Seagrass debris as potential food source to enhance Holothuria arguinensis' growth in aquaculture

Holothuria arguinensis aquaculture started to be developed in 2014, being the first sea cucumber species from Europe. However, some aspects of its aquaculture biotechnology, such diets, need to be assessed. This work aimed to evaluate seagrass debris of Zostera noltii and Cymodocea nodosa as food source for broodstock maintenance in tanks, during breeding periods. The given feed rations per tank were calculated as the 30% of the total sea cucumber biomass in each tank and reviewed each week. Then, feed rations of seagrass and sediment were calculated from this value, according to the following percentages: 40% sediment, 15% Z. noltii, 40% Z. noltii, 15% C. nodosa and 40% C. nodosa. H. arguinensis growth, feeding rate and nutritional value were assessed under these diets. H. arguinensis fed with 40% of Z. noltii showed the highest growth (specific growth rate = 0.09 +/- 0.06%/day, absolute growth rate = 0.11 +/- 0.07 g/day) increasing their final weight in 5.86 +/- 3.57% in 57 days. However, the individuals fed with C. nodosa showed a negative growth. H. arguinensis showed a reduction in its feeding rate as the organic matter content in the diets increased. H. arguinensis did not show any important change on proximate composition, protein, lipid, mineral contents and fatty acids profile among the feeding groups, or in comparison with the individuals collected from wild habitat. Therefore, H. arguinensis could be fed with Z. noltii debris during tanks maintenance along breeding period, ensuring its growth and maintaining its nutritional profile.Fundacao para a Ciencia e a TecnologiaPortuguese Foundation for Science and TechnologyEuropean Commission [CCMAR/SC/BI/02/2016, FRH/BD/105541/2014, IF/00049/2012, IF/00998/2014, PTDC/MAR-BIO/5948/2014, PTDC/MAR/119363/2010, SFRH/BPD/70689/2010]http://creativecommons.org/licenses/by/4.0

Feature Extraction for Murmur Detection Based on Support Vector Regression of Time-Frequency Representations

This paper presents a nonlinear approach for time-frequency representations (TFR) data analysis, based on a statistical learning methodology - support vector regression(SVR), that being a nonlinear framework, matches recent findings on the underlying dynamics of cardiac mechanic activity and phonocardiographic (PCG) recordings. The proposed methodology aims to model the estimated TFRs, and extract relevant features to perform classification between normal and pathologic PCG recordings (with murmur). Modeling of TFR is done by means of SVR, and the distance between regressions is calculated through dissimilarity measures based on dot product. Finally, a k-nn classifier is used for the classification stage, obtaining a validation performance of 97.85%

The regime of climate-related disturbance and nutrient enrichment modulate macroalgal invasions in rockpools

Patterns of invasion by the seaweeds Grateloupia turuturu Yamada and Sargassum muticum (Yendo) Fensholt under crossed combinations of the regime (mean intensity and temporal variability) of climate-related mechanical disturbance and constant nutrient enrichment were experimentally examined in rockpools in north Portugal. The cover of both species was larger under high compared to low intensity of disturbance, but this effect was enhanced by events more heterogeneously distributed over a period of 19 months. The invasion by G. turuturu was also larger in enriched pools, but only when disturbance was applied at high intensity. The richness of native taxa was increased by high intensity events of disturbance evenly distributed over time and by low intensity events heterogeneously distributed, while no differences were documented for other treatments. Temporal variability of disturbance and nutrients interactively affected the total cover of native taxa and the availability of bare rock in different directions. Enriched conditions increased the space occupancy by natives and reduced substratum availability only when associated to heterogeneous events of disturbance. At the same time, relatively more variable disturbances caused a reduced cover by native taxa and an increased availability of free space, but only under natural nutrient levels. Present findings contribute to understand the conditions that would be more likely to facilitate the spread of G. turuturu and S. muticum under current and predicted scenarios of compounded environmental changes and in relation to traits of recipient systems that are considered relevant for the success of invasions, including the native richness and the degree of usage of resources, i.e. primarily space

Chemicals released by male sea cucumber mediate aggregation and spawning behaviours

The importance of chemical communication in reproduction has been demonstrated in many marine broadcast spawners. However, little is known about the use of chemical communication by echinoderms, the nature of the compounds involved and their mechanism(s) of action. Here, the hypothesis that the sea cucumber Holothuria arguinensis uses chemical communication for aggregation and spawning was tested. Water conditioned by males, but not females, attracted both males and females; gonad homogenates and coelomic fluid had no effect on attraction. Male spawning water, but not female spawning water, stimulated males and females to release their gametes; the spermatozoa alone did not induce spawning. H. arguinensis male spawning water also induced spawning in the phylogenetically related H. mammata. This indicates that males release pheromones together with their gametes that induce spawning in conspecifics and possibly sympatric species. Finally, the male pheromone seems to be a mixture with at least one labile compound (biological activity is lost after four hours at ambient temperature) possibly including phosphatidylcholines. The identification of pheromones in sea cucumbers offers a new ecological perspective and may have practical applications for their aquaculture.FCT - Foundation for Science and Technology [UID/Multi/04326/2013, SFRH/BD/90761/2012]info:eu-repo/semantics/publishedVersio

Habitat traits and patterns of abundance of the purple sea urchin, Paracentrotus lividus (Lamarck, 1816), at multiple scales along the north Portuguese coast

