{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,9]],"date-time":"2026-05-09T00:09:35Z","timestamp":1778285375053,"version":"3.51.4"},"reference-count":44,"publisher":"Public Library of Science (PLoS)","issue":"5","license":[{"start":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T00:00:00Z","timestamp":1778198400000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:sec id=\"sec001\">\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Didymozoid trematodes represent poorly understood parasites of marine fish worldwide, with significant knowledge gaps in the Arabian Gulf region. The taxonomic identification of didymozoids from novel anatomical sites requires integrated morphological and molecular approaches to resolve species boundaries and phylogenetic relationships.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec002\">\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      We examined 2,530 fish specimens from nine\n                      <jats:italic>Epinephelus<\/jats:italic>\n                      species collected from Arabian Gulf waters (Saudi Arabia). Parasitological, histopathological, and ultrastructural analyses were combined with molecular characterization using 28S rDNA sequences. Phylogenetic relationships were inferred using Maximum Likelihood analysis with 1,000 bootstrap replicates.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec003\">\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      52 of 500\n                      <jats:italic>Epinephelus coioides<\/jats:italic>\n                      (10.4%) harbored distinctive golden-yellow cysts located solely in nasal cavities. No infections were found in other grouper species or anatomical sites. Histopathology revealed multiple cysts containing the didymozoid parasites, with characteristic numerous eggs; and the cysts were surrounded by thin layer of fibrous connective tissue capsule with mild host inflammatory response. Ultrastructural examination demonstrated characteristic didymozoid features including bean-shaped eggs and specialized tegument structures. Molecular analysis of four seasonal isolates yielded two haplotypes (99.81% similarity) with 1,042 nucleotide sequences deposited as GenBank accessions PQ736510-PQ736513. Phylogenetic analysis confirmed placement within\n                      <jats:italic>Didymodiclinus<\/jats:italic>\n                      (Didymozoidae), showing 99.52% sequence homology with\n                      <jats:italic>Didymodiclininae<\/jats:italic>\n                      sp. from the same host species.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec id=\"sec004\">\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>\n                      This study provides the first morphological, molecular, and histopathological characterization of nasal cavity didymozoids in\n                      <jats:italic>E. coioides<\/jats:italic>\n                      from Saudi Arabian waters of the Arabian Gulf. The infections were restricted to\n                      <jats:italic>E. coioides<\/jats:italic>\n                      among nine grouper species examined and occurred only in nasal cavities, demonstrating remarkable host and anatomical site specificity. These findings provide baseline data for\n                      <jats:italic>didymozoid<\/jats:italic>\n                      ecology in Arabian Gulf waters.