The host diversity, complex life cycle and distribution of digeneans underline their value as bioindicators of ecosystem health. We examined the intestinal digenean trematode Cephalotrema elasticum of insectivorous mammals, sampled from Gammarus balcanicus (Crustacea: Amphipoda) as second intermediate hosts. The species is particularly relevant as part of the helminth species complex associated with protected mammals. Our study is based on an intensive survey of helminths in 8920 gammarids collected from 38 localities in Slovakia, Poland, and France. DNA sequences for three markers (18S rDNA, 28S rDNA, and CO1 mtDNA) were analysed using Bayesian inference. Molecular data suggest that C. elasticum represents a distinct genetic lineage closely related to Cryptotropidae. Rare anatomical traits, such as the marginal or submarginal genital pore arrangement, may influence mating success and reproductive isolation within Microphalloidea. Genetic and morphological evidence supports establishing a new family, Cephalotrematidae, within Microphalloidea, to include Cephalotrema, Pseudocephalotrema, and Opisthioparorchis. A family diagnosis and a key to the genera are provided to facilitate further taxonomic studies. The geographic distribution of C. elasticum highlights its utility as a biological indicator, reflecting the decline of water shrew populations due to climate-induced ecological changes, particularly in the French Pyrenees.

While the identification of adult monogeneans primarily relies on morphological criteria, the morphology of a number of monogenean larvae (oncomiracidia) is to this day scarcely described. Yet, oncomiracidium plays a crucial role in the life cycle of the parasite, being responsible for the detection and localisation of its host, as well as for its attachment to this host. Few studies investigated the external morphological structures related to these functions, especially in Monopisthocotylea. The present study focuses on the early life stages (egg and oncomiracidium) of Lamellodiscus erythrini Euzet et Oliver, 1967, which are accurately described for the first time by light and scanning electron microscopy. Eggs of L. erythrini are smooth, tetrahedral and extended by a long polar filament. Freshly laid, the egg is brown, opaque, impermeable and becomes transparent as it matures, revealing the larva and its eye spots. When the egg matures, the egg casing exhibits functional weak points all around the operculum through which the larva emerges. The larva of L. erythrini is elongated, cylindrical and has a highly developed ciliation covering three areas: an anterior zone, a pleural zone, and a posterior cone. The ciliated cells are contiguous and are organised in a structured mosaic of spherical droplets, each cilium inserted into one. The larval tegument presents microvilli as well as 9 pairs of dorsal sensilla. The haptor is a closed structure consisting of 14 sclerotised hooklets, 12 arranged in a circle, and one pair positioned at the centre of the haptor. The possible link between these morphological structures and larval behaviour is discussed.

BACKGROUND:While teleost fishes represent two thirds of marine vertebrates, the role of their external microbiota in relationship with their environment remains poorly studied, especially in wild populations. Hence, the interaction of their microbiota with ectoparasites is largely unknown. Microbiota can act as a protective barrier against pathogens, and/or be involved in host recognition by parasites. Thus, host-parasite associations should now be considered as a tripartite interplay where the microbiota shapes the host phenotype and its relation to parasites. Monogeneans (Platyhelminthes) are direct life cycle ectoparasites commonly found on teleost skin and gills. The role of bacterial communities within skin and gill mucus which either pre-exist monogeneans infestation or follow it remain unclear. This is investigated in this study using the association between Sparidae (Teleostei) and their specific monogenean ectoparasites of the Lamellodiscus genus. We are exploring specificity mechanisms through the characterization of the external mucus microbiota of two wild sparid species using 16s rRNA amplicon sequencing. We investigated how these bacterial communities are related to constrated Lamellodiscus monogeneans parasitic load. RESULTS:Our results revealed that the increase in Lamellodiscus load is linked to an increase in bacterial diversity in the skin mucus of D. annularis specimens. The date of capture of D. annularis individuals appears to influence the Lamellodiscus load. Correlations between the abundance of bacterial taxa and Lamellodiscus load were found in gill mucus of both species. Abundance of Flavobacteriaceae family was strongly correlated with the Lamellodiscus load in gill mucus of both species, as well as the potentially pathogenic bacterial genus Tenacibaculum in D. annularis gill mucus. Negative correlations were observed between Lamellodiscus load and the abundance in Vibrionaceae in gill mucus of D. annularis, and the abundance in Fusobacteria in gill mucus of P. acarne specimens, suggesting potential applications of these bacteria in mitigating parasitic infections in fish. CONCLUSIONS:Our findings highlight the dynamic nature of fish microbiota, in particular in relation with monogeneans infestations in two wild sparid species. More generally, this study emphasizes the links between hosts, bacterial communities and parasites, spanning from the dynamics of co-infection to the potential protective role of the host's microbiota.

