Temperature modulates the response of the thermophilous sea urchin Arbacia lixula early life stages to CO2-driven acidification

The increasing abundances of the thermophilous black sea urchin Arbacia lixula in the Mediterranean Sea are attributed to the Western Mediterranean warming. However, few data are available on the potential impact of this warming on A. lixula in combination with other global stressors such as ocean acidification. The aim of this study is to investigate the interactive effects of increased temperature and of decreased pH on fertilization and early development of A. lixula. This was tested using a fully crossed design with four temperatures (20, 24, 26 and 27 C) and two pH levels (pHNBS 8.2 and 7.9). Temperature and pH had no significant effect on fertilization and larval survival (2d) for temperature <27 C. At 27 C, the fertilization success was very low (<1%) and all larvae died within 2d. Both temperature and pH had effects on the developmental dynamics. Temperature appeared to modulate the impact of decreasing pH on the % of larvae reaching the pluteus stage leading to a positive effect (faster growth compared to pH 8.2) of low pH at 20 C, a neutral effect at 24 C and a negative effect (slower growth) at 26 C. These results highlight the importance of considering a range of temperatures covering today and the future environmental variability in any experiment aiming at studying the impact of ocean acidificatio

The PAH composition in limpets (Patella vulgate L.) from the coasts of Sicily (Italy)

This article examines the presence, distribution, nature and sources of 19 Polycyclic Aromatic Hydrocarbons (PAH), in Patellae (patella vulgate L.) and seaweed (vulva) sampled in different stations of Sicilian coastal environments and analyzed for their polycyclic aromatic hydrocarbon (PAH) content. Analysis was performed by gas chromatography/mass spectrometry (GC/MS) with selected ion monitoring (SIM), after saponification of the sample and clean up of the extract. In the limpets the total concentration of polycyclic aromatic hydrocarbons ranged from 34 to 750 μg/Kg of dry matrix. The relative standard deviation (RSD) of the replicas on the concentrations of individual compounds ranged from 4 to 20%. The accuracy of method was estimated by analyzing "blank" samples spiked with known quantities of analytes and the recover percentage was 82 ± 12%. The detection limit (LOD) of analytical procedure was less than 0.2 μg/Kg d.w. for all analytes. The quantification limit (LOQ) of analytical procedure was less 0.7 μg/Kg d.w. The resulting distributions and weight ratios of specific compounds are discussed in terms of sampling location and origin. The results obtained show that levels of contamination vary from one sampling station to the next, while relative distributions of PAH is homogeneous in most stations. Lipidic content and total PAH concentrations were found not to be correlated and the compounds present in limpets were shown to be mainly of petrogenic origin. There is no evidence of coal-tar contamination. Copyright © 2006 Taylor & Francis Group, LLC

The rise of thermophilic sea urchins and the expansion of barren grounds in the Mediterranean Sea

Recent 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

The hydrophilie of the larval test of Ascidiae: functional role played by test cells

Ascidian swimming larvae are entirely surrounded by a hyaline extracellular coat, called as tunic or test, on which numerous test cells adhere. The functional role played by test cells in larvae of various ascidian species consists in depositing submicroscopic structures known as ornaments and/or substances of proteoglycan nature in the larval test surface. The deposition of ornaments would render the larval test hydrophilic and thus allow the larvae to swim being immersed in sea water. Ultrastructural investigations reported in literature on larvae of Cionidae and Ascididae families have not evidenced the presence of ornaments in the swimming larval test. For these Ascididae families it has been hypothesized that test cells secrete an amorphous substance that would let them to adhere to larval tunic. In order to clarify the functional role played by test cells of swimming larvae of the Ascididae family, ultrastructural and cytochemical investigations have been carried out on test cells of Ascidia malaca swimming larvae. The ultrastructural observations have evidenced that these cells are metabolically active and show an amoeboidic behaviour as they mainly adhere to the surface of the test. Their cytoplasm is characterized by the presence of a Golgi and large granules that gradually empty their contents and release the same on the test surface. The cytochemical investigastions carried out at ultrastructural level have evidenced that the substances secreted by test cells and deposited on the larval test consisting of glycosaminoglycans. According to the data reported in literature the results of the present investigations confirm that the deposition of glycosaminoglycans enables the adhesion of test cells on the surface of larval tunic and would render the Ascidia malaca larva hydrophilic and able to swim being immersed in sea water

Metallothionein gene family in the sea urchin Paracentrotus lividus: Gene structure, differential expression and phylogenetic analysis

Metallothioneins (MT) are small and cysteine-rich proteins that bind metal ions such as zinc, copper, cadmium, and nickel. In order to shed some light on MT gene structure and evolution, we cloned seven Paracentrotus lividus MT genes, comparing them to Echinodermata and Chordata genes. Moreover, we performed a phylogenetic analysis of 32 MTs from different classes of echinoderms and 13 MTs from the most ancient chordates, highlighting the relationships between them. Since MTs have multiple roles in the cells, we performed RT-qPCR and in situ hybridization experiments to understand better MT functions in sea urchin embryos. Results showed that the expression of MTs is regulated throughout development in a cell type-specific manner and in response to various metals. The MT7 transcript is expressed in all tissues, especially in the stomach and in the intestine of the larva, but it is less metal-responsive. In contrast, MT8 is ectodermic and rises only at relatively high metal doses. MT5 and MT6 expression is highly stimulated by metals in the mesenchyme cells. Our results suggest that the P. lividus MT family originated after the speciation events by gene duplications, evolving developmental and environmental sub-functionalization

Polycyclic Aromatic Hydrocarbons (PAH) in Volcano island (Aeolian archipelago) mud utilized for therapeutic purpose

This paper examines the possible presence, distribution, nature and sources of 18 Polycyclic Aromatic Hydrocarbons (PAHs) as constituent of the muds pool collected in Vulcano Aeolian Island. PAHs are important from environmental and toxicological point of view. Analysis was performed by gas chromatography/mass spectrometry (GC/MS) in selected ion monitoring (SIM). The total concentration of Polycyclic Aromatic Hydrocarbons ranged from 112 to 154 g/Kg of dry matrix. The volcanic muds, used for therapeutic purposes, are moderately contaminated

Chromatin dynamics of the developmentally regulated P. lividus neural alpha tubulin gene

Over 40 years ago, Allfrey and colleagues (1964) suggested that two histone modifications, namely acetylation and methylation, might regulate RNA synthesis. Nowadays it is universally accepted that activation of gene expression strictly depends on enzymatic mechanisms able to dynamically modify chromatin structure. Here, using techniques including DNaseI hypersensitive site analysis, chomatin immunoprecipitation and quantitative PCR analysis, we have analyzed the dynamics of histone post-translation modifications involved in developmentally/spatially controlled activation of the sea urchin PlTalpha2 tubulin gene. We have demonstrated that only when the PlTalpha2 core promoter chromatin is acetylated on H3K9, tri-methylated on H3K4 and not di-methylated on H3K27, RNA pol II can be enrolled. In contrast, we have shown that when chromatin is methylated both on H3K9 (me2/3) and H3K27 (me2) and mono methylated on H3K4 the promoter is not accessible to RNA pol II. Our results suggest that, during P. lividus embryogenesis, both HAT/HDAC and HMT/HDM activities, which are able to regulate accessibility of the PlTalpha2 basal promoter to RNA polymerase II, are coordinately switched-on