{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,17]],"date-time":"2026-09-17T15:32:05Z","timestamp":1789659125752,"version":"4.0.1"},"reference-count":46,"publisher":"PeerJ","license":[{"start":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T00:00:00Z","timestamp":1789516800000},"content-version":"unspecified","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"DFG","award":["PR626\/10-1"],"award-info":[{"award-number":["PR626\/10-1"]}]},{"name":"DFG","award":["RO5508\/2-1"],"award-info":[{"award-number":["RO5508\/2-1"]}]},{"name":"CONARE-DFG","award":["FS-DFG-01-2022"],"award-info":[{"award-number":["FS-DFG-01-2022"]}]},{"name":"The Vicerrectory for Research of the University of Costa Rica","award":["809-C2-654"],"award-info":[{"award-number":["809-C2-654"]}],"id":[{"id":"https:\/\/ror.org\/02yzgww51","id-type":"ROR","asserted-by":"crossref"}]},{"name":"Sistema Nacional de Investigaci\u00f3n"},{"name":"The Panama Amphibian Rescue and Conservation Project"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":[],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>\n                      Colour polymorphism in aposematic species is often associated with ecological divergence and predator selection. In amphibians, colouration is achieved through the chromatophore unit, a layered structure of pigment-containing cells (xanthophores, melanophores) and structural cells (iridophores) that interact to produce the final skin colouration. In dendrobatid frogs of the genus\n                      <jats:italic>Oophaga<\/jats:italic>\n                      , striking red and green morphs coexist within and across species, yet the cellular mechanisms underlying this variation remain poorly understood.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      We investigated the histological basis of colouration in three\n                      <jats:italic>Oophaga<\/jats:italic>\n                      species (\n                      <jats:italic>O. granulifera<\/jats:italic>\n                      ,\n                      <jats:italic>O. pumilio<\/jats:italic>\n                      , and\n                      <jats:italic>O. vicentei<\/jats:italic>\n                      ) by comparing chromatophore layer structure in red and green morphs and correlating these traits with spectrometric colour measurements. While all species have a chromatophore unit of xanthophores, iridophores, and melanophores, we observed interspecific and intraspecific variation in the organization, thickness, and relative area of these layers.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      In\n                      <jats:italic>O. pumilio<\/jats:italic>\n                      and\n                      <jats:italic>O. vicentei<\/jats:italic>\n                      , red morphs consistently exhibited greater xanthophore and iridophore coverage and more xanthophore contribution. In contrast,\n                      <jats:italic>O. granulifera<\/jats:italic>\n                      displayed minimal differences between morphs and a more disorganized chromatophore unit, however melanosome size was larger for green morphs. Spectral reflectance measurements correlated significantly with chromatophore traits, supporting a link between skin histology and colour phenotype. These findings suggest that colouration in\n                      <jats:italic>Oophaga<\/jats:italic>\n                      arises from less conserved chromatophore unit structure, reflecting diverse evolutionary routes to equivalent colouration.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.7717\/peerj.21696","type":"journal-article","created":{"date-parts":[[2026,9,16]],"date-time":"2026-09-16T08:20:21Z","timestamp":1789546821000},"page":"e21696","source":"Crossref","is-referenced-by-count":0,"title":["Frogs have layers: a comparative histological study of colour polymorphism in\n                    <i>Oophaga<\/i>\n                    poison frogs"],"prefix":"10.7717","volume":"14","author":[{"given":"Vasiliki","family":"Mantzana Oikonomaki","sequence":"first","affiliation":[{"name":"Institute of Zoology, Tier\u00e4rztliche Hochschule Hannover, Hannover, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mats Johannes","family":"Wiborg","sequence":"additional","affiliation":[{"name":"Institute of Zoology, Tier\u00e4rztliche Hochschule Hannover, Hannover, Germany"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Giselle","family":"Tamayo-Castillo","sequence":"additional","affiliation":[{"name":"Centro de Investigaciones en Productos Naturales (CIPRONA) & Escuela de Qu\u00edmica, Universidad de Costa Rica, San Jose, Costa Rica"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roberto","family":"Ib\u00e1\u00f1ez","sequence":"additional","affiliation":[{"name":"Smithsonian Tropical Research Institute, Panama, Panama"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ariel","family":"Rodr\u00edguez","sequence":"additional","affiliation":[{"name":"Institute of Zoology, Tier\u00e4rztliche Hochschule Hannover, Hannover, 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