{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T10:29:08Z","timestamp":1771237748134,"version":"3.50.1"},"reference-count":26,"publisher":"Wiley","license":[{"start":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T00:00:00Z","timestamp":1771200000000},"content-version":"vor","delay-in-days":0,"URL":"http:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"},{"start":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T00:00:00Z","timestamp":1771200000000},"content-version":"tdm","delay-in-days":0,"URL":"http:\/\/doi.wiley.com\/10.1002\/tdm_license_1.1"}],"funder":[{"DOI":"10.13039\/501100000038","name":"Natural Sciences and Engineering Research Council of Canada","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100000038","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["anatomypubs.onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["The Anatomical Record"],"abstract":"<jats:title>Abstract<\/jats:title>\n                  <jats:p>The conjunctival placodes of the avian eye form in an intriguing and conserved sequence in a circular annulus around the cornea. These 13\u201316 placodes develop into papillae that are essential for inducing underlying intramembranous flat bones, known as scleral ossicles, which form an important part of the ocular skeleton. The numbers of papillae present are used in almost all bird staging tables as an important anatomical feature for accurate staging. Despite this, we are lacking knowledge on how these papillae are induced and how the regular spacing between these placodes\/papillae is patterned, both within chicken embryos and in other bird species. In this study, we conduct a comparative assessment of the spacing of conjunctival placodes during ontogeny in chicken embryos and compare this to the spacing in quail and ducks, which develop at different rates and have different body sizes. Our results indicate that the average spacing between papillae changes over development in chicken embryos, but that no change in spacing occurs in the first set of induced placodes (group 1). We further show that placode spacing differs even in birds with similar eye diameters and placode\/papillae number (quail vs. duck). The position of the placode ring with respect to the cornea also varies in these species. Interestingly, despite different incubation durations, all three species develop placodes at 28%\u201333% of their incubation period. Overall, our data indicate that mathematical models describing the patterning of these regularly spaced placodes should consider both eye growth and papillae ring position.<\/jats:p>","DOI":"10.1002\/ar.70151","type":"journal-article","created":{"date-parts":[[2026,2,16]],"date-time":"2026-02-16T09:55:09Z","timestamp":1771235709000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Understanding the spacing of placodes in the eye: A comparative study across age and species"],"prefix":"10.1002","author":[{"given":"Florence","family":"Joseph","sequence":"first","affiliation":[{"name":"Department of Biology Mount Saint Vincent University  Halifax Nova Scotia Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4883-2677","authenticated-orcid":false,"given":"Tamara A.","family":"Franz\u2010Odendaal","sequence":"additional","affiliation":[{"name":"Department of Biology Mount Saint Vincent University  Halifax Nova Scotia Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"311","published-online":{"date-parts":[[2026,2,16]]},"reference":[{"key":"e_1_2_8_2_1","doi-asserted-by":"crossref","first-page":"3","DOI":"10.1111\/j.1469-7580.2009.01173.x","article-title":"Developmental stages of the Japanese quail","volume":"216","author":"Ainsworth S.","year":"2010","journal-title":"Journal of Anatomy"},{"key":"e_1_2_8_3_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pcbi.1006259"},{"key":"e_1_2_8_4_1","doi-asserted-by":"publisher","DOI":"10.1016\/0012-1606(62)90020-9"},{"key":"e_1_2_8_5_1","doi-asserted-by":"crossref","first-page":"225","DOI":"10.2307\/4078198","article-title":"The sclerotic ring in North American birds","volume":"55","author":"Curtis E. 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M.","year":"2025","journal-title":"Developmental Dynamics"},{"issue":"2","key":"e_1_2_8_7_1","doi-asserted-by":"crossref","first-page":"164","DOI":"10.1002\/dvdy.128","article-title":"An overlooked placode: Re\u2010characterizing the papillae in the embryonic eye of reptilia","volume":"249","author":"Drake P.","year":"2020","journal-title":"Developmental Dynamics"},{"key":"e_1_2_8_8_1","doi-asserted-by":"crossref","first-page":"251","DOI":"10.1016\/j.ydbio.2012.02.016","article-title":"BMP and Hedgehog signaling during the development of scleral ossicles","volume":"365","author":"Duench K.","year":"2012","journal-title":"Developmental Biology"},{"key":"e_1_2_8_9_1","doi-asserted-by":"publisher","DOI":"10.1002\/dvdy.21754"},{"key":"e_1_2_8_10_1","doi-asserted-by":"crossref","DOI":"10.1016\/j.gep.2020.119131","article-title":"Quantitative gene expression dynamics of key placode signalling factors in the embryonic chicken scleral ossicle system","volume":"38","author":"Giffin J. 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K. W.","year":"2019","journal-title":"PLoS Biology"},{"issue":"1","key":"e_1_2_8_16_1","doi-asserted-by":"crossref","first-page":"52","DOI":"10.1016\/j.ydbio.2015.07.014","article-title":"Vascular endothelial growth factor signaling affects both angiogenesis and osteogenesis during the development of scleral ossicles","volume":"406","author":"Jabalee J.","year":"2015","journal-title":"Developmental Biology"},{"key":"e_1_2_8_17_1","doi-asserted-by":"publisher","DOI":"10.1002\/dvdy.24489"},{"key":"e_1_2_8_18_1","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1146\/annurev-cellbio-020823-011522","article-title":"Control of tissue development by morphogens","volume":"39","author":"Kicheva A.","year":"2023","journal-title":"Annual Review of Cell and Developmental Biology"},{"issue":"8","key":"e_1_2_8_19_1","doi-asserted-by":"crossref","first-page":"3278","DOI":"10.3382\/ps\/pez133","article-title":"Comparison of whole embryonic development in the duck (Anas platyrhynchos) and goose (Anser cygnoides) with the chicken (Gallus gallus)","volume":"98","author":"Li S.","year":"2019","journal-title":"Poultry Science"},{"key":"e_1_2_8_20_1","doi-asserted-by":"publisher","DOI":"10.1038\/s41598-017-02755-4"},{"key":"e_1_2_8_21_1","doi-asserted-by":"crossref","first-page":"201","DOI":"10.1159\/000046499","article-title":"An additional bone in the sclera of the eyes of owls and the common Potoo (Nictibius griseus) and its role in the contraction of the nictitating membrane","volume":"163","author":"Mahecha B. G. A.","year":"1998","journal-title":"Acta Anatomica"},{"issue":"22","key":"e_1_2_8_22_1","doi-asserted-by":"crossref","DOI":"10.1242\/dev.202140","article-title":"Mesenchyme governs hair follicle formation","volume":"150","author":"M\u00e4kel\u00e4 O. J. M.","year":"2023","journal-title":"Development"},{"key":"e_1_2_8_23_1","doi-asserted-by":"publisher","DOI":"10.1016\/j.physd.2024.134480"},{"key":"e_1_2_8_24_1","doi-asserted-by":"publisher","DOI":"10.1371\/journal.pbio.2004412"},{"key":"e_1_2_8_25_1","doi-asserted-by":"publisher","DOI":"10.1002\/jez.1401740205"},{"issue":"6353","key":"e_1_2_8_26_1","doi-asserted-by":"crossref","first-page":"811","DOI":"10.1126\/science.aai7868","article-title":"Emergent cellular self\u2010organization and mechanosensation initiate follicle pattern in the avian skin","volume":"357","author":"Shyer A. 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