First record of a proseriate flatworm predating on a rhabdocoel (Platyhelminthes: Proseriata and Rhabdocoela).

Microturbellarian flatworms comprise a diverse assemblage amongst meiofauna. These animals primarily exhibit carnivorous feeding habits, preying on various organisms, such as crustaceans, annelids and even other microturbellarians. However, details of their diet are poorly known. This study represents the first documentation of a proseriate preying upon a rhabdocoel. The proseriate was extracted from the sediment and studied alive. Within its digestive tract, structures of the reproductive systems of its prey were observed and identified as belonging to Phonorhynchopsishaegheni, a predatory turbellarian as well. No remains of any other organisms were detected. This finding underscores the relevance of Proseriata as top-level predators within the meiofaunal trophic web, a role that warrants further consideration beyond what has been previously acknowledged.

Live Imaging in Planarians: Immobilization and Real-Time Visualization of Reactive Oxygen Species.

Imaging of living animals allows the study of metabolic processes in relation to cellular structures or larger functional entities. To enable in vivo imaging during long-term time-lapses in planarians, we combined and optimized existing protocols, resulting in an easily reproducible and inexpensive procedure. Immobilization with low-melting-point agarose eliminates the use of anesthetics, avoids interfering with the animal during imaging-functionally or physically-and allows recovering the organisms after the imaging procedure. As an example, we used the immobilization workflow to image the highly dynamic and fast-changing reactive oxygen species (ROS) in living animals. These reactive signaling molecules can only be studied in vivo and mapping their location and dynamics during different physiological conditions is crucial to understand their role in developmental processes and regeneration. In the current protocol, we describe both the immobilization and ROS detection procedure. We used the intensity of the signals together with pharmacological inhibitors to validate the signal specificity and to distinguish it from the autofluorescent nature of the planarian.

Sharing is caring? Barcoding suggests co-introduction of dactylogyrid monogeneans with Nile tilapia and transfer towards native tilapias in sub-Saharan Africa.

Invasive Nile tilapias negatively impact native tilapia species through hybridisation and competition. However, the co-introduction of parasites with Nile tilapia, and subsequent changes in parasite communities, are scarcely documented. Monogeneans are known pathogens of cultured Nile tilapia, although little is known about their fate once Nile tilapias establish in new ecosystems. We investigate the parasitological consequences of Nile tilapia introduction on native tilapias in basins in Cameroon, the Democratic Republic of the Congo (DRC), and Zimbabwe, focusing on ectoparasitic dactylogyrids (Monogenea). Using the mitochondrial cytochrome oxidase c subunit I (COI) and nuclear 18S-internal transcribed spacer 1 (18S-ITS1) rDNA region of 128 and 166 worms, respectively, we evaluated transmission of several dactylogyrid species. Parasite spillover from Nile tilapia was detected for Cichlidogyrus tilapiae to Coptodon guineensis in Cameroon, Cichlidogyrus thurstonae to Oreochromis macrochir in the DRC, and Cichlidogyrus halli and C. tilapiae to Coptodon rendalli in Zimbabwe. Parasite spillback to Nile tilapia was detected for Cichlidogyrus papernastrema and Scutogyrus gravivaginus from Tilapia sparrmanii and Cichlidogyrus dossoui from C. rendalli or T. sparrmanii in the DRC, and Cichlidogyrus chloeae from Oreochromis cf. mortimeri and S. gravivaginus from O. macrochir in Zimbabwe. 'Hidden' transmissions (i.e. transmission of certain parasite lineages of species that are naturally present on both alien and native hosts) were detected for C. tilapiae and Scutogyrus longicornis between Nile tilapia and Oreochromis aureus and C. tilapiae between Nile tilapia and Oreochromis mweruensis in the DRC, and Cichlidogyrus sclerosus and C. tilapiae between Nile tilapia and O. cf. mortimeri in Zimbabwe. A high density of Nile tilapia occurring together with native tilapias, and the broad host range and/or environmental tolerance of the transmitted parasites, are proposed as factors behind parasite transmission through ecological fitting. However, continuous monitoring and the inclusion of environmental variables are necessary to understand the long-term consequences of these transmissions on native tilapias and to elucidate other underlying factors influencing these transmissions.

All quiet on the western front? The evolutionary history of monogeneans (Dactylogyridae: Cichlidogyrus, Onchobdella) infecting a West and Central African tribe of cichlid fishes (Chromidotilapiini).

