1,720,983 research outputs found
First estimates of density and distribution of the alien crab Percnon gibbesi (Decapoda, Percnidae) in the “Capo Gallo-Isola delle Femmine” MPA
No full textHiding behaviour of Oxynoe olivacea (Mollusca: Opisthobranchia: Sacoglossa) in the invasive seaweed Caulerpa taxifolia
Full text linkThe occurrence of the invasive seaweed Caulerpa taxifolia in the Straits of Messina (Italy) provides an excellent opportunity to examine the spatial and temporal patterns of abundance of the endemic Mediterranean sacoglossan Oxynoe olivacea. Densities of this species were recorded in March, June and October 2000 on three different habitats: the underside of boulders (UNB), the upper side of boulders (UPB), and the surface of concrete blocks (CB). Results showed that in March, O. olivacea was consistently more abundant on UNB whereas in June it was present exclusively on CB. The density of O. olivacea was similar in the three habitats in October. The hiding behaviour of O. olivacea and its seeming disappearance in March did not coincide with a decline of abundance of phylloids of C. taxifolia. The results represent an important basis for further studies devoted to the investigation of abundance of these marine invertebrates, which has been traditionally thought of as unpredictable
Role of two co-occurring Mediterranean sea urchins in the formation of barren from-Cystoseira canopy
Full text linkGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Benthic megafauna distribution in two different algal assemblages of the Ustica Island rocky infralittoral (NW Mediterranean)
No full textCoralline barrens and benthic mega-invertebrates: An intimate connection
Full text link: Despite considerable progress in understanding the transition from algal forests to coralline barrens, knowledge of coralline barren ecosystems in terms of community composition and functioning is still sparse and important gaps remain to be filled. Using a barren/forest patch system, we tested the hypothesis that the presence of coralline barren enhances the abundance and diversity of benthic mega-invertebrates. We also analysed trophic functional diversity through isotopic analyses of δ13C and δ15N. The distribution of benthic mega-invertebrates biomass differed markedly between coralline barren and algal forest, being more abundant and diverse in the barren state. Isotopic diversity metrics of the benthic mega-invertebrates assemblage indicated comparable trophic structure between the two states, although higher isotopic uniqueness in coralline barren was determined by sea urchins, especially A. lixula, and carnivorous starfish. We showed that in a patchy coralline barren/algal forest system, a more diversified benthic mega-invertebrates assemblage in the barren caused limited trophodynamic changes. This was possibly determined by the behaviour of some trophic groups such as filter feeders, deposit feeders and omnivores. Finally, our results evidence the close association between coralline barrens and benthic mega-invertebrates, contradicting the common view of coralline barrens as depauperate habitats with low diversity and productivity
The rise of thermophilic sea urchins and the expansion of barren grounds in the Mediterranean Sea
Full text linkRecent ecological studies have shown a strong relation between temperature, echinoids and their grazing
effects on macro-algal communities. In this study, we speculate that climate warming may result in an
increasingly favourable environment for the reproduction and development of the sea urchin Arbacia lixula.
The relationship between increased A. lixula density and the extent of barren grounds in the Mediterranean
Sea is also discussed
Hydrodynamism and its influence on the reproductive condition of the edible sea urchin Paracentrotus lividus
No full textUnveiling the diet of the thermophilic starfish Ophidiaster ophidianus (Echinodermata: Asteroidea) combining visual observation and stable isotopes analysis
No full textThe starfish Ophidiaster ophidianus is an Atlanto-Mediterranean species protected under the EU’s Habitat Directive. Despite the wide distribution and the current range of expansion of this thermophilic species in the northern Mediterranean Sea, nothing is known about its diet. Using field observations and δ13C and δ15N Stable Isotopes Analysis (SIA), the feeding habits of O. ophidianus were explored in two Mediterranean rocky reef areas located in the southern Tyrrhenian (Ustica Island, Italy) and the eastern Adriatic Sea (Molunat, Croatia). According to field observations, O. ophidianus preys mainly on crustose coralline algae (CCA) and the keratose sponge Ircinia variabilis in both areas. SIA confirmed the role of CCA in the diet of O. ophidianus but not that of the sponge and highlighted a not negligible role played by other sessile invertebrates, such us small gastropods and small sedentary worms. It was concluded that O. ophidianus is a facultative herbivore in Mediterranean rocky reefs
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