Cephalopod Eggs and Hatchlings

DWhatley

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Diet composition and variability of wild Octopus vulgaris and Alloteuthis media (Cephalopoda) paralarvae through a metagenomic lens
Lorena Olmos Pérez, Álvaro Roura, Graham J. Pierce, Stéphane Boyer, Ángel F. González

The high mortality of cephalopod early stages is the main bottleneck to grow them from paralarvae to adults in culture conditions, probably because the inadequacy of the diet that results in malnutrition. Since visual analysis of digestive tract contents of paralarvae provides little evidence of diet composition, the use of molecular tools, particularly next generation sequencing (NGS) platforms, offers an alternative to understand prey preferences and nutrient requirements of wild paralarvae. In this work, we aimed to determine the diet of paralarvae of the loliginid squid Alloteuthis media and to enhance the knowledge of the diet of recently hatched Octopus vulgaris paralarvae collected in different areas and seasons in an upwelling area (NW Spain).
DNA from the dissected digestive glands of 32 A. media and 64 O. vulgaris paralarvae was amplified with universal primers for the mitochondrial gene COI, and specific primers targeting the mitochondrial gene 16S gene of arthropods and the mitochondrial gene 16S of Chordata. Following high-throughput DNA sequencing with the MiSeq run (Illumina), up to 4,124,464 reads were obtained and 234,090 reads of prey were successfully identified in 96.87% and 81.25% of octopus and squid paralarvae, respectively. Overall, we identified 122 Molecular Taxonomic Units (MOTUs) belonging to several taxa of decapods, copepods, euphausiids, amphipods, echinoderms, molluscs and hydroids.
Redundancy analysis (RDA) showed seasonal and spatial variability in the diet of O. vulgaris and spatial variability in A. media diet. General Additive Models (GAM) of the most frequently detected prey families of O. vulgaris revealed seasonal variability of the presence of copepods (family Paracalanidae) and ophiuroids (family Euryalidae), spatial variability in presence of crabs (family Pilumnidae) and preference in small individual octopus paralarvae for cladocerans (family Sididae) and ophiuroids. No statistically significant variation in the occurrences of the most frequently identified families was revealed in A. media. Overall, these results provide new clues about dietary preferences of wild cephalopod paralarvae, thus opening up new scenarios for research on trophic ecology and digestive physiology under controlled conditions.
 

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Preliminary Results on Light Conditions Manipulation in Octopus vulgaris(Cuvier, 1797) Paralarval Rearing
Diego Garrido, Diana B. Reis, Diego Orol, Rui A. Gonçalves, M. Virginia Martín, António V. Sykes, Covadonga Rodríguez, Beatriz C. Felipe, Xiaodong Zheng, Luis Lagos, Eduardo Almansa 2017 (subscription)
Abstract
High paralarvae mortality is a major bottleneck currently hindering the control over the lifecycle of common octopus (Octopus vulgaris Cuvier, 1797). It is believed that this problem might be related to either zoo-technical and/or nutritional aspects. The present paper is focused on the study of different zoo-technical aspects related to light conditions on the rearing of paralarvae, including the effects of polarization in prey ingestion, the use of a blue filter to simulate natural conditions, and the use of focused light to avoid reflections of the rearing tank’s walls. In the first experiment, O. vulgaris paralarvae ingestion of Artemia sp. and copepods (Tisbe sp.) was assessed under either normal or polarized light. In the second experiment, the effect of a blue filter with natural light or focused artificial light on growth and mortality was assessed over 15 days of rearing. Ingestion rate was not influenced by light polarization. Nonetheless, a significantly higher ingestion of Artemia sp. with respect to copepods was observed. The blue filter promoted the use of natural light conditions in Octopus paralarval culture, while focused light reduced the collision of the paralarvae against the walls. However, no significant differences were found in paralarval growth nor survival.
 

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Invertebrate predation on egg masses of the European cuttlefish, Sepia officinalis: An experimental approach
Catarina P.P. Martins,, Fernando Á. Fernández-Álvarez, Roger Villanueva

