New species in the cryptic genus Gloiocladia J.Agardh (Faucheaceae, Rhodophyta) from Hawaiian Mesophotic Coral Ecosystems

2025 ● 46 ● 5 AlgologieAlgologie Cryptogamie, Algologie est indexé dans / Cryptogamie, Algologie is indexed in: – Aquatic Sciences & Fisheries Abstracts Part I. – Biological Abstracts – Chemical Abstracts – Current Contents – Marine Science Contents Tables (FAO) – Science Citation Index – Publications bibliographiques du CNRS (Pascal) Cryptogamie, Algologie est distribué en version électronique par / Cryptogamie, Algologie is distributed electronically by: – BioOne® (http://www.bioone.org/loi/crya) Cryptogamie, Algologie est une revue en flux continu publiée par les Publications scientifiques du Muséum, Paris Cryptogamie, Algologie is a fast track journal published by the Museum Science Press, Paris Les Publications scientifiques du Muséum publient aussi / The Museum Science Press also publish: Adansonia, Geodiversitas, Zoosystema, Anthropozoologica, European Journal of Taxonomy, Naturae, Comptes Rendus Palévol, Cryptogamie sous-sections Bryologie, Mycologie. Diffusion – Publications scientifiques Muséum national d’Histoire naturelle CP 41 – 57 rue Cuvier F-75231 Paris cedex 05 (France) Tél. : 33 (0)1 40 79 48 05 / Fax : 33 (0)1 40 79 38 40 [email protected] / http://sciencepress.mnhn.fr © Publications scientifiques du Muséum national d’Histoire naturelle, Paris, 2025 ISSN (électronique / electronic) : 1776-0984 Directeur De la publication / Publication director: Gilles BLOCH Président du Muséum national d’Histoire naturelle réDactrice en chef / editor-in-chief: Line le Gall Muséum national d’Histoire naturelle assistant De réDaction / assistant editor: Violette GRUNENBERGER ([email protected]) Mise en paGe / Page layout: Violette GRUNENBERGER réDacteurs associés / associate editors Ecoevolutionary dynamics of algae in a changing world Stacy KRUEGER-HADFIELD Virginia Institute of Marine Science Eastern Shore Laboratory, Wachapreague, VA 23480 (United States) Jana KULICHOVA Department of Botany, Charles University, Prague (Czech Republic) Cecilia TOTTI Dipartimento di Scienze della Vita e dell’Ambiente, Università Politecnica delle Marche, Via Brecce Bianche, 60131 Ancona (Italy) Phylogenetic systematics, species delimitation & genetics of speciation Sylvain FAUGERON UMI3614 Evolutionary Biology and Ecology of Algae, Departamento de Ecología, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Av. Bernardo O’Higgins 340, Santiago (Chile) Marie-Laure GUILLEMIN Instituto de Ciencias Ambientales y Evolutivas, Universidad Austral de Chile, Valdivia (Chile) Diana SARNO Department of Integrative Marine Ecology, Stazione Zoologica Anton Dohrn, Villa Comunale, 80121 Napoli (Italy) Comparative evolutionary genomics of algae Nicolas BLOUIN Department of Molecular Biology, University of Wyoming, Dept. 3944, 1000 E University Ave, Laramie, WY 82071 (United States) Heroen VERBRUGGEN School of BioSciences, University of Melbourne, Victoria, 3010 (Australia) Algal physiology & photosynthesis Janet KÜBLER California State University Northridge, Department of Biology, California State University, Northridge, CA 91330-8303 (United States) Prokaryotic algae Nico SALMASO IASMA Research and Innovation Centre, Fondazione Mach-Istituto Agrario di S. Michele all’Adige, Limnology and River Ecology, Via E. Mach, 1, 38010 San Michele all’Adige, Trento (Italy) Vitor VASCONCELOS Faculdade de Ciências da Universidade do Porto and CIIMAR, Rua do Campo Alegre, s/n, 4169-007 Porto (Portugal) couverture / cover: Extrait de la Figure 4/Extract of Figure 4 67 CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) © Publications scientifiques du Muséum national d’Histoire naturelle, Paris. www.cryptogamie.com/algologie New species in the cryptic genus Gloiocladia J.Agardh (Faucheaceae, Rhodophyta) from Hawaiian Mesophotic Coral Ecosystems Kazumi R. ALLSOPP Feresa P. CABRERA James