction with the media and charge transport are involved. Herein we report on the colloidal synthesis of branched ceria NCs by means of a ligand-mediated overgrowth mechanism. In particular, the differential coverage of oleic acid as an X-type ligand at ceria facets with different atomic density, atomic coordination deficiency, and oxygen vacancy density resulted in a preferential growth in the [111] direction and thus in the formation of ceria octapods. Alcohols, through an esterification alcoholysis reaction, promoted faster growth rates that translated into nanostructures with higher geometrical complexity, increasing the branch aspect ratio and triggering the formation of side branches. On the other hand, the presence of water resulted in a significant reduction of the growth rate, decreasing the reaction yield and eliminating side branching, which we associate to a blocking of the surface reaction sites or a displacement of the alcoholysis reaction. Overall, adjusting the amounts of each chemical, well-defined branched ceria NCs with tuned number, thickness, and length of branches and with overall size ranging from 5 to 45 nm could be produced. We further demonstrate that such branched ceria NCs are able to provide higher surface areas and related oxygen storage capacities (OSC) than quasi-spherical NCs

Effect of increasing docosahexaenoic acid content in weaning diets on survival, growth and skeletal anomalies of longfin yellowtail (Seriola rivoliana, Valenciennes 1833)

Five isoproteic (54.8%) and isolipidic (24.1%) microdiets, which varied in their docosahexaenoic acid (DHA) content (0.25, 0.75, 1.64, 1.99 and 3.17%; dw), were manufactured to determine its effects on longfin yellowtail Seriola rivoliana larvae in terms of fish biological performance, whole body fatty acid profile and incidence of skeletal anomalies from 30 dah (11.31 ± 1.79 Total Length, TL) to 50 dah (19.80±0.58 mm TL). The inclusion of dietary DHA up to 3.17% (dw) improved larval resistance to air exposure, although DHA did not significantly affect fish final growth or final survival. Indeed, high levels of dietary DHA (1.99% and 3.17%, dw) tended to increase the incidence of skeletal anomalies in S. rivoliana larvae, albeit no significant differences were observed. Furthermore, the occurrence of severe anomalies such as kyphosis and lordosis, was mainly associated to the larvae fed with the highest levels of dietary DHA. In terms of survival, increasing dietary DHA levels did not significantly affect longfin yellowtail survival rate, despite a tendency for enhanced survival. The results of the present study proved that the inclusion of dietary DHA in inert diets up to a 3.17% (dw) and a DHA/EPA ratio above 3.1 increased the final survival and stress resistance in S. rivoliana larvae

Organic, inorganic and nanoparticles of Se, Zn and Mn in early weaning diets for gilthead seabream (Sparus aurata; Linnaeus, 1758)

Levels of the oxidative stress-related minerals selenium (Se), zinc (Zn) and manganese (Mn) that should be supplied in microdiets for marine fish larvae depend on the availability of the molecular form of these minerals. The objective of this study was to determine how effectively Se, Zn and Mn in organic, inorganic and nanoparticle forms promote larval performance and bone development. Microdiets supplemented with Se, Zn and Mn were fed for 24 days to 20 dah seabream larvae. Microdiets without Se, Zn and Mn supplementation were associated with poor growth, low bone mineralization and a high incidence of anomalies in the branchial arches. Including Zn, Mn and Se in an amino acid chelate organic form promoted maximum larval growth, increased body lipid reserves, enhanced early mineralization and prevented branchial arches anomalies. In contrast, feeding with inorganic forms of these minerals was less effective than organic minerals in improving larval weight or bone mineralization in comparison to the non-supplemented diet. Moreover, the larvae were less resistant to stress, and fish showed higher bone anomalies in the pre-hemal region. Adding Zn, Mn and Se in the form of nanometals did not enhance growth, but improved stress resistance and bone mineralization. The study showed the need to supplement seabream with early weaning diets based on squid meal and krill oil with one or more of the antioxidant minerals, to promote larval growth, bone mineralization and prevention of skeleton anomalies, organic minerals being more effective than inorganic forms and nanometals in promoting mineralization and stress resistance

Osmoregulatory Plasticity of Juvenile Greater Amberjack (Seriola dumerili) to Environmental Salinity

Osmotic costs in teleosts are highly variable, reaching up to 50% of energy expenditure in some. In several species, environmental salinities close to the isosmotic point (similar to 15 psu) minimize energy demand for osmoregulation while enhancing growth. The present study aimed to characterize the physiological status related to osmoregulation in early juveniles of the greater amberjack, Seriola dumerili, acclimated to three salinities (15, 22, and 36 psu). Our results indicate that plasma metabolic substrates were enhanced at the lower salinities, whereas hepatic carbohydrate and energetic lipid substrates decreased. Moreover, osmoregulatory parameters, such as osmolality, muscle water content, gill and intestine Na+-K+-ATPase activities, suggested a great osmoregulatory capacity in this species. Remarkably, electrophysiological parameters, such as short-circuit current (Isc) and transepithelial electric resistance (TER), were enhanced significantly at the posterior intestine. Concomitantly, Isc and TER anterior-to-posterior intestine differences were intensified with increasing environmental salinity. Furthermore, the expression of several adeno-hypophyseal genes was assessed. Expression of prl showed an inverse linear relationship with increasing environmental salinity, while gh mRNA enhanced significantly in the 22 psu-acclimated groups. Overall, these results could explain the better growth observed in S. dumerili juveniles kept at salinities close to isosmotic rather than in seawater.This research was funded by Project "Diversificacion de la Acuicultura Espanola mediante la optimizacion del cultivo de Seriola dumerili" JACUMAR 2016 (MAPAMA) and Fondo Europeo Maritimo y de Pesca (FEMP). The authors (A.B. and J.M.M.) belong to the FishWelfare and Stress Network (AGL2016-81808-REDT), supported by the Agencia Estatal de Investigacion (MINECO, Spanish Government)

