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Description

provided by NMNH Antarctic Invertebrates

"Flabellum curvatum Moseley, 1881

Flabellum curvatum Moseley, 1881, pp. 174, 175, pi. 6, figs. 3a-3d.—Gardiner, 1939, pp. 327, 328 (part: WS sta. 839 only) .—Squires, 1961 (part: not Vema sta. 14-18), pp. 7, 9, 29, 38, 39, figs. 5, 11-13, 20, 22, 30.—Not F. curvatum; Squires, 1962a, pp. 1-11, figs. 1-3 (is F. thouarsii Milne Edwards and Haime, 1848).—Squires, 1962b, p. 14; 1964a, p. 13; 1964c, pi. 1, fig. 1; 1969, p. 18, pi. 6, map 3.—Cairns, 1979, p. 206.

Flabellum antarcticum; Keller, 1974, pp. 203-205, pi. 5, figs. 1-7.

Description. Corallum ceratoid to trochoid, rarely attached above GCD of 12 mm. Pedicel long, slender (2.5-3.3 mm in diameter), and usually bent; base of pedicel often worn to a point in older specimens. Corallum usually curved, enlarging gradually from pedicel to calice. Largest specimen examined 44 x 30 mm in CD and 47 mm tall. Theca usually worn or encrusted with bryozoans, serpulids, or other corals; sometimes thin, incised costal lines present, one corresponding to each septum. Calice elliptical, with GCD/LCD ratios of 1.4-1.6; calicular profile arched. Septa hexamerally arranged in five cycles. S1

and S2 equal in size and usually slightly larger than S3. S4 about half size of S3; S5 rudimentary and sometimes fenestrate because of weakly calcified trabeculae. Septa not exsert; upper edge of each larger septum forming shallow, concave notch near calicular edge. This notch often dentate but not always. Inner edges of larger septa straight to slightly sinuous and thickened lower in fossa. This thickening, along with

loose fusion of irregular processes from lower inner edges of larger septa, forming rudimentary columella. Septal granulation variable, ranging from low and rounded to high, slender, pointed granules, usually arranged in rows subparallel to septal edges. Fossa elongate and relatively shallow. Stereome present in elongate specimens.

Remarks. F. curvatum usually settles on pebbles 3-4 times the diameter of its original attachment. Its bent pedicel and curved corallum probably reflect a reorientation of the polyp after it detaches from its substrate or when it becomes so heavy that it topples sideways. It also attaches to coralla of its own species, echinoid spines, and branching bryozoans. In turn, the theca of the living coral provides a substrate for numerous species of Bryozoa, serpulid polychaetes, barnacles, hydrocorals, and other scleractinians. F. curvatum probably occurs in fairly high density off East Falkland island, indicated by the recovery of over 2500 specimens from a 68-min trawl.

Discussion. As is indicated by the synonymy, F. curvatum has often been confused with F. thouarsii, a closely related species. In fact, both Wells (1958) and Keller (1974) have synonymized these species. After thorough reexamination of this species complex I find that F. curvatum can be distinguished by a combination of the following characters: (1) the pedicel is usually bent and the corallum is usually curved; (2) the pedicel is longer; (3) the maximum size of the corallum is larger; (4) the septal notch is sometimes dentate; (5) the S4 are relatively larger than those of F. thouarsii; and (6) the fossa is usually shallower, sometimes partially occupied by a crispate columella. Characteristics of attachment and pedicel diameter mentioned by Squires (1961) are of no diagnostic value. Furthermore, although their depth ranges overlap, F. curvatum is usually found deeper than F. thouarsii. F. curvatum is distinguished from F. impensum by its coarser septal granulation, smaller PD, usually curved corallum, shallower fossa, and geographical distribution.

Material. Eltanin sta. 339 (73), USNM 47238; sta. 340 (139), USNM 47253; sta. 556 (8),. USNM 47243; sta. 558 (about 2500), USNM 47254; sta. 740 (6), USNM 47239; sta. 1536 (11), USNM 47242. Hero sta. 715-875 (126), USNM 47251; sta. 715-885 (1), USNM 47245; sta.715-895 (35), USNM 47252. Vema sta. 14-12 (4), USNM 45652, and (8), AMNH; sta. 15-PD3 (5), USNM 47240; sta. 15-PD4 (39), USNM 47250; sta. 15-PD9 (3), USNM 47241; sta. 15-PD10 (5), USNM 45626, and (11), AMNH; sta. 17-59 (2), USNM 45653; sta. 17-100 (24), USNM 45621, and (37), AMNH; sta. 17-101 (9), USNM 45624, and (32), AMNH; sta. 18-8 (7), USNM 45620; sta.. 18-12 (16), USNM 45622. Calypso sta. 171 (2), USNM 47246; sta. 172 (4), SME. BR sta.. 25149 (5), USNM 47244. Specimens of Squires (1961, 1962a), USNM; specimens of Gardiner (1939) from WS sta. 839, BM 1939.7.20.129. Two syntypes (BM 1880.11.25.85 and 1974.8.5.10).

Types. The eight syntypes of F. curvatum are deposited at the British Museum. Type-locality: 37°17’S, 53°52'W (off Rio de la Plata, Uruguay); 1097 m.

