The tolerance of a keystone ecosystem engineer to extreme heat stress is hampered by microplastic leachates

Plastic pollution and ongoing climatic changes exert considerable pressure on coastal ecosystems. Unravelling the combined effects of these two threats is essential to management and conservation actions to reduce the overall environmental risks. We assessed the capacity of a coastal ecosystem engineer, the blue mussel Mytilus edulis, to cope with various levels of aerial heat stress (20, 25, 30 and 35°C) after an exposure to substances leached from beached and virgin low-density polyethylene pellets. Our results revealed a significant interaction between temperature and plastic leachates on mussel survival rates. Specifically, microplastic leachates had no effect on mussel survival at 20, 25 and 30°C. In turn, mussel survival rates significantly decreased at 35°C, and this decrease was even more significant following an exposure to leachates from beached pellets; these pellets had a higher concentration of additives compared to the virgin ones, potentially causing a bioenergetic imbalance. Our results stress the importance of adopting integrated approaches combining the effects of multiple environmental threats on key marine species to understand and mitigate their potential synergistic effects on ecosystem dynamics and resilience in the face of the changing environment.

Size-dependent response of the mussel collective behaviour to plastic leachates and predator cues

Both individual and collective anti-predator behaviours are essential for the survival of many species. This is particularly true for ecosystem engineers such as intertidal mussels, which through their collective behaviour create novel habitats for a range of organisms and biodiversity hotspots. However, contaminants may disrupt these behaviours and consequently indirectly affect exposure to predation risk at the population level. Among these, plastic litter is a major and ubiquitous contaminant of the marine environment. Here, we assessed the impact of microplastic (MP) leachates of the most produced plastic polymer, polypropylene (PlasticsEurope, 2022), at a high but locally relevant concentration (i.e. ca. 12 g L^-1) on the collective behaviours and anti-predator responses of both small and large Mytilus edulis mussels. Indeed, in contrast to large mussels, small ones reacted to MP leachates, showing a taxis towards conspecifics and stronger aggregations. All mussels reacted to the chemical cues of the predatory crab, Hemigrapsus sanguineus, but with two different collective anti-predator behaviours. Small mussels only showed a taxis towards conspecifics when exposed to predator cues. This response was also found in large ones with a tendency to form more strongly bound aggregations and a considerable reduced activity, i.e. they significantly delayed their time to start to form aggregations and decreased their gross distance. These anti-predator behaviours were respectively inhibited and impaired in small and large mussels by MP leachates. The observed collective behavioural changes may reduce individual fitness by enhancing predation risk, particularly in small mussels that are the crab H. sanguineus's favourite preys. Given the key role of mussels as ecosystem engineers, our observations suggest that plastic pollution may have implication on M. edulis at the species level, but also enhancing a cascading effect towards a higher level of organisation such as population, community and ultimately structure and function of intertidal ecosystem.

A whale of a plastic tale: A plea for interdisciplinary studies to tackle micro- and nanoplastic pollution in the marine realm

Plastic is one of the most ubiquitous sources of both contamination and pollution of the Anthropocene, and accumulates virtually everywhere on the planet. As such, plastic threatens the environment, the economy and human well-being globally. The related potential threats have been identified as a major global conservation issue and a key research priority. As a consequence, plastic pollution has become one of the most prolific fields of research in research areas including chemistry, physics, oceanography, biology, ecology, ecotoxicology, molecular biology, sociology, economy, conservation, management, and even politics. In this context, one may legitimately expect plastic pollution research to be highly interdisciplinary. However, using the emerging topic of microplastic and nanoplastic leachate (i.e., the desorption of molecules that are adsorbed onto the surface of a polymer and/or absorbed into the polymer matrix in the absence of plastic ingestion) in the ocean as a case study, we argue that this is still far from being the case. Instead, we highlight that plastic pollution research rather seems to remain structured in mostly isolated monodisciplinary studies. A plethora of analytical methods are now available to qualify and quantify plastic monomers, polymers and the related additives. We nevertheless show though a survey of the literature that most studies addressing the effects of leachates on marine organisms essentially still lack of a quantitative assessment of the chemical nature and content of both plastic items and their leachates. In the context of the ever-increasing research effort devoted to assess the biological and ecological effects of plastic waste, we subsequently argue that the lack of a true interdisciplinary approach is likely to hamper the development of this research field. We finally introduce a roadmap for future research which has to evolve through the development of a sound and systematic ability to chemically define what we biologically compare.

