Excessive CO 2 in the present-day ocean-atmosphere system is causing ocean acidification, and is likely to cause a severe biodiversity decline in the future, mirroring effects in many past mass extinctions. Fossil records demonstrate that organisms surviving such events were often smaller than those before, a phenomenon called the Lilliput effect. Here, we show that two gastropod species adapted to acidified seawater at shallow-water CO 2 seeps were smaller than those found in normal pH conditions and had higher mass-specific energy consumption but significantly lower whole-animal metabolic energy demand. These physiological changes allowed the animals to maintain calcification and to partially repair shell dissolution. These observations of the long-term chronic effects of increased CO 2 levels forewarn of changes we can expect in marine ecosystems as CO 2 emissions continue to rise unchecked, and support the hypothesis that ocean acidification contributed to past extinction events. The ability to adapt through dwarfing can confer physiological advantages as the rate of CO 2 emissions continues to increase

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Structured sampling designs are important in the assessment of environmental impacts of variable ecological systems. Recent developments have provided a useful framework extending existing univariate techniques into a multivariate context. Measures of taxonomic relatedness have also been introduced, which complement existing measures of diversity of assemblages. In this study, the potential effects of sewage discharge on spatial patterns of highly diverse molluscan assemblages in a Mediterranean rocky subtidal habitat were investigated. Nine 20 cm•20 cm quadrats were taken from each of three sites (80 m-100 m apart) within a putatively impacted location near a sewage outfall (I) and at each of two control locations (Cs) by destructive sampling by SCUBA divers at a depth of 3 m-4 m. A total of 5507 specimens of 151 species were collected. The average and the variance in total abundance of molluscs were greater, on average, at I than at Cs. Higher abundances at the sewage outfall were largely driven by greater numbers of juvenile molluscs. The Shannon diversity of molluscs (H¢) was significantly lower at I, but no difference among locations was detected for the total number of species (S). In addition, the taxonomic distinctness (D*) of molluscs was greater at Cs, although it was more variable at I. Multivariate analyses showed that there was a significant difference in the structure of assemblages at I compared with Cs. The location near the outfall was characterized by greater abundances of several species, including especially the gastropods Pusillina philippi, Bittium latreilli, and Bittium reticulatum. There was also greater variability in the structure of assemblages among sites and among quadrats at control locations compared to those near the outfall. Using a suite of univariate and multivariate measures, including diversity indices, detailed information on taxonomic structure and analyses of variability at different spatial scales, provided useful insights into the effects of sewage impacts on these diverse assemblages. These results also highlighted the importance of analysing measures of variance, as well as mean in considering effects of stress in natural communities.

The distribution of molluscan assemblages across and along a vertical rocky cli¡ near Otranto (southern Adriatic Sea, Italy) was studied. Sampling was undertaken in May and November 2000 at three sites approximately 100 m apart. Three depths (5, 15, 25 m) were sampled at each site, by scraping o¡ three replicate 20 Â 20 cm quadrats. Samples yielded 6722 specimens, referred to as 133 species. Multivariate analyses showed that the structure of the assemblages signi¢cantly di¡ered among depths with a clear gradient of distribution from shallow to deep stands. However, a considerable variation in the structure of the assemblage was also observed among sites at each of the three depths. The species contributing most to characterize depths and/or di¡erentiating sites at each level of the shore were identi¢ed. Some potential causes of the observed di¡erences are discussed.

