Teresa Balbi’s research while affiliated with University of Genoa and other places

Selective Serotonin Reuptake Inhibitors (SSRIs) are among the most prescribed antidepressants, whose increasing consumption results in a continuous discharge into aquatic compartments, where they are detected at ng-µg/L levels. Whilst designed to modulate endogenous levels of circulating Serotonin (5-HT) in humans by selectively interfering with serotonin reuptake transporters (SERTs), SSRIs have been shown to induce a variety of adverse effects in non-target species, including aquatic invertebrates. In bivalve molluscs, adult exposure to environmental concentrations of SSRIs results in tissue bioaccumulation and induces different biomarker responses. However, the effects were not related to the mechanisms of action of SSRIs, due to poor knowledge of their direct molecular targets, SERT in particular. Much less information is available in embryo-larval stages. In this work, the effects of different SSRIs (Fluoxetine, Citalopram, Sertraline, 1–100 µg/L) were compared in the model of Mytilus galloprovincialis embryo-larval development. SSRIs showed small or no effects on normal larval development at 48 h post fertilization (hpf). The possible direct or indirect molecular targets of SSRIs were thus investigated in mussel larvae. Two conserved SERT sequences, SERT1-like and SERT2-like, were identified in M. galloprovincialis genome: their developmental expression showed increased transcription only from 44 and 20 hpf, respectively. A much higher and earlier expression (from 12 hpf) was observed for TPH (Tryptophan Hydroxylase), the rate limiting enzyme in 5-HT synthesis. Double in situ Hybridization Chain Reaction (HCR) showed partial colocalisation of TPH with SERT1-like and SERT2-like transcripts in 48 hpf larvae. At this stage, SSRIs induced a small but significant decrease in the number of TPH-positive cells. Finally, 19 Nose Resistance to Fluoxetine (nrf) sequences were identified, that were highly expressed across all early stages (0–48 hpf). At 48 hpf, nrf expression was associated with the digestive system. The results represent the first data on the establishment of the serotonergic system in mussel early larvae, representing the molecular basis for understanding the effects of SSRIs and their mechanisms of action in model non-target marine invertebrates.

Although Antarctica is the most isolated continent on Earth, its remote location does not protect it from the impacts of human activities. Antarctic metazoans such as filter-feeding invertebrates are a crucial component of the Antarctic benthos. They play a key role in the benthic-pelagic carbon flux in coastal areas by filtering particles and planktonic organisms from the sediment–water interface. Due to their peculiar ecological niche, these organisms can be considered a wasp-waist in the ecosystem, making them highly sensitive to marine pollution. Recently, anthropogenic particles such as micro-nanoplastics and manufactured nanoparticles (MNP) have been classified as contaminants of emerging concern (CEC) due to their small size range, which also overlaps with the preferred particle size ingested by aquatic metazoans. Indeed, it has been demonstrated that some species such as Antarctic krill can ingest, transform, and release MNPs, making them newly bioavailable for other Antarctic filter-feeding organisms. Similarly, the production and use of anthropogenic MNP are rapidly increasing, leading to a growing presence of materials, such as nano-sized metal-oxides, in the environment. For these reasons, it is important to provide evidence of the adverse effects of such emerging contaminants at sub-lethal concentrations in environmental risk assessments. These contaminants may cause cascade effects with consequences not only on individuals but also at the community and ecosystem levels. In this review, we discuss the state-of-the-art knowledge on the physiological and molecular effects of anthropogenic MNP in Antarctic aquatic metazoans. We further highlight the importance of identifying early biomarkers using sessile metazoans as sentinels of environmental health.

