Step-by-Step Regeneration of Tentacles after Injury in Anemonia viridis-Morphological and Structural Cell Analyses.

Benthic marine invertebrates, such as corals, are often subjected to injury caused by several sources. Here, the differences and characteristics in injured and health tissues in terms of cellular components are shown through a histological investigation of the soft coral Anemonia viridis at 0 h, 6 h, 24 h, and 7 days after injury caused by tentacle amputation. In addition, a new tool was used for the first time in invertebrates, positron emission tomography, in order to investigate the events that occur during regeneration within a longer time period (0 h, 24 h, and 14 days after the tentacles were cut). Higher integrated density values were measured through a densitometric analysis in sections stained with Fontana-Masson at 24 h after the tentacles were cut. This suggests an increase in melanin-like containing cells and a subsequent increase in fibroblast-like cells differentiated by amoebocytes that converge to the lesion site in the early stages of inflammation and regeneration. This work provides, for the first time, an elucidation of the events that occur during wound-healing and regeneration in basal metazoan, focusing on the characterisation of immune cells and their role. Our results indicate that Mediterranean anthozoan proves to be a valuable model for studying regeneration. Many events highlighted in this research occur in different phyla, suggesting that they are highly conserved.

Hirudo verbana as a freshwater invertebrate model to assess the effects of polypropylene micro and nanoplastics dispersion in freshwater.

Plastics are a heterogeneous class of synthetic compounds that, due to their unique characteristics find numerous applications both in industrial and civil fields. However, despite the great advantages that these materials brought in everyday life, the plastic wastes resulting from their massive use represent one of the main environmental problems at the global level. Once released, plastics persist for a long time and are subjected both to biotic and abiotic processes leading to the formation of small particles, known as micro and to nanoplastics, that interact with organisms, accumulating inside tissues and risking to enter in the trophic chain. Among the different types of plastic, polypropylene (PP) is one of the diffused, widely exploited in food and textile industries for disposable packaging and to produce surgical masks. Owing to the huge distribution and the resultant abundant presence of PP waste products, it results necessary investigate the possible toxicity on living organisms. For these reasons, here we analyzed the effects of PP micro and nanoplastics dispersed in freshwater, using the medicinal leech Hirudo verbana as invertebrate model. To better follow the plastics fate, fluorescent particles, labeled with a fluorophore, have been used. Animals were examined at various timings after plastics exposure and results were analyzed by means of microscopy, immunofluorescent and molecular biology analyses. After assessing the entrance of PP fragments into leech tissues, the activation of the innate immune response was evaluated. The results show that the presence of micro and nanoplastics induces an initial physical protection that consists in the secretion of mucus, followed by an increase of blood vessels and the recruitment of immune cells, in particular macrophages. Moreover, macrophages were directly involved in both phagocytic and encapsulation processes, as demonstrated by acid phosphatase (ACP) histoenzymatic and Thioflavin-T assays, expressing specific pro-inflammatory factors, such as HvRNASET2 and HmAIF-1, as demonstrated by immunolocalization and qPCR experiments. Finally, the expression levels of genes related to oxidative stress-induced enzymes have been investigated, in order to evaluate the possible increase in reactive oxygen species (ROS), due to the entry into the leech tissues of PP micro and nanoplastics. This work allows deepening the current knowledge of the possible harmful effects on human health deriving from micro and nanoplastics dispersion, leading new insight about freshwater ecosystems that often represent the first environments interested in plastic pollution.