Most of accumulation curves tend to underestimate species richness, as they do not consider spatial heterogeneity in species distribution, or are structured to provide lower bound estimates and limited extrapolations. The total‐species (T–S) curve allows extrapolations over large areas while taking into account spatial heterogeneity, making this estimator more prone to attempt upper bound estimates of regional species richness. However, the T–S curve may overestimate species richness due to (1) the mismatch among the spatial units used in the accumulation model and the actual units of variation in β‐diversity across the region, (2) small‐scale patchiness, and/or (3) patterns of rarity of species. We propose a new framework allowing the T–S curve to limit overestimation and give an application to a large dataset of marine mollusks spanning over 11 km2 of subtidal bottom (W Mediterranean). As accumulation patterns are closely related across the taxonomic hierarchy up to family level, improvements of the T–S curve leading to more realistic estimates of family richness, that is, not exceeding the maximum number of known families potentially present in the area, can be considered as conducive to more realistic estimates of species richness. Results on real data showed that improvements of the T–S curve to accounts for true variations in β‐diversity within the sampled areas, small‐scale patchiness, and rarity of families led to the most plausible richness when all aspects were considered in the model. Data on simulated communities indicated that in the presence of high heterogeneity, and when the proportion of rare species was not excessive (>2/3), the procedure led to almost unbiased estimates. Our findings highlighted the central role of variations in β‐diversity within the region when attempting to estimate species richness, providing a general framework exploiting the properties of the T–S curve and known family richness to estimate plausible upper bounds in γ‐diversity.

Herein we revise several Recent Mediterranean species of the rissoid genus Alvania Risso, 1826: Alvania scabra (Philippi, 1844), Alvania sculptilis (Monterosato, 1877), Alvania sororcula Granata-Grillo, 1877, Alvania lucinae Oberling, 1970, Alvania josefoi Oliver & Templado, 2009 and Alvania scuderii Villari, 2017. They represent a rather homogeneous group of morphologically similar species, referred to as the Alvania scabra complex, which includes also some other species from the northeastern Atlantic. We designate a neotype for Rissoa scabra Philippi, 1844 and a lectotype for Rissoa oranica Pallary, 1900 to stabilize the use of the names. Alvania oranica (Pallary, 1900) is confirmed as a synonym of Alvania scabra (Philippi, 1844), and Alvania asperella (Granata-Grillo, 1877) is proposed as a synonym of Alvania sororcula (Granata-Grillo, 1877) [new synonymy]. Finally, we describe one new Mediterranean species: Alvania pizzinii Amati, Smriglio & Oliverio n. sp. from Levanzo Is., Sicily.

After a winter storm, with sirocco wind, hundreds of specimens of the "mole crab" Albunea carabus (Linnaeus, 1758) (Decapoda Anomura Hippoidea) were beached along the sandy coast of "Playa" Catania (E-Sicily). Even though this species was previously recorded in some scattered localities of the Mediterranean, among which a couple were found in Sicily, the present record appears relevant on account of the massive finding of specimens, which is a quite rare event according to literature data. Considerations on the reasons of this wide beaching complete the present note.

The earliest reported alien species that entered the Mediterranean after only nine years from the inauguration of the Suez Canal was "Meleagrina" sp., which was subsequently identified as the Gulf pearl-oyster, Pinctada radiata (Leach, 1814) (Bivalvia Pteriidae). Thereafter, an increasing series of records of this species followed. In fact, nowadays it can be considered a well-established species throughout the Mediterranean basin. Since the Red Sea isthmus was considered to be the only natural way of migration, nobody has ever doubted about the name to be assigned to the species, P. radiata, since this was the only Pinctada Röding, 1798 cited in literature for the Mediterranean Sea. Taxonomy of Pinctada is complicated since it lacks precise constant morphological characteristics to distinguish one species from the others. Thus, distribution and specimens location are particularly important since different species mostly live in different geographical areas. Some researchers also used a molecular phylogenetic approach, but the results were discordant. This taxonomic conundrum was reexamined this time applying morphological taxonomy. Increasing vessel traffic and records of vast amounts of Pinctada specimens with morphologically different shells led us to formulate the hypothesis that a separate Pinctada population of different geographical provenance could be present. Specimens were grouped according to the site of collection in the Mediterranean basin. Results from these morphological studies confirmed that, according to us, there were two distinct species, P. radiata and P. fucata (Gould, 1850). Morphological comments and interpretations on the taxonomical status of both species together with autoecological notes and a literature review of the molecular phylogenetic studies conducted will be here presented.