taxonID	type	description	language	source
03CA4536FF8BFFAEFC8A24E8FE3C5FC0.taxon	description	In total, 51 % (CI 42 – 60 %) of the skates harbored one to four taxa of metazoan parasites, with a taxa richness of 0.8 ± 0.2 parasite taxa per individual and an abundance of 8.7 ± 4.5 parasites per individual (Tables 2 and 3). According to morphological identification, 11 parasite taxa occurred in the whole sampling of skates: one Myxosporea (unidentified) and one Monogenea (Rajonchocotyle emarginata) on gills, and six Cestoda (Grillotia erinaceus, Tritaphros retzii, and the genera Echeneibothrium, Nybelinia, Onchobothrium, and Rockacestus) and three Nematoda (Anisakis simplex, and the genera Phocanema and Proleptus), all trophically transmitted (Table 2). Based on DNA-sequencing made on 27 isolated nematodes from skates, 20 individuals were molecularly identified, i. e., seven Phocanema krabbei, five Proleptus sp., four Phocanema azarasi, and four Anisakis simplex s. s. (Table 4). All sequences had an identity percentage with sequences present in the National Center for Biological Information database above 99 %, and percentage of coverage was always at least 99 % for all sequences (Table 4). All the sequences generated in this study were deposited in GenBank. A total of 16 new host – parasite associations are documented in Table 2 (in bold). Parasites were mainly recorded in the digestive tract (38 % of the skates, CI 29 – 47 %), then in the body cavity (23 %, CI 16 – 31 %) and to a lesser extent on the gills (11 %, CI 6 – 18 %). No infections were found in the other organs examined (eyes, skin, heart, and liver). Trophically transmitted (vs gill) parasites were largely dominant, with prevalence and abundance of 48 % (CI 39 – 57 %) and 5.8 ± 2.4 parasites per skate individual, respectively. Among trophically Rajidae IUCN N Overall P % (CI) Pth % (CI) Lful Vu 9 100 (70 – 100) a 100 (70 – 100) a Lnae LC 15 47 (25 – 70) bc 33 (15 – 58) c Rbra NT 21 29 (14 – 47) c 29 (14 – 47) c Rcla NT 20 40 (22 – 61) c 40 (22 – 61) c Rmic NT 14 93 (69 – 99) a 93 (69 – 99) a Rmon LC 21 19 (8 – 40) c 19 (8 – 40) c Rund NT 14 79 (52 – 92) ab 71 (42 – 60) b Overall A ± CI Ath ± CI Parasite taxa 29.7 ± 45.1 a 18.6 ± 19.9 a Myxo, Nybe, Asim, Phoc, Prol 7.6 ± 9.8 a 0.9 ± 0.8 b Myxo, Rema, Eche, Geri, Asim, Phoc 0.8 ± 1.0 b 0.8 ± 1.0 b Geri, Asim, Prol 1.9 ± 1.8 b 1.9 ± 1.8 b Eche, Tret, Asim, Prol 28.3 ± 22.9 a 19.3 ± 10.6 a Myxo, Eche, Onch, Asim, Phoc, † Prol 1.3 ± 1.6 b 1.3 ± 1.6 b Eche, Phoc, Prol 9.7 ± 6.9 a 9.4 ± 7.0 a Myxo, Nybe, Onch, Rock, Phoc † Note: Parasite taxa: Myxosporea (Myxo), Rajonchocotyle emarginata (Rema), Echeneibothrium spp. (Eche), Grillotia erinaceus (Geri), Nybelinia spp. (Nybe), Onchobothrium spp. (Onch), Rockacestus sp. (Rock), Tritaphros retzii (Tret), Anisakis simplex (Asim), Phocanema spp. (Phoc), Proleptus sp. (Prol). First records of parasites in bold. N = sample size, CI = confidence interval (95 %). Due to the generally high specificity of Cestoda for their definitive host (Caira and Jensen, 2014 for review), we considered that Eche, Nybe and Onch recorded in several skate species in our study corresponded to several parasite species (one per skate host species). Different letters indicated statistical differences between skate species for each parasitological parameter. † Both Phocanema azarasi and Phocanema krabbei molecularly identified and recorded for the first time. et al. (2023) Parasite taxa MH P % (CI) A ± CI Myxozoa Max A Infection pathways Myxosporea G 9.6 (6.7 – 19.8) 3.52 ± 3.29 100 Random contact with spores Monogenea Rajonchocotyle emarginata G 1.1 (0.2 – 5.8) 0.01 ± 0.02 1 Active attachment on gill lamellae Cestoda Echeneibothrium spp. SV 7.9 (4.2 – 14.3) 0.30 ± 0.29 15 Ingestion of crustaceans, teleosts (Hi 2, Hp) Grillotia erinaceus ES, SV 3.5 (1.4 – 8.7) 0.04 ± 0.05 2 Ingestion of teleosts (Hi 2) Nybelinia spp. ES, SV 7.9 (4.2 – 14.3) 0.46 ± 0.43 20 Ingestion of cephalopods, fish (Hi 2) Onchobothrium spp. SV 7.9 (4.2 – 14.3) 0.15 ± 0.11 4 Ingestion of crustaceans, cephalopods, fish (Hi 2, Hp) Rockacestus sp. SV 0.9 (0.2 – 4.8) 0.01 ± 0.02 1 Ingestion of benthic invertebrates, fish (Hi 2, Hp) Tritaphros retzii SV 0.9 (0.2 – 4.8) 0.01 ± 0.02 1 Ingestion of teleosts (Hi 2) Nematoda Anisakis simplex BC, SV 9.6 (5.5 – 16.5) 1.05 ± 1.05 55 Ingestion of crustaceans, cephalopods, fish (Hi, Hp) Phocanema spp. a BC 18.4 (12.4 – 26.5) 3.04 ± 1.67 56 Ingestion of crustaceans, cephalopods, fish (Hi, Hp) Proleptus sp. ES 14.0 (8.8 – 21.6) 0.74 ± 0.61 30 Ingestion of decapods (Hi) Abbreviations: BC, body cavity; CI, confidence interval (95 %); ES, esophagous and stomach; G, gills; Hd, definitive host; Hi, intermediate host; Hp, paratenic host; SV, spiral valve. a Two species of Phocanema were molecularly identified (P. azarasi and P. krabbei). transmitted parasites, nematodes were the most prevalent infecting 37 % (CI 29 – 46 %) of the skates with an abundance of 1.6 ± 1.2 parasites per individual, followed by cestodes for which total prevalence and abundance were, respectively, 25 % (CI 18 – 33 %) and 0.2 ± 0.2 parasite per individual. The dominant taxa of metazoan parasites were, in decreasing order, the nematodes Phocanema spp., Proleptus sp., and Anisakis simplex, each taxon being encountered in five of the seven skate species (Tables 2 and 3).	en	Gérard, Claudia, Trochard, Caroline, Hervé, Maxime R., Hamel, Héloïse, Gay, Mélanie, Barbier, Michel, Trancart, Thomas, Barreau, Thomas (2024): Communities of metazoan parasites in seven sympatric skate species (Elasmobranchii, Rajidae) from the English Channel and Celtic Sea differing in conservation status. Journal of Fish Biology 105 (3): 975-987, DOI: 10.1111/jfb.15845, URL: https://doi.org/10.1111/jfb.15845
03CA4536FF80FFA3FFC227EDFE705B7F.taxon	description	Comparison with previous parasitological surveys (e. g., Alvarez´et al., 2006; McVicar, 1977; Sanmartín et al., 2000) is difficult because of differences in methods (fish previously frozen before parasitological examination in our study vs. freshly euthanized), but also in sampling effort, areas, and timing that can at least partially account for some differences between the component communities of metazoan parasites. In particular, the freezing of skates before parasite research can partly explain why we found far fewer platyhelminths such as cestodes and monogeneans than in previous surveys. Indeed, these soft-bodied helminths can be damaged or even destroyed by the ice crystals formed during freezing, in contrast to nematodes that are highly resistant to freezing due to their protective outer cuticle and were dominant in our study. However, despite research on defrosted skates and relatively low sampling size, our exploratory study revealed 16 new host – parasite associations in Rajidae from the English Channel and Celtic Sea, among them 10 involving nematodes (Table 2). In the case of L. fullonica, despite the lack of a specific parasitological study and other data on prevalences, at least 11 species among them eight platyhelminths were registered according to the online bibliographical database of Pollerspöck and Straube (2023) and Williams (1964), versus five in our study, among them four new records, i. e., the three nematode taxa (A. simplex, Phocanema spp., and Proleptus sp.) and an unidentified gill myxosporean. Concerning L. naevus, 19 species of metazoan parasites were listed by Pollerspöck and Straube (2023), and 14 parasite taxa of which eight platyhelminths occurred with a prevalence of 100 % in the 263 L. naevus studied by McVicar (1977) in British waters including the English Channel, whereas 47 % of our 14 specimens were infected by six taxa. Among them, only two cestodes, Echeneibothrium spp. and Grillotia erinaceus, were in common; A. simplex, previously considered accidental, was the most prevalent species in our study, and we recorded Phocanema spp. for the first time in L. naevus. Note that recent taxonomical studies by Bao et al. (2023) have resulted in the resurrection of the genus Phocanema, previously included in the genus Pseudoterranova. On the northwest coast of Spain, both Raja brachyura (60 individuals) and Raja microocellata (52) harbored 18 parasite taxa with prevalences up to 92 % and 96 %, respectively (Alvarez´et al., 2006), versus respectively three and seven taxa in R. brachyura (21 individuals) and R. microocellata (14) in our study in the northeast Atlantic with overall prevalences of 29 % and 93 %. Phocanema azarasi, Phocanema krabbei and an unidentified gill myxosporean were registered for the first time in R. microocellata; no new records occurred for R. brachyura. Note that 28 and 24 species of metazoan parasites, respectively, were listed in R. brachyura and R. microocellata by Pollerspöck and Straube (2023). Concerning Raja undulata, among the 17 parasite species enumerated by Pollerspöck and Straube (2023), 16 were recorded with a total prevalence