Spatial and temporal patterns of abundance and distribution of sea urchins (Paracentrotus lividus) from intertidal rockpools of the north Portuguese coast were examined in relation to physical (surface, altitude, depth, topographic complexity and exposure) and biological (substrate cover by dominant organisms) habitat traits. The methodology was based on a multi-factorial design where the total number and the abundance of urchins in each of six size classes were sampled over a range of spatial scales, from 10s of cm to kms, and a temporal scale of five months. The results highlighted three main features of the studied system: (1) the largest proportion of variability of sea urchins occurred at the smallest scale examined; (2) urchins from different size classes showed different patterns of abundance in relation to habitat traits; (3) variables normally invoked as potential drivers of distribution of urchins at a range of scales, such as hydrodynamics and shore height, were relatively less important than other abiotic (i.e. pool area, pool mean depth calculated over five replicate measures and sand cover) and biological (i.e. space occupancy by the reef-forming polychaete Sabellaria alveolata and mussels vs. availability of bare rock) variables to provide a considerable contribution to the variability of sea urchins. Intertidal populations of sea urchins are abundant on many rocky shores, where they are socially and economically important as food resource and ecologically key as habitat modelers. This study provides new clues on relatively unstudied populations, with relevant implications for possible management decisions, including the implementation of protection schemes able to preserve the main recruitment, settlement and development areas of P. lividus

Genetic signature of a recent invasion: the ragged sea hare Bursatella leachii in Mar Menor (SE Spain)

In the last years, bioinvasions are increasing their ecological and economic impacts on different habitats all over the world, and are therefore becoming the target of much recent research (Ricciardi et al., 2004; Bernardi et al., 2010; Zenetos et al., 2012). The leading hypothesis for the origin of invasions is that colonization by invasive species is most often associated with founder events of introduction by occasional windows of opportunity (Montefalcone et al., 2010; Zhan et al., 2010), although distinct invasion processes might occur simultaneously in different parts of the invaded range, and some can create local accumulation of genetically distinct invaders. In a typical invasion scenario, however, the few founders are then the source of rapid demographic expansions in the new habitats. Such processes result in extreme genetic diversity loss. Biological invasions thus contradict the paradigm of genetic diversity being essential for adaptation to novel habitats

A new species for sea cucumber ranching and aquaculture: breeding and rearing of Holothuria arguinensis

Multi-species sea cucumber fisheries, including the speciesHolothuria arguinensis, have developed recently in the North-eastern Atlantic and Mediterranean Sea. In this context, the current study evaluated the potential use of H. arguinensis in aquaculture and to enhance natural populations, describing the embryonic and larval development for a better understanding and application in marine conservation and population genetics. Wild broodstock collected in Ria Formosa (37°0′33.92″N, 7°59′44.99″W; Faro, South Portugal) was induced to spawn using established methodology of thermal stimulation from June to August. The larval development under controlled conditions exhibited the classic five stages described for most aspidochirote holothurians, reaching the juvenile stage after 18 days post-spawning. Low mortality was registered during the pelagic larval stage, however high mortality (85–95%) was registered at doliolaria and juvenile stages. Results indicate that H. arguinensis is suited to hatchery rearing for aquaculture and enhancement of natural populations. Nevertheless, as this is the first European sea cucumber species reproduced in a hatchery, further research is required to improve the survival of post-settlement stages and optimize the rearing of juveniles.info:eu-repo/semantics/publishedVersio

Multiple effects of harvesting on populations of the purple sea urchin Paracentrotus lividus in north Portugal

We compared patterns of abundance and distribution of the sea urchin Paracentrotus lividus between shores subject to commercial harvesting of this species and unexploited reference shores in north Portugal. Harvesting was associated to a significant reduction in total density and abundance of individuals of commercially valuable size (i.e. larger than 40 mm in test diameter), with patterns, respectively, fully or mostly consistent over a study period of about one year. In addition, the spatial variance in the distribution of the largest individuals was higher under the harvested compared to the reference condition at the scale of sampled shores (i.e. kms apart), while the opposite pattern was documented for the temporal variance of the same response variable. These findings suggest that commercial harvesting has an actual impact on the studied populations of P. lividus, with potential implications for their conservation and for the management of the associated local fishery

Improving the fitness of Holothuria arguinensis larvae through different microalgae diets

Development and design of adequate feeding protocols on sea cucumber larvae are necessary for improvements on larvae growth, survival and production of competent juveniles. This work assessed the Holothuria arguinensis larvae growth and survival, fed with three different single microalgae diets of Chaetoceros calcitrans, Isochrysis galbana and Tetraselmis chui, and two microalgae diets based on a combination of C. calcitrans and T. chuii (C:T 1:1) and C. calcitrans, T. chuii and I. galbana (C:T:I 1:1:1) during 2 months. Holothuria arguinensis larvae fed with T:C:I, showed higher survival and larger larval and stomach sizes than the ones fed with the other diets. Comparing the results obtained from the single diets, H. arguinensis larvae fed with I. galbana grew and survived better during the first 5 days. However, higher growth was obtained on the larvae fed with C. calcitrans from day 5 to day 12 since this day, larvae fed with T. chuii showed the largest size. These results could be related to the different microalgae size and morphology, in addition to the nutritional value of the different microalgae used. However, no competent larvae that metamorphosed into doliolaria were obtained during this experiment. The tanks used were transparent, which could be causing light stress to the larvae, since competent larvae were obtained in opaque production tanks in our aquaculture installations during the same time period. The combined diet of C. calcitrans, T. chuii and I. galbana (C:T:I) could improve the growth and larvae competency of H. arguinensis.Fundacao para a Ciencia e a TecnologiaPortuguese Foundation for Science and Technology [CCMAR/BI/0007/2015, IF/00998/2014, PTDC/MAR-BIO/5948/2014