{{About-distinguish|a cnidarian with uncertain affinities within Hexacorallia|Relicanth}}{{Short description|Species of incertae sedis hexacorallian}}{{Use American English|date=June 2026}} {{Speciesbox | authority = (Daly, 2006) | image = Expn7312 (25854388108).jpg | parent = Relicanthus | grandparent_authority = Rodríguez & Daly, 2014 | parent_authority = Rodríguez & Daly, 2014 | greatgrandparent_authority = Daly & Rodríguez, 2019 | taxon = Relicanthus daphneae | synonyms = * ''Boloceroides daphneae'' <small>Daly, 2006</small> (unaccepted: junior synonym) }} thumb|A ''Relicanthus'' attached to a dead sponge stalk '''''Relicanthus daphneae''''' is a cnidarian which occurs in the depths of the East Pacific Rise and was described in 2006. It is the only known member of the suborder '''Helenmonae''' within the order Actiniaria.<ref>{{cite WoRMS|author=Daly|year=2006|title=''Relicanthus daphneae''|id=1338746|accessdate=April 24, 2025}}</ref>
==Taxonomy== ''Relicanthus daphneae'' was originally described as a member of the genus ''Boloceroides'',<ref name="Daly2006">{{cite journal |last1=Daly |first1=Marymegan |year=2006 |title=''Boloceroides daphneae'', a new species of giant sea anemone (Cnidaria: Actiniaria: Boloceroididae) from the deep Pacific |journal=Marine Biology |volume=148 |issue=6 |pages=1241–1247 |doi=10.1007/s00227-005-0170-7 |bibcode=2006MarBi.148.1241D |s2cid=85396602 }}</ref> but the name (and synonym) ''Boloceroides daphneae'' is no longer accepted after it was determined that this species belongs in the genus ''Relicanthus''.<ref name="Bdaphneae">{{cite WoRMS|author=Daly|year=2006|title=''Boloceroides daphneae''|id=288924|accessdate=2025-04-24}}</ref>
A phylogenetic study was completed in 2014, in which three genes of mitochondrial DNA and two genes from the nucleus of over a hundred different sea anemones were compared, suggesting that the species instead belonged in a new order of Hexacorallia.<ref name="Amnh2014">{{cite web |author=<!--Staff writer(s); no by-line.--> |date=May 7, 2014 |title=Sea Anemone Tree of Life Reveals Giant Species as Impostor |url=http://www.amnh.org/explore/news-blogs/research-posts/sea-anemone-tree-of-life-reveals-giant-species-as-impostor |access-date=May 10, 2014 |website=[www.amnh.org American Museum of Natural History] |publisher=}}</ref><ref name="RodriguezDaly2014">{{cite journal |doi=10.1371/journal.pone.0096998|doi-access=free |title=Hidden among Sea Anemones: The First Comprehensive Phylogenetic Reconstruction of the Order Actiniaria (Cnidaria, Anthozoa, Hexacorallia) Reveals a Novel Group of Hexacorals |date=2014 |last1=Rodríguez |first1=Estefanía |last2=Barbeitos |first2=Marcos S. |last3=Brugler |first3=Mercer R. |last4=Crowley |first4=Louise M. |last5=Grajales |first5=Alejandro |last6=Gusmão |first6=Luciana |last7=Häussermann |first7=Verena |last8=Reft |first8=Abigail |last9=Daly |first9=Marymegan |journal=PLOS ONE |volume=9 |issue=5 |article-number=e96998 |pmid=24806477 |pmc=4013120 |bibcode=2014PLoSO...996998R }}</ref> A new genus, ''Relicanthus'', was named to accommodate this alternate classification. The specific name ''daphneae'' was chosen after Daphne Gail Fautin, a scientist who primarily studied sea anemones, "in honor of her contributions to actiniarian systematics".<ref name="Daly2006"/>
In December 2019 the American Museum of Natural History announced that new research had classified ''R. daphneae'' as a new suborder of Actiniaria, Helenmonae, rather than as a new order.<ref name="Amnh2019">{{Cite web |last= |first= |date=December 12, 2019 |title=Mystery marine organism classified as sea anemone |url=https://www.amnh.org/explore/news-blogs/research-posts/mystery-marine-organism-classified-sea-anemone |url-status=live |archive-url=https://web.archive.org/web/20191219122559/https://www.amnh.org/explore/news-blogs/research-posts/mystery-marine-organism-classified-sea-anemone |archive-date=December 19, 2019 |access-date=December 19, 2019 |website=American Museum of Natural History}}</ref><ref name="XiaoRodriguezDaly2019">{{cite journal |doi=10.1038/s41598-019-54637-6 |title=Mitogenomics suggests a sister relationship of Relicanthus daphneae (Cnidaria: Anthozoa: Hexacorallia: Incerti ordinis) with Actiniaria |date=2019 |last1=Xiao |first1=Madelyne |last2=Brugler |first2=Mercer R. |last3=Broe |first3=Michael B. |last4=Gusmão |first4=Luciana C. |last5=Daly |first5=Marymegan |last6=Rodríguez |first6=Estefanía |journal=Scientific Reports |volume=9 |issue=1 |page=18182 |pmid=31796816 |pmc=6890759 |bibcode=2019NatSR...918182X }}</ref> This new classification was later confirmed by another phylogenetic study.<ref name="McFadden2021">{{cite journal|doi=10.1093/sysbio/syaa103 |doi-access=free |title=Phylogenomics, Origin, and Diversification of Anthozoans (Phylum Cnidaria) |date=2021 |last1=McFadden |first1=Catherine S. |last2=Quattrini |first2=Andrea M. |last3=Brugler |first3=Mercer R. |last4=Cowman |first4=Peter F. |last5=Dueñas |first5=Luisa F. |last6=Kitahara |first6=Marcelo V. |last7=Paz-García |first7=David A. |last8=Reimer |first8=James D. |last9=Rodríguez |first9=Estefanía |journal=Systematic Biology |volume=70 |issue=4 |pages=635–647 |pmid=33507310 }}</ref>
==Description== ''R. daphneae'' has a pink-colored cylindrical body capable of reaching a meter ({{Convert|1|m|ft|0|disp=out}}) across, with long, thin, whitish tentacles up to {{Convert|2|m|ft|0|sp=us|spell=in}} in length. The body is divided into 24 septa. The muscles of the mesenteries are less developed. The spirocysts, which are stinging cells in which the stinging tube is spirally rolled up and which are covered with adhesive threads instead of spines, are larger than those of any other deep-sea species and among the largest of all cnidarians.<ref name="Daly2006"/><ref name="RodriguezDaly2014"/>
==Habitat and range== Its habitat is the ocean floor, associated with the periphery of hydrothermal vents.<ref name="XiaoRodriguezDaly2019"/> Its range is known to be in the Lau Basin, Eastern Pacific, from where the type specimen was collected by the submersible DSV ''Alvin'', but it may extend beyond that.<ref name="Daly2006"/>
==References== {{Wikispecies|Relicanthus daphneae}} {{Reflist|35em}}
{{Taxonbar|from=Q16822617}}
Category:Boloceroididae Category:Animals described in 2006 Category:Animals living on hydrothermal vents Category:Cnidarians of the Pacific Ocean