Research Article |
Corresponding author: Odalisca Breedy ( odaliscab@gmail.com ) Academic editor: Bert W. Hoeksema
© 2023 Odalisca Breedy, Catherine S. McFadden, Jorge Cortés.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Breedy O, McFadden CS, Cortés J (2023) An enigmatic new octocoral species (Anthozoa, Octocorallia, Malacalcyonacea) from Isla del Coco National Park. ZooKeys 1169: 317-331. https://doi.org/10.3897/zookeys.1169.100576
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Aliena parva gen. et sp. nov. is described from Cocos Island, Costa Rica. The species was found at various islets and rocky outcrops north and northwest of the island, 20–30 m in depth. The genus is characterised by polyps, retracting into calyces, that form thin encrusting mats extending on dead or live substrates. Sclerites are mostly asymmetrical spindles. Anthocodial rods are arranged in points, not forming a collaret. Colonies and coenenchymal sclerites are red, and polyps are transparent. Using an integrative taxonomic approach, we found the new genus to morphologically and genetically differ from all other described taxa. The molecular phylogenetic analyses provide strong support for the placement of this new genus in the family Pterogorgiidae. Morphologically it is unlike any of the other members of this family, necessitating an amendment to the diagnosis of Pterogorgiidae. Like several other known taxa of octocorals with encrusting growth forms, Aliena gen. nov. appears to have evolved from a gorgonian ancestor by loss of an internal skeletal axis. It is the first member of Pterogorgiidae to be reported from the eastern Pacific, contributing further to the knowledge of marine biodiversity in the eastern tropical Pacific and to the octocoral biodiversity of Cocos Island in particular.
Biodiversity, new genus, new species, oceanic island, soft corals, taxonomy
The occurrence of shallow-water octocorals in Isla del Coco National Park is rare in comparison to other oceanic islands, like the Galápagos Islands (Ecuador) or the Revillagigedo Archipelago (México), where the number of reported species is higher (
Recently, a new octocoral was collected and photographed at several sites at the northern part of the Island. Herein, we describe a new genus and species using an integrative taxonomic approach, combining morphological and molecular analyses to phylogenetically position this monospecific genus within Octocorallia. This study is a contribution to the knowledge of the octocoral biodiversity of Isla del Coco and marine biodiversity of the eastern tropical Pacific oceanic islands.
Isla del Coco National Park is an oceanic island located between 5°30'–5°34'N and 87°01'–87°06'W in the eastern Tropical Pacific approximately 500 km southwest of Costa Rica and more than 600 km northeast of the Galápagos Islands, Ecuador (
For taxonomic identification, external characters of the colony were analysed from the in situ photographs and dissection of collected samples under a stereoscope. For internal characters, sclerites from polyps and coenenchyme were obtained by dissolving the tissue in 5% sodium hypochlorite; dissociated sclerites were washed several times in distilled water until organic matter was completely removed, dehydrated with 100% ethanol, and subsequently dried in an oven. Sclerites were prepared for light microscopy, mounted in glycerine, and photographed with an Olympus LX 51 inverted microscope. For scanning electron microscopy (SEM), sclerites were mounted on SEM stubs by double stick carbon tape and silver paint, then sputter-coated with gold, 30–60 nm layer, in EMS 550X Ion Coater; the images were obtained using a FESEM Zeiss Sigma 300 and a Hitachi NSEM 3700 (at 15kV). Measurements of the sclerites were obtained from optical and SEM images. Taxonomic terminology follows
DNA was isolated from ethanol-preserved tissue of two specimens using the modified salting-out protocol of
Phylogenetic analyses were run separately for each alignment. ML analyses were run using IQTree v. 2.1.2 (
SubPhylum Anthozoa Ehrenberg, 1831
Class Octocorallia Haeckel, 1866
Order Malacalcyonacea McFadden, van Ofwegen & Quattrini, 2022
Family Pterogorgiidae McFadden, van Ofwegen & Quattrini, 2022
Colonies are encrusting mats of irregular shape, consisting of clusters of 3–25 polyps that may be interconnected by thin coenenchymal extensions forming bridge-like bands between them. Colonies lack an axis. Polyps are retractile into calyces that are covered by a dense layer of small sclerites producing a granular appearance. Coenenchyme is thin without differential sclerite layers. Coenenchymal sclerites are mostly red asymmetrical spindles with simple tubercles and irregular ends. Anthocodial sclerites are mostly red flat rods, with serrated or prickly borders and sparse thorns on the surface, and spine-like rods. They are arranged “en chevron”, forming points but not a collaret. Flat rods form longitudinal rows along the polyp body. Tentacular sclerites are mostly yellow, biscuit-like rods. Colonies are dark red in life and maintain that colour in ethanol.