T. FUMO School of Life Sciences, 3190 Maile Way, University of Hawai‘i at Mānoa, Honolulu, Hawai‘i 96822 (United States) [email protected] [email protected] [email protected] Heather L. SPALDING Taylor M. WILLIAMS Department of Biology, College of Charleston, 66 George St, Charleston, South Carolina 29424 (United States) [email protected] [email protected] Randall K. KOSAKI Jason LEONARD Brian HAUK Papahānaumokuākea Marine National Monument, National Oceanic and Atmospheric Administration (NOAA), 1845 Wasp Boulevard, Building 176, Honolulu, Hawai‘i 96818 (United States) [email protected] [email protected] [email protected] Richard L. PYLE Daniel WAGNER Department of Natural Sciences, Bernice Pauahi Bishop Museum, 1525 Bernice St., Honolulu, Hawai‘i, 96817 (United States) [email protected]g [email protected]g Celia M. SMITH Alison R. SHERWOOD Ocean Exploration Trust, Honolulu, Hawaiʻi (United States) [email protected] [email protected] (corresponding author) Submitted on 6 December 2023 | Accepted on 12 August 2024 | Published on 17 October 2025 Allsopp K. R., Cabrera F. P., Fumo J. T., Spalding H. L., Williams T. M., Kosaki R. K., Leonard J., Hauk B., Pyle R. L., Wagner D., Smith C. M. & Sherwood A. R. 2025. — New species in the cryptic genus Gloiocladia J.Agardh (Faucheaceae, Rhodophyta) from Hawaiian Mesophotic Coral Ecosystems. Cryptogamie, Algologie 46 (5): 67-80. https:// doi.org/10.5252/cryptogamie-algologie2025v46a5. http://cryptogamie.com/algologie/46/5 68 CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) Allsopp K. R. et al. KEY WORDS COI, rbcL, cryptic diversity, mesophotic coral ecosystem, morphology, phylogeny, new species. MOTS CLÉS COI, rbcL, diversité cryptique, écosystèmes coralliens mésophotiques, morphologie, phylogénie, espèce nouvelle. ABSTRACT Crypsis – high morphological similarities of adult thalli of distinct species of algae – is a common challenge in algal taxonomy, where multiple taxa are characterized as the same species due to identical morphologies. Algal genera with cryptic species and similar morphologies may contain underestimates of both diversity and endemism. Extensive studies of Mesophotic Coral Ecosystems (MCEs; from c. 30 to >150 m depths) have revealed high levels of endemism in the Hawaiian Archipelago using DNA sequence-based analyses augmented by morphological analyses. Here, we characterize specimens collected from both the Papahānaumokuākea Marine National Monument and the Main Hawaiian Islands corresponding to the genus Gloiocladia J.Agardh; previous reports from Hawai‘i included only a single subtidal species (G. iyoensis (Okamura) R.E.Norris). Phylogenetic analyses using both plastidial (ribulose-1.5-biphosphate carboxylase/oxygenase) and mitochondrial (cytochrome oxidase subunit 1) markers revealed three clades of Hawaiian specimens with strong sequence divergence. However, the gross morphology of these specimens was nearly identical, except for small differences in the number of layers and sizes of cortical and medullary cells, which can easily be overlooked. This study extended the depth record of G. iyoensis to 63 m (aside from a previous report of a dredge sample from 66 m) and revealed one new species exclusive to MCEs (described here as G. laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov.), as well as one new intertidal species (formal description awaiting analysis of further collections) present in the Hawaiian Archipelago, including the Papahānaumokuākea Marine National Monument (PMNM) and the Main Hawaiian Islands. RÉSUMÉ Nouvelle espèce du genre cryptique Gloiocladia J.Agardh (Faucheaceae, Rhodophyta) des écosystèmes coralliens mésophotiques hawaïens. La Crypsis – similitudes morphologiques élevées des thalles adultes d’espèces d’algues distinctes – est un défi courant dans la taxonomie des algues, où plusieurs taxons sont caractérisés comme la même espèce en raison de morphologies identiques. Les