What do we know about the ecotoxicological implications of the rare earth element Gadolinium in aquatic ecosystems?

Gadolinium (Gd) is one of the most commercially exploited rare earth elements, commonly employed in magnetic resonance imaging as a contrast agent. The present review was performed aiming to identify the Gd concentrations in marine and freshwater environments. In addition, information on Gd speciation in the environment is discussed, in order to understand how each chemical form affects its fate in the environment. Biological responses caused by Gd exposure and its bioaccumulation in different aquatic invertebrates are also discussed. This review was devoted to aquatic invertebrates, since this group of organisms includes species widely used as bioindicators of pollution and they represent important resources for human socio-economic development, as edible seafood, fishing baits and providing food resources for other species. From the literature, most of the published data are focused on freshwater environments, revealing concentrations from 0.347 to 80 μg/L, with the highest Gd anomalies found close to highly industrialized areas. In marine environments, the published studies identified a range of concentrations between 0.36 and 26.9 ng/L (2.3 and 171.4 pmol/kg), reaching 409.4 ng/L (2605 pmol/kg) at a submarine outfall. Concerning the bioaccumulation and effects of Gd in aquatic species, most of the literature regards to freshwater species, revealing concentration ranging from 0.006 to 0.223 μg/g, with high variability in the bioaccumulation extent according to Gd complexes chemical speciation. Conversely, no field data concerning Gd bioaccumulation in tissues of marine species have been published. Finally, impacts of Gd in invertebrate aquatic species were identified at different biological levels, including alterations on gene expression, cellular homeostasis, shell formation, metabolic capacity and antioxidant mechanisms. The information here presented highlights that Gd may represent an environmental threat and a risk to human health, demonstrating the need for further research on Gd toxicity towards aquatic wildlife and the necessity for new water remediation strategies

Additional taxonomic coverage of the doubly uniparental inheritance in bivalves: Evidence of sex-linked heteroplasmy in the razor clam Solen marginatus Pulteney, 1799, but not in the lagoon cockle Cerastoderma glaucum (Bruguière, 1789)

In animals, doubly uniparental inheritance (DUI) is a major exception to the common strict maternal inheritance of mitochondria. To date, DUI has only been found in many bivalve species, but its distribution is still unclear. Given the great species richness of the class, much effort is needed to further investigate the occurrence of DUI in unsampled species. A compelling evidence of DUI is generally the presence of a sex-linked heteroplasmy, where two divergent mitochondrial lineages are found: One is isolated from the male germline, and the other one is isolated from the female germline and, normally, from the soma of both sexes. In the present study, we investigated the sex-linked heteroplasmy in the razor clam Solen marginatus Pulteney, 1799 and in the lagoon cockle Cerastoderma glaucum (Bruguière, 1789) using two mitochondrial markers (cox1 and rrnL). We found evidence of DUI in the species S. marginatus, with a divergence up to 21% for the rrnL gene, but not in C. glaucum. Moreover, our phylogenetic reconstruction includes all the available data for heterodont species with sex-linked heteroplasmy and suggests multiple origins of DUI in this subclass, as well as the presence of DUI in other species of the genus Solen

Euryhaline Aliens Invading Italian Inland Waters: The Case of the Atlantic Blue Crab Callinectes sapidus Rathbun, 1896

none6Alien invasive species represent a major threat in Italian freshwaters. Despite national and European regulations aimed at the control and prevention of new invasive species, the number of allochthonous species is increasing and so is the rate of spread. One of the most widespread invasive animals in coastal areas of the Mediterranean Sea is the blue crab Callinectes sapidus, a native of the Western Atlantic from Nova Scotia to Argentina. The species is euryhaline, and besides coastal waters, it is also commonly recorded in upper estuaries and lower reaches of rivers. Considering its fast adaptability and invasiveness, the main purpose of this work is to assess whether its biological plasticity and invasive capability may represent, in addition to marine and coastal habitats, also a potential threat for inland waters. Samples were collected in seven sites distributed between Southern and Central Italy. The new records are herein presented, starting from the original introduction by ballast waters and the actual westward migration in inland waters of Latium and Tuscany. In addition, the threat to biodiversity is also discussed, considering the blue crab aggressiveness toward both vertebrates and invertebrates, which may limit the distribution of native freshwater fish and macrofauna.Massimiliano Scalici, Stefania Chiesa , Giorgio Mancinelli, Pietro Maria Rontani, Andrea Voccia, Francesco Nonnis MarzanoScalici, Massimiliano; Chiesa, Stefania; Mancinelli, Giorgio; Maria Rontani, Pietro; Voccia, Andrea; Nonnis Marzano, Francesc

