Background: The red swamp crayfish Procambarus clarkii (Girard, 1852), native to the United States and northern Mexico, has been introduced in many countries worldwide. The species has a remarkable invasiveness, due to its high reproductive rate and to its ability to tolerate broad ranges of water parameters like salinity. Nevertheless, no consistent observations of P. clarkii have been reported in the marine environment until now. Methods: Through the observations of a personal acquaintance and of two volunteers who published photos of the species on Facebook marine biology and fishing groups, we collected data showing the presence of the crayfish within marine ecosystems. Results: P. clarkii has been spotted in three different localities, in two of which observations are recurrent. The species can live miles from the nearest freshwater stream, and can colonise the depths up to 20 meters. Conclusions: The multiple observations of P. clarkii collected in our study uncover a persistent presence of the species within some marine areas, rather than its mere sporadic occurrence. As resistance to increasing salinities is influenced by multiple genes, genetic admixture between genetically-differentiated individuals coming from distinct geographical origins could have brought together different salinity-resistance genes, leading to the formation of these resilient phenotypes.

Regular physical activity is considered one of the most valid tools able to reduce the risk of on-set of many diseases in humans. However, it is known that intense physical activity is able to induce high levels of genomic damage, while a moderate exercise was found to induce a favora-ble adaptive response by the organism. We evaluated, in a sample of amateur athletes practicing different disciplines, the level of genomic damage by means of the buccal micronuclei assay, comparing obtained data with those of subjects who practiced sport occasionally or that do not practiced any sport. The aim was to evaluate whether physical activity affects background levels of genomic damage and whether the different sports disciplines, as well as some genes poly-morphisms, differentially affect these levels. A total of 206 subjects, 125 athletes and 81 controls, were recruited. Athletes showed significantly lower values of micronuclei, nuclear buds and bi-nucleated cells with respect to controls. Sprinters and martial arts athletes showed significantly higher frequencies of micronuclei than other categories of athletes. Finally, neither sex nor gene polymorphisms seem to influence the levels of genomic damage, confirming that the observed genomic damage is probably due to the type of the sport activity.