1,721,025 research outputs found
Preferential assimilation of seagrass detritus by two coexisting Mediterranean sea cucumbers: Holothuria polii and Holothuria tubulosa
No full textHolothuria polii and Holothuria tubulosa are two of the most commercially exploited sea cucumbers of the Mediterranean Sea. As deposit-feeders, they represent an important component of the benthic community. Hence, knowledge of their feeding behaviour is crucial for understanding their function in terms of benthic ecology and sediment dynamics. Using information obtained from stable isotope analysis, the food selectivity/assimilation, temporal variations in diet and trophic niche of H. polii and H. tubulosa were investigated. Analysis of carbon and nitrogen isotopic ratios in body wall tissue showed a preferential assimilation of seagrass detritus among multiple food sources, with a total contribution to the diet ranging from 63% to 74%. The temporal changes in δ13C and δ15N values followed the seagrass isotopic dynamics with depleted values in winter and enriched values in summer. Additionally, δ13C and δ15N measurements were used to outline the species' trophic niche width. The two species coexist, showing an overlap on the δ13C axis and a partial degree of niche segregation on the δ15N axis. Our results provide an overview on the feeding activity of H. polii and H. tubulosa, providing evidence of their crucial role on the seagrass detrital pathways for Mediterranean coastal ecosystems
The effect of the quantitative feeding regime on the larval survival rate of the purple sea urchin (Paracentrotus lividus)
No full textPurple sea urchin Paracentrotus lividus (Lamarck, 1816) is distributed in the Mediterranean Sea and eastern Atlantic Ocean. It constitutes a keystone species in benthic ecosystems for its trophic behavior and it has a considerable economical value derivative of its delicious gonads. Being the most consumed sea urchin species in Europe, natural populations are exposed to overfishing in many Mediterranean and non‐Mediterranean coastal areas, causing a sharp decline of the stock. In this scenario, artificial breeding of purple sea urchin is arising great interest and several attempts to reproduce are underway. The present study focused on testing survival and metamorphosis rates of P. lividus larvae fed a microalgal mix of Chaetoceros calcitrans, Tetraselmis suecica and Isochrysis galbana (1:1:1) at three different concentrations: i) 1000‐2000 cells/ml; ii) 5000‐10000 cells/ml and iii) 20000‐40000 cells/ml, three replicates for each condition. Obtained results enhanced the concentration with higher survival and metamorphosis rates
Artificial reproduction of Holothuria polii: A new candidate for aquaculture
Full text linkHolothuria polii (Delle Chiaje, 1823) is a common Mediterranean sea cucumber and has recently become a highly exploited target species destined mainly to the Asian markets. Unregulated harvesting is putting the natural stocks at risk, with potential consequences for the benthic communities to which these organisms belong. In response aquaculture, sea ranching and restocking could become solutions to this issue in the Mediterranean region. In this study, we present the first results on artificial breeding of H. polii, describing the spawning induction, larval development and early juvenile growth in hatchery cultures, our goal is to develop a rearing protocol for this species. The trials were conducted between July and September 2016. Holothuria polii was induced to spawn by testing two different methods. The thermal shock proved a simple and effective method for obtaining healthy gametes from this species. Larval development in H. polii progressed through five stages, reaching the pentactula stage in 10 days. Three different microalgal feeding regimens were tested for larval breeding; the higher feeding concentration 20,000-40,000 cells mL(-1) proved to be the best, with 14% of the larvae metamorphosed into settled juveniles by adhering to the artificial substrates at 15 days. Our results indicate that H. polii performs very well in the hatchery rearing during the larval and juvenile phases; this indicates that this species could be a valuable new candidate for aquaculture in the Mediterranean region both for production and for restocking purposes
Risultati preliminari sulla riproduzione artificiale di Holothuria tubulosa (Holothuroidea, Echinodermata)
No full textHolothuria tubulosa is a key species widely distributed in the Atlantic-Mediterranean region were is used as fishing bait and as a food source. Will be useful in the future to develop the aquaculture of H.tubulosa, in order to avoid over-exploitation of this resource. Here we show some preliminary results on the artificial reproduction of this specie
Sea cucumber Holothuria polii (Delle Chiaje, 1823) as new model for embryo bioassays in ecotoxicological studies
No full textThe sea cucumbers are common members of marine benthic communities, widespread distributed, easily available and handled. Nevertheless, no data are available on embryo toxicity assays using sea cucumbers, despite some of these species could fully meet the requirements for model test organisms. Holothuria polii is a key species in soft sediments and seagrass meadows; the aim of the present study was the standardization of a new embryo bioassay with this species, as an ecologically relevant test to evaluate the effects of environmental stressors. Sequential experiments were carried out, allowing to define the test acceptability, and a minimum sample size of 240 embryos. Temperature of 26 °C, salinity at 36‰ and a density of 60 eggs/ml were identified as optimum experimental conditions for performing the bioassay. The EC50 calculated for Cd2+ and Cu2+ in dose-response experiments indicated a good sensitivity of H. polii, with comparable values with those obtained in embryo toxicity bioassays of other marine invertebrates. An Integrative Toxicity Index (ITI) was calculated by integrating the frequency of abnormal embryos with the severity of observed abnormalities. The index allows to better discriminate different levels of toxicity, appearing particularly relevant for validating the usefulness of H. polii in embryo assays and ecotoxicological studies on environmental quality
Modalità di reclutamento su substrati artificiali in due impianti di acquacoltura nel Mar Maditerraneo
No full textThe development of fouling communities on artificial structures at two aquaculture farms
in Gulf of Gaeta (Tyrrhenian Sea) and Gulf of Taranto (Ionian Sea) was assessed to select organisms
potentially useful in bioremediation. Samples have been collected trimonthly and fouling communities
showed a higher species richness at the aquaculture site of Taranto than at Gaeta. Overall community
composition was significantly different between two sites, while seasonal similarities in recruitment
periods of common species were also observe
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