Tuning branching in ceria nanocrystals

Branched nanocrystals (NCs) enable high atomic surface exposure within a crystalline network that provides avenues for charge transport. This combination of properties makes branched NCs particularly suitable for a range of applications where both interaction with the media and charge transport are involved. Herein we report on the colloidal synthesis of branched ceria NCs by means of a ligand-mediated overgrowth mechanism. In particular, the differential coverage of oleic acid as an X-type ligand at ceria facets with different atomic density, atomic coordination deficiency, and oxygen vacancy density resulted in a preferential growth in the [111] direction and thus in the formation of ceria octapods. Alcohols, through an esterification alcoholysis reaction, promoted faster growth rates that translated into nanostructures with higher geometrical complexity, increasing the branch aspect ratio and triggering the formation of side branches. On the other hand, the presence of water resulted in a significant reduction of the growth rate, decreasing the reaction yield and eliminating side branching, which we associate to a blocking of the surface reaction sites or a displacement of the alcoholysis reaction. Overall, adjusting the amounts of each chemical, well-defined branched ceria NCs with tuned number, thickness, and length of branches and with overall size ranging from 5 to 45 nm could be produced. We further demonstrate that such branched ceria NCs are able to provide higher surface areas and related oxygen storage capacities (OSC) than quasi-spherical NCs

Wreckfish (Polyprion americanus). New Knowledge about reproduction, larval husbandry and nutrition. Promise a new species for aquaculture

Four different wreckfish (Polyprion americanus) broodstock batches were maintained in research facilities under different photo and thermo-period conditions, one in Greece, the Helenic Center for Marine Research (HCMR, n = 3) and three in Spain: Instituto Español de Oceanografía (IEO, n = 13) in Vigo, Aquarium Finisterrae (MC2, n = 21) in A Coruña and Consellería do Mar (CMRM, n = 11). The CMRM includes two centers that work together: Instituto Galego de Formación en Acuicultura (IGAFA) and Centro de Investigacións Mariñas (CIMA), both in Pontevedra. During the five years of the project DIVERSIFY (Exploring the biological and socio-economic potential of new-emerging candidate fish species for the expansion of the European aquaculture industry, 2013–2018) works focused on the reproductive biology of the species, broodstock, and larvae nutrition and development of incubation and larval rearing protocols have been carried out. In terms of reproduction, catch methods of new wild animals, the reproductive cycle, sperm characteristics evaluation, and spontaneous and induced spawning methods have been described for wreckfish. Regarding nutrition, the positive effect of two types of enrichment on the fatty acid profiles of Artemia and rotifer has been verified. The relationship between the fatty acid profile of the diets supplied to the broodstock and the fatty acid profile obtained in the oocytes and eggs of the females fed with different diets, has also been demonstrated. Finally, early larval ontogeny has been described and incubation and larval rearing protocols have been proposed based on the results obtained in the different experiments of temperature, growth, survival, and larval feeding that were carried out.Versión del edito

First description of parasitation by Agregata octopiana in common octopus, Octopus vulgaris, in Canary Islands

The negative effects that infections with the coccidian parasite Aggregata octopiana has in cephalopods is widely known. However, the assessment of this pathology is fundamental to optimize the intensive culture of octopus. In the present report a total of 35 octopuses were studied, 6 coming from the wild, 5 grown in land tanks, 11 grown in benthic sea cages and 13 grown in floating cages. Each octopus was individually identified by a microchip and fed a fresh diet based on discarded bogue and crab during two months for then being sacrificed and sampled. Experimental animals were weighed weekly to calculate their growing rate and, at the end of the trial, segments from intestine, stomach and gills were fixed in buffered formalin for their histopathological evaluation. Furthermore, caecum smears were studied in fresh and after Giemsa staining. In each studied group the prevalence of infection was up to 70%, being 100% in the case of animals grown in land tanks. Weight gain was high, around 38 g.day(-1), excepting for animals grown in land tanks (only 9 g.day(-1)). Sexual and asexual reproductive forms of this parasite were observed in studied organs, being macroscopically observed as white nodules distributed all along the digestive tract. Histologically, lesions observed in intestines consisted of a marked dilatation of lamina propria and presence of a moderate inflammatory reaction at intestinal villi, which were invaded by parasitic structures. In gills, parasites were observed both in epithelial and connective tissue, generating haemocytic infiltrates. This paper reports the first description of an apicomplexan of the genus Aggregata in Octopus vulgaris from northeastern central Atlantic waters and proves that growing of octopus in cages is optimal for this species