Microplastic leachates disrupt the chemotactic and chemokinetic behaviours of an ecosystem engineer (Mytilus edulis)

The massive contamination of the environment by plastics is an increasing global scientific and societal concern. Knowing whether and how these pollutants affect the behaviour of keystone species is essential to identify environmental risks effectively. Here, we focus on the effect of plastic leachates on the behavioural response of the common blue mussel Mytilus edulis, an ecosystem engineer responsible for the creation of biogenic structures that modify the environment and provide numerous ecosystem functions and services. Specifically, we assess the effect of virgin polypropylene beads on mussels' chemotactic (i.e. a directional movement in response to a chemical stimulus) and chemokinetic (i.e. a non-directional change in movement properties such as speed, distance travelled or turning frequency in response to a chemical stimulus) responses to different chemical cues (i.e. conspecifics, injured conspecifics and a predator, the crab Hemigrapsus sanguineus). In the presence of predator cues, individual mussels reduced both their gross distance and speed, changes interpreted here as an avoidance behaviour. When exposed to polypropylene leachates, mussels moved less compared to control conditions, regardless of the cues tested. Additionally, in presence of crab cues with plastic leachates, mussels significantly changed the direction of movement suggesting a leachate-induced loss of their negative chemotaxis response. Taken together, our results indicate that the behavioural response of M. edulis is cue-specific and that its anti-predator behaviour as well as its mobility are impaired when exposed to microplastic leachates, potentially affecting the functioning of the ecosystem that the species supports.

Dysbaric osteonecrosis among professional divers: a literature review

AIM

Dysbaric osteonecrosis (DON) continues to be a significant occupational hazard that has significant medical and social consequences for professional divers. This review aims to evaluate the prevalence and risk factors of DON among professional divers and to summarize the scientific knowledge regarding distribution of the lesions as well as disease prognosis and treatment.

METHOD

A literature review using the Medline database.

RESULTS

The prevalence of DON varies between 0 and 70.6% in professional divers, and its prevalence is highest in Turkey, Hawaii, Korea and Japan but is dependent on activity and medical monitoring. The risk of DON is very low for military divers who strictly obey the decompression rules and who undergo periodic medical examination. DON pre- dominately occurs in the proximal part of the femur and humerus. In a majority of cases, DON will progress despite the absence of further dysbaric exposure.

CONCLUSION

The pathophysiology of the disease is incompletely understood and other etiological factors are perhaps being overlooked.

Preclinical evaluation of the abuse potential of Pitolisant, a histamine H₃ receptor inverse agonist/antagonist compared with Modafinil

BACKGROUND AND PURPOSE

Pitolisant, a histamine H₃ receptor inverse agonist/antagonist is currently under Phase III clinical trials for treatment of excessive daytime sleepiness namely in narcoleptic patients. Its drug abuse potential was investigated using in vivo models in rodents and monkeys and compared with those of Modafinil, a psychostimulant currently used in the same indications.

EXPERIMENTAL APPROACH

Effects of Pitolisant on dopamine release in the nucleus accumbens, on spontaneous and cocaine-induced locomotion, locomotor sensitization were monitored. It was also tested in three standard drug abuse tests i.e. conditioned place preference in rats, self-administration in monkeys and cocaine discrimination in mice as well as in a physical dependence model.

KEY RESULTS

Pitolisant did not elicit any significant changes in dopaminergic indices in rat nucleus accumbens whereas Modafinil increased dopamine release. In rodents, Pitolisant was without any effect on locomotion and reduced the cocaine-induced hyperlocomotion. In addition, no locomotor sensitization and no conditioned hyperlocomotion were evidenced with this compound in rats whereas significant effects were elicited by Modafinil. Finally, Pitolisant was devoid of any significant effects in the three standard drug abuse tests (including self-administration in monkeys) and in the physical dependence model.

CONCLUSIONS AND IMPLICATIONS

No potential drug abuse liability for Pitolisant was evidenced in various in vivo rodent and primate models, whereas the same does not seem so clear in the case of Modafinil.