genres d’algues comportant des espèces cryptiques et des morphologies similaires peuvent contenir des sous-estimations de la diversité et de l’endémisme. Des études approfondies des écosystèmes coralliens mésophotiques (MCE ; d’environ 30 à >150 m de profondeur) ont révélé des niveaux élevés d’endémisme dans l’archipel hawaïen à l’aide d’analyses basées sur des séquences d’ADN complétées par des analyses morphologiques. Nous caractérisons ici les spécimens collectés à la fois dans le monument national marin de Papahānaumokuākea et dans les principales îles hawaïennes correspondant au genre Gloiocladia J.Agardh, qui était auparavant représenté à Hawai’i par une seule espèce subtidale (G. iyoensis (Okamura) R.E.Norris). Les analyses phylogénétiques utilisant à la fois des marqueurs chloroplastiques (ribulose-1,5-biphosphate carboxylase/oxygénase) et mitochondriaux (sous-unité 1 de la cytochrome oxydase) ont révélé trois clades de spécimens hawaïens présentant de fortes divergences entre les séquences d’ADN. Cependant, la morphologie globale de ces spécimens est presque identique, à l’exception du nombre de couches et de la taille des cellules corticales et médullaires. Cette étude étend la gamme de profondeur de G. iyoensis aux MCE supérieurs (63 m, confirmant une occurence précédente sur un échantillon de drague à 66 m) et a révélé une espèce exclusive aux MCE, G. laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov., ainsi qu’une espèce intertidale (description formelle en attente d’analyse de collections ultérieures), présente dans l’archipel hawaïen, notamment le monument national marin de Papahānaumokuākea (PMNM) et les principales îles hawaïennes. INTRODUCTION Species in the red algal order Rhodymeniales exhibit a high level of morphological similarity and cryptic diversity associated with their plastic body plan, which can lead to misidentifications and taxonomic reassessments at various levels within the order (Saunders et al. 2006). In particular, the families Faucheaceae and Rhodymeniaceae contain many species that are barely distinguishable based on gross morphology (Le Gall et al. 2008). Within the family Faucheaceae, considerable debate has surrounded the separation of two genera, Gloiocladia J.Agardh and Gloioderma J.Agardh (e.g. Le Gall et al. 2008; Nelson & Dalen 2016; Norris 1991; Sánchez & Rodríguez-Prieto 2005). Although morphological features were originally used to distinguish the two genera based on the presence of tela arachnoidea in the cystocarp (Kylin 1956; Norris 1991), recent genetic and morphological analyses have yielded considerable confusion regarding their separation (Sánchez & Rodríguez-Prieto 2005; Rodríguez-Prieto et al. 2007). Currently, the family Faucheaceae comprises eight genera and 59 species (Guiry & Guiry 2023), with 34 (58%) currently classified in Gloiocladia and five (8%) in Gloioderma, following phylogenetic re-evaluation of the family and the subsequent transfer of many species from Gloioderma and Fauchea to Gloiocladia (Rodríguez-Prieto et al. 2007). 69 Hawaiian mesophotic Gloiocladia J.Agardh CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) Gloiocladia, including the species that were originally described as Gloioderma, is characterized by a lubricous thallus with a discoid holdfast and erect, solid, cylindrical, compressed or flattened fronds that are dichotomously, pinnately or radially branched (Norris 1991; Abbott 1999; Rodríguez-Prieto et al. 2007). Often, but not always, specimens have marginal protrusions or branchlets that do not extend to full length branches along the edges of blades. Reproductive plants often produce sori along the blade edges as well. Thalli are multiaxial and are composed of small cortical cells, a layer of subcortical cells laterally connected via secondary pit connections, and a medulla of large, axially elongated cells (Agardh 1842; Norris 1991). The first Hawaiian