Umbellapathes litocrada, Opresko & Wagner, 2020

Opresko, Dennis M. & Wagner, Daniel, 2020, New species of black corals (Cnidaria: Anthozoa: Antipatharia) from deep- sea seamounts and ridges in the North Pacific, Zootaxa 4868 (4), pp. 543-559 : 554-558

Umbellapathes litocrada sp. nov.

( Fig. 9–12 )

Material examined. Holotype: USNM 1404092 , Hutchinson Seamount , South of Johnston Atoll, 15.47°N, 169.07°W, R / V Okeanos Explorer EXP1504 L4_D2_ DIVE06 _ SPEC03 BIO, 1,528.62 m, NOAA, 19 Sep. 2015 . Paratype: USNM 1468988 , Musicians Seamounts, Wagner Seamount, 31.85°N, 162.9°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1708 _D2_ DIVE08 _ SPEC 02BIO_A02, 2,352.47 m, NOAA, 14 Sep. 2017 . Other material examined: USNM 1467527 , Hawaiian Islands , Tropic of Cancer Seamount , R / V Okeanos Explorer, ROV Deep Discoverer , 23.3085°N, 158.358°W , EX1708 _D2_ DIVE01 _ SPEC04 GEO_A01, 1,773.49 m, NOAA, 7 Sep. 2017. Underwater photo records . EX1504 L2_03_20150804 T181251 Z, Northwestern Hawaiian Islands , St. Rogatien Bank, 25.62617°N, 167.24109°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1504 L2_D2_ DIVE03 , 1,984 m, NOAA, 4 Aug. 2015 ; EX1504 L2_06_20150807 T200232 Z, Northwestern Hawaiian Islands , West Northhampton Seamount, 25.0817°N, 172.48898°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1504 L2_D2_ DIVE06 , 1,993 m, NOAA, 7 Aug. 2015 ; EX1504 L4_06_20150919 T181659 Z, Johnston Seamounts , Hutchinson Seamount, 15.46722°N, 169.07112°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1504 L2_D2_ DIVE06 , 1,607 m, NOAA, 19 Sep. 2015 ; EX1504 L4_06_20150919 T181659 Z, Johnston Seamounts , Hutchinson Seamount, 15.46831°N, 169.07161°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1504 L2_D2_ DIVE06 , 1,527 m, NOAA, 19 Sep. 2015 ; EX1504 L4_06_20150919 T181659 Z, Johnston Seamounts , Hutchinson Seamount, 15.46471°N, 169.07863°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1504 L2_D2_ DIVE06 , 1,504 m, NOAA, 20 Sep. 2015 ; EX1504 L4_07_20150920 T182043 Z, Johnston Seamounts , unnamed seamount, 15.20901°N, 168.06245°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1504 L2_D2_ DIVE07 , 1,940 m, NOAA, 20 Sep. 2015 ; EX1706 _14_20170728 T195500 Z, Johnston Seamounts , Keli Ridge Seamount (unofficial), 15.09462°N, 167.95984°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1706 _D2_ DIVE14 , 2,373 m, NOAA, 29 Jul. 2017 ; EX1706 _15_20170729 T193000 Z, Johnston Seamounts , New Seamount, 15.16062°N, 167.03595°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1706 _D2_ DIVE15 , 2025 m, NOAA, 29 Jul. 2017 ; EX1708 _08_ 20170914 T194500 Z, Musicians Seamounts , Wagner Seamount, 31.85186°N, 162.8951°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1708 _D2_ DIVE08 , 2,413 m, NOAA, 14 Sep. 2017 ; EX1708 _17_20170923 T193000 Z, Musicians Seamounts , Rapano Ridge, 26.59703°N, 160.6707°W , R / V Okeanos Explorer, ROV Deep Discoverer, EX1708 _D2_ DIVE17 , 1,973 m, NOAA, 23 Sep. 2017; NA101_H1717_20180921 T060359 Z, Northwestern Hawaiian Islands , Naifeh Seamount, 26.86292°N, 168.08038°W, E / V Nautilus, ROV Hercules, NA 101_ DIVEH1717 , 1,839 m, 21 Sep. 2018; NA101_H1717_20180921 T060359 Z, Northwestern Hawaiian Islands , Naifeh Seamount, 26.86331°N, 168.08089°W, E / V Nautilus, ROV Hercules, NA 101_ DIVEH1717 , 1,807 m, 21 Sep. 2018; NA101_ H1723_20180926 T120412 Z, Northwestern Hawaiian Islands , Unnamed Seamount 3, 25.55511°N, 164.20308°W, E / V Nautilus, ROV Hercules, NA 101_ DIVEH1723 , 1,968 m, 26 Sep. 2018; NA101_H1723_20180926 T120412 Z, Northwestern Hawaiian Islands , Unnamed Seamount 3, 25.55611°N, 164.20497°W, E / V Nautilus, ROV Hercules, NA 101_ DIVEH1723 , 1,924 m, 26 Sep. 2018.

Type locality. Hutchinson Seamount , South of Johnston Atoll, 1,528 m .

