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Over the past 80 years, tilapia have been translocated globally for aquaculture; active production is recorded in >124 countries. Of 7 million tonnes of tilapia produced in aquaculture, 79% is from 79 countries outside the natural range of tilapia. Capture fisheries account for a further 723,627 tonnes of tilapia, and >47% of this is landed from established invasive populations outside Africa. Tilapias host a rich fauna of parasites, many of which have been translocated with their hosts. This review summarises >2500 host-parasite records from 73+ countries and >820 recorded tilapia translocations (provided in the supplementary materials). This work focuses on the notable pathogens that threaten the health of cultured populations of tilapia, providing a description of their pathology and includes species that also have substantial impacts on wild tilapia populations, where relevant. For each major parasite taxonomic group, we highlight which parasites have been translocated or have been acquired from the new environments into which tilapia have been introduced, together with remarks on standard treatment approaches and research on them and their management and control. Regarding the theme 'Tilapia health: quo vadis?', Africa has enormous potential for aquaculture growth, but substantial knowledge gaps about tilapia parasites in many African states remain, which creates associated production and biosecurity risks. For each parasitic group, therefore, the risks of parasite translocation to new regions as tilapia aquaculture industries expand are highlighted. Norwegian Agency for Development Cooperation (Norad), Grant/Award Numbers: GCP/GLO/352/NOR, GCP/GLO/979/NOR; This study was supported by two FAO projects, namely, GCP/GLO/ 979/NOR: Improving Biosecurity Governance and Legal Framework for Efficient and Sustainable Aquaculture Production and GCP/GLO/ 352/NOR: Responsible use of fisheries and aquaculture resources for sustainable development, both funded by the Norwegian Agency for Development Cooperation (Norad). We also acknowledge the support from Regular Programme funds under FAO's strategic framework on better production and three relevant programme priority areas, that is Blue Transformation, One Health and Safe Food. The authors gratefully acknowledge the following funding agencies: Annemarie Avenant-Oldewage would like to thank the University of Johannesburg, Faculty, and the Central Research Committee Funding in support of this work. Adriana García-Vásquez and Miguel Rubio-Godoy gratefully acknowledge INECOL Institutional Funds supporting their participation in this study. Roman Kuchta was supported by the Czech Science Foundation (grant no. 19-28399X). Jesús S. Hernández-Orts benefited from a postdoctoral fellowship from the Consejo Nacional de Ciencia y Tecnología, CONACyT, Mexico (no. 177603). Gerardo Pérez-Ponce de Leon gratefully acknowledges Institutional funds from ENES-Mérida and Instituto de Biología, UNAM. Maarten P. M. Vanhove was mainly supported for tilapia parasite research by the Research Foundation—Flanders (FWO-Vlaanderen) (research grant 1513419N), the Special Research Fund of Hasselt University (BOF20TT06 and BOF21INCENT09), and the Belgian Federal Science Policy Office (BRAIN-be Pioneer Project BR/132/PI/TILAPIA). Pravata Kumar Pradhan and Neeraj Sood would like to thank the Director of ICAR—National Bureau of Fish Genetic Resources, Lucknow for kindly providing the facilities for aspects of this work to be undertaken. Melba G. Bondad-Reantaso gratefully acknowledges the Food and Agriculture Organisation of the United Nations (FAO). In addition, we would like to extend our grateful thanks to the following for their kind permission to use selected images in this study: Liesl Van As and Andri Grobbelaar from the Faculty of Natural and Agricultural Sciences, University of the Free State, Bloemfontein, Republic of South Africa and the Editorial Office of African Zoology; Harrison Charo-Karisa, Shimaa Ali and John Benzie from WorldFish, Abbassa, Egypt and Penang, Malaysia and the Editorial Office of Aquaculture (Elsevier); Heba Hassan Mahboub and Adel A. Shaheen, Zagazig University, Egypt; Kwanprasert Panchai, Nakhon Ratchasima Rajabhat University and Chutima Hanjavanit, Khon Kaen University, Thailand; Mahmoud Abou-Okada from the Faculty of Veterinary Medicine, Cairo University, Egypt; Ha Thanh Dong, Asian Institute of Technology, Pathum Thani, Thailand; Supranee Chinabut, Bangkok, Thailand; Tarinee Limakom, Fish Vet Group Asia, Thailand; Nehemiah Rindoria, Kisii University, Kenya; Johan Theron from the University of Limpopo, South Africa; Patience Chwe Igeh and Quinton Dos Santos from the University of Johannesburg, South Africa; Wouter Fannes, Royal Museum for Central Africa, Tervuren, Belgium; Volodimir Sarabeev, Zaporizhzhia National University, Ukraine; Radmila Repová, Institute ˇ of Parasitology, BC, CAS, Ceské Bud ˇ ejovice, Czech Republic; Leo Galli, ˇ Uruguay; and, to Giuseppe Paladini from the Institute of Aquaculture, University of Stirling, Scotland, UK. We are indebted to Greta Hanako Rosas Saito BSc, Scanning Electron Microscopy Technician, Red de Estudios Moleculares Avanzados, and to Mrs Gina Gallo Cadena, Graphic Designer, Red TIC's, Instituto de Ecología, A.C., Xalapa, Mexico for their invaluable contribution in the preparation and photography of parasite specimens for the figure plates. We would also like to thank Beng-Chu Kua from the National Fish Health Research Division, Fisheries Research Institute, Department of Fisheries Malaysia for kindly donating fixed samples of Zeylanicobdella arugamensis and Ratchakorn Wongwaradechkul, INVE (Thailand) Ltd. for photographs of leeches. Wilmien J. Luus-Powell (University of Limpopo), Maarten Van Steenberge (Royal Belgian Institute of Natural Sciences) and Arnaud Collard are cordially thanked for their input. Tim Benson, South Australian Museum, provided comment on the Latin names and parasite taxonomy. Open access publishing facilitated by James Cook University, as part of the Wiley-James Cook University agreement via the Council of Australian University Librarians

