Shift in Sabella spallanzanii (Polychaeta, Sabellidae) spawning period in the Central Mediterranean Sea: a consequence of climate change?

Sabella spallanzanii is a large tubicolous filter feeder polychaete common in the Mediterranean fouling assemblages where it plays an important role in structuring the community. Its reproductive biology is well known and had been investigated since 1993. During the past few years a shift in its reproductive period has been observed. In 2008 the presence of ripe eggs in the females was observed at least two months in advance compared to the past. This was confirmed during the 2009 when spawning and fertilization were observed three months in advance compared to the past. Possible causes of this shift may be related to the increasing surface temperature in the Central Mediterranean Sea

Behavioural responses of the colonial sea squirt botrylloides violaceus oka to suspended food micro‐ particles in laboratory cultures

Violet sea squirts are noteworthy model organisms, because they provide insights into various physiologic processes, including cell senescence, ageing, apoptosis and allorecognition. Consequently, their culture is critical to permit experimental studies. Most papers refer to short periods of rearing using various feeds, both living and conserved, missing a formal justification for their use or indications of their actual nutritional value. Here, we use two behavioural responses— the percentage of open siphons and the frequency of zooid contractions—as compared to the abundance of suspended microparticles during feeding tests, to identify feeds able to promote filter-feeding. The results will enable to formulate compound diets that maximise positive physiological responses. Our tests demonstrated that plant items, such as dry microalgae and cyanobacteria (Arthrospira platensis, commercially known as Spirulina), along with living planktonic Haptophyta (Isochrysis galbana), trigger clear positive reactions, represented by a higher frequency of zooid contractions and larger proportions of open siphons. These responses correspond to decreases in the concentrations of suspended microparticles during the experiment and indicate higher filter-feeding activity. In contrast, feeds commonly administered to colonies, such as milk powder, dried eggs and artificial plankton, triggered negative behavioural responses, and their intake was lower during the feeding trials

Sperm ultra-structure of <i>Odontosyllis ctenostoma</i> (Polychaeta: Syllidae) with inferences on syllid phylogeny and reproductive biology

The analysis of the complex reproductive patterns of Syllidae may drastically change the taxonomic hierarchy of the family. To further contribute to the knowledge of Syllidae we have described the sperm ultra-structure and some steps of spermiogenesis of Odontosyllis ctenostoma Claparède, 1868, the first non interstitial eusylline investigated. The mature sperm has a bell-shaped acrosome and contains electron-dense granular material and thin filaments. The barrel-shaped nucleus bears two depressions: one anterior facing the acrosome and the other posterior partially containing the distal centriole and up to six mitochondria. Odontosyllis ctenostoma spermatozoa can be ascribed to the ect-aquasperm type typical of species practising external fertilisation. This morphology is not in complete accordance either with the particular brood protection reported for the species or the egg size. The sperm is similar to those of the Syllinae species thus far investigated, but the acrosome resembles that of the exogonine spermatid. Some authors consider Odontosyllis to be phylogenetically closer to Syllinae, though it shares epigamy with Exogoninae. Others have hypothesised that the exogonine sperm could have been derived from sylline sperm by simplification. In our hypothesis this could have happened through a gradual passage from an Odontosyllis-like eusylline ancestor

Critical Phenomena in Neutron Stars I: Linearly Unstable Nonrotating Models

We consider the evolution in full general relativity of a family of linearly unstable isolated spherical neutron stars under the effects of very small, perturbations as induced by the truncation error. Using a simple ideal-fluid equation of state we find that this system exhibits a type-I critical behaviour, thus confirming the conclusions reached by Liebling et al. [1] for rotating magnetized stars. Exploiting the relative simplicity of our system, we are able carry out a more in-depth study providing solid evidences of the criticality of this phenomenon and also to give a simple interpretation of the putative critical solution as a spherical solution with the unstable mode being the fundamental F-mode. Hence for any choice of the polytropic constant, the critical solution will distinguish the set of subcritical models migrating to the stable branch of the models of equilibrium from the set of subcritical models collapsing to a black hole. Finally, we study how the dynamics changes when the numerically perturbation is replaced by a finite-size, resolution independent velocity perturbation and show that in such cases a nearly-critical solution can be changed into either a sub or supercritical. The work reported here also lays the basis for the analysis carried in a companion paper, where the critical behaviour in the the head-on collision of two neutron stars is instead considered [2].Comment: 15 pages, 9 figure

The date mussel Lithophaga lithophaga: Biology, ecology and multiple impacts of its illegal fishery

