Assessment of the Health Status of Mussels Mytilus galloprovincialis Along the Campania Coastal Areas: A Multidisciplinary Approach

The bivalve Mytilus galloprovincialis has a broad geographic distribution, represent an important species for the ecology of coastal waters, also constituting a major aquaculture species. In the present work, molecular and tissue biomarkers were examined in mussel populations (M. galloprovincialis) located in four different areas of the coastal water of the Campania Region. During an annual life cycle, we analyzed the expression patterns of several genes commonly used to estimate cellular stress response and damage, namely p53, p63, HSP70, MT-10, and MT-20, related tissue lesions (pathogens, inflammations, digestive tubules damage), oxidative stress indicators (H2O2, SOD specific activity) and associated environmental data. The computed Principal Component Analysis showed that the areas were discernible based on the environmental data and biomarker results. About animal health status, mussels from Gulf of Pozzuoli and Naples's harbor did show a thinnest epithelial cell of digestive tubules compared to mussels sampled from other sampling sites; moreover, high prevalence of cases of intersex in three of the examinated areas were observed. The presence of a potential zoonotic pathogen (Nocardia crassostreae) was identified, appearing as an important possible emerging disease. We also reported the OIE notifiable protozoa Marteilia refringens in three areas out of four. The likely impact of both observed pathogens on the mussel health and shellfish aquaculture needs to be urgently addressed. Results are discussed considering animal histopathological health parameters and biological effects.

Gorgonian disease outbreak in the Gulf of Naples: pathology reveals cyanobacterial infection linked to elevated sea temperatures

In recent years, mass mortality events of benthic invertebrates in the Mediterranean Sea have been documented to coincide with the increased seawater temperatures associated with global climate change. Following a disease outbreak in gorgonians during the summer seasons of 2008 and 2009 in the Gulf of Naples (Tyrrhenian Sea), we conducted gross and microscopic analyses of healthy and diseased specimens of Eunicella cavolinii and E. singularis using both light and electron microscopy (SEM). Macroscopically, diseased colonies exhibited evident tissue thinning, and dead colonies showed a complete loss of polyps and coenenchyme, exposing their skeletons to settlement by fouling organisms. Histopathology revealed chronic inflammatory lesions at the polyp and axial level, characterized by amoebocyte infiltration of tissue accompanied by new apposition of melanin/gorgonin sheets. We interpreted this response as a defense against different kinds of pathogens-identified as mainly a heterogeneous consortium of filamentous cyanobacteria-and which gradually led to enlargement and hardening of the coral axis, which resembled a wood-like structure at the final stage of the disease. These processes elicited the formation of multiple inflammatory nodules and capsules, some of which were macroscopically visible. A parallel 16S rRNA and ITS analysis of the diseased tissue identified Synechococcus, Arthrospira and other uncultured cyanobacteria grouped within the Oscillatoriales. These results suggest that a cyanobacterial consortium is involved in the pathogenesis of the inflammatory disease leading to the mortality of Gorgoniaceae in the area. Finally, there were anomalously high temperatures (up to 25°C) between 10 and 20 m depth during the sampling period, particularly in June 2009. This supports the hypothesis that the coral skeleton may serve as a reservoir for the pathogens in cooler seasons, with warmer conditions leading to pathogen reactivation and recurring mortality events.