Fish belonging to Gobiidae are well represented in the Marchica lagoon on the Moroccan Mediterranean coast, both in terms of species richness and abundance, with the black goby (Gobius niger Linnaeus, 1758) being the dominant species. The present study aims to examine (1) the ecological traits of Gobius niger and its environmental drivers in the lagoon and (2) the potential lagoon-related footprint using morphometric, genetic and parasitological proxies. Systematic sampling covering the whole lagoon basin performed between October 2015 and November 2016 revealed year-long presence of G. niger throughout the lagoon with significantly low densities in winter. The higher abundances were recorded in the shallow bottoms of the lagoon inner margins on a variety of substrates (mud, muddy-sand, sandy-mud and fine sand) mostly covered by macroalgae and/or seagrass meadows. Multivariate analysis evidenced that depth and temperature were the important predictor variables explaining the spatial distribution of G. niger in the lagoon, with depth being the best model explaining about 33% of the total variability. Comparison of black goby populations from the Marchica lagoon with their counterparts from the adjacent Mediterranean coast of Morocco revealed that specimens caught at the sea are of a bigger size compared to the ones from the lagoon without any effect of the colour morphs observed (dark vs clear). Of the 180 gobies investigated, not a single one hosted the parasites we targeted in the parasitological approach, monogenean flatworms. The absence of population structuring, low genetic diversity and presence of common haplotypes indicate no apparent restriction in the gene flow between the two populations. Moreover, the morphometric differences and colour morphs observed seems to be due to the external environment rather than genetic differences. Gobius niger plays a key eco-trophic role by providing a link between benthic invertebrates and large predators. Therefore, ultimately, the shallow beds of the lagoon, where the species is abundant, are key habitats in the Marchica lagoon and need to be considered in all management plans aiming at the conservation of biodiversity and ecological processes.

Two specimens of Coptodon guineensis (Günther, 1862) were unexpectedly found in the Canal de Nador, Moulay Bousselham lagoon, almost 1000 km north of the Aabar River the northernmost river previously recorded. To confirm this identification nineteen measurements were recorded from each specimen and compared with other specimens of C. guineensis from Morocco and Mauritania. The COI gene was partially sequenced and compared with formerly published sequences of Coptodon species of the region. Both morphology and DNA revealed no differences with specimens from known populations of C. guineensis in Morocco.

To date, 41 species of Gyrodactylus have been described from Africa. However, none of these have been reported in Morocco. After identifying and examining 738 cyprinid host specimens, 26 specimens belonging to Gyrodactylus were found to parasitize the gills of nine species of Luciobarbus, Carasobarbus, and Pterocapoeta. The current study provides new information about the presence of a new parasitic species in Morocco, the first to be characterized on a species level in the Maghreb region. It describes in detail 12 specimens of Gyrodactylus isolated from the gills of Luciobarbus pallaryi (Pellegrin, 1919) and Luciobarbus ksibi (Boulenger, 1905). Based on morphoanatomical observations, the characterization of the specimens collected indicates a species of Gyrodactylus that is new to science, described here as Gyrodactylus nyingiae n. sp. The new species is different from previously described gyrodactylids infecting African cyprinid hosts because it has a longer hamulus total length, a longer hamulus root, a downward projecting toe of the marginal hook, and a trapezium-shaped ventral bar membrane with a slightly striated median portion and small rounded anterolateral processes. This study increases the total number of Gyrodactylus spp. found in African cyprinids to four. This research was funded by the Special Research Fund (BOF) of Hasselt University, grant number BOF22DOCLI04, to M.I.S., BOF20TT06 and BOF21INCENT09 to M.P.M.V and by research grant 1513419N of the Research Foundation—Flanders (FWO-Vlaanderen) The authors would like to sincerely thank Abdelaziz Benhoussa for allowing us to work in the Biodiversity, Ecology and Genome Laboratory (Mohammed V University in Rabat). Bouabid Badaoui and Hocein Bazairi are thanked for their statistical advice. Nikol Kmentová, Walter Boeger, Daniel Mungai Ndegwa, Kelly Thys, Tiziana Gobbin and Hervé Mandtoumbi are thanked for their laboratory assistance and help with statistical analysis