The date mussel Lithophaga lithophaga is an edible endolithic bivalve, protected by the EU Habitats Directive and other international agreements, living inside carbonate rocks. Its illegal harvesting is carried by breaking the rocks where the bivalve grows. The impact has cascade consequences as it causes permanent changes in the substrate characteristics, the removal of benthic species, a shift from highly complex to structurally simplified habitats. As a result, the rich biodiversity of rocky reefs turns into a biological desert, named “barren”. Along with the over exploitation of fish, this practice leads to the increase of sea urchin density and grazing pressure on habitats, hampering the resilience of the associated biodiversity and functions. This paper summarizes the information on date mussel biology, ecology, ecotoxicology, fishery and the legal framework regulating its protection. Evidence indicates that illegal harvesting is still operated and widespread along the Mediterranean and has huge costs in terms of loss of natural capital and ecosystem services, and in terms of active ecological restoration. Two case study areas (the Sorrento and Salento peninsulas) were selected to assess the economic costs of this practice. Tangible economic costs in terms of ecosystems services' loss are huge (from ca. 35,000 to more than 400,000 euros/year in 6.6 km of Sorrento and ca. 1.8 million euros/year along the 69 km of Salento). These costs are, on average, ca. 30 times lower than those of ecosystem restoration. Data mining from websites indicates that date mussels are presently commercialized in hundreds of restaurants in Greece, Balkan countries, Spain and Italy, favoured also by the lack of appropriate consumer information. This practice should be controlled and contrasted at local scale, enforced by national legislations, and implemented by transnational initiatives. Social campaigns are needed to increase public awareness of the serious consequences of date-mussel fishery and consumption

Concern about the spread of the invader seaweed Caulerpa taxifolia var. distichophylla (Chlorophyta: Caulerpales) towards the West Mediterranean

The new Australian alien seaweed Caulerpa taxifolia var. distichophylla, after being established along the Turkish Mediterranean coast in 2006, was recorded in Southern Sicily in 2007. Since then local fishermen claimed support to counteract the effects of entanglement of large amounts of the alien strain wrack in their trammel nets, causing the gear to become ineffective. The further northward and westward spread of the new alien strain is supposed to be limited by winter temperature. We present novel data confirming that the new alien strain is fully naturalized in Central Mediterranean and is expanding its range beyond such limit (i.e. the 15°C February isotherm), thus becoming potentially able to colonize the western basin. By means of a preliminary estimation of effects on native polychaete assemblages, and considering some peculiarities of Sicily (mostly linked to its geographical position in the Mediterranean Sea), the risk linked to the increasing range of distribution of the invasive algae is highlighted

Distribution patterns of shallow water polychaetes (Annelida) along the Alexandria coast, Egypt (eastern Mediterranean)

Shallow hard bottom and intertidal soft bottom polychaete assemblages of the Alexandria coast, southeastern Mediterranean (Levantine Sea), were studied during a complete annual cycle in order to analyze spatial temporal patterns of variation in assemblages, and relevant factors related to polychaete distribution. The present study recorded a total of 73 species, belonging to Syllidae (22 species), Nereididae (9 species), Serpulidae (6 species), Eunicidae (5 species) and other 19 families. The assemblages experienced pronounced spatial and temporal variation throughout the study area, but spatial variation appeared more important in determining the observed patterns. Polychaete distribution related to variation of grain size and sessile macrobenthos cover suggesting that these structural variables accounted more than the physical-chemical ones (namely BOD, dissolved oxygen, organic carbon, organic matter, salinity, temperature, pH) in influencing the patterns of assemblages’ distribution. The present study is the southeastern-most one dealing with ecology and distribution patterns of hard bottom polychaetes from the Mediterranean Sea, as well as one of the few studies dealing with intertidal soft bottom polychaetes in the Levant Basin

Oxygen supersaturation mitigates the impact of the regime of contaminated sediment reworking on sea urchin fertilization process

Dismissed industrial plants with chronic environmental contamination globally affect all levels of biological organization in concert with other natural and anthropogenic perturbations. Assessing the impact of such perturbations and finding effective ways to mitigate them have clear ecological and societal implications. Through indoor manipulative experiments, we assessed here the effects of the temporal regime of reworking of contaminated sediment from the Bagnoli-Coroglio brownfield (Tyrrhenian Sea, Italy) on the fertilization process in Paracentrotus lividus. Adult sea urchins were kept for one month in tanks containing contaminated sediment that was re-suspended according to two temporal patterns of water turbulence differing in the time intervals between consecutive events of agitation (mimicking the storms naturally occurring in the study area) in seawater with natural vs. supersaturated oxygenation levels. At the end of the treatment, gametes were collected and used to test the hypothesis that the regime of contaminated sediment reworking negatively, but reversibly, affects morphological and physiological traits of the fertilized eggs. We found that aggregated events of sediment re-suspension had profound negative effects on gamete interactions and Ca2+ signaling at fertilization. The same experimental condition also inflicted marked ultrastructural changes in eggs. Importantly, however, such detrimental effects were inhibited by increased oxygenation. By contrast, the regime of sediment re-working with a longer interval between consecutive turbulent events had only marginal effects. Thus, the current and predicted changes of climate-related disturbance appear to modulate the biological effects of chronic contamination in post-industrial areas, suggesting that environmental rehabilitation via restoration of habitat-forming primary producers such as seagrasses or algal canopies could alleviate the pollutants’ effects on resident biota