Background: Phospholipids are highly diverse molecules with pleiotropic biological roles, from membrane components and signaling molecules, whose composition can change in response to both endogenous and external stimuli. Recent lipidomic studies on edible bivalve mollusks were focused on lipid nutritional value and growth requirements. However, no data are available on phospholipid profiles during bivalve larval development. In the model marine bivalve Mytilus galloprovincialis, early larvae (up to 48 hours post fertilization-hpf) undergo dramatic molecular and functional changes, including shell biogenesis and neurogenesis, that are sustained by egg lipid reserves. Changes in phospholipid composition may also occur participating in the complex processes of early development. Objective: The lipidome of M. galloprovincialis eggs and early larval stages (24 and 48 hpf) was investigated in order to identify possible changes in phospholipid classes and related metabolic pathways that may play a role in key steps of development. Materials and methods: Lipidomic analysis were performed by NMR spectroscopy and liquid chromatography-mass spectrometry (LC-MS), with focus on phospholipids. Shifts in relative species composition of phosphatidylcholine, phosphatidylethanolamine, plasmalogen, and ceramide aminoethylphosphonate-CAEP, the bivalve analogue of the main mammalian ceramide sphingomyelin, were observed. Expression of genes involved in ceramide homeostasis was also modulated from eggs to early larval stages. Results: The results represent the first data on changes in phospholipid composition in bivalve larvae and suggest a functional role of phospholipids in mussel early development. Conclusion: The results underline the importance of lipidomic studies in bivalve larvae, in both physiological conditions and in response to environmental stress.

Vibrio aestuarianus is a bacterium related to mass mortality outbreaks of the Pacific oyster, Crassostrea gigas in Europe. In this study, the role of different planktonic substrates (phytoplankton cells, marine aggregates and chitin fragments) in mediating V. aestuarianus 02/041 infection of oysters was evaluated by controlled infection experiments. It was shown that phytoplankton cells and, to a greater extent, marine aggregates, significantly promote V. aestuarianus 02/041 intake by C. gigas maintained under stressful conditions in the laboratory. Such intake is associated with higher concentration of the pathogen in the bivalve hemolymph and compromised health status of infected oysters. In contrast, chitin particles do not play a significant role as transmission vector for V. aestuarianus 02/041 infecting its bivalve host. Interestingly, incorporation into marine aggregates foster extracellular proteases (ECPs) activity and a higher expression of bacterial virulence genes, that are potentially involved in bivalve infection. Results from this study contribute to elucidate transmission patterns of V. aestuarianus 02/041 to C. gigas that may be useful for the development of efficient measures to prevent and control oyster disease outbreaks.

The broadly utilized biocide triclosan (TCS) is continuously discharged in water compartments worldwide, where it is detected at concentrations of ng-µg/L. Given its lipophilicity and bioaccumulation, TCS is considered potentially harmful to human and environmental health and also as a potential endocrine disruptor (ED) in different species. In aquatic organisms, TCS can induce a variety of effects: however, little information is available on its possible impact on invertebrate development. Early larval stages of the marine bivalve Mytilus galloprovincialis have been shown to be sensitive to environmental concentrations of a number of emerging contaminants, including EDs. In this work, the effects of TCS were first evaluated in the 48 h larval assay in a wide concentration range (0.001–1,000 μg/L). TCS significantly affected normal development of D-veligers (LOEC = 0.1 μg/L; EC50 = 236.1 μg/L). At selected concentrations, the mechanism of action of TCS was investigated. TCS modulated transcription of different genes involved in shell mineralization, endocrine signaling, ceramide metabolism, and biotransformation, depending on larval stage (24 and 48 h post-fertilization-hpf) and concentration (1 and 10 μg/L). At 48 hpf and 10 μg/L TCS, calcein staining revealed alterations in CaCO3 deposition, and polarized light microscopy showed the absence of shell birefringence due to the mineralized phase. Observations by scanning electron microscopy highlighted a variety of defects in shell formation from concentrations as low as 0.1 μg/L. The results indicate that TCS, at environmental exposure levels, can act as a developmental disruptor in early mussel larvae mainly by interfering with the processes of biomineralization. Supplementary Information The online version contains supplementary material available at 10.1007/s11356-023-29854-2.