Research Article |
Corresponding author: Yehuda Benayahu ( yehudab@tauex.tau.ac.il ) Academic editor: Bert W. Hoeksema
© 2017 Yehuda Benayahu, Catherine S. McFadden, Erez Shoham.
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, McFadden CS, Shoham E (2017) Search for mesophotic octocorals (Cnidaria, Anthozoa) and their phylogeny: I. A new sclerite-free genus from Eilat, northern Red Sea. ZooKeys 680: 1-11. https://doi.org/10.3897/zookeys.680.12727
|
This communication describes a new octocoral, Altumia delicata gen. n. & sp. n. (Octocorallia: Clavulariidae), from mesophotic reefs of Eilat (northern Gulf of Aqaba, Red Sea). This species lives on dead antipatharian colonies and on artificial substrates. It has been recorded from deeper than 60 m down to 140 m and is thus considered to be a lower mesophotic octocoral. It has no sclerites and features no symbiotic zooxanthellae. The new genus is compared to other known sclerite-free octocorals. Molecular phylogenetic analyses place it in a clade with members of families Clavulariidae and Acanthoaxiidae, and for now we assign it to the former, based on colony morphology. The polyphyletic family Clavulariidae is, however, in need of a thorough revision once the morphological distinctions among its phylogenetically distinct clades are better understood.
Octocorallia , new genus, taxonomy, mesophotic coral ecosystem, Eilat, Red Sea
Sclerites are microscopic, calcitic skeletal elements embedded in the tissues of certain groups of invertebrates, such as holothurians, tunicates and octocorals. Amongst the latter, they are considered to be one of the most prominent characteristic features and their form and anatomical arrangement are of major taxonomic importance (
Octocorals that completely lack sclerites or other calcitic skeletal elements have been described previously within seven octocoral families. These include the Acanthoaxiidae: Acanthoaxis wirtzi Ofwegen & McFadden, 2010; Acrossotidae: Acrossota amboinensis (Burchardt, 1902) (see also
The majority of species in the families Alcyoniidae, Clavulariidae and Xeniidae have sclerites, however species without sclerites represent unusual exceptions. The families Alcyoniidae and Clavulariidae are highly polyphyletic (
Samples were collected by ROV (ECA H800) operated at a depth range of 50-190 m, by Sam Rothberg R/V of the Interuniversity Institute for Marine Sciences in Eilat (IUI). In situ photography was carried out by a low-light black and white camera VS300 (Eca Robotics) and 1CAM Alpha HD camera (SubCimaging). Samples were obtained by the ROV arm; fragments were removed on board and preserved in 100% ethanol for molecular work. The original samples were placed in 70% ethanol for taxonomic identification, and deposited at the Steinhardt Museum of Natural History, Israel National Center for Biodiversity Studies (ZMTAU).
DNA was extracted from EtOH-preserved samples, and two mitochondrial gene regions (mtMutS, igr1 + COI) were sequenced using previously published primers and protocols (
Clavulariinae with a thin and soft encrusting base, sometimes resembling a short stolon. Polyps erect when expanded, separate from each other; the stolon may feature a few polyps, occasionally only one. Polyps fully retractile into base of the colony, forming low truncated dome-shaped mounds. No sclerites in any part of the colony. Colonies lack symbiotic algae (zooxanthellae). Type species: Altumia delicata sp. n. by original designation and monotypy.
The generic name is derived from the Latin ‘altum’, deep, referring to the habitat of the new genus at MCE depths and beyond. Gender female.
Maximum likelihood and Bayesian analyses yielded identical tree topologies that both support the phylogenetic placement of Altumia n. gen. as the sister taxon to Acanthoaxis wirtzi (Acanthoaxiidae), within a larger well-supported clade that also includes the Clavulariidae genera Carijoa F. Müller, 1867 and Cryptophyton Williams, 2000 (Figure
Phylogenetic relationships among species of octocorals that lack sclerites (red asterisks) and members of family Clavulariidae (blue labels), including Altumia delicata gen n. sp. n. (red label). Solid circles at nodes indicate strong support from both maximum-likelihood (bootstrap value >70%) and Bayesian (posterior probability >0.90) analyses; split circles indicate strong support from one analysis only (left half solid: supported by ML; right half solid: supported by Bayesian analysis). Strongly supported clades that include no clavulariid or sclerite-free species have been collapsed. Hexacorallian outgroup taxa used to root tree are not shown. For a comprehensive list of taxa and sequences included in the analyses see
ZMTAU CO 37427, Israel, Gulf of Aqaba, Eilat, 29°30'38.31"N, 34°55'59.30"E, 132 m, 30 May 2016, collected by ROV, coll. M. Weis; paratype: ZMTAU CO 37495, Israel, Gulf of Aqaba, Eilat, 29°30'37.29"N, 34°55'59.28"E, 118 m, 8 March 2017, collected by ROV, coll. M. Weis
The ethanol-preserved holotype is comprised of thin patches of short stolon-like crusts growing over the dead branch of a black coral (Antipatharia) (Figure
When alive, the delicate, semi-transparent expanded polyps are distinct and are up to 20 mm long, featuring eight pinnate tentacles (Figure
There are no differences between the holotype and the paratype except for the size of the colonies.
The species name is formed from the Latin ‘delicata’, delicate, referring to the fine texture of the colonies and their polyps. Gender female.
Assignment of Altumia gen. n. to family Clavulariidae is complicated by the recognition that this family is highly polyphyletic, comprising at least seven distinct clades distributed across the Octocorallia (
Despite its morphological similarity to Cervera and Phenganax, the molecular phylogenetic analyses suggest that Altumia gen. n. is not closely related to either of those genera (Figure
At present there is only scant information on MCE octocorals (
The current study highlights the possibility that MCEs may host octocorals also found below the deepest fringes of these MCEs; and that specifically, deep-water octocorals may populate the zone alongside those of the lower MCEs, contributing to the biodiversity there. Consequently, questions related to the genetic/demographic connectivity between MCEs and shallower reefs (
We thank the Interuniversity Institute for Marine Sciences in Eilat (IUI) for the use of the Sam Rothberg R/V and the professional assistance of its crew members. We are indebted to EcoOcean staff members for operating the ROV. The reviewers are acknowledged for their important comments which improved the manuscript. We acknowledge M. Weis and R. Liberman for help in the field work, A. Gonzalez for laboratory assistance, A. Shlagman for curatorial skills, V. Wexler for digital editing and N. Paz for editorial assistance. This research was supported by the TASCMAR project (Tools and Strategies to access original bioactive compounds from cultivated marine invertebrates and associated symbionts) that has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 634674; and by the Israel Cohen Chair in Environmental Zoology to YB. Collection of animals complied with a permit issued by the Israel Nature and National Parks Protection Authority.