Owing to the largely unexplored diversity of metazoan parasites, their speciation mechanisms and the circumstances under which such speciation occurs - in allopatry or sympatry - remain vastly understudied. Cichlids and their monogenean flatworm parasites have previously served as a study system for macroevolutionary processes, e.g., for the role of East African host radiations on parasite communities. Here, we investigate the diversity and evolution of the poorly explored monogeneans infecting a West and Central African lineage of cichlid fishes: Chromidotilapiini, which is the most species-rich tribe of cichlids in this region. We screened gills of 149 host specimens (27 species) from natural history collections and measured systematically informative characters of the sclerotised attachment and reproductive organs of the parasites. Ten monogenean species (Dactylogyridae: Cichlidogyrus and Onchobdella) were found, eight of which are newly described and one redescribed herein. The phylogenetic positions of chromidotilapiines-infecting species of Cichlidogyrus were inferred through a parsimony analysis of the morphological characters. Furthermore, we employed machine learning algorithms to detect morphological features associated with the main lineages of Cichlidogyrus. Although the results of these experimental algorithms remain inconclusive, the parsimony analysis indicates that West and Central African lineages of Cichlidogyrus and Onchobdella are monophyletic, unlike the paraphyletic host lineages. Several instances of host sharing suggest occurrences of intra-host speciation (sympatry) and host switching (allopatry). Some morphological variation was recorded that may also indicate the presence of species complexes. We conclude that collection material can provide important insights on parasite evolution despite the lack of well-preserved DNA material.

Title: À l'Ouest, rien de nouveau ? L'histoire évolutive des monogènes (Dactylogyridae : Cichlidogyrus, Onchobdella) infectant une tribu de poissons cichlidés (Chromidotilapiini) d'Afrique occidentale et centrale. Abstract: En raison de la nature largement inexplorée de la diversité des parasites métazoaires, leurs mécanismes de spéciation et les circonstances dans lesquelles cette spéciation se produit­allopatrie ou sympatrie­restent très peu étudiés. Les cichlidés et leurs parasites Plathelminthes monogènes ont déjà servi de modèle pour l'étude des processus macro-évolutifs, par exemple pour le rôle des radiations d'hôtes de l'Afrique de l'Est sur les communautés de parasites. Ici, nous étudions la diversité et l'évolution des monogènes peu étudiées qui infestent une lignée de poissons cichlidés d'Afrique occidentale et centrale : les Chromidotilapiini, qui est la tribu de cichlidés la plus riche en espèces dans cette région. Nous avons examiné les branchies de 149 spécimens hôtes (27 espèces) provenant de musées d'histoire naturelle et mesuré systématiquement les caractères informatifs des pièces sclérifiées du hapteur et des organes copulateurs des parasites. Dix espèces de monogènes (Dactylogyridae : Cichlidogyrus et Onchobdella) ont été trouvées ; huit sont nouvelles pour la science et une est redécrite. Les positions phylogénétiques des espèces de Cichlidogyrus infectant les chromidotilapiines ont été déduites par une analyse de parcimonie des caractères morphologiques. En outre, nous avons utilisé des algorithmes d'apprentissage automatique pour détecter les caractéristiques morphologiques associées aux principales lignées de Cichlidogyrus. Bien que les résultats de ces algorithmes expérimentaux restent peu concluants, l'analyse de parcimonie indique que les lignées de Cichlidogyrus et d'Onchobdella de l'Afrique de l'Ouest et Central sont monophylétiques, contrairement aux lignées d'hôtes qui sont paraphylétiques. Plusieurs cas de partage d'hôtes suggèrent des occurrences de spéciation synxénique (sympatrie) et de changement d'hôte (allopatrie). Certaines variations morphologiques ont été enregistrées et peuvent également indiquer la présence de complexes d'espèces. Nous concluons donc que le matériel de collection peut fournir des informations importantes sur l'évolution des parasites malgré le manque d'ADN exploitable.

Green roofs and pollinators, useful green spots for some wild bee species (Hymenoptera: Anthophila), but not so much for hoverflies (Diptera: Syrphidae).