Abstract
The eggs of the European cuttlefish, Sepia officinalis, develop attached to the seafloor in shallow water habitats and possess a relatively thick black capsule that protects them from the surrounding environment. Since embryological development may take several months, eggs are vulnerable to a variety of threats present in shallow waters, including predation. This study investigates predation of S. officinalis eggs by benthic invertebrates. Twenty-eight invertebrate species from 6 different phyla and with diverse feeding habits were tested as potential predators under laboratory conditions. We also investigated how the feeding traits of these species are related to the mechanical ability to break the egg capsule and prey upon cuttlefish embryos. Species that fed on cuttlefish eggs were the sea snail Bolinus brandaris, the crab Cancer pagurus, the hermit crab Dardanus arrosor, the lobster Homarus gammarus, the invasive blue crab Callinectes sapidus, the shrimp Squilla mantis, the sea urchins Echinus melo, Cidaris sp. and Paracentrotus lividus and the starfish Astropecten aranciacus. It is of note that C. sapidus is a potential predatory crab, which raises the concern that this invasive species may constitute a novel threat for cuttlefish eggs as more populations become established in NE Atlantic waters. Of the biological traits examined, prey capture tools in the tested species best explained the experimental feeding results, suggesting that predation of S. officinalis eggs was determined generally by a mechanical factor and highlighting the importance of the protective egg capsule against predators. However, chemosensory factors are likely to be implicated as well. Thus, this work contributes to the understanding of the ecology of early life stages of cuttlefish and the factors that can affect offspring survival and subsequently impact the recruitment of this species.
 

DWhatley

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Light conditions and heterogeneity in illumination affect growth and survival of Octopus vulgaris paralarvae reared in the hatchery
R Tur, A Roura, L. Marquez, C. Lopez, M.J. Lago, M. Mallorquin, E. Almansa 2018 (Subscription Elsevier)
Abstract
In order to succeed in common octopus (Octopus vulgaris) aquaculture, it is necessary to overcome the massive paralarval mortalities, which are likely related to zootechnical and/or nutritional aspects. Among the zootechnical aspects, the effect of light could be vital for the development of paralarvae given their sophisticated visual system. O. vulgaris paralarvae display vertical behavior in the wild, being in deeper waters during the day and close to the surface at night. For this reason, the present study traces a collection of light assays in captivity, to test ecologically-driven hypotheses on the growth and survival of octopus paralarvae.
The first assay tested a factorial combination of light colors (blue vs white) and intensity (low ~13 lx (36 W/m2), medium ~87 lx (151 W/m2) and high ~265 lx (422 W/m2)). The results pointed to a significant negative impact of low light intensities (13 and 87 lx) on paralarval growth. The second assay was designed to contrast light colors (blue vs white), different levels of intensities (300 lx (478 W/m2) vs 600 lx (1077 W/m2)) and partial coverage of the tanks using a shade mesh, named as “shadow zone” (half-covered vs non-covered tanks). In half-covered tanks, survival was significantly improved, with the best results coming from half-covered tanks with blue light and 600 lx, but no differences in dry weight were observed. The third experiment tested a factor called “light source position” with two levels: “Control” when the light incidence angle was 0° with respect to the normal direction (i.e. perpendicular to the water surface), and “Oblique” when the light incidence angle was 60° with respect to the normal direction. In this experiment, survival significantly improved under oblique light but no differences in dry weight were detected. The last experiment was an unifactorial design combining “light source position” and “tank partial coverage” with three treatments: i) control light with uncovered tanks, ii) oblique light with uncovered tanks, iii) control light with semi-covered tanks. Oblique light with uncovered tanks was associated with a higher survival rate but without statistical significance, probably due to data variability. It can be concluded that light intensity tended to affect paralarval dry weight, whereas the existence of a shadow zone or oblique light are more related with an improvement of survival rates.
 

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Morphological and physiological changes of Octopus bimaculoides: From embryo to juvenile
lL.E.Ibarra-García, J.M.Mazón-Suástegui, C.Rosas, D.Tovar-Ramírez, Guadalupe Bárcenas-Pazos, R.Civera-Cerecedo, A.I.Campa-Córdova 2018 (subscription Science Direct)
Abstract
Octopus bimaculoides is a holobenthic species with fishery importance in Mexico and aquaculture potential because of its high growth rate and direct development from embryo to juvenile, which increases survival in captivity. In cephalopods, transition from yolk utilization to independent active feeding is considered a critical period. Information about the digestive physiology ontogeny of O. bimaculoides is needed to determine the digestive capacity and to improve feed and feeding protocols in captivity for early life stages. Thus, this study assessed changes in morphological and digestive enzymatic activities, as well as biochemical composition of embryos and hatchlings. Internal and external yolk areas and total mantle and arm lengths were measured in embryos; total wet weight was measured in hatchlings. Activities of lipase, acidic phosphatase, trypsin and chymotrypsin were determined by fluorometric techniques; total lipid, triglyceride and soluble protein concentrations were biochemically measured. Embryonic development lasted around 65 days at an incubation temperature of 18 °C. Embryos grew exponentially while external yolk decreased linearly throughout the embryonic developmental stages. Hatchlings grew exponentially the first 14 days after hatching (DAH). Enzymatic activities were evident since embryo stages, mainly at final development stages. Higher activities of acidic phosphatases and lipases in embryos were detected after the end of organogenesis; while trypsin and chymotrypsin activities, only were at final stages detected previous to hatching. In hatchlings, acidic phosphatase and lipase activities increased the first 12 and 20 DAH, respectively, and protease activities were erratic the first 30 DAH. Lipid concentrations did not show variations in embryo stages but decreased the first 10 DAH. Triglycerides increased in last embryo stages and decreased the first 14 DAH. Soluble proteins decreased in the last embryo stages and in the first 10 DAH. The results of lipases, acidic phosphatases, as well as lipid, triglyceride and soluble protein contents suggested that embryos started to mobilise reserves from the external to internal yolk sac at final developmental stages, and hatchlings were consuming their reserves during the first 10–14 DAH. Protease activity showed that the digestive gland started secretory activity from late embryo stages but continued maturation even after hatching. The results showed that in late embryonic development stages and first days after hatching, enzymatic activity and biochemical components respond to the mobilisation, accumulation and use of yolk reserves in O. bimaculoides.
 