record of Gloiocladia was reported by Abbott (1999), as G. iyoensis (Okamura) R.E.Norris. Its Hawaiian distribution includes Manawai (Pearl & Hermes), Kapou (Lisianski), Mokumanamana (Necker), O‘ahu, Maui, and Hawai‘i from the low intertidal to 66 m depth (Abbott 1999). This depth record suggests that the species occurs throughout the Hawaiian Archipelago from the intertidal to depths within the range of Mesophotic Coral Ecosystems (MCEs). The type locality of G. iyoensis is Ehime Prefecture, N = G. iyonensis = G. laukuamoo K.R.Allsopp, F. P. Cabrera& A.R.Sherwood, sp. nov. = Lineage 3 500 km 85 m 75 m 59 m 82 m 61 m 104 m 3 m 155° 160° 170° 175°W 20°N 0 10 20 30 40 50 60 70 80 90 90 110 24° 28° 165° 55 m Kapou Lalo Middle bank Maui Lanai Manawai 84 m B A fiG. 1. — Map showing the collection localities and depths for the specimens analyzed for this study (A), and depth distribution diagram of all Gloiocladia J.Agardh records in the Hawaiian Islands (B). Red shade represents the biogeographical distribution of G. iyoensis (Okamura) R.E.Norris, while blue shade represents that of G. laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov. Previously collected specimens (from Abbott 1999) are indicated with grey dots, and specimens examined in this study as black dots. 70 CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) Allsopp K. R. et al. Japan, and the species can be found worldwide in the Atlantic, Pacific, and Indian Oceans (Guiry & Guiry 2023). Although depth data are limited, records suggest the presence of collections from shallow reefs at 1-5 m worldwide. Recent collections from Hawaiian mesophotic reefs present an opportunity to more fully characterize the diversity of this genus across an expanded range of depths in Hawai‘i, and explore the possibility of novel and cryptic diversity. Exploration of MCEs has intensified in recent years, resulting in the discovery and description of numerous new species and genera in Hawai‘i (e.g., Paiano et al. 2020; Sherwood et al. 2020a, b; Cabrera et al. 2022; Alvarado et al. 2022). These novel taxa have been shown to contribute to unique and diverse algal assemblages in MCEs and exhibit a high degree of endemism. Recent research has also expanded the known native range of some species (Sherwood & Guiry 2023). In this study, molecular and morphological characterization of Gloiocladia specimens from Hawaiian MCEs was conducted to investigate the cryptic diversity and distribution of the genus in Hawai‘i. MATERIAL AND METHODS Extensive surveys of Hawaiian MCEs have been conducted since 2006, and the algal specimens characterized in this study were collected from the Papahānaumokuākea Marine National Monument (PMNM) and the Main Hawaiian Islands by technical diving or submersibles (Table 1; Fig. 1). Specimens were preserved in silica gel and/or pressed as herbarium vouchers. Specimens resembling Gloiocladia were selected for further characterization. Small pieces of tissue of G. iyoensis specimens collected from 1936-1956 were also sent from the personal collection of Dr. Segawa Japan (type locality) to attempt to establish a molecular type concept for this species. DNA was extracted using the Nucleospin® Plant II Kit (Macherey-Nagel GmbH & Co., Düren, Germany) or a cetyltrimethylammonium bromide (CTAB) protocol (Doyle & Doyle 1987) with overnight lysis steps and Qiagen (Valencia, California, United States) purification spin columns for washing and elution. The mitochondrial cytochrome oxidase subunit I (COI) barcode marker was amplified following the protocols outlined in Saunders & Moore (2013) and Saunders (2005). The plastidial ribulose-1.5-bisphosphate carboxylase/ oxygenase large subunit (rbcL) marker was amplified following Saunders & Moore (2013), Gavio & Fredericq (2005) or Freshwater & Rueness (1994). PCR products were submitted for sequencing by Azenta (South Plainfield, NJ, United States ). Raw sequence