Merobenthic octopods like
Octopus vulgaris
undergo a transitional period between the planktonic and benthic phases, known as settlement stage. In this work, three sub-stages (“pre-settlement”, ...“settlement” and “post-settlement”) have been defined based on morphological, anatomical, and behavioural changes. At the end of the planktonic phase advanced paralarvae are transparent with 65–80 chromatophores, iridophores covering eyes and digestive system, Kölliker organs, circular pupils, ~ 20 suckers per arm (spa), and mantle length (ML) bigger than total length (TL; ML/TL > 60%). The “pre-settlement” sub-stage (ML/TL from 65 to 55%, ~ 20–25 spa) is marked by the onset of clinging reflexes, where the pre-settlers touch the walls and bottom of the tank and start crawling clumsily. Morphologically, they are transparent with increased chromatophores along the arms and iridophores around the eyes and head. During the “settlement” sub-stage (~ 55–48% ML/TL, ~ 25–35 spa) there is an exponential increase of chromatophores in the dorsal area of head and mantle, and the settlers show strong negative phototaxis, crawling for shelter when disturbed. The skin is still transparent but new chromatic cells (leucophores) develop and Kölliker organs are almost lost. During the “post-settlement” sub-stage (~ 48–40% ML/TL, > 35 spa) the post-settlers display very fast and coordinated movements, have horizontal pupils, and develop the “eye-bar”. The chromatic cells keep increasing exponentially, giving a pale appearance to the skin. The beginning of the benthic phase in
O. vulgaris
juveniles is marked by the presence of skin sculptural components (papillae) and a complex display of chromatic, postural, and cryptic patterns.
Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates ...are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.
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.
•There is a lack of research about the effect of lighting conditions on the culture performance of Octopus vulgaris paralarvae and this work contribute to this research ítem.•LED-lights and light oceanic filters can be used to control the lighting environment in culture tanks•The intensity of blue or white light is positively related with the dry weight of Octopus vulgaris paralarvae•Introducing heterogeneity in the lighting environment of culture tanks can be a way to promote the survival of Octopus vulgaris paralarvae
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 8days and their FA composition resembled that from hatchlings produced under culture conditions. However, when compared with the FA composition of up to 20days 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.
Artemia does not fulfil paralarval fatty acid requirements.
•For the very first time, the fatty acid profile of wild O. vulgaris paralarvae of estimated age was individually analyzed.•Beak reading is a more accurate tool than dorsal mantle length-based equations to estimate the age of wild individuals.•The fatty acid profile of wild paralarvae significantly differs to that observed in reared paralarvae.
Abstract
Space-based research can provide a major leap forward in the study of key open questions in the fundamental physics domain. They include the validity of Einstein’s Equivalence principle, the ...origin and the nature of dark matter and dark energy, decoherence and collapse models in quantum mechanics, and the physics of quantum many-body systems. Cold-atom sensors and quantum technologies have drastically changed the approach to precision measurements. Atomic clocks and atom interferometers as well as classical and quantum links can be used to measure tiny variations of the space-time metric, elusive accelerations, and faint forces to test our knowledge of the physical laws ruling the Universe. In space, such instruments can benefit from unique conditions that allow improving both their precision and the signal to be measured. In this paper, we discuss the scientific priorities of a space-based research program in fundamental physics.
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 <1 increment d−1 was recorded at 14°C. The width of the reading area grew accordingly with age; therefore, this beak region may be suitable for age estimation. A general linear model (GLM) analysis showed that temperature and the interaction of age × temperature significantly influenced increment deposition, whereas diet did not. The number of growth rings recorded in wild paralarvae beaks ranged from 0–8 on the coast, 7–11 on the continental shelf and 2–28 in the open ocean. Corrected age estimates of wild paralarvae were obtained with the GLM using the mean temperatures recorded in the wild, supporting the hypothesis that O. vulgaris leave the coastal area and develop in the open ocean transported by upwelling filaments.
Samples of anadromous Alosa alosa (Clupeidae) (n = 163) and Alosa fallax (Clupeidae) (n = 223), caught in Western Iberian Peninsula Rivers from 2008 to 2013, were examined for buccal, branchial and ...internal macroparasites, which were identified using morphological and molecular methods. Alosa alosa were infected with Anisakis simplex s.s., Anisakis pegreffii, Hysterothylacium aduncum, Rhadinorhynchus pristis, Mazocraes alosae, Hemiurus appendiculatus, Ceratothoa italica and an unidentified ergasilid copepod. Ceratothoa italica represents a new host record for A. alosa. Alosa fallax were infected with A. simplex s.s., A. pegreffii, H. aduncum, H. appendiculatus, Clavellisa emarginata and an unidentified cymothoid isopod. This is the first report of C. italica, C. emarginata and M. alosae in the Iberian Peninsula. The phylogenetic positions of M. alosae, H. appendiculatus and C. emarginata were assessed using 18S and 28S ribosomal RNA (rRNA); our contributions provide a better understanding of the phylogenetic relationships within their groups. Qualitative and quantitative differences in the parasite faunas of these two shad species are consistent with different feeding strategies. The results provide information about host migration behaviour and transmission pathways through diet during the marine trophic phase of the shad’s life cycle and their roles as paratenic or final hosts and transporters of parasites between seawater and freshwater environments. The zoonotic parasites A. simplex s.s. and A. pegreffii pose a risk for consumers or riverine mammals (e.g. European otter). The use of parasites as biological tags for shad stocks in Western Iberian Rivers could be a useful approach in multidisciplinary studies concerning fish stock delimitation and characterization.
T 3-Interferometer for atoms Zimmermann, M.; Efremov, M. A.; Roura, A. ...
Applied physics. B, Lasers and optics,
04/2017, Letnik:
123, Številka:
4
Journal Article
Recenzirano
Odprti dostop
The quantum mechanical propagator of a massive particle in a linear gravitational potential derived already in 1927 by Kennard 2, 3 contains a phase that scales with the third power of the time T ...during which the particle experiences the corresponding force. Since in conventional atom interferometers the internal atomic states are all exposed to the same acceleration a, this T 3 -phase cancels out and the interferometer phase scales as T 2 . In contrast, by applying an external magnetic field we prepare two different accelerations a 1 and a 2 for two internal states of the atom, which translate themselves into two different cubic phases and the resulting interferometer phase scales as T 3 . We present the theoretical background for, and summarize our progress towards experimentally realizing such a novel atom interferometer.
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