Urbanisation has become one of the major anthropogenic drivers behind insect decline in abundance, biomass and species richness over the past decades. As a result, bees and other pollinators' natural habitats are reduced and degraded. Green roofs are frequently recommended as ways to counter the negative impacts of urbanisation on nature and enhance the amount of green space in cities. In this study we evaluated the pollinator (more specifically wild bees and hoverflies) diversity, abundance and species richness on twenty green roofs in Antwerp, Belgium. We analysed the influence of roof characteristics (age, surface area, height, percent cover of green space surrounding each site) on species richness or abundance of pollinators. In total we found 40 different wild bee species on the green roofs. None of the physical roof characteristics appear to explain differences in wild bees species richness and abundance. Neither could we attribute the difference in roof vegetation cover, i.e. roofs build-up with only Sedum species and roofs with a combined cover of Sedum, herbs and grasses, to differences in diversity, abundance, or species richness. We found a positive trend, although not significant, in community weighted mean body size for wild bees with an increase in green roof surface area. Roof wild bee communities were identified as social polylectic individuals, with a preference for ground nesting. Only eleven individuals from eight different hoverfly species were found. Our results show that green roofs can be a suitable habitat for wild bee species living in urban areas regardless of the roofs' characteristics, but hoverflies have more difficulties conquering these urban green spaces.

Can avian flyways reflect dispersal barriers of clinostomid parasites? First evidence from the mitogenome of Clinostomum complanatum.

Clinostomum complanatum (Rudolphi, 1814) is an economically important parasitic flatworm (Trematoda, Digenea), yet little is known on the population structure of these animals. We characterise a new mitochondrial genome for C. complanatum, derived from an Iranian specimen. The newly obtained sequence is used to position the species in the digenean tree of life. The first-ever intraspecific comparison at mitogenome scale within C. complanatum revealed a high degree of similarity to the previously sequenced mitogenome of a distant (Italian) population. Avian migratory routes mirror phylogenetic clustering, and hence we suggest that infection of a flying host enables genetic exchange between parasites across large geographic distances. Comparative mitogenomic work in Clinostomum spp. at both the intra- (C. complanatum) and interspecific (C. complanatum-C. sinensis) level further shows that usage of new and/or additional mitochondrial markers is preferred over single-gene methods for high-resolution diagnostics and population biology.

Explosive networking: The role of adaptive host radiations and ecological opportunity in a species-rich host-parasite assembly.

Many species-rich ecological communities emerge from adaptive radiation events. Yet the effects of adaptive radiation on community assembly remain poorly understood. Here, we explore the well-documented radiations of African cichlid fishes and their interactions with the flatworm gill parasites Cichlidogyrus spp., including 10,529 reported infections and 477 different host-parasite combinations collected through a survey of peer-reviewed literature. We assess how evolutionary, ecological, and morphological parameters determine host-parasite meta-communities affected by adaptive radiation events through network metrics, host repertoire measures, and network link prediction. The hosts' evolutionary history mostly determined host repertoires of the parasites. Ecological and evolutionary parameters predicted host-parasite interactions. Generally, ecological opportunity and fitting have shaped cichlid-Cichlidogyrus meta-communities suggesting an invasive potential for hosts used in aquaculture. Meta-communities affected by adaptive radiations are increasingly specialised with higher environmental stability. These trends should be verified across other systems to infer generalities in the evolution of species-rich host-parasite networks.

Population genomics of introduced Nile tilapia Oreochromis niloticus (Linnaeus, 1758) in the Democratic Republic of the Congo: Repeated introductions since colonial times with multiple sources.

During colonial times, Nile tilapia Oreochromis niloticus (Linnaeus, 1758) was introduced into non-native parts of the Congo Basin (Democratic Republic of the Congo, DRC) for the first time. Currently, it is the most farmed cichlid in the DRC, and is present throughout the Congo Basin. Although Nile tilapia has been reported as an invasive species, documentation of historical introductions into this basin and its consequences are scant. Here, we study the genetic consequences of these introductions by genotyping 213 Nile tilapia from native and introduced regions, focusing on the Congo Basin. Additionally, 48 specimens from 16 other tilapia species were included to test for hybridization. Using RAD sequencing (27,611 single nucleotide polymorphisms), we discovered genetic admixture with other tilapia species in several morphologically identified Nile tilapia from the Congo Basin, reflecting their ability to interbreed and the potential threat they pose to the genetic integrity of native tilapias. Nile tilapia populations from the Upper Congo and those from the Middle-Lower Congo are strongly differentiated. The former show genetic similarity to Nile tilapia from the White Nile, while specimens from the Benue Basin and Lake Kariba are similar to Nile tilapia from the Middle-Lower Congo, suggesting independent introductions using different sources. We conclude that the presence of Nile tilapia in the Congo Basin results from independent introductions, reflecting the dynamic aquaculture history, and that their introduction probably leads to genetic interactions with native tilapias, which could lower their fitness. We therefore urge avoiding further introductions of Nile tilapia in non-native regions and to use native tilapias in future aquaculture efforts.

