Research Article |
Corresponding author: Yehuda Benayahu ( yehudab@tauex.tau.ac.il ) Academic editor: Bert W. Hoeksema
© 2018 Yehuda Benayahu, Leen P. van Ofwegen, Catherine S. McFadden.
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:
Benayahu Y, van Ofwegen LP, McFadden CS (2018) Evaluating the genus Cespitularia MilneEdwards & Haime, 1850 with descriptions of new genera of the family Xeniidae (Octocorallia, Alcyonacea). ZooKeys 754: 63-101. https://doi.org/10.3897/zookeys.754.23368
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Several species of the family Xeniidae, previously assigned to the genus Cespitularia Milne Edwards & Haime, 1850 are revised. Based on the problematical identity and status of the type of this genus, it became apparent that the literature has introduced misperceptions concerning its diagnosis. A consequent examination of the type colonies of Cespitularia coerulea May, 1898 has led to the establishment of the new genus Conglomeratusclera gen. n. and similarly to the assignment of Cespitularia simplex Thomson & Dean, 1931 to the new genus, Caementabunda gen. n. Both new genera are described and depicted and both feature unique sclerite morphology, further highlighting the importance of sclerite microstructure for generic position among Xeniidae. Freshly collected material was subjected to molecular phylogenetic analysis, whose results substantiated the taxonomic assignment of the new genera, as well as the synonymies of several others.
Indo-Pacific Ocean, new genera, phylogeny, sclerite microstructure, taxonomy
Members of the octocoral family Xeniidae form a major faunistic component on shallow Indo-Pacific coral reefs (e.g.,
The majority of the described Xeniidae taxa have a high density of minute sclerites in their tissues, although some have only a few or none (e.g.,
There is considerable confusion in the literature concerning the diagnosis of the xeniid genus Cespitularia. This genus was erected by Valenciennes in an unpublished manuscript and later published by Milne Edwards and Haime (1850). The type of Cornularia multipinnata Quoy & Gaimard, 1833 collected in Tonga (West-Pacific) was designated to be the type species of the genus;
Drawings of the type of Cornularia multipinnata Quoy & Gaimard (1833) (plate 22, figs 1–4), depict a colony with a distinct dome–shaped capitulum bearing polyps as well as a bare stalk with no polyps (fig. 4), thus resembling Xenia (see e.g.,
The genus Cespitularia Milne Edwards & Haime, 1850 was first revised by
The ambiguity concerning the diagnosis of Cespitularia is further demonstrated in C. mollis (Brundin, 1896), originally described as Suensonia mollis, whose type locality is the Korean Straits (120 m depth).
At present, the literature refers to 18 species of the genus Cespitularia (
The study examined preserved type specimens obtained on loan from the British Museum of Natural History (
Morphological features of the preserved colonies were recorded, comprising dimensions, branching and stalk length, and width of the stalk at the colony base. The number of rows of pinnules and number of pinnules on the aboral side of the tentacles were counted under a dissecting microscope, whenever possible from multiple polyps. The length of the anthocodiae, consisting of the polyp body and extended tentacles, and the dimensions and shape of the pinnules were also recorded (see also
Freshly collected material used for molecular and morphological studies was collected by YB in Yonaguni Is., Ryukyu Archipelago, Japan (in 2010); Green Is., Taiwan (2012) and Nosy Be, Madagascar (2015). Xeniidae colonies tend to release large quantities of mucus, especially when being detached from the reef and brought onboard, which is particularly relevant to the taxa studied here. This usually causes rapid colony disintegration and poor condition of museum material. Therefore, upon collection samples were immediately preserved in 95 % ethanol and subsamples were removed and preserved in absolute ethanol for molecular studies and then placed on ice in cool boxes until brought to the laboratory. In order to ensure appropriate preservation, the fixatives were replaced twice within 24 hours after collection, and throughout all preservation steps, the bottles were shaken to enhance infiltration of the fixative into the tissues.
