A new bubblegum coral from the Nazca Ridge reveals chitin as the structural scaffold of skeleton

Abstract Bubblegum corals (Paragorgia; Corallidae) form among the largest branching colonies in deep-sea environments despite lacking an axial skeleton. How these octocorals maintain structural cohesion using only sub-millimeter sclerites has remained unexplained. Here we describe Paragorgia quitinosa Sánchez & Easton n. sp., collected at 670 m depth on the Nazca Ridge (southeastern Pacific) during the Schmidt Ocean Institute RV Falkor (too) expedition FKt240708, and report the first evidence of visible chitin in octocoral tissues. The new species is diagnosed by autozoids and siphonozoids retracted on prominent, rounded mounds, large 8-derived radiate capstan sclerites (mean 0.095 mm), and canal walls composed of a polysaccharide substance resistant to dilute hypochlorite digestion. Scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), FTIR, RAMAN and TMS/GC-MS analyses confirm the presence of chitin in the perforating and boundary canals of the coenenchyme in this species and a second Paragorgia sp. Micro-XCT imaging reveals that the holotype is a reproductively active female bearing multiple oocyte cohorts exclusively in siphonozoids. Phylogenetic analyses based on ultraconserved elements (UCEs) and concatenated mitochondrial protein-coding genes place P. quitinosa within Paragorgia, sister to P. johnsoni and P. jamesi, and confirm that Sibogagorgia is polyphyletic. These findings establish that chitin forms a structural canal network throughout the coenenchyme of skeleton-less bubblegum corals—the third report of chitin in Anthozoa after sea anemones and black corals—and suggest a biomechanical role of chitin in the octocoral coenenchyme, potentially explaining the remarkable size and flexibility of skeleton-less branching octocoral colonies. Acknowledgements Special thanks to organizers and participants of the Species Discovery Workshop at UCN-Chile during April 2024: Maria de los Angeles Gallardo, Cathalina Miranda, Maritza Castro, Belén Arias, Thalia Stinton, Verity Nye, Isla Monaghan, Caroline Park, Tina Molodtsova, Asako Matsumoto, Marcello Kitahara, Javier Cristobo, Pilar Ríos, and Maximiliano Jan Tapia-Guerra. The authors acknowledge the Schmidt Ocean Institute, the RV Falkor (too) crew and science parties as well as the Coral Reefs of the High Seas Coalition and The Nippon Foundation-Nekton Ocean Census Programme (https://oceancensus.org/) for supporting the discovery and description of these species. This species is assigned Ocean Census Species Number OC-SP-0003448. The Department of Chemistry (Faculty of Sciences), Universidad de Los Andes, kindly and patiently (Juan Alberto Correa) supported the FTIR analyses of specimens. SEM analyses in Coquimbo (María Romero, UCN) and Bogotá (Nydia Arias and Juan Camilo Orozco, Microcore, Core-Conectar grant, Vicerrectoria de Investigación y Creación, Uniandes) (JAS). Funding for micro-XCT imaging was supported by Conservation International grant CI-116385, which also supported sequencing, and NSF Division of Earth Science Instrumentation and Facilities Program (NSF EAR-2223808) and NASA (80NSSC23K0199) awards (EEE). Funding from Facultad de Ciencias (Universidad de los Andes) programme INV-2025-213-3436 to JAS and Schmidt Ocean Institute, ANID ATE 220044 (BiodUCT) and Fondecyt 1241386 to JS. Funding EEE: Schmidt Ocean Institute, Conservation International grant CI-116385, The Nippon Foundation-Nekton Ocean Census Programme, and NSF Division of Earth Science Instrumentation and Facilities Program (NSF EAR-2223808) and NASA (80NSSC23K0199) awards. JAS: The Nippon Foundation-Nekton Ocean Census Programme, Facultad de Ciencias (Universidad de los Andes), programme INV-2025-213-3436. JS: Schmidt Ocean Institute, ANID ATE 220044 (BiodUCT) and Fondecyt 1241386. Author information Authors and Affiliations Corresponding author Ethics declarations Competing interests The authors declare no competing interests. Additional information Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Supplementary Information Below is the link to the electronic supplementary material. Rights and permissions Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. About this article Cite this article Sánchez, J.A., Easton, E.E., Garcia, N. et al. A new bubblegum coral from the Nazca Ridge reveals chitin as the structural scaffold of skeleton-less Paragorgia colonies. Sci Rep (2026). https://doi.org/10.1038/s41598-026-71127-8 Received: Accepted: Published: DOI: https://doi.org/10.1038/s41598-026-71127-8