Somewhere I belong: phylogeny and morphological evolution in a species-rich lineage of ectoparasitic flatworms infecting cichlid fishes.

A substantial portion of biodiversity has evolved through adaptive radiation. However, the effects of explosive speciation on species interactions remain poorly understood. Metazoan parasites infecting radiating host lineages could improve our knowledge because of their intimate host relationships. Yet limited molecular, phenotypic and ecological data discourage multivariate analyses of evolutionary patterns and encourage the use of discrete characters. Here, we assemble new molecular, morphological and host range data widely inferred from a species-rich lineage of parasites (Cichlidogyrus, Platyhelminthes: Monogenea) infecting cichlid fishes to address data scarcity. We infer a multimarker (28S/18S rDNA, ITS1, COI mtDNA) phylogeny of 58 of 137 species and characterize major lineages through synapomorphies inferred from mapping morphological characters. We predict the phylogenetic position of species without DNA data through shared character states, a morphological phylogenetic analysis, and a classification analysis with support vector machines. Based on these predictions and a cluster analysis, we assess the systematic informativeness of continuous characters, search for continuous equivalents for discrete characters, and suggest new characters for morphological traits not analysed to date. We also model the attachment/reproductive organ and host range evolution using the data for 136 of 137 described species and multivariate phylogenetic comparative methods (PCMs). We show that discrete characters not only can mask phylogenetic signals, but also are key for characterizing species groups. Regarding the attachment organ morphology, a divergent evolutionary regime for at least one lineage was detected and a limited morphological variation indicates host and environmental parameters affecting its evolution. However, moderate success in predicting phylogenetic positions, and a low systematic informativeness and high multicollinearity of morphological characters call for a revaluation of characters included in species characterizations.

Orostylis gen. nov., a new genus of Dalytyphloplanida with seven new species (Platyhelminthes: Rhabdocoela).

We describe a new genus of dalytyphloplanid rhabdocoels, with seven new species. Orostylis gen. nov. has a unique combination of characters including the presence of a sclerotised stylet, an anteriorly positioned male copulatory organ with the male genital pore in the buccal cavity, and the absence of an oviduct. The ovary empties directly into the intestinal lumen. Orostylis dohae sp. nov., Orostylis asinaraensis sp. nov., Orostylis caecus sp. nov., Orostylis distortus sp. nov., Orostylis donanae sp. nov., Orostylis gallicus sp. nov., and Orostylis timucuorum sp. nov. are distinguished from each other by the structure of the sclerotised parts of the male copulatory organ. Molecular and morphological evidence place the new genus in Neodalyellida Willems et al. 2006, and similarities with other taxa are discussed.

Mosaic or melting pot: The use of monogeneans as a biological tag and magnifying glass to discriminate introduced populations of Nile tilapia in sub-Saharan Africa.

The origin of introduced Nile tilapia stocks in sub-Saharan Africa is largely unknown. In this study, the potential of monogeneans as a biological tag and magnifying glass is tested to reveal their hosts' stocking history. The monogenean gill community of different Nile tilapia populations in sub-Saharan Africa was explored, and a phylogeographic analysis was performed based on the mitogenomes of four dactylogyrid species (Cichlidogyrus halli, C. sclerosus, C. thurstonae, and Scutogyrus longicornis). Our results encourage the use of dactylogyrids as biological tags. The magnifying glass hypothesis is only confirmed for C. thurstonae, highlighting the importance of the absence of other potential hosts as prerequisites for a parasite to act as a magnifying glass. With the data generated here, we are the first to extract mitogenomes from individual monogeneans and to perform an upscaled survey of the comparative phylogeography of several monogenean species with unprecedented diagnostic resolution.

Dactylogyridae 2022: a meta-analysis of phylogenetic studies and generic diagnoses of parasitic flatworms using published genetic and morphological data.