DNA was extracted from ethanol-preserved tissue samples using the Qiagen DNEasy Blood & Tissue kit, and three gene regions were subsequently amplified by polymerase chain reaction (PCR) using previously published primers and PCR protocols (
Cespitularia coerulea May, 1898: 21
Colonies soft with a short but distinct stalk, ramified into primary branches and occasionally into secondary ones. Polyps monomorphic, found along the branches, sometimes down on the stalk; most are non-retractile. Sclerites of a wide diversity of forms and dimensions, many lacking a distinct repetitive morphology. They include spheres, spherules, and small dumbbell-like sclerites. They are commonly cemented together, forming heterogeneous morphologies of various shapes and sizes. Occasionally, the aggregates form plate-like structures, embedded with spheres and/or spherules. The abundance of sclerites can vary greatly; in some specimens they are rare and then mostly found only at the colony base, and occasionally they may be found in all parts of the colonies, or may even be entirely absent. Zooxanthellate.
The generic name is derived from Latin conglomerātus, which refers to anything composed of heterogeneous materials or elements and sclera from Greek meaning sclerite. Here it denotes the sclerites that resemble the geological structures termed conglomerates, a feature comprising rounded to sub-angular clast of granules, pebbles or cobbles cemented together. Gender female.
Cespitularia
coerulea
May, 1898: 21;
Cespitularia
taeniata
May, 1899: 89–90;
Syntypes: ZANZIBAR:
JAPAN:
The original description of C. coerulea by
Conglomeratusclera coerulea (May, 1898), syntypes
The type material of Cespitularia taeniata (
A colony labeled as
The original descriptions of Cespitularia coerulea by
Since the original description of C. coerulea a number of studies have assigned specimens to that species.
When alive, the color of colonies ranges from vibrantly bluish-purple, light green, light yellow-beige, light cream to almost white (see Figure
Live colonies on the reefs of Green Is. Taiwan. A–B Conglomeratusclera coerulea (May, 1898). C Caementabunda simplex (Thomson & Dean, 1931) with expanded polyps D C. simplex (Thomson & Dean, 1931) with partially retracted polyps. Photo credit Chang-Feng Dai, National Taiwan University, Taiwan.
In the current study, examination of the colonies from Green Is., Yonaguni Is. and Madagascar was based on both morphological characters (colony shape, pinnule count, and sclerite features), along with DNA sequencing; the latter enabled us to construct a phylogenetic tree (Figure
The following findings denote the number of pinnules found in some of the sequenced colonies (Figure
Maximum likelihood tree of family Xeniidae based on a partitioned analysis of concatenated mtMutS, COI and 28S rDNA gene regions. Numbers above nodes: ML bootstrap percentages; numbers below nodes: Bayesian posterior probabilities. All genera and major clades of Xeniidae other than Caementabunda and Conglomeratusclera have been collapsed to facilitate readability. Specimens of Caementabunda and Conglomeratusclera are identified by
The sclerites of the colonies noted above featured the full array of morphologies, mostly corresponding to that of the syntypes (Figures
The molecular results indicate that despite the differences in pinnule count and sclerite morphology, all the colonies should be assigned to the same species (Figure
Material that was examined, but not sequenced, comprised both freshly collected colonies and museum specimens. Their colony and polyp morphologies, including the pinnule counts, are in agreement with the findings presented above. Noteworthy are some colonies for which SEM or light microscopy could not detect any sclerites. There are several suggested reasons for this: (1) actual lack of sclerites; (2) their low incidence which led to a failure to detect them by SEM; or (3) preservation procedures, such as acidic conditions that may have caused sclerite dissolution.
The museum material examined included colonies from the
Kenya; Zanzibar; Tanzania; Glorioso Islands; Mauritius; Seychelles; Mayotte; Taiwan; Philippines; Japan (Tanabe, Wakayama, Shikoku); Ryukyu Archipelago; Indonesia.
Cespitularia
robusta
Tixier-Durivault, 1966: 335–356;
Examination of the type material of Cespitularia robusta Tixier-Durivault, 1966 (MNH00000167) revealed five colonies (Figure
The colonies assigned by us to C. coerulea feature one row of pinnules along the margins of the tentacles, whereas C. robusta has two rows. In order to determine whether a difference in pinnule-row count is indeed diagnostic for species delineation in Conglomeratusclera, corresponding fresh colonies with two pinnule-rows should be sequenced. Therefore, for the time being only the generic status of C. robusta is changed, making it the second species in the new genus.
Mayotte; Aride Island, Seychelles.
Cespitularia simplex Thomson & Dean, 1931
Colonies quite flaccid with a distinct but short encrusting base bearing primary lobes, sometimes divided into secondary ones. Non-retractile monomorphic polyps found on the lobes and occasionally down on some parts of the base. The spherical-oval sclerites are composed of a myriad of densely packed chip-like microscleres. Zooxanthellate.