Aliena parva sp. nov. by original designation.
Alienus (L) foreign, strange, not related. The generic name refers to the unexpected appearance or unnoticed presence of a new shallow-water taxon. It also alludes to its surprising phylogenetic relationship to a group of gorgonian octocorals, a relationship not predicted by its morphology. Gender feminine.
Holotype . MZUCR 3679, lot 1, ethanol-preserved, Manuelita Afuera, Isla del Coco, 05°33.791'N, 087°02.934'W, 22 m depth, J. Cortés and M. Cruz, 4 December 2021. Paratypes. MZUCR 3680, lot 2, same data as holotype. MZUCR 3681, lot 1, lot 2, ethanol-preserved, Manuelita Canal, Isla del Coco, 05°33.524'N, 087°02.940'W, 20–30 m depth, B. Naranjo, 12 October 2021. MZUCR 3682, ethanol-preserved, Bajo Manuelita, Isla del Coco, 05°33.849'N, 087°02.676'W, 23 m, J. Cortés and A. Klapfer, 6 December 2021. MZUCR 3683, Manuelita Afuera, Isla del Coco, 05°33.791'N, 087°02.934'W, 29 m depth, O. Breedy, 28 September 2022. MZUCR 3684, Manuelita Afuera, Isla del Coco, 05°33.791'N, 087°02.934'W, 25 m depth, O. Breedy, 4 October 2022.
Isla del Coco, Pacific Costa Rica, at depths of 20–30 m.
The holotype is formed of 15 scattered clusters of polyps encrusting the surface of a barnacle about 4 cm in diameter; the barnacle plates are covered by many epibionts and several small, unbranched hydroids (Fig.
Colonies are dark red in life and when preserved (Fig.
The colonies are overgrowing dead or live substrates, encrusting small rocks, barnacle plates, shells, or among turf. They were frequently found among the worm tubes occupied by the endemic fish Acanthemblemaria atrata Hastings & Robertson, 1999 from Isla del Coco (Figs
Colonies were found at various localities north of Isla del Coco around Manuelita Afuera, Manuelita Canal and Bajo Manuelita; and northwest at Roca Sucia, 05°32.875'N, 087°04.956'W and Viking Rock (Isla Cáscara), 05°33.006'N, 087°03.865'W, NW of the island (Fig.
Parvus (L), in allusion to the small size of the polyps. Gender feminine: parva.
Phylogenetic analyses of both the mitochondrial mtMutS and nuclear 28S rDNA genes strongly supported the placement of Aliena parva gen. nov. et sp. nov. in the octocoral family Pterogorgiidae (Fig.
Maximum-likelihood tree of Malacalcyonacea based on mtMutS. Support values indicated by symbols at nodes. Black circles: maximum-likelihood bootstrap value (bs) > 70% and Bayesian posterior probability (pp) > 0.9); open circles: bs > 70, no support (pp <0.9) from Bayesian analysis. Families have been collapsed to facilitate readability. All collapsed clades have bs > 70% and pp > 0.9 unless otherwise noted. The branch leading to Anthogorgiidae has been shortened to fit the page. Inset shows Pterogorgiidae clade from analysis of 28S rDNA.
The external morphology of Aliena gen. nov. suggests it could belong to one of the families of stoloniferous octocorals, several of which (e.g., Carijoidae, Incrustatidae, Sarcodictyonidae, Tubiporidae) include genera of encrusting colonies that produce mats extending on hard substrata (
The gross colony morphology of Aliena gen. nov. is unlike any of the other genera in Pterogorgiidae, all of which have internal skeletal axes of gorgonin that support an erect growth form. Its sclerome is, however, reasonably consistent with that of the other Pterogorgiidae, all of which have asymmetrically spiny or curved spindles in the coenenchyme and flattened rods in the polyps (
Aliena gen. nov. lacks the additional sclerite forms that are typical of some of the other genera of Pterogorgiidae, such as the capstans of Pterogorgia and Stenogorgia or the balloon clubs of Dacrygorgia McFadden, van Ofwegen & Quattrini, 2022. The simple thorn-like ornaments on the coenenchymal spindles of Aliena gen.nov. also differ markedly from the asymmetrical spines and high, complex tubercles that characterize the spindles of Muriceopsis and Tobagogorgia Sánchez, 2007.