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.1371\/journal.pone.0343608","type":"journal-article","created":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T23:10:37Z","timestamp":1778281837000},"page":"e0343608","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Morphological, molecular, and pathological characterization of didymozoid trematode infection in the nasal cavity of orange-spotted grouper (Epinephelus coioides) from Arabian Gulf waters"],"prefix":"10.1371","volume":"21","author":[{"given":"Mohsen A.","family":"Khormi","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mohamed","family":"Abdelsalam","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hanadi B.","family":"Baghdadi","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mustafa M.","family":"Ibrahim","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-9385-2549","authenticated-orcid":true,"given":"Mahmoud A.","family":"Mahmoud","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1383-4851","authenticated-orcid":true,"given":"Marwa M.","family":"Attia","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2026,5,8]]},"reference":[{"key":"pone.0343608.ref001","first-page":"67","article-title":"Trematodes Didymozoidae fauna, distribution and biology","volume-title":"Parasitology and pathology of marine organisms of the world ocean","author":"VM. Nikolaeva","year":"1985"},{"key":"pone.0343608.ref002","first-page":"631","article-title":"Family Didymozoidae Monticelli, 1888","author":"SE Pozdnyakov","year":"2008","journal-title":"Keys to the Trematoda. CABI"},{"issue":"5","key":"pone.0343608.ref003","doi-asserted-by":"crossref","first-page":"475","DOI":"10.1007\/s11259-006-3207-6","article-title":"Histopathology of five species of Didymocystis spp. (Digenea: Didymozoidae) in cage-reared Atlantic bluefin tuna (Thunnus thynnus thynnus)","volume":"30","author":"I Mladineo","year":"2006","journal-title":"Vet Res Commun"},{"issue":"4","key":"pone.0343608.ref004","doi-asserted-by":"crossref","first-page":"187","DOI":"10.1046\/j.1365-2761.2003.00454.x","article-title":"Diseases of tunas, Thunnus spp","volume":"26","author":"BL Munday","year":"2003","journal-title":"J Fish Dis"},{"key":"pone.0343608.ref005","first-page":"153","article-title":"Gonapodasmius williamsoni sp. n. (Digenea: Didymozoidae) from the pink snapper, Pagrus auratus (Teleostei: Sparidae) in western Australia","volume":"59","author":"TH Cribb","year":"1992","journal-title":"Journal of Helminthological Society of Washington"},{"issue":"7","key":"pone.0343608.ref006","doi-asserted-by":"crossref","first-page":"407","DOI":"10.1016\/j.ijpara.2021.11.012","article-title":"First elucidation of a didymozoid life cycle: Saccularina magnacetabula n. gen. n. sp. infecting an arcid bivalve","volume":"52","author":"C Louvard","year":"2022","journal-title":"Int J Parasitol"},{"issue":"2","key":"pone.0343608.ref007","doi-asserted-by":"crossref","first-page":"87","DOI":"10.1023\/A:1006024128098","article-title":"Inference of phylogeny and taxonomy within the Didymozoidae (Digenea) from the second internal transcribed spacer (ITS2) of ribosomal DNA","volume":"41","author":"GR Anderson","year":"1998","journal-title":"Syst Parasitol"},{"issue":"6","key":"pone.0343608.ref008","doi-asserted-by":"crossref","first-page":"1013","DOI":"10.1017\/S0031182009991703","article-title":"Multilocus phylogenetic analyses reveal that habitat selection drives the speciation of Didymozoidae (Digenea) parasitizing Pacific and Atlantic bluefin tunas","volume":"137","author":"I Mladineo","year":"2010","journal-title":"Parasitology"},{"issue":"7","key":"pone.0343608.ref009","first-page":"733","article-title":"Phylogeny and classification of the Digenea (Platyhelminthes: Trematoda)","volume":"33","author":"PD Olson","year":"2003","journal-title":"Int J Parasitol"},{"issue":"1","key":"pone.0343608.ref010","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1023\/A:1025546001611","article-title":"Molecular phylogenetic analysis of the Microphalloidea Ward, 1901 (Trematoda: Digenea)","volume":"56","author":"VV Tkach","year":"2003","journal-title":"Syst Parasitol"},{"issue":"3","key":"pone.0343608.ref011","doi-asserted-by":"crossref","first-page":"221","DOI":"10.1006\/mpev.1994.1024","article-title":"Molecular phylogenetics of cupped oysters based on partial 28S rRNA gene sequences","volume":"3","author":"DT Littlewood","year":"1994","journal-title":"Mol Phylogenet