{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,4]],"date-time":"2026-05-04T05:31:04Z","timestamp":1777872664889,"version":"3.51.4"},"reference-count":58,"publisher":"Public Library of Science (PLoS)","issue":"4","license":[{"start":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T00:00:00Z","timestamp":1777507200000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100005835","name":"American Museum of Natural History","doi-asserted-by":"publisher","award":["N\/A"],"award-info":[{"award-number":["N\/A"]}],"id":[{"id":"10.13039\/100005835","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100017515","name":"Regis University","doi-asserted-by":"publisher","award":["URSC2025MJG"],"award-info":[{"award-number":["URSC2025MJG"]}],"id":[{"id":"10.13039\/100017515","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.plosone.org"],"crossmark-restriction":false},"short-container-title":["PLoS One"],"abstract":"<jats:p>\n                    Ponyfishes in the Family Leiognathidae uniquely possess a complex bioluminescent system with an esophageal light-producing organ containing bioluminescent bacterial symbionts, a reflective gas bladder, and transparent windows through adjacent tissues that allow light emission distant from the esophageal source to produce camouflaging counterillumination and, in some species, intraspecific communication and possibly illumination of prey. Despite having bacterial light production, a type of light production that in fishes is not known to be able to be rapidly initiated and terminated, researchers have observed many species of ponyfishes rapidly blinking. The tribe Equulitini is a well diagnosed clade of sexually dimorphic ponyfishes in which males have lateral transparent windows on the body, and males of one species,\n                    <jats:italic>Equulites elongatus,<\/jats:italic>\n                    were observed in the wild to blink rapidly through their lateral windows. This group allowed us to explore bioluminescent organ anatomy in a sexually dimorphic group and describe the morphology associated with blinking. In this study we used gross anatomical, histological, and radiological methods to investigate and describe the light organ-system of ponyfishes in the Tribe Equulitini. Although previously described generally, we provide the first detailed description of the internal structure of the bioluminescent light organ in Leiognathidae, identify the esophageal homologs of the light organ\u2019s tissues, and describe the novel mechanism for blinking. Blinking occurs when transparent longitudinal muscle that extends over the dorsal and ventral surfaces of the light organ contract or relax extending or retracting mucosal connective tissue shutters with respect to the light emitting transparent windows on the light organ. Although males have larger light organs and transparent lateral windows on their flanks, both males and females have a similar morphology and have structures consistent with the ability to blink. We also discuss variation in bioluminescent anatomy within Tribe Equulitini.\n                  <\/jats:p>","DOI":"10.1371\/journal.pone.0347687","type":"journal-article","created":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T17:43:35Z","timestamp":1777571015000},"page":"e0347687","update-policy":"https:\/\/doi.org\/10.1371\/journal.pone.corrections_policy","source":"Crossref","is-referenced-by-count":0,"title":["Morphology of the light-organ system and bioluminescent blinking in the ponyfish tribe Equulitini (Teleostei: Leiognathidae)"],"prefix":"10.1371","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-3240-6382","authenticated-orcid":true,"given":"Michael J.","family":"Ghedotti","sequence":"first","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jordon J.","family":"Valdez","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Rene P.","family":"Martin","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7985-863X","authenticated-orcid":true,"given":"Emily M.","family":"Carr","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"John S.","family":"Sparks","sequence":"additional","affiliation":[],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"340","published-online":{"date-parts":[[2026,4,30]]},"reference":[{"issue":"1","key":"pone.0347687.ref001","doi-asserted-by":"crossref","first-page":"23","DOI":"10.1002\/jez.1402270105","article-title":"Adaptations