The generic name refers to the microstructure of the sclerites, which are composed of multitudes of microscleres, resembling aggregates of cement chips. The name is derived from the Latin caementum, cement, and abunda meaning copious. Gender feminine.
Cespitularia
simplex
Thomson & Dean, 1931: 33–34;
Syntype: INDONESIA: ZMA 2344, Siboga Exped., Sta. 40, 12 m depth, Kawassang. Other material: SEYCHELLES:
The syntype
Live colonies are brown with yellow polyps (Figures
The original description of the type by Thomson & Dean (1931: 34) is in agreement with the current findings, and indicates 10–12 pinnules compared to 12–14 noted by us. The sclerite size of 0.01 mm as given in the original description is incorrect and was later corrected by
Examination of the type of Cespitularia turgida Verseveldt, 1971 (
Dr. Zena Dinesen (Department of Agriculture, Fisheries and Forestry, Queensland) provided us with an unpublished taxonomic manuscript dealing with some Xeniidae of Flinders Reefs, Great Barrier Reef. Under the collection numbers
All other material (see above) features the same sclerites described above for the syntype (Figure
Sequences of mtMutS (582 bp), igr1+COI (767 bp) and 28S rDNA (755 bp) were obtained from 46 individuals of Conglomeratusclera and nine individuals of Caementabunda from three different geographical locations: Madagascar; Green Is., Taiwan; Yonaguni Is., Japan (GenBank accession nos. MH071812–MH071969). All phylogenetic analyses of individual gene regions as well as the concatenated alignment (2104 bp) recovered trees in which specimens of Conglomeratusclera and Caementabunda formed two separate, well-supported clades (Figure
All individuals of Conglomeratusclera shared identical sequences at mtMutS and COI, with just two exceptions: a single individual from Taiwan (
All Caementabunda specimens also shared identical mtMutS and COI sequences, with the exception of a single individual (
Morphological and molecular phylogenetic analyses support the reassignment of the former species Cespitularia coerulea and C. simplex into two separate genera; Conglomeratusclera n. gen. and Caementabunda n. gen., respectively. They are distinguished by differences in sclerite microstructure as well as genetic distances comparable to those among other well-defined genera of the family Xeniidae. In addition, the findings justify synonymy of C. taeniata and C. turgida with each of these two new genera, respectively. We are at present only able to distinguish a single species in each of the new genera, based on both morphology and genetics. It should be noted that the status of C. robusta as a second species of Conglomeratusclera remains to be verified genetically. A recent study of the xeniid genus Ovabunda found a lack of congruence between the morphological characters traditionally used to diagnose species, in particular the number of rows of pinnules and pinnules per row, and genetic evidence of species boundaries (
Part of this research (Applications DE-TAF-662 and GB TAF 3027) received support from the SYNTHESYS Project http://www.synthesys.info/ which is financed by the European Community Research Infrastructure Action under the FP7 “Capacities” Program. It was also in part supported by a Temminck Fellowship, Naturalis Biodiversity Center, and the Israel Cohen Chair in Environmental Zoology to Y.B. We thank the curators at the following museums for enabling examination of material in their possession: A. Cabrinovic, The Natural History Museum London; C. Lüter, Zoologisches Museum Berlin; A. Schmidt-Rhaesa, Zoologisches Museum, Hamburg; J. van Egmond, Naturalis Biodiversity Center, formerly Rijksmuseum van Natuurlijke Historie, Leiden; S.D. Cairns, Smithsonian National Museum of Natural History, Washington DC and A. Andouche, Musee d’Histoire Naturelle, Paris. Support for collection field trips was generously provided in Taiwan by M-S. Jeng, Biodiversity Research Center, Academia Sinica; in Japan by J. Tanaka, Department of Chemistry, Biology and Marine Science, University of the Ryukyus, and in Madagascar by M. Aknin, University of Reunion Island. We acknowledge A. Shlagman for professional curatorial skills, V. Wexler for digital editing, N. Paz for editorial assistance, M. Weis and A. Gonzalez, S. Shi, and P. Hong for technical assistance. We are grateful to the reviewers and the editor for their constructive comments that greatly improved the manuscript.