Dermanyssus gallinae is a hematophagous ectoparasite on poultry. Accidentally, this parasite could reach human, leading to itchy cutaneous rash. In dermato-allergology or allergology, red and icthy rashes are a quite usual reason for medical consultation. We describe two cases of red itchy rashes in two patients, which made us suspect the implication of ectoparasite Dermanyssus gallinae. In both cases, the parasite has been recognized by families. The source of these parasites was a chicken coop (with an intermediary vector, possible rats) and, in the other case, a nest of birds in communication to the bedroom of the child implicated. Treatment is firstly eviction of the parasite by reducing potential sources of infestation, or vectors of Dermanyssus gallinae in contact with human environment. Symptomatic treatment of pruritus could be applied (dermocorticoids and antihistamines) but these treatments will be efficient only when the parasite eradication will be effective. When a patient is addressed with the initial suspicion of allergy in a context of red and itchy cutaneous rash, diagnosis of parasite bites must be evoked. Active research of clinical elements in favor of parasite implication is fundamental. As in all allergology medical consultations, precise collection of medical history is fundamental and differential diagnoses has to be in the mind of allergology physicians.(c) 2023 Elsevier Masson SAS. All rights reserved.

Nous rapportons deux cas d’éruptions faisant suspecter cet acarien chez une enfant et une adolescente. Les deux fois, l’arthropode avait été objectivé à l’œil nu au domicile des patients. L’origine de ces parasites a été pour l’un la présence d’un poulailler proche de l’habitat et d’un vecteur de type rats entre les deux ; pour l’autre, il existait des nids d’oiseaux dans la gouttière proche d’une fenêtre avec communication avec la chambre de l’enfant. Le traitement est tout d’abord l’éviction de l’animal du domicile en détruisant les sources d’infestations proches ou les vecteurs de Dermanyssus gallinae pouvant être en contact avec l’Homme ou l’habitat humain. Le traitement symptomatique du prurit (dermocorticoïdes et antihistaminiques) n’est pleinement efficace qu’une fois éradication complète du parasite réalisé. Le diagnostic de piqûres ou morsures d’arthropodes est un diagnostic clinique qu’il faut savoir évoquer même quand le motif de consultation est la recherche d’une allergie causale. En déterminer l’origine est plus difficile et repose sur la recherche active des éléments d’anamnèse par l’interrogatoire et qui à l’heure de biologies toujours plus performantes reste et demeure la pierre angulaire de toute consultation d’allergologie.

BACKGROUND:The microbiota in fish external mucus is mainly known for having a role in homeostasis and protection against pathogens, but recent evidence suggests it is also involved in the host-specificity of some ectoparasites. In this study, we investigated the influence of seasonality and environmental factors on both fish external microbiota and monogenean gill ectoparasites abundance and diversity and assessed the level of covariations between monogenean and bacterial communities across seasons. To do so, we assessed skin and gill microbiota of two sparid species, Oblada melanura and Diplodus annularis, over a year and collected their specific monogenean ectoparasites belonging to the Lamellodiscus genus.RESULTS:Our results revealed that diversity and structure of skin and gill mucus microbiota were strongly affected by seasonality, mainly by the variations of temperature, with specific fish-associated bacterial taxa for each season. The diversity and abundance of parasites were also influenced by seasonality, with the abundance of some Lamellodiscus species significantly correlated to temperature. Numerous positive and negative correlations between the abundance of given bacterial genera and Lamellodiscus species were observed throughout the year, suggesting their differential interaction across seasons.CONCLUSIONS:The present study is one of the first to demonstrate the influence of seasonality and related abiotic factors on fish external microbiota over a year. We further identified potential interactions between gill microbiota and parasite occurrence in wild fish populations, improving current knowledge and understanding of the establishment of host-specificity.