for reflection of bioluminescent light in the gas bladder of Leiognathus equulus (Perciformes: Leiognathidae)","volume":"227","author":"MJ McFall-Ngai","year":"1983","journal-title":"J Exp Zool"},{"issue":"3","key":"pone.0347687.ref002","doi-asserted-by":"crossref","first-page":"227","DOI":"10.1007\/BF00392247","article-title":"Three new modes of luminescence in the leiognathid fish Gazza minuta: Discrete projected luminescence, ventral body flash, and buccal luminescence","volume":"73","author":"MJ McFall-Ngai","year":"1983","journal-title":"Mar Biol"},{"issue":"4","key":"pone.0347687.ref003","first-page":"315","article-title":"Comparative morphology of light organ systems in ponyfishes (Leiognathidae)","volume":"36","author":"N Jayabalan","year":"1989","journal-title":"Indian J Fish"},{"key":"pone.0347687.ref004","volume-title":"The pony fish\u2019s glow: and other clues to plan and purpose in nature","author":"GC Williams","year":"1997"},{"issue":"2","key":"pone.0347687.ref005","doi-asserted-by":"crossref","first-page":"539","DOI":"10.1002\/jmor.1976.150.2.539","article-title":"The luminescent systems of ponyfishes","volume":"150","author":"Y Haneda","year":"1976","journal-title":"J Morphol"},{"issue":"2","key":"pone.0347687.ref006","doi-asserted-by":"crossref","first-page":"410","DOI":"10.2307\/1541286","article-title":"Physiological and morphological state of the symbiotic bacteria from light organs of ponyfish","volume":"167","author":"PV Dunlap","year":"1984","journal-title":"Biol Bull"},{"issue":"24","key":"pone.0347687.ref007","doi-asserted-by":"crossref","first-page":"7471","DOI":"10.1128\/AEM.01619-08","article-title":"Developmental and microbiological analysis of the inception of bioluminescent symbiosis in the marine fish Nuchequula nuchalis (Perciformes: Leiognathidae)","volume":"74","author":"PV Dunlap","year":"2008","journal-title":"Appl Environ Microbiol"},{"issue":"2","key":"pone.0347687.ref008","doi-asserted-by":"crossref","first-page":"324","DOI":"10.1111\/j.1574-6976.2010.00250.x","article-title":"Phylogeny, genomics, and symbiosis of Photobacterium","volume":"35","author":"H Urbanczyk","year":"2011","journal-title":"FEMS Microbiol Rev"},{"issue":"4001","key":"pone.0347687.ref009","doi-asserted-by":"crossref","first-page":"1016","DOI":"10.1126\/science.173.4001.1016","article-title":"Light to hide by: ventral luminescence to camouflage the silhouette","volume":"173","author":"JW Hastings","year":"1971","journal-title":"Science"},{"issue":"1","key":"pone.0347687.ref010","doi-asserted-by":"crossref","first-page":"71","DOI":"10.1002\/jmor.1051820105","article-title":"External and internal sexual dimorphism in leiognathid fishes: morphological evidence for sex-specific bioluminescent signaling","volume":"182","author":"MJ McFall-Ngai","year":"1984","journal-title":"J Morphol"},{"issue":"1","key":"pone.0347687.ref011","doi-asserted-by":"crossref","first-page":"119","DOI":"10.1242\/jeb.156.1.119","article-title":"Camouflage by disruptive illumination in leiognathids, a family of shallow-water, bioluminescent fishes","volume":"156","author":"MJ Mcfall-Ngai","year":"1991","journal-title":"J Exp Biol"},{"issue":"6","key":"pone.0347687.ref012","doi-asserted-by":"crossref","first-page":"704","DOI":"10.1002\/jmor.10941","article-title":"Evolution of the light organ system in ponyfishes (Teleostei: Leiognathidae)","volume":"272","author":"P Chakrabarty","year":"2011","journal-title":"J Morphol"},{"issue":"824","key":"pone.0347687.ref013","doi-asserted-by":"crossref","first-page":"285","DOI":"10.1098\/rstb.1970.0037","article-title":"Review lecture: on the organization of reflecting surfaces in some marine animals","volume":"258","author":"EJ Denton","year":"1970","journal-title":"Philos Trans R Soc Lond B Biol Sci"},{"key":"pone.0347687.ref014","doi-asserted-by":"crossref","first-page":"137","DOI":"10.14203\/mri.v19i0.377","article-title":"The leiognathidae (teleosts): an hypothesis relating their mean depth occurrence to the intensity of their countershading bioluminescence","volume":"19","author":"D Pauly","year":"1977","journal-title":"Mar Res Indones"},{"issue":"4","key":"pone.0347687.ref015","doi-asserted-by":"crossref","first-page":"305","DOI":"10.1111\/j.1096-0031.2005.00067.x","article-title":"Evolution