Evol"},{"issue":"4","key":"pone.0343608.ref012","doi-asserted-by":"crossref","first-page":"359","DOI":"10.3390\/pathogens14040359","article-title":"Integrative Taxonomy of Didymozoids Parasitizing Thunnus obesus (Scombridae) from Southwest Atlantic Ocean: A New Genus and Species","volume":"14","author":"YC Meneses","year":"2025","journal-title":"Pathogens"},{"issue":"1","key":"pone.0343608.ref013","doi-asserted-by":"crossref","first-page":"161","DOI":"10.32360\/acmar.v55i1.44427","article-title":"NEW GEOGRAPHIC OCCURRENCE: DIGENEA Lobatozoum multisacculatum (DIDYMOZOIDAE) ON LITTLE TUNNY, Euthynnus alletteratus (SCOMBRIDAE)","volume":"55","author":"CG Da Silva","year":"2022","journal-title":"ACMAR"},{"issue":"3","key":"pone.0343608.ref014","doi-asserted-by":"crossref","first-page":"297","DOI":"10.1645\/15-772","article-title":"Novel infection site and ecology of cryptic Didymocystis sp. (Trematoda) in the fish Scomberomorus maculatus","volume":"102","author":"MN Schrandt","year":"2016","journal-title":"The Journal of Parasitology"},{"key":"pone.0343608.ref015","first-page":"1","article-title":"Digenetic trematodes of marine fishes from the Kuwaiti coast of the Arabian Gulf","volume":"3","author":"FY Al-Yamani","year":"1981","journal-title":"Kuwait Bulletin of Marine Science"},{"key":"pone.0343608.ref016","first-page":"231","article-title":"Helminth parasites of fishes from the Arabian Gulf. 2. The digenetic trematode genera Hamacreadium Linton, 1910 and Cainocreadium Nicoll, 1909","volume":"6","author":"MFA Saoud","year":"1986","journal-title":"Qatar University Science Bulletin"},{"issue":"1","key":"pone.0343608.ref017","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0295668","article-title":"First report of Kudoa species (Myxozoa, Multivalvulida) infection in purple-spotted Bigeye (Priacanthus tayenus) from the Saudi Arabian Gulf","volume":"19","author":"MM Ibrahim","year":"2024","journal-title":"PLoS One"},{"issue":"1","key":"pone.0343608.ref018","doi-asserted-by":"crossref","first-page":"332","DOI":"10.1186\/s12917-024-04156-y","article-title":"Dasyrhynchus giganteus plerocercoids encysting in the musculature of Indian halibut (Psettodes erumei): seasonal prevalence, morpho-molecular characterization, and histopathological alterations","volume":"20","author":"MM Ibrahim","year":"2024","journal-title":"BMC Vet Res"},{"issue":"2","key":"pone.0343608.ref019","doi-asserted-by":"crossref","first-page":"67","DOI":"10.1007\/BF00009792","article-title":"Gonapodasmius epinepheli n. sp. (Didymozoidae) from the grouper Epinephelus tauvina from the Arabian Gulf","volume":"17","author":"J Abdul-Salam","year":"1990","journal-title":"Syst Parasitol"},{"key":"pone.0343608.ref020","unstructured":"Abdul-Salam J, Khalil LF. The helminth parasites of the grouper Epinephelus tauvina in the Arabian Gulf. Abstracts of Spring Meeting of the British Society for Parasitology, Edinburgh University, 25-27 1987:31\u20132."},{"issue":"1","key":"pone.0343608.ref021","doi-asserted-by":"crossref","first-page":"249","DOI":"10.1007\/s10499-022-00978-5","article-title":"Studies on endoparasitic copepods: Sarcotaces arcticus (Copepoda: Phylichthyid) infested dotted grouper (Epinephelus epilistictus) from the Arabian Gulf water, Saudi Arabia","volume":"31","author":"MM Ibrahim","year":"2022","journal-title":"Aquacult Int"},{"issue":"4","key":"pone.0343608.ref022","doi-asserted-by":"crossref","first-page":"980","DOI":"10.1007\/s12639-021-01394-x","article-title":"Morphological and pathological appraisal of Huffmanela sp. (Nematoda: Trichosomoididae) infecting orange-spotted grouper (Epinephelus coioides, Hamilton, 1822) at Jubail Province, Saudi Arabia: A case report","volume":"45","author":"MM Attia","year":"2021","journal-title":"Journal of Parasitic Diseases"},{"issue":"4","key":"pone.0343608.ref023","doi-asserted-by":"crossref","first-page":"987","DOI":"10.1093\/icesjms\/fsz006","article-title":"Comparative analysis of