Aliena gen. nov. is one of several genera of octocorals with a simple, encrusting growth form that belong to clades whose other members are all gorgonians, i.e., species with an internal skeletal axis of proteinaceous or calcareous material. Other examples include the encrusting genera Thrombophyton McFadden & Hochberg, 2003, which falls within the gorgonian family Paramuriceidae, and Discophyton McFadden & Hochberg, 2003 (recently assigned to the monotypic family Discophytidae), which belongs to a larger clade that consists almost exclusively of gorgonians (
Placement of Aliena gen. nov. in Pterogorgiidae requires amending the diagnosis of that family to accommodate a species that lacks an axis (changes in bold):
Octocorals with (or rarely without) a proteinaceous skeletal axis. Axis hollow with wide, cross-chambered central core. Colonies encrusting or erect, sparsely to profusely branched (dichotomous, pinnate), planar or bushy; branches may be flattened, oval or triangular in cross-section. Polyps monomorphic, retractile into coenenchyme or into low calyces, distributed evenly over branch surface or arranged biserially in recessed grooves along branch margins. Polyp sclerites small, flattened rods or slender spindles only rarely arranged as collaret and points. Sclerites of coenenchyme typically include asymmetrically spiny or curved spindles with or without complex tubercular ornamentation; capstans, asymmetrical clubs or balloon-clubs, double-heads or plates may also be present. Zooxanthellate or azooxanthellate.
Aliena gen. nov. is the second genus of Pterogorgiidae known to have a distribution in the Pacific, and the only one recorded so far from the eastern Pacific. The majority of the taxa in this family are distributed in the tropical Atlantic.
We are grateful to the anonymous reviewers, Kaveh Samimi-Namin and Bert Hoeksema for their suggestions and comments that improved our publication. We thank the Servicio Nacional de Áreas Protegidas de Costa Rica and the personnel of the Parque Nacional Isla del Coco for allowing our research at the Island. Our appreciation to the crew of the M/V Argo (UnderSea Hunter Group) and the M/V Okeanos Aggressor I. We thank Avi Klapfer and Anuar Patjane for the submarine pictures, Beatriz Naranjo for collecting samples and photographs, Fiorella Vásquez for helping with the microscope photographs and Katie Erickson for laboratory assistance.
The authors have declared that no competing interests exist.
No ethical statement was reported.
The research was funded by Vicerrectoría de Investigación, Universidad de Costa Rica (projects C1081, C1083, and C2014) and Fundación Amigos de la Isla del Coco, FAICO.
OB Conception and design of the work, data collection, collection and curation of specimens, morphological analyses, taxonomic interpretation, preparation of figures and writing the article. CMF Molecular and phylogenetic analyses, design and interpretation, writing the article and final approval of the version to be submitted. JC Specimen collection and photographs. Financial support.
Odalisca Breedy https://orcid.org/0000-0001-5686-4164
Catherine S. McFadden https://orcid.org/0000-0002-8519-9762
Jorge Cortés https://orcid.org/0000-0001-7004-8649
All of the data that support the findings of this study are available in the main text or Supplementary Information.
Sequences included in molecular phylogenetic analyses of Order Malacalcyonacea
Data type: Phylogenetic
Phylogenetic relationships of Order Malacalcyonacea based on maximum likelihood analysis of 28S rDNA
Data type: Phylogenetic
Explanation note: Numbers on branches are bootstrap percentages from 1000 ultrafast bootstrap replicates.
Phylogenetic relationships of Order Malacalcyonacea based on Bayesian analysis of mtMutS
Data type: Phylogenetic
Explanation note: Numbers on branches are posteriori probabilities.
Phylogenetic relationships of Order Malacalcyonacea based on Bayesian analysis of 28S rDNA
Data type: Phylogenetic
Explanation note: Numbers on branches are posteriori probabilities.