and diversification of a sexually dimorphic luminescent system in ponyfishes (Teleostei: Leiognathidae), including diagnoses for two new genera","volume":"21","author":"JS Sparks","year":"2005","journal-title":"Cladistics"},{"issue":"4","key":"pone.0347687.ref016","doi-asserted-by":"crossref","first-page":"829","DOI":"10.1017\/S0025315407056433","article-title":"Sex with the lights on? A review of bioluminescent sexual dimorphism in the sea","volume":"87","author":"PJ Herring","year":"2007","journal-title":"J Mar Biol Assoc UK"},{"issue":"1","key":"pone.0347687.ref017","first-page":"118","article-title":"Biology of the silver-belly, Leiognathus bindus (Val.) of the Calicut coast","author":"V Balan","year":"1967","journal-title":"Indian J Fish"},{"issue":"6","key":"pone.0347687.ref018","doi-asserted-by":"crossref","first-page":"1009","DOI":"10.1007\/s00227-007-0869-8","article-title":"Synchronized development of gonad and bioluminescent light organ in a highly sexually dimorphic leiognathid fish, Photoplagios rivulatus","volume":"153","author":"K Ikejima","year":"2008","journal-title":"Mar Biol"},{"issue":"13","key":"pone.0347687.ref019","doi-asserted-by":"crossref","first-page":"2818","DOI":"10.1111\/j.1365-294X.2011.05112.x","article-title":"Is sexual selection driving diversification of the bioluminescent ponyfishes (Teleostei: Leiognathidae)?","volume":"20","author":"P Chakrabarty","year":"2011","journal-title":"Mol Ecol"},{"issue":"6","key":"pone.0347687.ref020","doi-asserted-by":"crossref","DOI":"10.1371\/journal.pone.0155154","article-title":"Repeated and widespread evolution of bioluminescence in marine fishes","volume":"11","author":"MP Davis","year":"2016","journal-title":"PLoS One"},{"issue":"1","key":"pone.0347687.ref021","first-page":"29","article-title":"On the luminescence of the fishes belonging to the family Leiognathidae of the tropical Pacific","volume":"2","author":"Y Haneda","year":"1940","journal-title":"Palao Trop Biol Stn Stud"},{"issue":"3","key":"pone.0347687.ref022","first-page":"214","article-title":"Luminous organs of fish which emit light indirectly","volume":"4","author":"Y Haneda","year":"1950","journal-title":"Pac Sci"},{"issue":"2","key":"pone.0347687.ref023","doi-asserted-by":"crossref","first-page":"159","DOI":"10.1071\/MF01157","article-title":"A synchronized rhythmic flashing light display by schooling Leiognathus splendens (Leiognathidae\u00a0: Perciformes)","volume":"53","author":"DJ Woodland","year":"2002","journal-title":"Mar Freshw Res"},{"issue":"4","key":"pone.0347687.ref024","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1023\/A:1023959123422","article-title":"Field evidence for bioluminescent signaling in the pony fish, Leiognathus elongatus","volume":"66","author":"A Sasaki","year":"2003","journal-title":"Environ Biol Fish"},{"key":"pone.0347687.ref025","first-page":"7","article-title":"The luminous organs of two species of leiognathid fishes recently found in Ambon, Indonesia","volume":"19","author":"Y Haneda","year":"1972","journal-title":"Sci Rep Yokosuka City Mus"},{"issue":"1","key":"pone.0347687.ref026","doi-asserted-by":"crossref","first-page":"79","DOI":"10.6024\/jmbai.2019.61.1.2081-12","article-title":"Role of bioluminescent organ in Photopectoralis bindus (Valenciennes, 1835) (Family: Leiognathidae) from Kerala Coast","volume":"61","author":"H Sebastian","year":"2024","journal-title":"J Mar Biol Assoc India"},{"key":"pone.0347687.ref027","first-page":"157","article-title":"Bau und Entwicklung eines Eigenartigen Leuchtorgan by Equula spec","volume":"131","author":"JW Harms","year":"1928","journal-title":"Z wiss Zool"},{"key":"pone.0347687.ref028","first-page":"90","article-title":"Untersuchungen am Leuchtorgan Von Leiognathus klunzingeri (Steindachner)","volume":"173","author":"G Ahrens","year":"1965","journal-title":"Z Angew Zool"},{"key":"pone.0347687.ref029","first-page":"415","article-title":"Family Leiognathidae, Ponyfishes or Slipmouths.","volume-title":"Coastal fishes of the western Indian Ocean. Vol 3","author":"P Chakrabarty","year":"2022"},{"issue":"2","key":"pone.0347687.ref030","doi-asserted-by":"crossref","first-page":"213","DOI":"10.1007\/s10228-023-00935-z","article-title":"Taxonomic revision of the genus Equulites Fowler 1904 (Acanthuriformes: Leiognathidae)","volume":"71","author":"H Suzuki","year":"2024","journal-title":"Ichthyol Res"},{"key":"pone.0347687.ref031","article-title":"FishBase [Internet]","author":"R Froese","journal-title":"World Wide Web electronic publication"},{"issue":"2","key":"pone.0347687.ref032","doi-asserted-by":"crossref","first-page":"805","DOI":"10.1007\/s11160-025-09935-w","article-title":"Phylogeny, biology, and evolution of acanthopterygian fish clades","volume":"35","author":"CE Thacker","year":"2025","journal-title":"Rev Fish Biol Fish"},{"issue":"2","key":"pone.0347687.ref033","doi-asserted-by":"crossref","first-page":"298","DOI":"10.11646\/zootaxa.3964.2.10","article-title":"Formalizing the names of subfamilies and tribes of ponyfishes (Leiognathidae Gill 1893)","volume":"3964","author":"P Chakrabarty","year":"2015","journal-title":"Zootaxa"},{"issue":"3","key":"pone.0347687.ref034","doi-asserted-by":"crossref","first-page":"622","DOI":"10.1643\/0045-8511(2007)2007[622:ANSOPT]2.0.CO;2","article-title":"A new species of ponyfish (Teleostei: Leiognathidae: Photoplagios) from the Philippines","volume":"2007","author":"JS Sparks","year":"2007","journal-title":"Copeia"},{"issue":"2","key":"pone.0347687.ref035","doi-asserted-by":"crossref","first-page":"181","DOI":"10.11646\/zootaxa.3947.2.2","article-title":"Description of a new genus of ponyfishes (Teleostei: Leiognathidae), with a review of the current generic-level composition of the family","volume":"3947","author":"JS Sparks","year":"2015","journal-title":"Zootaxa"},{"issue":"4","key":"pone.0347687.ref036","doi-asserted-by":"crossref","first-page":"884","DOI":"10.2307\/1445333","article-title":"Leiognathus elongatus (Perciformes: Leiognathidae): two distinct species based on morphological and light organ characters","volume":"1984","author":"PV Dunlap","year":"1984","journal-title":"Copeia"},{"issue":"3929","key":"pone.0347687.ref037","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1206\/3929.1","article-title":"Description of a New Species of Ponyfish (Teleostei: Leiognathidae: Equulitini: Photolateralis) from the Gulf of Oman","volume":"2019","author":"JS Sparks","year":"2019","journal-title":"Am Mus Novit"},{"key":"pone.0347687.ref038","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1206\/0003-0082(2004)459<0001:ACONDP>2.0.CO;2","article-title":"A clade of non-sexually dimorphic ponyfishes (Teleostei: Perciformes: Leiognathidae): phylogeny, taxonomy, and description of a new species","volume":"3459","author":"JS Sparks","year":"2004","journal-title":"Am Mus Novit"},{"key":"pone.0347687.ref039","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1206\/0003-0082(2006)3526[1:ANSOPT]2.0.CO;2","article-title":"A new species of ponyfish (Teleostei: Leiognathidae: Photoplagios) from Madagascar, with a phylogeny for Photoplagios and comments on the status of Equula lineolata Valenciennes","volume":"3526","author":"JS Sparks","year":"2006","journal-title":"Am Mus Novit"},{"issue":"3","key":"pone.0347687.ref040","doi-asserted-by":"crossref","first-page":"593","DOI":"10.1643\/ASIHCODONS2020","article-title":"Codes for natural history collections in Ichthyology and Herpetology","volume":"108","author":"MH Sabaj","year":"2020","journal-title":"Copeia"},{"key":"pone.0347687.ref041","article-title":"Codes for natural history collections in Ichthyology and Herpetology (online supplement). Version 9.7 (3 Mar 2025)","author":"MH Sabaj","journal-title":"Washington (DC): American Society of Ichthyologists and Herpetologists"},{"key":"pone.0347687.ref042","volume-title":"Animal tissue techniques","author":"GL Humason","year":"1979","edition":"4"},{"key":"pone.0347687.ref043","volume-title":"Theory and practice of histological techniques","author":"J Bancroft","year":"1982","edition":"2"},{"key":"pone.0347687.ref044","volume-title":"Theory and practice of histotechnology","author":"D Sheehan","year":"1980","edition":"2"},{"issue":"3","key":"pone.0347687.ref045","doi-asserted-by":"crossref","first-page":"370","DOI":"10.1177\/1947603518764262","article-title":"A standardized method of applying toluidine blue metachromatic staining for assessment of chondrogenesis","volume":"10","author":"NL Bergholt","year":"2019","journal-title":"Cartilage"},{"key":"pone.0347687.ref046","unstructured":"The GIMP Development Team. GIMP: GNU Image Manipulation Program. [Free Computer Software] Berkeley: GNU Project. Version 3.0.4. 