Dactylogyridae is one of the most studied families of parasitic flatworms with more than 1000 species and 166 genera described to date including ecto- and endoparasites. Dactylogyrid monogeneans were suggested as model organisms for host-parasite macroevolutionary and biogeographical studies due to the scientific and economic importance of some of their host lineages. Consequently, an array of phylogenetic research into different dactylogyrid lineages has been produced over the past years but the last family-wide study was published 16 years ago. Here, we provide a meta-analysis of the phylogenetic relationships of Dactylogyridae including representatives of all genera with available molecular data (n = 67). First, we investigate the systematic informativeness of morphological characters widely used to diagnose dactylogyrid genera through a parsimony analysis of the characters, character mapping, and phylogenetic comparative methods. Second, we provide an overview of the current state of the systematics of the family and its subfamilies, and summarise potentially poly- and paraphyletic genera. Third, we elaborate on the implications of taxonomic, citation, and confirmation bias in past studies. Fourth, we discuss host range, biogeographical, and freshwater-marine patterns. We found two well-supported macroclades which we assigned to the subfamilies Dactylogyrinae and Ancyrocephalinae. These subfamilies further include 16 well-supported clades with only a few synapomorphies that could be deduced from generic diagnoses in the literature. Furthermore, few morphological characters considered systematically informative at the genus level display a strong phylogenetic signal. However, the parsimony analysis suggests that these characters provide little information on the relationships between genera. We conclude that a strong taxonomic bias and low coverage of DNA sequences and regions limit knowledge on morphological and biogeographical evolutionary patterns that can be inferred from these results. We propose addressing potential citation and confirmation biases through a 'level playing field' multiple sequence alignment as provided by this study.

Rush or relax: migration tactics of a nocturnal insectivore in response to ecological barriers.

During their annual migration, avian migrants alternate stopover periods, for refuelling, with migratory flight bouts. We hypothesise that European Nightjars (Caprimulgus europaeus) adapt their daily migration tactics in association with biomes. We tracked the autumn migration of 24 European Nightjars, from breeding populations in Mongolia, Belgium and UK, using GPS-loggers and multi-sensor data loggers. We quantified crepuscular and nocturnal migration and foraging probabilities, as well as daily travel speed and flight altitude during active migration in response to biomes. Nightjars adopt a rush tactic, reflected in high daily travel speed, flight altitude and high migration probabilities at dusk and at night, when travelling through ecological barriers. Migration is slower in semi-open, hospitable biomes. This is reflected in high foraging probabilities at dusk, lower daily travel speed and lower migration probabilities at dusk. Our study shows how nightjars switch migration tactics during autumn migration, and suggest nightjars alternate between feeding and short migratory flight bouts within the same night when travelling through suitable habitats. How this may affect individuals' fuel stores and whether different biomes provide refuelling opportunities en route remains to be investigated, to understand how future land-use change may affect migration patterns and survival probabilities.

From the Atlantic Coast to Lake Tanganyika: Gill-Infecting Flatworms of Freshwater Pellonuline Clupeid Fishes in West and Central Africa, with Description of Eleven New Species and Key to Kapentagyrus (Monogenea, Dactylogyridae).

Unlike their marine counterparts, tropical freshwater clupeids receive little scientific attention. However, they sustain important fisheries that may be of (inter)national commercial interest. Africa harbours over 20 freshwater clupeid species within Pellonulini. Recent research suggests their most abundant parasites are gill-infecting monogenean flatworms within Kapentagyrus. After inspecting specimens of 12 freshwater clupeids from West and Central Africa, mainly sourced in biodiversity collections, we propose 11 new species of Kapentagyrus, which we describe using their haptoral and genital morphology. Because of their high morphological similarity, species delineation relies mostly on the morphometrics of anchors and hooks. Specifically, earlier, molecular taxonomic work indicated that the proportion between the length of the anchor roots, and between the hook and anchor length, is diagnostic. On average, about one species of Kapentagyrus exists per pellonuline species, although Pellonula leonensis harbours four species and Microthrissa congica two, while Microthrissa moeruensis and Potamothrissa acutirostris share a gill monogenean species. This study more than quadruples the number of known species of Kapentagyrus, also almost quadrupling the number of pellonuline species of which monogeneans are known. Since members of Kapentagyrus are informative about their hosts' ecology, evolutionary history, and introduction routes, this enables a parasitological perspective on several data-poor African fisheries.

Contrasting Host-Parasite Population Structure: Morphology and Mitogenomics of a Parasitic Flatworm on Pelagic Deepwater Cichlid Fishes from Lake Tanganyika.