Molecular identification of Sarcocystis spp. in cattle: partial sequencing of Cytochrome C Oxidase subunit 1 (COI)

Sarcocystis spp. are protozoan parasites with an obligatory two-host life cycle, with herbivores as intermediate hosts and carnivores as definitive hosts. Cattle are intermediate hosts for several species of Sarcocystis: indeed, in addition to S. cruzi, S. hirsuta and S. hominis, at least four new species were recently identified in bovine muscle: S. bovifelis, S. rommeli, S. bovini and S. heydorni. Since is not possible to unambiguously discriminate between S. hominis and the new species either morphologically or by the analysis of the 18S ribosomial (rRNA) gene, the aim of the present study was to use molecular techniques to discriminate cattle Sarcocystis species, taking advantage of the higher discriminative power of the Cytochrome C Oxidase subunit I mitochondrial (mtDNA COI) gene. Therefore, 119 bovine muscle samples were tested to identify S. hominis-like sarcocystis using a multiplex PCR of the 18S rRNA gene; later, positive samples were tested using a newly designed primer set for the PCR amplification of COI gene. Species identification was achieved by sequencing the amplified products: 16 sequences were confirmed to belong to S. bovifelis, while 12 sequences didn’t constitute the best BLAST match of any of the published sequences, allowing to speculate the possible presence of S. hominis. This study confirms the higher discriminatory power of COI mitochondrial gene; besides, our work provides the first report of S. bovifelis in Italy

Bioaccumulation and biochemical patterns of Ruditapes philippinarum clams: responses to seasonality and low contamination levels

Shellfish farming and shellfish harvesting have been practiced for a long time in the Ria de Aveiro coastal lagoon (Portugal). Among commercial bivalves, Manila clam Ruditapes philippinarum represents one of the most important species inhabiting this coastal system. Introduced in Portugal in 1984, naturalised R. philippinarum clam populations have been subjected to several pressures that may threaten this resource sustainable management: illegal fishing, harvesting in chemically polluted sites with impacts on human health and lack of control in terms of productivity with the risk of a progressive decline of the biomass. On behalf of the ASARISAFE project (with the title Safety and sustainable management of valuable clam product in Portugal and China) the environmental quality of Manila clam harvesting sites was evaluated, focusing on inorganic pollution and health status of clams in terms of bioaccumulation as well as biochemical performance. Seasonal sampling campaigns were conducted in six R. philippinarum harvesting areas evaluating inorganic pollution levels, in clam's tissues, sediment and water. Clams biochemical performance in terms of metabolism, energy reserves and oxidative stress was also assessed. The results obtained showed that mercury (Hg) and arsenic (As) were the elements with the highest BAF (Bioaccumulation factor) values, but contamination levels in tissues and sediments varied among sampling areas and seasonal campaigns. The amount of clams consumed per week to exceed Provisional Tolerable Week Intake (PTWI, kg) was the lowest for As, revealing that less 0.05 kg of clams was enough to exceed PTWI. However, the results obtained further demonstrated that the clam's biochemical performance was not responding to tissues contamination levels but were closely related to seasons, with distinct metabolic capacity and oxidative stress levels among distinct sampling periods during the year.publishe

A history of invasion: COI phylogeny of Manila clam Ruditapes philippinarum in Europe

The Manila clam Ruditapes philippinarum – synonym Venerupis philippinarum (Adams and Reeve, 1850) is now one of the top 5 most commercially valuable bivalve species worldwide. Originally from the Indo-Pacific region, it has been introduced in many countries for fisheries and aquaculture, including estuarine environments along Atlantic and Mediterranean European coasts. Yet despite its commercial value and widespread distribution, the precise origins of stocks remain speculative and the genetic diversity of introduced populations is poorly known. Thus, the aim of this work was to collect mtDNA COI (Cytochrome oxidase I) gene sequences from 5 European countries with Manila clam stocks and compare them with native Asian populations to evaluate their genetic diversity and identify possible routes of invasion. The COI gene sequencing supported a strong founder effect in the European populations with 3 main haplotypes occurring at high frequencies, derived from Japan. However, high haplotype diversity was also observed due to the occurrence of 10 rare haplotypes. This supports hypotheses (i) there have been additional, previous unrecorded, introductions as previously hypothesized by analysis of 16S rDNA, and (ii) there has been a limited loss of genetic diversity in introduced populations, as previously suggested by microsatellite data. This is the first genetic comparison of Manila clam populations introduced in to Europe with native clams. Genetic data herein presented are fundamentally important for the traceability of clam products and stock management programmes and will also inform discussion on the potential resilience of exploited Manila clam populations