of 99 % in 78 individuals from the northwest coast of Spain (Alvarez´et al., 2006; Sanmartín et al., 2000). Among them, only the cestode Onchobothrium spp. was found in our 14 R. undulata studied, of which 79 % were parasitized. In total, we detected six parasite taxa in R. undulata, including five new records, i. e., P. azarasi and P. krabbei, the cestodes Rockacestus sp. and Nybelinia spp., and an unidentified gill myxosporean. Parasite diversity was also higher in the six Spanish R. montagui studied by Alvarez´et al. (2006) harboring seven parasite taxa (prevalence not available), compared to our 21 specimens from the northeast Atlantic parasitized with a total prevalence of 19 % by three taxa, including the new record of Phocanema spp. According to Pollerspöck and Straube (2023), 22 species of metazoan parasites have been registered in R. montagui. For R. clavata, despite 71 parasite species listed by Pollerspöck and Straube (2023) (even if all of these are probably not valid), only four taxa were recorded in the 28 skates from the west coast of Ireland studied by Henderson and Dunne (1999) as in our 20 individuals. Proleptus sp. was the single parasite taxon recorded in both studies with respective prevalences of 21 % and 30 %. Interestingly, no cestodes occurred in Irish R. clavata (Henderson & Dunne, 1999), despite at least 27 species mentioned in the database of Pollerspöck and Straube (2023). In addition to Proleptus sp., we found two cestode species, Echeneibothrium spp. and Tritaphros retzii, in R. clavata, and A. simplex recorded for the first time. Notwithstanding the fact that we recorded 16 new host – parasite associations, the parasite communities we described in skates from the English Channel and Celtic Sea appeared depauperate. As previously evoked, this could be partially explained by the possible loss of soft-bodied helminths due to freezing and our lower sampling effort, but it could also reflect environmental changes over time, encompassing a potential decrease of free-living biodiversity affecting heteroxenous parasites such as trophically transmitted helminths (e. g., Hatcher et al., 2012; Hudson et al., 2006; Marcogliese, 2005; Timi & Poulin, 2020 for reviews). Intensive fishing can drive declines in fish parasite diversity, especially trophically transmitted parasites that require multiple host species, some of which are the top predators most sensitive to fishing impacts (Wood et al., 2014). In this way, MacKenzie & Pert (2018) showed evidence for the decline and possible extinction of a digenean parasite species caused by intensive fishing of the near-threatened Raja clavata, suggesting that the population size of the final host was below the threshold required for successful transmission of the parasite. Differences between parasite component communities can also originate from differences in sampling areas potentially inhabited by different intermediate, paratenic, and / or definitive host species, as observed for R. undulata between the continental shelf and the estuary of Muros – Noia in northwest Spain (Alvarez´et al., 2006; Sanmartín et al., 2000). Our record of 16 new host – parasite associations involving Rajidae may also result from modifications of both abiotic conditions and biocenoses in the context of global change. Indeed, water temperatures in the English Channel and Celtic Sea have increased 0.17 – 0.45 C per decade between 1985 and 2014, with consequences on free-living species from plankton to seabirds (Hughes et al., 2017; Lauria et al., 2013). Moreover, the occurrence of both Phocanema spp., the dominant parasite taxon of our study and firstly recorded in Rajidae (i. e., L. fullonica, L. naevus, R. microocellata, R. montagui, and R. undulata), and Rajidae Fish Decapods Other crustaceans Cephalopods Other mollusks Polychetes Leucoraja fullonica 65.46 22.15 6.82 Leucoraja naevus 45.57 20.31 19.17 Raja brachyura 34.32 25.58 35.13 Raja clavata 21.03 55.37 14.02 Raja microocellata 49.21 46.39 1.69 Raja montagui 6.17 65.11 17.83 Raja undulata 7.90 91.64 0	en	Gérard, Claudia, Trochard, Caroline, Hervé, Maxime R., Hamel, Héloïse, Gay, Mélanie, Barbier, Michel, Trancart, Thomas, Barreau, Thomas (2024): Communities of metazoan parasites in seven sympatric skate species (Elasmobranchii, Rajidae) from the English Channel and Celtic Sea differing in conservation status. Journal of Fish Biology 105 (3): 975-987, DOI: 10.1111/jfb.15845, URL: https://doi.org/10.1111/jfb.15845