Monogeneans are highly diverse fish ectoparasites with a direct life cycle, widely distributed, and are known to generally display strict host specificity. Factors related to the hosts and the parasite have been suggested to explain this high specificity. Monogeneans have also been observed to colonise fish species not in their natural host range under experimental conditions. We developed a specific metabarcoding protocol and applied it on the Sparidae-Lamellodiscus host-parasite system, to assess parasite diversity on skin and gills of several sparid host species. We first demonstrated that the use of a metabarcoding approach provided a better understanding of the diversity of monogeneans associated with teleost skin and gills than traditional approaches based on morphological identification. We identified a high diversity of both expected and unexpected (never observed on this host species) Lamellodiscus spp. on each host species and on skin and gills. No significant difference in parasite diversity was found between skin and gills. These results suggest that the establishment of the observed host specificity in monogeneans relies on multiple levels of regulation, involving the survival capacity of the larvae and host recognition mechanisms.

Almost sixty years ago, Bdellovibrio and like organisms (BALOs) were discovered as the first obligate bacterial predators of other bacteria known to science. Since then, they were shown to be diverse and ubiquitous in the environment, and to bear astonishing ecological, physiological, and metabolic capabilities. The last decade has seen important strides made in understanding the mechanistic basis of their life cycle, the dynamics of their interactions with prey, along with significant developments towards their use in medicine, agriculture, and industry. This review details these achievements, identify current understanding and knowledge gaps to encourage and guide future BALO research.

Bdellovibrio and like organisms (BALOs) are obligate bacterial predators of other Gram-negative bacteria. Here, we used quantitative PCR (qPCR) and recently developed specific primers which target the 16S rRNA gene to explore the abundance and distribution of three families of BALO belonging to the Oligoflexia class (i.e., Bdellovibrionaceae, Peredibacteraceae and Bacteriovoracaceae) over one year in the epilimnion and hypolimnion of Lakes Annecy and Geneva. Peredibacteraceae was the dominant group at all sampling points except at the bottom of Lake Geneva, where Bdellovibrionaceae was found in higher number. In addition, the abundance of BALOs increased significantly during the warmer months. Using high-throughput sequencing (Illumina Miseq), hundreds of OTUs were identified for Bdellovibrionaceae and Peredibacteraceae. Phylogenetic analysis suggests that Bdellovibrionaceae are more diverse than Peredibacteraceae and that some OTUs belong to new species of Bdellovibrionaceae. We also found that dominant OTUs were present simultaneously in the two lakes, while some others were specific to each lake, suggesting an adaptive pattern. Finally, both abundance and diversity of BALOs were poorly associated with abiotic factors except temperature, suggesting the importance of studying biotic relationships, assumed to play a greater role than physico-chemical variables in BALOs' dynamics and distribution.

Besides his work on marine biology which legacy is undisputed, Henri de LacazeDuthiers, as other 19th century zoologists, extended his interests to many fields of natural history. He was generally a keen observer (and very talented illustrator) of the anatomy of complex natural structures. In particular, he initiated studies on insect-induced galls addressed in his article "Recherches pour servir a l'histoire des galles" (Lacaze-Duthiers 1853) and illustrated his research on the subject by magnificent drawings. The purpose of this essay is to report this lesser-known aspect of the work of H. de Lacaze-Duthiers. Without judging the value of LacazeDuthiers' research, we aim at extending the questions he raised at his time, and attempt to provide answers using recent knowledge on insect-induced gall diversity, ecology and physiology. In the process, we stress how the issues raised by Lacaze-Duthiers are connected to more general questions that apply to all biological associations between species (including parasitism). We will see that H. de Lacaze-Duthiers paper not only constitutes a pioneering work on insect galls but also addresses concepts that are still very relevant in current research, in particular on the genesis and development of galls.

Despite considerable research effort, many aspects of the host-parasite relationships and parasite spatial distribution in invasive hosts remain poorly understood due to complex and context-dependent phenomena related to both the bioinvasions and the parasitism. Using macroecological patterns and theory is a useful approach to analyzing parasitological observations, but in practice parasite ecology and classical macroecology are disconnected. We propose a new framework that can use the conventional parasitology sampling data much more effectively. The innovative concept combines the data inferred from populations, infra- and component communities of parasites and the application of a macroecological approach in the analysis of complex and frequently hidden relationships in host-parasite systems. This comparative analysis draws on parasite data across regions and host species at different organizational (population vs. community) and hierarchical (infra vs. component community) levels of parasites. Our framework based on assessing and analysis of parasitological and ecological indexes, including descriptors of parasite species richness (individual and total), infection parameters, parasite aggregation (Taylor´s power law) and macroecological models (abundance-variance and abundance-occupancy relationships), can produce mechanistic explanations of the Enemy Release Hypothesis and unravel host-parasite relationships of an invasive host and its parasites. Moreover, abundance-variance and abundance-occupancy relationships, core-satellite species hypothesis, patterns on the aggregation and the frequency distribution of prevalence, infrapopulation size and individual parasite species richness provide useful tools to distinguish co-introduced and acquired parasites in communities of the invasive host based on quantitative descriptors. We hope that our framework becomes widely applied as it can potentially contribute to enhance future practice and research in biodiversity conservation and control of invasive species.