data were edited in Geneious Prime 2019.1.3 (http:// www.geneious.com) and aligned using the MUSCLE v. 3.8.425 plug-in (Edgar 2004), along with available sequences for Gloiocladia and related genera from NCBI GenBank (Table 3), following Filloramo & Saunders (2018). Sequences of Fryeella gardneri (Setchell) Kylin were used as an outgroup for both alignments. The COI and rbcL alignments were concatenated with partitioning of COI from bp 1-663, table 1. — Collection details for Gloiocladia J.Agardh specimens examined in this study. Lineage and Taxon Sherwood lab accession Herbarium accession Collection details COI accession rbcL accession Lineage 1 G. iyoensis (Okamura) R.E.Norris ARS10720 BISH789098 Middle Bank, Hawai‘i, 22°39’43”N, 161°2’31”W, 61 m, coll. H. Spalding (NWHI-1081) OR881946 OR881954 Lineage 1 G. iyoensis (Okamura) R.E.Norris ARS11146 BISH789099 Lalo, Hawai‘i, 20 May 2013, 23°37’44”N, 166°11’38”W, 63 m, coll. D. Wagner (NWHI-174-3) – OR881956 Lineage 2 G. laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov. (Holotype) ARS10279 BISH789091 Kapou, Hawai‘i, 14 September 2014, 26°2’13”N, 173°47’31”W, 59 m, coll. J. Leonard (NWHI-246) OR881945 OR881952 Lineage 2 G. laukuamoo sp. nov. (Paratype) ARS10164 BISH789092 Kapou, Hawai‘i, 30 July 2019, 26°1’30”N, 174°9’24”W, 55 m, coll. B. Hauk (NWHI-847) – OR881951 Lineage 2 G. laukuamoo sp. nov. ARS10286 BISH789093 Lalo, Hawai‘i, 8 September 2015, 23°43’36”N, 166°21’17”W, 82 m, coll. D. Wagner (NWHI-347) – OR881953 Lineage 2 G. laukuamoo sp. nov. ARS11120 BISH789094 Manawai, Hawai‘i, 6 August 2019, 27°44’28”N, 175°57’30”W, 75 m, coll. B. Hauk (NWHI-1025) OR881947 OR881955 Lineage 2 G. laukuamoo sp. nov. ARS11147 BISH789095 Kapou, Hawai‘i, 16 September 2014, 25°52’56”N, 173°57’43”W, 84 m, coll. R. Pyle & D. Wagner (NWHI-265-b) OR881948 OR881957 Lineage 2 G. laukuamoo sp. nov. ARS11148 BISH789096 Manawai, Hawai‘i, 18 September 2014, 27°44’23”N, 175°57’41”W, 85 m, coll. R. Kosaki (NWHI-294-b) OR881949 OR881958 Lineage 2 G. laukuamoo sp. nov. ARS11390 BISH789097 Maui, Hawai‘i, 5 April 2009, 104 m, coll. H. Spalding (P5-736-68) –OR881959 Lineage 3 Gloiocladia J.Agardh sp. ARS03705 N/A Kaumalapau Harbor, Lāna‘i intertidal, 26 March 2008, coll. A. Kurihara HQ422982.1 OR881950 71 Hawaiian mesophotic Gloiocladia J.Agardh CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) and rbcL from bp 664-2026. ML analysis and Bayesian Inference (BI) were performed on Geneious Prime 2020.2.3 (http://www.geneious.com). For ML, GTR GAMMA I was used as the evolutionary model with 1 000 bootstrap replicates using RAxML plug-in v.8.2.11 (Stamatakis 2014). For BI, the MrBayes plug-in v.3.2.7 (Huelsenbeck & Ronquist 2001) was used with four chains of Metropolis-coupled Markov Chain Monte Carlo (MCMC) for 1 000 000 generations, sampling every 500 generations, burn-in of 100 000 generations, and GTR as the substitution model. Specimens were photographed in the Joseph F. Rock Herbarium (HAW) with a Canon EOS 5D Mark II Digital Camera (Tokyo, Japan) in an MK Direct Photo-eBox PLUS 1419. Microscope slides for light microscopy were prepared by hydrating specimens in water for 30-60 min and crosssectioning with a razor blade under a dissecting scope. Samples were stained with 0.5% aniline blue for 5 min, washed, and mounted in 30-50% Karo™. Photomicrographs were taken on a Zeiss AxioImager A1 compound light microscope (Pleasanton, CA) with an Infinity2-1RC digital camera (Lumenera Corporation, Ottawa, Ontario, Canada) to observe the thallus structure and other morphological and anatomical features. AbbreviAtions Institutional Abbreviations BISH Bishop Museum’s Herbarium Pacificum, Honolulu; NCBI National Center for Biotechnology Information, Bethesda; PMNM Papahānaumokuākea Marine National Monument; northwestern Hawaiian archipelago. Other Abbreviations bp base pair; COI Cytochrome C Oxidase Subunit I; * * * * * * ** * * * * * Webervanbossea