Little phylogeographic structure is presumed for highly mobile species in pelagic zones. Lake Tanganyika is a unique ecosystem with a speciose and largely endemic fauna famous for its remarkable evolutionary history. In bathybatine cichlid fishes, the pattern of lake-wide population differentiation differs among species. We assessed the congruence between the phylogeographic structure of bathybatine cichlids and their parasitic flatworm Cichlidogyrus casuarinus to test the magnifying glass hypothesis. Additionally, we evaluated the use of a PoolSeq approach to study intraspecific variation in dactylogyrid monogeneans. The lake-wide population structure of C. casuarinus ex Hemibates stenosoma was assessed based on a portion of the cox1 gene combined with morphological characterisation. Additionally, intraspecific mitogenomic variation among 80 parasite samples from one spatially constrained metapopulation was assessed using shotgun NGS. While no clear geographic genetic structure was detected in parasites, both geographic and host-related phenotypic variation was apparent. The incongruence with the genetic north-south gradient observed in H. stenosoma may be explained by the broad host range of this flatworm including eupelagic bathybatine host species that form panmictic populations across the lake. In addition, we present the first parasite mitogenome from Lake Tanganyika and propose a methodological framework for studying the intraspecific mitogenomic variation of dactylogyrid monogeneans.

A Spatiotemporal Characterisation of Redox Molecules in Planarians, with a Focus on the Role of Glutathione during Regeneration.

A strict coordination between pro- and antioxidative molecules is needed for normal animal physiology, although their exact function and dynamics during regeneration and development remains largely unknown. Via in vivo imaging, we were able to locate and discriminate between reactive oxygen species (ROS) in real-time during different physiological stages of the highly regenerative planarian Schmidtea mediterranea. All ROS signals were strong enough to overcome the detected autofluorescence. Combined with an in situ characterisation and quantification of the transcription of several antioxidant genes, our data showed that the planarian gut and epidermis have a well-equipped redox system. Pharmacological inhibition or RNA interference of either side of the redox balance resulted in alterations in the regeneration process, characterised by decreased blastema sizes and delayed neurodevelopment, thereby affecting tails more than heads. Focusing on glutathione, a central component in the redox balance, we found that it is highly present in planarians and that a significant reduction in glutathione content led to regenerative failure with tissue lesions, characterised by underlying stem cell alterations. This exploratory study indicates that ROS and antioxidants are tightly intertwined and should be studied as a whole to fully comprehend the function of the redox balance in animal physiology.

A revision of the genus Cheliplana de Beauchamp, 1927 (Rhabdocoela: Schizorhynchia), with the description of six new species.

A comprehensive morphological and taxonomic account of the members of the genus Cheliplana de Beauchamp, 1927 is presented. Six new species are described: Cheliplana asinaraensis n. sp., C. cubana n. sp., C. curacaoensis n. sp., C. hawaiiensis n. sp., C. longissima n. sp. and C. mauii n. sp. The new species are mainly distinguished from each other and from other representatives of Cheliplana by the organisation of the reproductive system and the structure of the cirrus. Furthermore, C. triductibus Van Steenkiste, Volonterio, Schockaert Artois, 2008 is considered a junior synonym of Cheliplana deverticula Ax, 2008. The two subspecies of Cheliplana asica Marcus, 1952, C. asica asica and C. asica terminalis Brunet, 1968, are considered separate species. The systematic position of the genus Dactyloplana Armonies, 2018 is discussed, and its synonymy with Cheliplana is retained. As such, this brings the total number of species of Cheliplana to 49. Finally, we provide an identification key to the members of the genus, based on characters that enable identification to species level in the field.

Taxonomy and phylogeny of Koinocystididae (Platyhelminthes, Kalyptorhynchia), with the description of three new genera and twelve new species.