Background Animal-associated microbial communities appear to be key factors in host physiology, ecology, evolution and its interactions with the surrounding environment. Teleost fish have received relatively little attention in the study of surface-associated microbiota. Besides the important role of microbiota in homeostasis and infection prevention, a few recent studies have shown that fish mucus microbiota may interact with and attract some specific parasitic species. However, our understanding of external microbial assemblages, in particular regarding the factors that determine their composition and potential interactions with parasites, is still limited. This is the objective of the present study that focuses on a well-known fish-parasite interaction, involving the Sparidae (Teleostei), and their specific monogenean ectoparasites of the Lamellodiscus genus. We characterized the skin and gill mucus bacterial communities using a 16S rRNA amplicon sequencing, tested how fish ecological traits and host evolutionary history are related to external microbiota, and assessed if some microbial taxa are related to some Lamellodiscus species. Results Our results revealed significant differences between skin and gill microbiota in terms of diversity and structure, and that sparids establish and maintain tissue and species-specific bacterial communities despite continuous exposure to water. No phylosymbiosis pattern was detected for either gill or skin microbiota, suggesting that other host-related and environmental factors are a better regulator of host-microbiota interactions. Diversity and structure of external microbiota were explained by host traits: host species, diet and body part. Numerous correlations between the abundance of given bacterial genera and the abundance of given Lamellodiscus species have been found in gill mucus, including species-specific associations. We also found that the external microbiota of the only unparasitized sparid species in this study, Boops boops, harbored significantly more Fusobacteria and three genera, Shewenella, Cetobacterium and Vibrio, compared to the other sparid species, suggesting their potential involvement in preventing monogenean infection. Conclusions This study is the first to explore the diversity and structure of skin and gill microbiota from a wild fish family and present novel evidence on the links between gill microbiota and monogenean species in diversity and abundance, paving the way for further studies on understanding host-microbiota-parasite interactions.

On the occasion of the 200th anniversary of the birth of Henri de Lacaze-Duthiers, one of the most curious and active scientific minds among 19th century naturalists, this article retraces his scientific career and recalls the long-term changes he made in the practice of science: promotion of experimental zoology, foundation of a modern scientific journal and establishment of the marine stations of Roscoff and Banyuls.

The rate of failure of French students during their first years at university is substantial, with only 42% graduating in the expected three or 4 years. As a result, French universities have called for a “pedagogical transformation” encouraging innovative teaching practices to improve undergraduate students’ academic success, notably the introduction of blended learning methods. In 2015, teachers from the three marine stations of Sorbonne Université created the online blended learning platform e-marin’lab for their marine science programs. In this paper, we investigated the participating teachers’ cognitions with regard to teaching and learning. Despite the success of the project that relied on their substantial voluntary commitment, the teachers demonstrated an adhesion to more traditional views (i.e., directive teacher-student transmission of knowledge is more efficient for students’ learning). Perhaps more paradoxically, our data reveal that the same teachers saw themselves as teaching in a student-oriented way, and that their students’ lack of engagement in class was due to their poor study skills and intrinsic motivation. Among other factors that will be discussed, we believe that these results are influenced by a context that does not provide many teacher training opportunities and that places little importance on teaching in university professors’ career recognition. Finally, the importance of the e-marin’lab platform in the context of the SARS-CoV-2 pandemic situation from 2020 and the massive use of distance teaching in marine sciences during national lockdown periods is discussed.