splachnoides (HM916011.1; KR085186.1) Australia Webervanbossea tasmanensis (HM915887.1; KR085196.1) Australia Leptofauchea chiloensis (KR140338.1) Chile Leptofauchea pacifica (HM916176.1; KR085195.1) British Columbia Leptofauchea nitophylloides (KR085173.1; KR085190.1) Australia - Leptofauchea munseomica (HQ544094.1; KR140337.1) South Korea Leptofauchea cocosana (KR140330.1; KR140340.1) Australia Leptofauchea earleae (HQ400570.1) Gulf of Mexico Leptofauchea leptophylla (KR140329.1; KR140339.1) South Korea Gloiocladia saccata (KT154694.1) New Zealand Gloioderma australe (JX969722.1; JX969786.1) Australia Gloioderma halymenioides (HQ919528.1; KR085192.1) Australia Gloiocladia spinulosa (KF547031.1: KF547023.1) South Korea Gloiocladia pelicana (FJ713144.1) Gulf of Mexico Gloiocladia repens (KR140326.1; KR140335.1) Italy Gloiocladia microspora (FJ713145.1) Spain Gloiocladia furcata (FJ713146.1) Spain Gloiocladia fryeana (KU687762.1; KU687880.1) British Columbia Gloiocladia vigneaultii (KU687823.1) British Columbia Gloiocladia laciniata (KU687578.1; KU687841.1) British Columbia Gloiocladia media (KM254874.1; KU687877.1) CA United States Faucheocolax attenuata (KU687787.1; KU687886.1) British Columbia Gloiocladia japonica (KF547029.1; KF547021.1) South Korea Gloiocladia tenuissima (FJ713141.1) Gulf of Mexico ARS03705 Lineage 3 Lineage 1 Lineage 2 Gloiocladia iyoensis Gloiocladia iyoensis (FJ713142.1) Australia (Laua'enohokai) Gloiocladia laukuamoo sp. nov. (Laukuamo'o) ARS11146 ARS10720 ARS11148 ARS11120 ARS11390 ARS10286 ARS11147 ARS10164 ARS10279 92/1.00 83/0.99 98/1.00 75/1.00 0.77 97/1.00 78/0.97 75/0.80 50/0.82 99/1.00 86/0.87 96/0.94 86/0.99 97/0.82 fiG. 2 . — Phylogenetic tree inferred in RAxML and MrBayes from the analysis of concatenated COI-rbcL sequences from Hawaiian Gloiocladia J.Agardh specimens and other representatives of the family Faucheaceae. The topology of the shown tree is represented by the Bayesian Inference. A member of the Gigartinaceae (Fryeella gardneri (Setchell) Kylin was used as the outgroup, which was pruned to facilitate presentation. Sequences from this study are indicated in bold. The numbers next to tree nodes indicate maximum likelihood bootstrap values and Bayesian posterior probability support values. Full support (100/1.00) is indicated with an asterisk (*). Support values smaller than 50 or 0.5 are not shown. 72 CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) Allsopp K. R. et al. CTAB Cetyltrimethylammonium bromide; DRRH Deep Reef Refugia Hypothesis; MCE Mesophotic Coral Ecosystem; MCMC Markov Chain Monte Carlo; MHI Main Hawaiian Islands; ML Maximum Likelihood; NHCWG/CWG Native Hawaiian Cultural Working Group; rbcL ribulose-1.5-bisphosphate carboxylase. RESULTS Of three Japanese Gloiocladia iyoensis specimens, only one was successfully sequenced. We were able to generate an rbcL sequence; however, the sequence BLASTed at 94% similarity to the gigartinalean species Cubiculosporum koronicarpis Kraft (KC174802), and 99% to Cubiculosporum sp. (KC174803), which were both collected from Taiwan. Thus, we were not able to confidently generate a topotype sequence for G. iyoensis, and current sequences labeled as this species in GenBank must be considered provisionally identified. Phylogenetic analysis of Hawaiian Gloiocladia specimens resolved three Hawaiian lineages, which included one previously reported species (G. iyoensis) and two undescribed species (Fig. 2). The COI-rbcL concatenated analysis yielded relatively small divergences among lineages; the divergence between some Gloiocladia species was as low as 1.1% (e.g., BC DEF H GI A mc mc sc cc pc pc pc pc cc mc a g fiG. 3. — Vegetative morphology of Gloiocladia laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov: A, in situ photograph of the holotype collection (BISH 789091, ARS 10279). Dark red plant is a species of Amansia (A), and Gloiocladia laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov. (G) is the yellowish-brown epiphyte; B, hydrated holotype collection (BISH 789091, ARS 10279); C, pressed specimens of holotype (BISH 789091, ARS 10279); D, branched blade with pinnate sawtooth branchlets along the blade margins. Some sawtooth branchlets developing dichotomous apices. (BISH 789095, ARS 11147); E, apical region of the plant, showing cortical filaments and gelatinous layer around the apex (BISH 789095, ARS 11147); F, cross section of thallus showing medullary (mc) and cortical cells (cc) (BISH 789091, ARS 10279); G, surface view of cortical cells (BISH 789091, ARS 10279); H, top-down microscopy of subcortical cells forming lateral secondary pit connections (BISH 789091, ARS 10279); I, cross section of G. laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov. showing (mc), subcortical (sc), and (cc) cells connected via pit connections (pc) (BISH 789091, ARS 10279). Scale bars: A, 20 mm; B, C, 10 mm; D, 500 μm; E, I, 50 μm; F, 100 μm; G, H, 10 μm. Photo credits: all microscopy images and pressed specimens, K. R. Allsopp; The in situ and live specimen images, L. Spalding, Taylor M. Williams, Randall K. Kosaki, Jason Leonard & Brian Hauk. 73 Hawaiian mesophotic Gloiocladia J.Agardh CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) G. vigneaultii Filloramo & G.W.Saunders and G. laciniata (J.Agardh) N.Sánchez & Rodríguez-Prieto). Lineage 1 was composed of two sequences from Hawaiian MCE specimens (ARS11146 and ARS10720) and an Australian G. iyoensis sequence from GenBank. Based on morphological similarity to the published description of G. iyoensis (i.e., Norris 1991; Abbott 1999), this lineage may correspond to that species, but this identification will remain unconfirmed until comparison with type material can be accomplished. The remaining Hawaiian MCE specimens were resolved as Lineage 2, which was sister to G. iyoensis (with full support), and was 2.2-3.3% divergent from G. iyoensis. Lastly, a COI sequence in NCBI GenBank listed as G. iyoensis (HQ422982, Sherwood et al. 2010) was shown to represent a distinct species in the phylogenetic tree (Lineage 3). This lineage currently consists of a single specimen positioned in a broader clade with G. japonica (Okamura) Yoshida and G. tenuissima Gavio & Fredericq (Fig. 2). Based on the phylogenetic analyses (Fig. 2) and morphological comparisons of gross vegetative features presented below (Table 2), we confirm the presence of one previously reported species (Lineage 1, G. iyoensis), formally propose the description of one new species (Lineage 2), and note one additional species (Lineage 3) to be described at a later date once additional material is collected and characterized. Family FAucheAceAe Strachan, G.W.Saunders & Kraft Genus Gloiocladia J.Agardh Gloiocladia laukuamoo K.R.Allsopp, F.P.Cabrera & A.R.Sherwood, sp. nov. (Fig. 3A-I) type mAteriAl. — Hawai‘i • Kapou (Lisianski), Papahānaumokuākea Marine National Monument; 26°2’13”N, 173°47’31”W; 59 m a.s.l.; 14.IX.2014; collected by J. Leonard (NWHI-246); BISH 789091 (ARS 10279); GenBank accessions OR881954 (rbcL) and OR881946 (COI). etymology. — Laukuamo‘o (noun in apposition, and hence nondeclinable) is derived from multiple Hawaiian nouns. The name was developed using traditional Hawaiian naming practices in collaboration with the Nomenclature Subcommittee of the Papahānaumokuākea Native Hawaiian Cultural Working Group (CWG) (Appendix 1). “Lau” refers to a leaf or blade of a plant and can also refer to multiplicity. “Kua” refers to the back or the shape of a human spine, while “mo‘o” refers to the mourning gecko species found in Hawai‘i (Lepidodactylus lugubris Duméril & Bibron), which exhibits a similar sawtooth-like pattern on its back. By connecting all three terms, the name accentuates the intertwined sawtooth-like body plan and the biogeography of the species found in the “geological backbone” of the