Two Benthic Diatoms, Nanofrustulum shiloi and Striatella unipunctata, Encapsulated in Alginate Beads, Influence the Reproductive Efficiency of Paracentrotus lividus by Modulating the Gene Expression

Physiological effects of algal metabolites is a key step for the isolation of interesting bioactive compounds. Invertebrate grazers may be fed on live diatoms or dried, pelletized, and added to compound feeds. Any method may reveal some shortcomings, due to the leaking of wound-activated compounds in the water prior to ingestion. For this reason, encapsulation may represent an important step of bioassay-guided fractionation, because it may assure timely preservation of the active compounds. Here we test the effects of the inclusion in alginate (biocompatible and non-toxic delivery system) matrices to produce beads containing two benthic diatoms for sea urchin Paracentrotus lividus feeding. In particular, we compared the effects of a diatom whose influence on P. lividus was known (Nanofrustulum shiloi) and those of a diatom suspected to be harmful to marine invertebrates, because it is often present in blooms (Striatella unipunctata). Dried N. shiloi and S. unipunctata were offered for one month after encapsulation in alginate hydrogel beads and the larvae produced by sea urchins were checked for viability and malformations. The results indicated that N. shiloi, already known for its toxigenic effects on sea urchin larvae, fully conserved its activity after inclusion in alginate beads. On the whole, benthic diatoms affected the embryogenesis of P. lividus, altering the expression of several genes involved in stress response, development, skeletogenesis and detoxification processes. Interactomic analysis suggested that both diatoms activated a similar stress response pathway, through the up-regulation of hsp60, hsp70, NF-kappa B, 14-3-3 epsilon and MDR1 genes. This research also demonstrates that the inclusion in alginate beads may represent a feasible technique to isolate diatom-derived bioactive compounds

Morphologic and genic effects of waste pollution on the reproductive physiology of Paracentrotus lividus lmk: a mesocosm experiment

: A considerable amount of coastal contamination is caused by wastes deriving from household and the degradation and the metabolism of plants and animals, even if our attention is commonly focused on industrial pollutants and contaminants. Waste pollutants are mainly represented by highly diluted soluble compounds and particles deriving from dead organisms. This complex combination, consisting of suspended particles and dissolved nutrients, has a significant impact on coastal planktonic and benthic organisms, also playing an active role in the global cycles of carbon. In addition, production practices are nowadays shifting towards recirculated aquaculture systems (RAS) and the genic responses of target organisms to the pollution deriving from animal metabolism are still scarcely addressed by scientific investigations. The reservoir of organic matter dissolved in the seawater is by far the least understood if compared to that on land, cause only a few compounds have been identified and their impacts on animals and plants are poorly understood. The tendency of these compounds to concentrate at interfaces facilitates the absorption of dissolved organic compound (DOC) onto suspended particles. Some DOC components are chemically combined with dissolved metals and form complexes, affecting the chemical properties of the seawater and the life of the coastal biota. In this research, we compared the reproductive performances of the common sea urchin Paracentrotus lividus cultured in open-cycle tanks to those cultured in a recirculating aquaculture system (RAS), where pollution progressively increased during the experiment due to animal escretions. Sea urchins were cultured for 7 months under these two conditions and their gametes were collected. Embryos resulting by in vitro fertilization were analyzed by Real Time qPCR to identify possible effects of pollution-induced stress. The fertility of sea urchins was evaluated, as well as the gonadosomatic indices and the histological features of gonads. Our results indicate that pollution due to excess of nutrients, event at sub-lethal concentrations, may hardly impact the reproductive potential of this key species and that chronic effects of stress are revealed by the analyses of survival rates and gene expression

Inducers of settlement and metamorphosis of the shrimp Hippolyte inermis Leach in Posidonia oceanica

Larvae of the caridean shrimp Hippolyte inermis persist in the plankton of the Mediterranean up to about one month. Since they need to reach appropriate coastal areas for their recruitment in seagrass meadows, we hypothesized that leaves of Posidonia oceanica or, alternatively, algae present in their epiphytic biofilms, might be physically recognised as target substrates and trigger larval metamorphosis and settlement. Chemical cues could improve the finding of suitable habitats for settlement. Thus, the effects of leaves of P. oceanica and biofilms of the diatom Cocconeis scutellum parva, seasonally abundant in the leaf epiphytic stratum, were investigated along with the effect of volatile organic compounds (VOCs) extracted from the epiphytic diatom. The physical induction with P. oceanica accelerated larval settlement, stimulating an earlier and faster metamorphosis of larvae. C. scutellum parva produced a weaker effect on settlement; however, diatom's VOCs had evident influence and accelerated metamorphosis and settlement. We concluded that such chemical cues as the VOCs produced by epiphytic diatoms, reinforce the effect of physical cues for the identification of suitable settlement locations for this shrimp

Gene Expression Detects the Factors Influencing the Reproductive Success and the Survival Rates of <i>Paracentrotus lividus</i> Offspring