2025. Available from: https:\/\/www.gimp.org\/"},{"issue":"6","key":"pone.0347687.ref047","doi-asserted-by":"crossref","first-page":"889","DOI":"10.1111\/joa.12449","article-title":"Diffusible iodine-based contrast-enhanced computed tomography (diceCT): an emerging tool for rapid, high-resolution, 3-D imaging of metazoan soft tissues","volume":"228","author":"PM Gignac","year":"2016","journal-title":"J Anat"},{"issue":"4","key":"pone.0347687.ref048","doi-asserted-by":"crossref","first-page":"893","DOI":"10.1111\/jfb.15320","article-title":"DiceCT for fishes: recommendations for pairing iodine contrast agents with \u03bcCT to visualize soft tissues in fishes","volume":"102","author":"MA Kolmann","year":"2023","journal-title":"J Fish Biol"},{"issue":"1","key":"pone.0347687.ref049","article-title":"The diffusion diaries: diffusible iodine-based contrast-enhanced computed tomography for vertebrate natural history specimens","volume":"7","author":"JA Gray","year":"2025","journal-title":"Integr Org Biol"},{"key":"pone.0347687.ref050","volume-title":"ImageJ (Version 1.54r)","author":"C Schneider","year":"2023"},{"issue":"9","key":"pone.0347687.ref051","doi-asserted-by":"crossref","first-page":"1323","DOI":"10.1016\/j.mri.2012.05.001","article-title":"3D Slicer as an image computing platform for the Quantitative Imaging Network","volume":"30","author":"A Fedorov","year":"2012","journal-title":"Magn Reson Imaging"},{"key":"pone.0347687.ref052","unstructured":"3D Slicer Community. 3D Slicer. [Free Computer Software] Boston: Kitware Inc. Version 5.8.1; 2024. Available from: https:\/\/www.slicer.org\/"},{"key":"pone.0347687.ref053","unstructured":"Inkscape Project. Inkscape. [Free Computer Software] New York: Software Freedom Conservancy. Version 1.4; 2025. Available from: https:\/\/inkscape.org"},{"issue":"1050","key":"pone.0347687.ref054","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1098\/rspb.1971.0051","article-title":"Mechanism of reflexion in silvery layers of fish and cephalopods","volume":"178","author":"EJ Denton","year":"1971","journal-title":"Proc R Soc Lond B Biol Sci"},{"issue":"2","key":"pone.0347687.ref055","doi-asserted-by":"crossref","first-page":"507","DOI":"10.1021\/cg0704753","article-title":"Biogenic guanine crystals from the skin of fish may be designed to enhance light reflectance","volume":"8","author":"A Levy-Lior","year":"2008","journal-title":"Cryst Growth Des"},{"issue":"1","key":"pone.0347687.ref056","doi-asserted-by":"crossref","first-page":"65","DOI":"10.1111\/j.1096-3642.1988.tb00882.x","article-title":"Mechanisms of light organ occlusion in flashlight fishes, family Anomalopidae (Teleostei: Beryciformes), and the evolution of the group","volume":"94","author":"GD Johnson","year":"1988","journal-title":"Zool J Linn Soc"},{"key":"pone.0347687.ref057","doi-asserted-by":"crossref","first-page":"545217","DOI":"10.3389\/fmars.2021.545217","article-title":"Digestive tract and the muscular pharynx\/esophagus in wild leptocephalus larvae of European eel (Anguilla anguilla)","volume":"8","author":"HR Knutsen","year":"2021","journal-title":"Front Mar Sci"},{"issue":"1","key":"pone.0347687.ref058","doi-asserted-by":"crossref","first-page":"8","DOI":"10.1007\/s10388-015-0497-1","article-title":"Structure and motility of the esophagus from a mechanical perspective","volume":"13","author":"M Mir","year":"2015","journal-title":"Esophagus"}],"container-title":["PLOS One"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0347687","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,30]],"date-time":"2026-04-30T17:43:45Z","timestamp":1777571025000},"score":1,"resource":{"primary":{"URL":"https:\/\/dx.plos.org\/10.1371\/journal.pone.0347687"}},"subtitle":[],"editor":[{"given":"Caio Santos","family":"Nogueira","sequence":"first","affiliation":[],"role":[{"role":"editor","vocabulary":"crossref"}]}],"short-title":[],"issued":{"date-parts":[[2026,4,30]]},"references-count":58,"journal-issue":{"issue":"4","published-online":{"date-parts":[[2026,4,30]]}},"URL":"https:\/\/doi.org\/10.1371\/journal.pone.0347687","relation":{},"ISSN":["1932-6203"],"issn-type":[{"value":"1932-6203","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,30]]}}}