Microbial communities, which drive major ecosystem functions, consist of a wide range of interacting species. Understanding how microbial communities are structured and the processes underlying this is crucial to interpreting ecosystem responses to global change but is challenging as microbial interactions cannot usually be directly observed. Multiple efforts are currently focused to combine next-generation sequencing (NGS) techniques with refined statistical analysis (e.g., network analysis, multivariate analysis) to characterize the structures of microbial communities. However, most of these approaches consider a single table of sequencing data measured for several samples. Technological advances now make it possible to collect NGS data on different taxonomic groups simultaneously for the same samples, allowing us to analyse a pair of tables. Here, an analytical framework based on co-correspondence analysis (CoCA) is proposed to study the distributions, assemblages and interactions between two microbial communities. We show the ability of this approach to highlight the relationships between two microbial communities, using two data sets exhibiting various types of interactions. CoCA identified strong association patterns between autotrophic and heterotrophic microbial eukaryote assemblages, on the one hand, and between microalgae and viruses, on the other. We demonstrate also how CoCA can be used, complementary to network analysis, to reorder co-occurrence networks and thus investigate the presence of patterns in ecological networks.

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The epicontinental fauna of the Iberian Peninsula is strongly influenced by its geographical history. As the possibilities for dispersion of organisms into and from this region were (and still are) limited, the local fauna consists almost exclusively of endemic species. Almost all Iberian freshwater fishes of the families Leuciscidae and Cyprinidae are endemic and on-going research on these taxa continually uncovers new species. Nevertheless, information on their host-specific parasites remains scarce. In this study, we investigate the diversity and phylogenetic relationships in monogeneans of the genus Dactylogyrus (gill ectoparasites specific to cyprinoid fish) in the Iberian Peninsula. Twenty-two species were collected and identified from 19 host species belonging to Cyprinidae and Leuciscidae. A high degree of endemism was observed, with 21 Dactylogyrus species reported from Iberia only and a single species, D. borealis, also reported from other European regions. Phylogenetic analysis split the endemic Iberian Dactylogyrus into two well-supported clades, the first encompassing Dactylogyrus parasitizing endemic Luciobarbus spp. only, and the second including all Dactylogyrus species of endemic leuciscids and four species of endemic cyprinids. Species delimitation analysis suggests a remarkable diversity and existence of a multitude of cryptic Dactylogyrus species parasitizing endemic leuciscids (Squalius spp. and representatives of Chondrostoma s.l.). These results suggest a rapid adaptive radiation of Dactylogyrus in this geographically isolated region, closely associated with their cyprinoid hosts. Moreover, phylogenetic analysis supports that Dactylogyrus parasites colonized the Iberian Peninsula through multiple dispersion events.

The study of host-parasite coevolution is one of the cornerstones of evolutionary biology. The majority of fish ectoparasites belonging to the genus Dactylogyrus (Monogenea) exhibit a high degree of host specificity. Therefore, it is expected that their evolutionary history is primarily linked with the evolutionary history of their cyprinoid fish hosts and the historical formation of the landmasses. In the present study, we used a cophylogenetic approach to investigate coevolutionary relationships between endemic Cyprinoidea (Cyprinidae and Leuciscidae) from selected regions in southern Europe and their respective Dactylogyrus species. A total of 49 Dactylogyrus species including endemic and non-endemic species were collected from 62 endemic cyprinoid species in the Balkan and Apennine Peninsulas. However, 21 morphologically identified Dactylogyrus species exhibited different genetic variants (ranging from 2 to 28 variants per species) and some of them were recognized as cryptic species on the basis of phylogenetic reconstruction. Phylogenetic analyses revealed several lineages of endemic and non-endemic Dactylogyrus species reflecting some morphological similarities or host affinities. Using distance-based and event-based cophylogenetic methods, we found a significant coevolutionary signal between the phylogenies of parasites and their hosts. In particular, statistically significant links were revealed between Dactylogyrus species of Barbini (Cyprinidae) and their hosts belonging to the genera Aulopyge, Barbus and Luciobarbus. Additionally, a strong coevolutionary link was found between the generalist parasites D. alatus, D. sphyrna, D. vistulae, and their hosts, and between Dactylogyrus species of Pachychilon (Leuciscidae) and their hosts. Cophylogenetic analyses suggest that host switching played an important role in the evolutionary history of Dactylogyrus parasitizing endemic cyprinoids in southern Europe. We propose that the high diversification of phylogenetically related cyprinoid species in the Mediterranean area is a process facilitating the host switching of specific parasites among highly diverse congeneric cyprinoids.