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. This research was funded by Czech Science Foundation (GACˇ R) standard project GA19-13573S. N.K. (BOF21PD01), A.J.C.L. (BOF19OWB02) and M.P.M.V. (BOF20TT06) are financed by the Special Research Fund of Hasselt University, Belgium. Walter A. Boeger (Universidade Federal do Paraná, Brazil) is thanked for fruitful discussions on this matter

Simple Summary: Monogenean flatworms are mainly parasitic in lower aquatic vertebrates including fish, anurans and chelonians. Gyrodactylus is one of the 23 genera of Gyrodactylidae,. With only 41 species described, the total number of Gyrodactylus species described from African freshwater fish still remains low. The known species represent only a fraction of the expected species richness of Gyrodactylus in Africa. In this study, we examined the gills of 738 cyprinid specimens. We isolated 26 Gyrodactylus individuals from these hosts. Twelve of these were morphologically characterized and proposed to belong to one single newly described species. In view of the importance of the cyprinid-monogenean system in studying the aquatic biodiversity and biogeography of North Af-rica, the present study is a substantial contribution to the parasite species inventory of these fishes. Abstract: To date, 41 species of Gyrodactylus have been described from Africa. However, none of these have been reported in Morocco. After identifying and examining 738 cyprinid host specimens, 26 specimens belonging to Gyrodactylus were found to parasitize the gills of nine species of Lucio-barbus, Carasobarbus, and Pterocapoeta. The current study describes in detail 12 specimens of Gyro-dactylus isolated from the gills of Luciobarbus pallaryi (Pellegrin, 1919) and Luciobarbus ksibi (Bou-lenger, 1905). Based on morphoanatomical observations, the characterization of the specimens collected suggests a species of Gyrodactylus new to science, described here as Gyrodactylus nyingiae n. sp. The new species is different from previously described gyrodactylids infecting African cyprinid hosts because it has a longer hamulus total length, a longer hamulus root, a downward projecting toe, a trapezium shaped ventral bar membrane with slightly striated median portion and small rounded anterolateral processes. This study brings the total number of Gyrodactylus spp. found in African cyprinids to four. Funding: This research was funded by the Special Research Fund of Hasselt University, grant number BOF22DOCLI04 to MIS; BOF20TT06 and BOF21INCENT09 to MPMV and by research grant 1513419N of the Research Foundation – Flanders (FWO-Vlaanderen). Acknowledgments: The authors would like to sincerely thank Prof. Abdelaziz Benhoussa for allowing us to work in the Biodiversity, Ecology and Genome Laboratory (Mohammed V University, Rabat). Prof. Bouabid Badaoui and Hocein Bazairi are thanked for their statistical advice. Daniel Mungai Ndegwa, Kelly Thys, Tiziana Gobbin and Hervé Mandtoumbi for their laboratory assistance and help with statistical analysis.

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 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 Greenwood, 1987, 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:CichlidogyrusandOnchobdella) were found, eight of which are described and one redescribed herein. The phylogenetic positions of chromidotilapiines-infecting species ofCichlidogyruswere inferred through a parsimony analysis of the morphological characters. Furthermore, we employed machine learning algorithms to detect morphological features associated with the main lineages ofCichlidogyrus. Although the results of these experimental algorithms remain inconclusive, the parsimony analysis indicates that West and Central African lineages ofCichlidogyrusandOnchobdellaare 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.Data availability statementType material was deposited in the invertebrate collection of the Royal Museum for Central Africa (Tervuren, Belgium) (RMCA) (RMCA_VERMES_XXXXX–XXX), the collection of the Research Group Zoology: Biodiversity and Toxicology of Hasselt University (Diepenbeek, Belgium) (HU XXX–XXX), the Finnish Museum of Natural History (Helsinki, Finland) (MZH XXXXX–XXX), and the Iziko South African Museum (Cape Town, South Africa) (SAMC-XXXXXXX-XXX). The morphological data that support the findings of this study are openly available in MorphoBank atwww.morphobank.org, at https://dx.doi.org/XXXXXXXX. Phylogenetic trees and data matrices for the analysis in TNT are included as additional data in MorphoBank.