Distribution. Off southeastern South America from Rio de la Plata, Uruguay, to Cape Horn; Burdwood Bank; off Falkland Islands (Islas Malvinas); off South Georgia. Depth range: 115-1137 m; however, most

common between 400 and 800 m." Cairns 1982, pp. 35-38, Plate 10, figs. 10, 11; Plate 11, figs. 6-9.

Flabellum curvatum

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Flabellum curvatum is a species of marine, cold water coral in the family Flabellidae. It is an azooxanthellate coral, that is to say without symbiotic zooxanthellae. The species is native to deep waters around Antarctica.

Description

F. curvatum is a small, solitary coral growing to a height of some 3 to 4 cm (1.2 to 1.6 in). The slit-like mouth of the fleshy polyp is surrounded by a whorl of tentacles. The polyp secretes the corallum, the stony skeleton which supports it. In this species, the corallum is not attached to the seabed, but may be semi-immersed in soft sediment.[2]

Distribution

F. curvatum occurs in the Southern Ocean around Antarctica, but is also known from the southwestern Pacific Ocean and the southwestern Atlantic Ocean. It occurs on the continental slope, but it appears to have a disjunct distribution, with gaps between the various locations in which it has been found.[3] It is a deep water coral, an azooanthellate species, the tissues of which do not harbour symbiotic algae.[1] Its depth range is 115 to 1,137 m (377 to 3,730 ft), with breeding corals off the west Antarctic Peninsula being at around 500 m (1,640 ft).[4]

Biology

The sexes are separate in F. curvatum, and like a number of other deep sea corals, the female broods its planular larvae. They are retained in the gastrovascular cavity where they are embedded in the mesenterial gastrodermis, with up to four per mesentery. Before they are released, the larvae have developed tentacle buds and an oral disc. In this and in other deep sea brooding corals, the oocytes are large (maximum diameter of 5120 μm in this species) and have large yolks to nourish the developing larvae. Fecundity is high, with a mean of 1618 oocytes per polyp. It is not clear why some scleractinian species brood their young, whereas others in similar habitats do not, but brooding does result in the ability of the larvae to settle almost immediately after liberation, and avoid a lengthy and risky planktonic stage.[5][6]

In some corals that brood their young, the larvae are released in batches along with quantities of mucus and often seem to be forced out by an expulsive effort by the polyp. This is not the case with F. curvatum; the larvae are released singly, without mucus, and appear to be wafted out by cilia on the wall of the polyp's pharynx. The larvae soon sink to the sea floor nearby, and some are found to settle on the corallum of an adult.[2] Within days of expulsion they are upright, each with twelve stumpy tentacles, twelve pairs of mesenteries, an oral disc and a mouth.[2] Newly settled juveniles have been found at various times of year, so breeding appears to take place at any time of year.[2]

References

  1. ^ a b Cairns, Stephen (2010). "Flabellum (Flabellum) curvatum Moseley, 1881". WoRMS. World Register of Marine Species. Retrieved 29 August 2017.
  2. ^ a b c d Squires, Donald F. (1962). "Deep Sea Corals Collected by the Lamont Geological Observatory. 3 Larvae of the Argentine Scleractinian Coral Flabellum curvatum Moseley" (PDF). American Museum Novitates (2078). hdl:2246/3449.
  3. ^ Williams, R.B.; Cornelius, P.F.S.; Hughes, R.G.; Robson, E.A. (2012). Coelenterate Biology: Recent Research on Cnidaria and Ctenophora: Proceedings of the Fifth International Conference on Coelenterate Biology, 1989. Springer Science & Business Media. pp. 483–. ISBN 978-94-011-3240-4.
  4. ^ Freiwald, André; Roberts, J. Murray (2006). Cold-Water Corals and Ecosystems. Springer Science & Business Media. p. 694. ISBN 978-3-540-27673-9.
  5. ^ Tony J. Pitcher; Telmo Morato; Paul J. B. Hart; Malcolm R. Clark; Nigel Haggan; Ricardo S. Santos (2008). Seamounts: Ecology, Fisheries & Conservation. John Wiley & Sons. pp. 146–147. ISBN 978-0-470-69126-7.
  6. ^ Waller, Rhian G.; Tyler, Paul A.; Smith, Craig R. (2008). "Fecundity and embryo development of three Antarctic deep-water scleractinians: Flabellum thouarsii, F. curvatum and F. impensum". Deep Sea Research Part II: Topical Studies in Oceanography. 55 (22–23): 2527–2534. doi:10.1016/j.dsr2.2008.07.001.
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Flabellum curvatum: Brief Summary

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Flabellum curvatum is a species of marine, cold water coral in the family Flabellidae. It is an azooxanthellate coral, that is to say without symbiotic zooxanthellae. The species is native to deep waters around Antarctica.

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Biology

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azooxanthellate
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van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).
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Jacob van der Land [email]
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Jacob van der Land [email]

Depth range

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115-1137 m
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bibliographic citation
van der Land, J. (ed). (2008). UNESCO-IOC Register of Marine Organisms (URMO).
contributor
Stephen Cairns [email]
contributor
Stephen Cairns [email]