life history traits and trends of abundance in coral reefs of the orange-spotted grouper (Epinephelus coioides) from two regions of the Arabian Gulf","volume":"76","author":"Y-J Lin","year":"2019","journal-title":"ICES Journal of Marine Science"},{"issue":"3","key":"pone.0343608.ref024","doi-asserted-by":"crossref","first-page":"1779","DOI":"10.1016\/j.sjbs.2020.12.020","article-title":"Assessment of genetic diversity and phylogenetic relationship among grouper species Epinephelus spp. from the Saudi waters of the Arabian Gulf","volume":"28","author":"HA Hassanien","year":"2021","journal-title":"Saudi J Biol Sci"},{"key":"pone.0343608.ref025","article-title":"The trematodes of groupers (Serranidae: Epinephelinae): knowledge, nature and evolution","author":"TH Cribb","year":"2002","journal-title":"Parasitology"},{"issue":"1","key":"pone.0343608.ref026","doi-asserted-by":"crossref","first-page":"86","DOI":"10.1017\/S0022149X1300062X","article-title":"Parasites of the grouper fish Epinephelus coioides (Serranidae) as potential environmental indicators in Indonesian coastal ecosystems","volume":"89","author":"S Kleinertz","year":"2015","journal-title":"J Helminthol"},{"issue":"3","key":"pone.0343608.ref027","doi-asserted-by":"crossref","first-page":"407","DOI":"10.1111\/j.1095-8312.2005.00503.x","article-title":"Towards integrative taxonomy","volume":"85","author":"B Dayrat","year":"2005","journal-title":"Biological Journal of the Linnean Society"},{"issue":"2","key":"pone.0343608.ref028","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1016\/j.jare.2015.07.004","article-title":"Morphological, molecular and pathological appraisal of Callitetrarhynchus gracilis plerocerci (Lacistorhynchidae) infecting Atlantic little tunny (Euthynnus alletteratus) in Southeastern Mediterranean","volume":"7","author":"M Abdelsalam","year":"2016","journal-title":"Journal of Advanced Research"},{"key":"pone.0343608.ref029","doi-asserted-by":"crossref","first-page":"119","DOI":"10.3354\/dao018119","article-title":"Light and electron microscopic study of the pathology of a species of didymozoid (Trematoda, Digenea) infecting the gill arches of Scomber australasicus (Teleostei, Scombridae)","volume":"18","author":"K Perera","year":"1994","journal-title":"Dis Aquat Org"},{"issue":"2","key":"pone.0343608.ref030","doi-asserted-by":"crossref","first-page":"207","DOI":"10.1590\/S0074-02762008000200014","article-title":"First record in South America of Didymosulcus palati and Didymosulcus philobranchiarca (Digenea, Didymozoidae) with new hosts records and pathological alterations","volume":"103","author":"MCN Justo","year":"2008","journal-title":"Mem Inst Oswaldo Cruz"},{"issue":"1","key":"pone.0343608.ref031","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1007\/s11230-010-9229-z","article-title":"Gut wash, body soak, blender and heat-fixation: approaches to the effective collection, fixation and preservation of trematodes of fishes","volume":"76","author":"TH Cribb","year":"2010","journal-title":"Syst Parasitol"},{"key":"pone.0343608.ref032","volume-title":"Theory and Practice of Histological Techniques","author":"JD Bancroft","year":"2008","edition":"6"},{"issue":"4","key":"pone.0343608.ref033","doi-asserted-by":"crossref","first-page":"1219","DOI":"10.1007\/s00436-020-06939-2","article-title":"Hemiuroidean trematodes from freshwater Patagonian fishes: Description of a new species, distribution and molecular phylogeny","volume":"120","author":"K Tsuchida","year":"2021","journal-title":"Parasitol Res"},{"key":"pone.0343608.ref034","doi-asserted-by":"crossref","first-page":"473","DOI":"10.1017\/S0031182003002993","article-title":"Parasite specialization from a phylogenetic perspective: A new index of host specificity","volume":"126","author":"R Poulin","year":"2003","journal-title":"Parasitology"},{"key":"pone.0343608.ref035","first-page":"325","article-title":"Aquatic Parasite Conservation","author":"M