Citation: Mushagalusa Mulega, A.; Van Steenberge, M.; Kmentová, N.; Muterezi Bukinga, F.; Rahmouni, I.; Masilya, P.M.; Benhoussa, A.; Pariselle, A.; Vanhove, M.P.M. Abstract: The ichthyofauna of Lake Tanganyika consists of 12 families of fish of which five belong to Siluriformes (catfishes). Studies on Siluriformes and their parasites in this lake are very fragmentary. The present study was carried out to help fill the knowledge gap on the monogeneans infesting the siluriform fishes of Lake Tanganyika in general and, more particularly, Clarias gariepinus. Samples of gills of Clarias gariepinus (Clariidae) were examined for ectoparasites. We identified the monogenean Gyrodactylus transvaalensis (Gyrodactylidae). This is the first time this parasite was found infecting gills. We are the first to observe a large spine in the male copulatory organ of this species and to provide measurements of its genital spines; this completes the description of the male copulatory organ, which is important in standard monogenean identification. This is the first monogenean species reported in C. gariepinus at Lake Tanganyika and the third known species on a representative of Siluriformes of this lake. It brings the total number of species of Gyrodactylus recorded in Lake Tanganyika to four. Knowing that other locations where this species has been reported are geographically remote from Lake Tanganyika, we propose a "failure to diverge" phenomenon for G. transvaalensis.

BackgroundMonogenean parasites have never been formally reported on fish from the Lufira basin. Then it is hypothesised that multiple monogenean species are to be recorded that are new to the region. This study aimed to record the gill monogenean parasite fauna of three cichlid fish species in the Upper Lufira basin by inventorying their diversity (species composition) and analysing their infection parameters (prevalence, mean intensity and abundance).MethodsOreochromis mweruensis, Coptodon rendalli, and Serranochromis macrocephalus were selected for the study, given their economic value and their abundance in the Upper Lufira basin. Monogeneans were isolated from the gills and stomach, mounted on glass slides with either Hoyer’s medium or ammonium picrate-glycerin for further identification under a stereomicroscope, based on morphological analysis of genital and haptoral hard parts. Indices of diversity and infections parameters were calculated.ResultsA total of thirteen gill monogenean parasite species (Cichlidogyrus dossoui, C. halli, C. karibae, C. mbirizei, C. papernastrema, C. quaestio, C. sclerosus, C. tiberianus, C. tilapiae, C. zambezensis, Scutogyrus gravivaginus, S. cf. bailloni and Gyrodactylus nyanzae) and one stomach monogenean (Enterogyrus malmbergi) were reported. A species richness of S= 10 for O. mweruensis, S= 6 for C. rendalli and S= 2 for S. macrocephalus were recorded. Five parasite species were reported to be common amongst O. mweruensis and C. rendalli. The most prevalent parasite species were C. halli (P= 80.9%) on O. mweruensis, C. dossoui (P= 92.9%) on C. rendalli and C. karibae and C. zambezensis (both of which P = 9.1%) on S. macrocephalus with a respective mean infection intensity of 7.9 on O. mweruensis, 9.8 on C. rendalli and 5 and 15, respectively, on S. macrocephalus. Results of this study reported new host ranges for five parasites species (C. quaestio, S. cf. bailloni, E. malmbergi on O. mweruensis, C. halli on C. rendalli and C. karibae on S. macrocephalus) as well as new geographical records for three of them (S. cf. bailloni, E. malmbergi, C. karibae).ConclusionsThis study highlights the richness of monogenean communities in the Upper Lufira basin and is a starting point for future helminthological studies, e.g. on the use of fish parasites as indicators of anthropogenic impacts.

In the framework of the study of Siluriform fish monogeneans of Lake Tanganyika, we described two new species of Bagrobdella Paperna, 1969 from Auchenoglanis occidentalis (Valenciennes, 1840). Bagrobdella vanhovei sp. nov. is characterized by the morphology of its MCO which is unique among its congeners, presenting a non-terminal opening, whereas the other species have a terminal opening, and Bagrobdella vansteenbergei sp. nov. characterized by the size of its hooks, which are almost all of the same size, and its male copulating organ with a unique shape: a sub-terminal opening and no membrane surrounding. The Multivariate analysis done on morphometrical characters shows that the new and already described species are well individualized, except for Bagrobdella parauchenoglanii Akoumba, Pariselle, Tombi & Bilong Bilong, 2017 and Bagrobdella fraudulenta Euzet & Le Brun, 1990 (but these two species are easily distinguishable by their morphology), and that B. vanhovei sp. nov. has a great intra-specific morphometrical variation.