Hawaiian Archipelago, the Northwestern Hawaiian Islands or Papahānaumokuākea Marine National Monument. mAteriAl exAmined. — BISH 789092 (ARS 10164), BISH 789093 (ARS 10286), BISH 789094 (ARS 11120), BISH 789095 (ARS 11147), BISH 789096 (ARS 11148), BISH 789097 (ARS 11390). substrAte/host. — Small pebbles (epilithic), or other larger macroalgae such as Amansia sp. (epiphytic). h Abit And vegetAtive morphology . — Thalli are thin and elongated, oval in cross section, rounded at tips and exhibiting a distinctive construction of the blades with sawtooth-like branchlets, although a few specimens lack branchlets. Plants prostrate, and can be epiphytic on other macroalgae such as Amansia, by entangling their sawtooth-like branchlets with host thalli. Plants appear brownyellow in situ when compared to Amansia (Fig. 3A). The alga exhibits a deep wine-red color when living (Fig. 3B). Generally, thalli are irregularly-dichotomously branched. A single branch can extend up to 20 mm in length and 4 mm in width, including branchlets (Fig. 3C). Sawtooth-like branchlets are positioned c. 300 µm apart and can extend into full branches (Fig. 3D). A gelatinous layer surrounds the outermost cortical layer of apices (Fig. 3E). Blades are up to 350 µm thick in cross section, and are composed of multiple layers of small, densely packed cortical cells, and larger medullary cells (Fig. 3F). Outer cortical cells are loosely arranged, 5 µm in diameter and visible from the surface (Fig. 3G). Laterally arranged subcortical cells connected via secondary pit connections (Fig. 3H). Tightly arranged medullary cells have dimensions of 40-80 × 3050 µm in cross section (Fig. 3I). Primary pit connections can be observed between individual medullary cells, subcortical cells, and cortical cells (Fig. 3I). No reproductive features were observed. distribution. — Exclusive to MCE depths of 55-104 m throughout the Hawaiian Islands, including Kapou (Lisianski), Manawai (Pearl and Hermes), Lalo (French Frigate Shoals), and Maui. description Plants epiphytic on other algae or lithophytic on rubble via rhizoidal attachment or entanglement. Thallus decumbent, up to 60 mm long. Stipes appear oval to circular in cross section, holdfasts not present in collected specimens. Plants irregularly dichotomously branched, deep wine red when alive, and pale pink when dried. Vegetative axes are narrow, up to 2 mm wide excluding sawtooth branchlets, with branchlets extending up to an additional 2 mm on either side of the axis. Branchlets can extend in opposite or alternating distichous patterns. Axes are flattened except in basal regions, 300-400 µm thick, and covered in a gelatinous layer that is seemingly thin and delicate at apices to allow the cell division of loosely-arranged cortical cells. Thallus multiaxial with 1-3 layers of loosely arranged rounded outer cortical cells, 5 µm in diameter from the surface view of the thallus. No lateral secondary pit connections observed between cortical filaments. Subcortical cells appear elongated and triangular, up to 16 × 9 µm in cross section, connected via primary pit connections to the medullary and cortical cells. Laterally arranged subcortical cells connected via secondary pit connections, forming a network. Medulla cellular and compact, consisting of large hyaline cells that decrease in size toward the cortex. Medullary cells forming 5-9 layers, axially elongated, ranging in size up to 80 × 50 µm in cross-section, forming frequent pit connections to adjacent medullary cells. Gametophytic and tetrasporic reproductive structures not observed. Gloiocladia iyoensis (Okamura) R.E.Norris (Fig. 4A-H) Homotypic synonym: Gloioderma iyoense Okamura. 80 CRYPTOGAMIE, ALGOLOGIE • 2025 • 46 (5) Allsopp K. R. et al. appenDix 1 . — Hawaiian and scientific names for three Sawtooth (GloIocladia J.Agardh) species, available at: https://doi.org/10.5252/cryptogamie-algologie2025v46a5_s1 APPENDIX