The increase in the demand for Paracentrotus lividus roe, a food delicacy, causes increased pressure on its wild stocks. In this scenario, aquaculture facilities will mitigate the effects of anthropogenic pressures on the wild stocks of P. lividus. Consequently, experimental studies should be conducted to enhance techniques to improve efficient aquaculture practices for these animals. Here, we for the first time performed molecular investigations on cultured sea urchins. We aimed at understanding if maternal influences may significantly impact the life of future offspring, and how the culture conditions may impact the development and growth of cultured specimens. Our findings demonstrate that the outcomes of in vitro fertilization of P. lividus are influenced by maternal influences, but these effects are largely determined by culture conditions. In fact, twenty-three genes involved in the response to stress and skeletogenesis, whose expressions were measured by Real Time qPCR, were differently expressed in sea urchins cultured in two experimental conditions, and the results were largely modified in offspring deriving from two groups of females. The findings herein reported will be critical to develop protocols for the larval culture of the most common sea urchin, both for research and industrial production purposes for mass production

Distribution of Toxigenic <i>Halomicronema</i> spp. in Adjacent Environments on the Island of Ischia: Comparison of Strains from Thermal Waters and Free Living in <i>Posidonia Oceanica</i> Meadows

Organisms adaptable to extreme conditions share the ability to establish protective biofilms or secrete defence toxins. The extracellular substances that are secreted may contain monosaccharides and other toxic compounds, but environmental conditions influence biofilm characteristics. Microorganisms that are present in the same environment achieve similar compositions, regardless of their phylogenetic relationships. Alternatively, cyanobacteria phylogenetically related may live in different environments, but we ignore if their physiological answers may be similar. To test this hypothesis, two strains of cyanobacteria that were both ascribed to the genus Halomicronema were isolated. H. metazoicum was isolated in marine waters off the island of Ischia (Bay of Naples, Italy), free living on leaves of Posidonia oceanica. Halomicronema sp. was isolated in adjacent thermal waters. Thus, two congeneric species adapted to different environments but diffused in the same area were polyphasically characterized by microscopy, molecular, and toxicity analyses. A variable pattern of toxicity was exhibited, in accordance with the constraints imposed by the host environments. Cyanobacteria adapted to extreme environments of thermal waters face a few competitors and exhibit a low toxicity; in contrast, congeneric strains that have adapted to stable and complex environments as seagrass meadows compete with several organisms for space and resources, and they produce toxic compounds that are constitutively secreted in the surrounding waters

Roe enhancement of Paracentrotus lividus: Nutritional effects of fresh and formulated diets

Sea urchin gonads are exploited both for gastronomic and scientific purposes; thus, the production of large and mature gonads is essential. Natural populations of the Mediterranean Sea urchin Paracentrotus lividus are subject to increasing fishing ef- forts, due to continuous intensification of consumptions. Aquaculture practices may represent an answer, but the availability of artificial feeds accelerating the produc- tion of high-quality gonads in terms of size, taste, colour, firmness, maturity and via- bility of gametes is critical to boost the productions. The accessibility of cheap and effective feeds promoting the fattening of gonads and the quality of gametes is still a bottleneck slowing down the expansion of echinoculture practices. This investiga- tion is aimed at enabling the development of this strategic sector, by comparing the dietetic effects of fresh foods and a commercial feed for aquaculture, to four newly formulated feeds. The protein contents of diets were strongly related to the GSIs. The abundance of fatty acids appeared inversely related to the viability of embryos and abnormalities of larvae. The features of an ideal diet for this sea urchin were defined, based on the results of experimental trials, and the need for increasing levels of plant-derived proteins during the grow-out period was demonstrated

Ocean Acidification Affects Volatile Infochemicals Production and Perception in Fauna and Flora Associated With Posidonia oceanica (L.) Delile

Communication among marine organisms are generally based on production, transmission, and interpretation of chemical cues. Volatile organic compounds (VOCs) can act as infochemicals, and ocean acidification can alter their production in the source organisms as well as the interpretation of the information they drive to target organisms. Two diatoms (Cocconeis scutellum var. parva and Diploneis sp.) and a macroalga (Ulva prolifera), all common epiphytes of Posidonia oceanica leaves, were isolated and cultured at two pH conditions (8.2 and 7.7). Their biomass was collected, and the VOCs produced upon wounding were extracted and analyzed using gas chromatography. Chemotactic reactions of invertebrates triggered by VOCs were tested using a static choice experimental arena and a flow-through flume system. Odor choice experiments were performed on several invertebrates associated with P. oceanica meadows to investigate the modification of behavioral responses due to the growth of algae in acidified environments. Complex patterns of behavioral responses were recorded after exposure to algal VOCs. This study demonstrated that a) ocean acidification alters the bouquet of VOCs released by diatoms and macroalgae and b) these compounds act as infochemicals and trigger peculiar behavioral responses in benthic invertebrates. In addition, behavioral responses are species-specific, dose-dependent, and are modified by environmental constraints. In fact, the static diffusion in choice arenas produced different responses as compared to flow-through flume systems. In conclusion, we demonstrate that in future marine environments higher CO2 concentrations (leading to a pH 7.7 by the end of this century) will modify the production of VOCs by micro- and macroalgae as well as the recognition of these infochemicals by marine invertebrates

Supplementary materials from Ferroptosis precedes apoptosis to facilitate specific death signalling by fatty acids

This file contains i) Supplementary methods; ii) Figs. S1 to S6; iii) Tables S1 to S