Truter","year":"2025","journal-title":"Aquatic Parasitology: Ecological and Environmental Concepts and Implications of Marine and Freshwater Parasites. Cham: Springer Nature Switzerland"},{"key":"pone.0343608.ref036","first-page":"547","article-title":"Climate Change and Parasitism in Aquatic Ecosystems","author":"DJ Marcogliese","year":"2025","journal-title":"Aquatic Parasitology: Ecological and Environmental Concepts and Implications of Marine and Freshwater Parasites. Cham: Springer Nature Switzerland"},{"issue":"2","key":"pone.0343608.ref037","first-page":"467","article-title":"The impact of climate change on the parasites and infectious diseases of aquatic animals","volume":"27","author":"DJ Marcogliese","year":"2008","journal-title":"Rev Sci Tech"},{"key":"pone.0343608.ref038","first-page":"463","article-title":"Seasonal dynamics of the cercarial and metacercarial stages of the microphallid trematode Maritrema eroliae (Digenea: Microphallidae)","volume":"53","author":"MA Al-Kandari","year":"2007","journal-title":"Acta Zoologica Sinica"},{"issue":"9","key":"pone.0343608.ref039","doi-asserted-by":"crossref","first-page":"1219","DOI":"10.1017\/S0031182022000762","article-title":"Morphological and molecular study of Didymodiclinus marginati n. sp. (Trematoda: Didymozoidae) gill parasite of Epinephelus marginatus from the central and western Mediterranean Sea","volume":"149","author":"S Mele","year":"2022","journal-title":"Parasitology"},{"issue":"9","key":"pone.0343608.ref040","doi-asserted-by":"crossref","first-page":"1385","DOI":"10.1111\/jfd.12836","article-title":"Ecological and histopathological aspects of Didymodiclinus sp. (Trematoda: Didymozoidae) parasite of the dusky grouper, Epinephelus marginatus (Osteichthyes: Serranidae), from the western Mediterranean Sea","volume":"41","author":"M Polinas","year":"2018","journal-title":"J Fish Dis"},{"issue":"11","key":"pone.0343608.ref041","doi-asserted-by":"crossref","first-page":"1422","DOI":"10.1017\/S0031182015000839","article-title":"Cross-fertilization as a reproductive strategy in a tissue flukes Didymosulcus katsuwonicola (Platyhelmintes: Didymozoidae) inferred by genetic analysis","volume":"142","author":"I Mladineo","year":"2015","journal-title":"Parasitology"},{"issue":"3","key":"pone.0343608.ref042","doi-asserted-by":"crossref","first-page":"641","DOI":"10.1007\/s00436-008-1025-1","article-title":"Ultrastructure of Didymocystis semiglobularis (Didymozoidae, Digenea) cysts in the gills of Pacific bluefin tuna (Thunnus orientalis)","volume":"103","author":"A Di Maio","year":"2008","journal-title":"Parasitol Res"},{"key":"pone.0343608.ref043","article-title":"New host records and new geographic distribution of Didymozoidae (Trematoda), parasites of Thunnus obesus (Scombridae)","volume":"90","author":"AM Moreira-Silva","year":"2019","journal-title":"RevMexBiodiv"},{"key":"pone.0343608.ref044","doi-asserted-by":"crossref","first-page":"4425","DOI":"10.1111\/are.15281","article-title":"Morphomolecular identification of two trichodinid coinfections (Ciliophora: Trichodinidae) and their immunological impacts on farmed Nile Tilapia","volume":"52","author":"MM Attia","year":"2021","journal-title":"Aquaculture Research"}],"container-title":["PLOS One"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0343608","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,5,8]],"date-time":"2026-05-08T23:10:47Z","timestamp":1778281847000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0343608"}},"subtitle":[],"editor":[{"given":"Tzong-Yueh","family":"Chen","sequence":"first","affiliation":[],"role":[{"role":"editor","vocabulary":"crossref"}]}],"short-title":[],"issued":{"date-parts":[[2026,5,8]]},"references-count":44,"journal-issue":{"issue":"5","published-online":{"date-parts":[[2026,5,8]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0343608","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,5,8]]}}}