DWhatley

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Soybean lecithin dietary supplementation in Octopus vulgaris formulated feeds: Growth, feed efficiency, digestibility and nutritional composition
Tania Rodríguez‐González, Jesús Cerezo Valverde, Benjamín García García 2018 (full article)

Abstract

Soybean lecithin dietary supplementation was tested on Octopus vulgaris performance in individual or grouped kept animals. Individually reared animals were fed two semi‐moist diets (N = 8) without (VEGENAT‐LS0) or with supplementation (VEGENAT‐LS2, substituting 20 g/kg of starch by lecithin). VEGENAT‐LS2 had higher polar and total lipid content (p < 0.05). Growth (1.1%–1.3%BW/day), feed intake (2.2%BW/day) and feed efficiency (48%–60%) were similar (p > 0.05). VEGENAT‐LS0 presented higher dry matter, protein and lipid digestibility (p < 0.05). VEGENAT‐LS2 increased lipids in carcass and whole animals (p < 0.05) but preserved lipid classes proportion. Group kept octopuses (N = 10) were fed a mixed natural diet (2BOGUE:1CRAB) or VEGENAT‐LS2. VEGENAT‐LS2 had lower protein but higher polar lipid content (p < 0.05). VEGENAT‐LS2 presented less growth (1.1% vs. 1.8%BW/day), feed intake (1.8% vs. 3.2%BW/day) and similar feed efficiency (53.5% vs. 59.9%). Dry matter and protein digestibility were similar while lipid digestibility was significantly lower in 2BOGUE:1CRAB (31.8% vs. 65.4%). VEGENAT‐LS2 digestive gland presented higher mineral and carbohydrate contents and lower triglycerides (p < 0.05), while a similar macronutrient composition was analysed in the carcass and whole animals. Individual or group keeping did not affect VEGENAT‐LS2 performance. In conclusion, dietary soybean lecithin supplementation did not promote a performance enhancement.
 

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On the relevance of vitamins C and E during embryonic and paralarval development of Patagonian red octopus Enteroctopus megalocyathus
Hernández J , Uriarte I. m Montes de Oca. Farías A.

Highlights


Under normal embryonic development culture, vitamin C levels decrease significantly.

Under hypo-osmotic stress, the vitamin C content of embryos is reduced significantly and vitamin E seems unaffected by this stress condition.

Paralarvae fed with vitamin C-enriched Artemia did not show significant differences in survival, growth or vitamin E content, only displaying higher vitamin C and E content at 21 DAH.
 

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Toxic effects of ammonia on the embryonic development of the cuttlefish Sepia pharaonis
Rui‐Bing Peng. Mao‐Wang Jiang. Chen Huang. Xia‐Min Jiang 2019 (full Aquaculture Research article)

Abstract
The objective of this study was to investigate the effects of ammonia nitrogen on the embryonic development of the cuttlefish Sepia pharaonis. Embryos were exposed to different concentrations (0, 1, 3, and 5 mg/L) of total ammonia–nitrogen (TAN) during incubation. The developmental rate, malformations, mortality, hatching rate, incubation period, yolk utilization efficiency ratio, and weight of the newly hatched cuttlefish were determined. The results showed that ammonia nitrogen significantly inhibited the development of S. pharaonis embryos and induced malformations and even death. Hatching was delayed, the hatching rate was reduced, mortality and the incubation period increased, and the yolk utilization efficiency ratio and weight of the newly hatched cuttlefish significantly decreased in a dose‐dependent manner after the embryos were exposed to more than 1 mg/L TAN for prolonged period. These variables could be used as an integrative biomarker or indicator of aquatic environmental ammonia contamination. In summary, our results indicated that ammonia caused toxicity in the embryos. When the concentration of TAN is greater than 1 mg/L, ammonia levels should be reduced to prevent toxic effects on embryonic development.
 



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