The authors have declared that no competing interests exist.
Conceived and designed the experiments: MD FR. Performed the experiments: MD. Analyzed the data: MD. Contributed reagents/materials/analysis tools: FR RZ. Wrote the manuscript: MD FR.
Exploration of the lower surface of the Ross Ice Shelf in Antarctica by the Submersible Capable of under-Ice Navigation and Imaging (SCINI) remotely operated vehicle discovered a new species of sea anemone living in this previously undocumented ecosystem. This discovery was a significant outcome of the Coulman High Project’s geophysical and environmental fieldwork in 2010-2011 as part of the ANDRILL (ANtarctic geologic DRILLing) program.
The biota associated with glacial ice is poorly documented because the habitat is largely inaccessible and is technologically difficult to access. As part of the multi-national ANtarctic geological DRILLing (ANDRILL) program, a remotely operated vehicle called the Submersible Capable of under-Ice Navigation and Imaging (SCINI) [
The site labeled A is at 77° 31.6’ S 171° 20.1’ E ; this corresponds to “Site 3” for the 2010-2011 SCINI dive series. The site labeled B is at 77° 28.03’ S 171° 36.28’ E ; this corresponds to “Site 4 (CH-1)” for the for the 2010-2011 SCINI dive series (Rack et al., 2012).
At 77° 31.6’ S 171° 20.1’ E (
A. Close up of specimens
These animals are sea anemones of a new species, here described as
This is the first species of sea anemone reported to live in ice. Previously described species of sea anemones from Antarctica are reported from hard [
The unprecedented habitat of
Specimens were removed from the ice using an improvised suction sampler mounted on the outside of the SCINI remotely operated vehicle. The sampler consists of a plastic tube with an opening positioned within the SCINI forward camera’s field of view that is connected through a one-way valve to a water filter and chamber where the samples are collected and stored until the vehicle is recovered to the surface. An external, inverted tunnel thruster powered by the vehicle is connected to the distal end of the plastic tube and sampling chamber to provide water suction. The SCINI vehicle was flown under the ice shelf and positioned so that the tube opening was close to the seawater-ice interface and thus able to capture the organisms as they floated by or were extracted from their ice shelf burrows. Hot water from the drill system was pumped down from the surface of the ice shelf and used to flood the basal ice to stun the organisms and assist with the extraction process. Once the vehicle was recovered, the suction sampler was disassembled and the specimens were placed in ethanol for the helicopter trip back to McMurdo Station, where some samples were transferred to formalin for long-term preservation and further study. More than 20 samples were collected using this device mounted on the SCINI vehicle during a series of dives through the ice shelf.
75 049-M (PI = F. Rack) based on a permit request that was processed by the U.S. National Science Foundation (NSF) pursuant to the Antarctic Conservation Act as amended by the Antarctic Science, Tourism and Conservation Act (NSF Form 1078). NSF determined that no specific permit was required to collect marine anemones from under the Ross Ice Shelf at this location.
Whole formalin-fixed specimens were examined and photographed under a dissecting microscope. Four formalin-fixed specimens were dehydrated and embedded in paraffin, serially-sectioned at 10 µm, and stained in Heidenhain’s Azan [
The electronic edition of this article conforms to the requirements of the amended International Code of Zoological Nomenclature, and hence the new names contained herein are available under that Code from the electronic edition of this article. This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information viewed through any standard web browser by appending the LSID to the prefix "http://zoobank.org/". The LSID for this publication is: urn:lsid:zoobank.org:pub:BB12B7B1-89F4-4DE3-ADCA-66CE0EA8D149. The electronic edition of this work was published in a journal with an ISSN, and has been archived and is available from the following digital repositories: PubMed Central, LOCKSS. The holotype and paratypes have been deposited in the American Museum of Natural History.
