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The ubiquitous presence of microplastics (MPs) in the environment is a major concern for the conservation of biodiversity. Numerous studies show the detrimental effects of MPs on marine species, especially because of their small size and their capacity to absorb organic contaminants from their surroundings. The bivalve mollusk Cerastoderma glaucum (Bruguière, 1789), because of its wide geographic distribution and immobile feeding habits, can be used as a sentinel and bioindicator species. By examining the presence, localization, and co-localization of Toll-like receptor 2 (TLR2) and inducible nitric oxide synthetase (iNOS), this study aims to evaluate the response of the internal defense system of C. glaucum to pristine MPs through the employment of confocal microscopy and bioinformatics techniques. The results show haemocytes immunoreactive to the antibodies tested; in particular, a higher number of TLR2-positive haemocytes can be observed in the group exposed to pristine MPs. These findings suggest that haemocytes can play a key biomarker role as sentinels to environmental pollutants. Furthermore, bioinformatics analyses on the antibodies tested confirmed an evolutionary conservation of these molecules. These data highlight the critical role of phagocytosis in identifying ecosystem damage and are helpful in developing biosensors with less negative effects on the environments in which they are applied. [ABSTRACT FROM AUTHOR]

Invertebrates show great diversity in their responses to neural damage. Numerous invertebrate phyla, including gastropods, can replace all or a portion of their nervous systems. Aplysia species have been utilized extensively in toxicology, ecology, and neuroscience because their neurological systems react to bodily harm by releasing trophic substances that can stimulate non-neural tissue regeneration and induce changes in the nervous system. This study aims to assess the putative role of hemocytes of Aplysia depilans (Gmelin, 1791) by analyzing the presence of Toll-like receptor 2, inducible nitric oxide synthetase, and, in particular, vimentin and α-tubulin, molecules potentially implicated in the process of neural regeneration. The results demonstrate that all the aforementioned proteins are present in hemocytes, suggesting their role in the defense response and their possible contribution to the neuronal regeneration process of this gastropod. These data provide deeper insight into the internal defense system of this mollusk. [ABSTRACT FROM AUTHOR]