The taxon Koinocystididae is the third most species-rich family within Eukalyptorhynchia. However, its diversity and phylogeny have been largely neglected in former studies. We introduce three new genera and twelve new species of Koinocystididae including Simplexcystis asymmetrica gen. n. sp. n., Galapagetula cubensis sp. n., eight species of Reinhardorhynchus gen. n. and two species of Itaipusa. This raises the total number of species within Koinocystididae from 51 to 63. We also report on new distribution records for six known species: I. divae (Cuba, Panama and New Caledonia), I. karlingi (Sardinia and Lanzarote), Reinhardorhynchus riegeri comb. n. (Cuba), R. ruffinjonesi comb. n. (Cuba and Panama), Utelga heinckei (Cuba and Lanzarote), and U. pseudoheinckei (Sardinia). Simplexcystis asymmetrica gen. n. sp. n. is characterised by a male duct running eccentrically through the copulatory bulb, lack of any hard structures in the male system, lack of a bursa, and the fact that the epithelia of the female, the male, and part of the common atrium are covered by a brush border. Galapagetula cubensis sp. n. has a caudal gonopore, a divisa-type copulatory bulb with an unarmed penis papilla, and a female duct without a sphincter. The new species of Itaipusa and Reinhardorhynchus gen. n. differ from their congeners in the detailed structure of the copulatory bulb and especially the hard structures associated with it. In a molecular phylogenetic analysis based on all available 18S and 28S rDNA sequences of koinocystidids, we found support for the monophyly of the family and the genus Utelga Marcus, 1949. The genus Itaipusa is not monophyletic in that I. sinensis forms a clade with Rhinolasius dillonicus, while other species of Itaipusa that have a copulatory bulb armed with hooks form a clade together with Sekerana stolzi. As the type species of Itaipusa (I. divae) is in neither of these clades, we erected a new genus for I. sinensis (Koinogladius gen. n.) and one for species of Itaipusa having a hook-bearing copulatory bulb (Reinhardorhynchus gen. n.), respectively. Whether the remaining species of Itaipusa form a monophylum remains uncertain.

Parasitic flatworms infecting thorny skate, Amblyraja radiata: Infection by the monogeneans Acanthocotyle verrilli and Rajonchocotyle emarginata in Svalbard.

Parasite diversity above the Arctic circle remains understudied even for commercially valuable host taxa. Thorny skate, Amblyraja radiata, is a common bycatch species with a growing commercial value. Its natural range covers both sides of the North Atlantic including the Arctic zone. Svalbard is a Norwegian archipelago located on the northwest corner of the Barents Shelf which sustains a spectacular species diversity. So far, several monogenean species have been reported infecting thorny skate across the Atlantic Ocean. In the present study, we intend to fill in the knowledge gap on monogenean parasites infecting thorny skate in the northern part of its range and thus indirectly assess the connectivity between the thorny skate populations off the Svalbard coast and from previously studied locations. 46 monogenean individuals were recovered from 11 specimens of thorny skate. Following morphological and molecular assessment, two species of monogeneans, Acanthocotyle verrilli and Rajonchocotyle emarginata, were identified. The results serve as the northernmost record for both parasite genera and the first record of monogenean species off Svalbard. Detailed morphometric evaluation revealed a relatively high level of morphological variation in A. verrilli compared to its congeners. Phylogenetic reconstruction placed A. verrilli in a well-supported clade with A. imo. Our study also suggests high diagnostic significance of sclerotised structures in the identification of Rajonchocotyle. Even though the occurrence of two directly transmitted parasite species supports the previously suggested long-distance migration of A. radiata, future studies employing highly variable genetic markers are needed to assess the ongoing and historical migration patterns.

Differential effect of silver nanoparticles on the microbiome of adult and developing planaria.

Silver nanoparticles (AgNPs) are widely incorporated in household, consumer and medical products. Their unintentional release via wastewaters raises concerns on their environmental impact, particularly for aquatic organisms and their associated bacterial communities. It is known that the microbiome plays an important role in its host's health and physiology, e.g. by producing essential nutrients and providing protection against pathogens. A thorough understanding of the effects of AgNPs on bacterial communities and on their interactions with the host is crucial to fully assess AgNP toxicity on aquatic organisms. Our results indicate that the microbiome of the invertebrate Schmidtea mediterranea, a freshwater planarian, is affected by AgNP exposure at the tested 10 µg/ml concentration. Using targeted amplification of the bacterial 16S rRNA gene V3-V4 region, two independent experiments on the microbiomes of adult worms revealed a consistent decrease in Betaproteobacteriales after AgNP exposure, mainly attributed to a decrease in Curvibacter and Undibacterium. Although developing tissues and organisms are known to be more sensitive to toxic compounds, three independent experiments in regenerating worms showed a less pronounced effect of AgNP exposure on the microbiome, possibly because underlying bacterial community changes during development mask the AgNP induced effect. The presence of a polyvinyl-pyrrolidone (PVP) coating did not significantly alter the outcome of the experiments compared to those with uncoated particles. The observed variation between the different experiments underlines the highly variable nature of microbiomes and emphasises the need to repeat microbiome experiments, within and between physiological states of the animal.