Order Actiniaria
Family Edwardsiidae Andres, 1881
Actiniaria with elongate, vermiform body usually divisible into two or more regions: between long scapus provided with periderm and short capitulum may be short scapulus lacking periderm and ectodermal specializations. Aboral end rounded, may be differentiated into physa. No sphincter or Acontia. Mesenteries divisible into macro- and micro-cnemes; always eight perfect macrocnemes and at least four microcnemes. Macrocnemes comprise two pairs of directives and four lateral mesenteries, two on each side, whose retractors face ventral directives. Retractors diffuse to strongly restricted; parietal muscles always distinct [
Genus
Edwardsiidae with column clearly differentiated into capitulum and scapus. Three or more cycles of tentacles. Tentacles hexamerously arranged, those of innermost cycle longest. Capitulum ridged; nematocysts concentrated on ridges. Scapus generally bears periderm, always lacks nemathybomes or tenaculi. Aboral end rounded but not differentiated into a physa. Ciliated tracts of filaments short, discontinuous [
All scale bars =100µm unless otherwise noted. A. Cross section through actinopharynx showing mesenteries and siphonoglyph. Scale = 500µm. B. Cross section through tentacle showing relatively strong ectodermal musculature and abundant spirocysts. C. Longitudinal section through oral disc showing relatively weak ectodermal musculature. Scale bar =20 µm. D. Gametogenic region of mesentery of female specimen. E. Cross section through distal column showing microcnemes. F. Close-up view of actinopharynx, showing histological differentiation of siphonoglyph. G. Trophonema of mature oocyte. Scale bar =30 µm. H. Retractor and parietal muscle of macrocnemic mesentery. I. Retractor muscle of Macrocneme. J. Musculature of base of tentacle. K. Junction between aboral end and mesentery. Note absence of basilar muscles. Scale bar =25 µm. L. Longitudinal section through distal column showing transition between tentacle and capitulum. M. Longitudinal section through scapus. Scale bar =30 µm. N. Longitudinal section through aboral end.
Abbreviations: Apx, actinopharynx; Cap; capituluar ectoderm; DD, dorsal directive mesentery; DL, dorsolateral mesentery; G, gastrodermal side of body wall; P; junction of mesentery and retractor muscle; S, siphonoglyph; T, tentacle; VD, ventrolateral directive mesentery; VL, ventrolateral mesentery.
Scale at bottom, in µm, applies to all images. See
Small basitrichs | none seen | 17-19.7 x 3-3.5 | ||
Basitrichs (A) | (29.5) 33.1-46.6 (48.5) x 3.5-5.3 | 2:2 | 58 | 17-24 x 4.2-5.6 |
Spirocysts (B, C) | 19.5-37.1 (39.9) x 2.9-6.3 | 2:2 | 62 | none reported |
Small basitrichs (D) | 15.4-20.2 x 2.2-3.0 | 2:2 | 16 | 14-21.5 x 3.5-4.2 |
Basitrichs (E) | 41.2-46.6 x 4.3-5.1 | 2:2 | 6 | (22.6) 26.8- 36.7 x 5.6-8.5 |
Small mi. mastigophores (F) | 9.9-13.7 x 2.4-4.0 | 2:2 | 22 | none reported |
Spirocysts (G) | 24.0-32.4 x 3.9-6.0 | 2:2 | 9 | none reported |
Small basitrichs | none seen | 15.5-19.7 x 2.5 | ||
Basitrichs (H) | 16.0-24.7 x 2.3-3.5 | 3:3 | 33 | 22.6-25.4 x 3.5-5 |
Mi. |
18.3-27.5 x (4.3) 4.3-6.7 | 3:3 | 65 | 18.3-24.0 x 3.5-5.6 |
Small basitrichs (J) | 20.0-31.3 x 2.0-3.1 | 2:2 | 14 | 15.5-19.7 x 2.8 |
Basitrichs (K) | 39.6-54.3 x 3.0-5.3 | 2:2 | 35 | none reported |
Mi. |
17.3-28.6 x 4.4-6.3 | 2:2 | 28 | 21.0-24.0 x 3.0-3.5 |
Specimens (S) indicates how many of the sampled specimens contained a particular type of cnida; Number (N) is the total number of capsules measured. The letter in parentheses after each type refers to
Column naked: no periderm or cuticle. In preserved specimens, capitulum short, same yellowish-white color as scapus, ridges faint; scapus long, smooth, tapers from widest point at junction with capitulum to slightly pointed aboral end (
Longitudinal muscles of tentacles (
Eight macrocnemes of equal size and development (
Parietal muscle strongly restricted, with thick mesoglea and few, globular folds; muscle approximately equally developed on both surfaces but not symmetrical (
Cnidom Spirocysts, basitrichs, microbasic
Specimens were observed at 77° 31.6’ S 171° 20.1’ E and 77° 28.03’ S 171° 36.28’ E (
This species is named after the
Although most edwardsiids are burrowers in soft sediments [
Most species of
All eggs in the sectioned individuals are at approximately the same developmental stage (
The means by which
FR and RZ are grateful for the field support received from both the US Antarctic Program and Antarctica New Zealand, and for the use of shared ANDRILL consortium equipment. We acknowledge the contributions of Dustin Carroll and Paul Mahacek, who helped pilot and maintain the SCINI vehicle during the Dives, and the rest of the ANDRILL CHP survey team, especially the drillers, who contributed to the discovery of this unusual environment and these organisms.
This manuscript was improved through comments by Estefania Rodriguez and an anonymous reviewer.