Diagnosis. Corallum monopodial, branched and pinnulate. Stem consisting of long lower unpinnulated section (stalk) and upper distal section with simple bilateral primary pinnules some of which develop into branches showing same pinnulation pattern as stem, and which together form a discoidally shaped crown. Secondary pinnules not present on primary pinnules of stem or branches. Branches developing mainly from basal-most pinnules on stem and a varying number of more distal ones. Corallum has up to three orders of branches. Pinnules on stem generally arranged alternately in two anterolateral to lateral rows. Pinnules not uniform in length; longest ones often in middle or on distal part of branch. Pinnular density 9–11 per 3 cm. Spines on pinnules short, triangular to semispherical in shape. Polypar spines up to 0.08 mm tall from midpoint of base to apex. Spines arranged in very irregular axial rows, five or six rows visible in lateral view, with about 4 spines per mm in each row. Polyps 3–4.5 mm in transverse diameter; with 2 to 3 polyps per cm.

Description of holotype. The holotype (USNM 1404092, Fig. 9 and 10A ) was collected with the basal holdfast intact. The colony consists of a stem about 62 cm tall, including a 52 cm long unpinnulated lower portion, and a 10 cm long branched and pinnulated upper section. The diameter of the stem near its basal end is 2.5 by 3 mm. The pinnulated section of the stem consists of two rows of lateral and alternating pinnules, the two basal-most ones and three smaller more distal ones are developed into pinnulated branches ( Fig 10A ). In situ photos ( Fig. 9 ) indicate that the unpinnulated part of the stem was relatively straight and upright; however, at the point where it becomes pinnulated it is sharply curved to one side, and the two lowermost stem pinnules that are developed into pinnulated branches are also curved or bent, and therefore lie in almost the same plane as the stem. These and the other pinnulated branches thus form a somewhat flattened discoidal plane. When viewed from the polyp side of the corallum, this discoidal crown has an irregularly circular shape roughly 21 by 19 cm in dimension. In situ photos indicate that the crown was tilted slightly to one side. The lowermost pinnulated branch is about 15 cm long and 1.3 mm in basal diameter.

The pinnules are not uniform in length, nor do they decrease regularly in length from the base to the distal end. Instead, the longest pinnules are often found in middle of a branch and are up to 7.5 cm long and 0.5 mm in basal diameter. On a branch 7.5 cm long, the longest pinnule is about 4.5 cm. There are about 13 pairs of pinnules on the stem, most of these occur in alternating pairs, although this pattern is not strictly maintained at the distal end of the stem. On the branches the pinnules start 1.5–4.0 cm from the base. Pinnules are spaced mostly 7 mm apart on one side of the axis, resulting in a pinnular density of 8–10 (total) per 3 cm. The interior angle formed by the two rows of lateral pinnules is very wide, such that the pinnules lie in much the same plane. The distal angle that the pinnules form with the stem or branches near their base is 70–90°, but distally this angle becomes less.

The spines on the pinnules are very small, and triangular to somewhat semispherical ( Fig. 11 ). Polypar spines can be up to twice as tall as the abpolypar spines (as measured from the midpoint of base to apex); however, in most places abpolypar and polypar spines are nearly equal in size. On sections of pinnules 0.23–0.31 mm in diameter, the polypar spines are 0.046 mm to 0.051 mm tall, whereas the abpolypar ones are mostly 0.025–0.03 mm tall, but can be up to 0.05 mm. The spines on the branches and stem are similar in size to those on the pinnules and generally not more than 0.05 mm tall. The abpolypar spines on the pinnules often appear more flattened, button-shaped, and in some cases more flared out along the base. The arrangement of the spines in longitudinal rows and the spacing of the spines within each row is very irregular; there are 4–6 rows of spines visible in lateral view of the axis, and where the spacing of the spines is uniform, there are four spines per millimeter in each row.

Polyps ( Fig. 10 B–C) occur in a single series, mostly facing out of the discoidal plane formed by the branches and pinnules. They are transversely elongated; 2.0– 4.5 mm in diameter from the proximal edge of the proximal tentacles to the distal edge of the distal tentacles. The polyp density is 2 to 2.5 per cm. In situ photos ( Fig. 9 ) indicate that, when expanded, the tentacles are subequal in length and about as long as the transverse diameter of the polyp. The tips of the tentacles are curved in an abpolypar direction and the oral cone is quite distinct. After preservation the tentacles and oral cone can be extremely contracted ( Fig. 10C ).

Description of paratype. The paratype (USNM 1468988) is an almost complete specimen, but broken in two pieces. It is a smaller colony than the holotype. The stem is about 23 cm long, but broken off at the tip. The unpinnulated stalk is 16.5 cm and the pinnulated section 6.5 cm long. Only the two lowermost stem pinnules are developed into branches and one of these has a small sub-branch. The pinnules are of variable lengths up to 4.2 cm, and there are no subpinnules. The pinnules are mostly 5–6 mm apart within each lateral row, and the pinnular density is about 11 per 3 cm. The spines are larger than those in the holotype; the polypar spines are 0.06 to 0.08 mm tall, and the abpolypar spines 0.03–0.04 mm. Three rows of spines are visible in lateral view and there are 3 spines per mm in the rows. The polyps are 3–4 mm in transverse diameter, with about 3 polyps per cm.

Remarks. A large number of colonies superficially resembling U. litocrada sp. nov. have been photographed in and around the Hawaiian Islands (see list of underwater photo records and Fig. 12 ). Some of these colonies appear to differ from the holotype in having fewer orders of branches, and pinnules that are more uniform in length. Further study is needed to determine whether any of these morphotypes represent a species distinct from U. litocrada .

Comparisons. This species differs from Umbellapathes helioanthes Opresko, 2005 , in not having secondary pinnules. It also has smaller spines (polypar spines up to 0.05–0.08 mm vs. up to 0.1 mm) and slightly larger polyps (up to 4.5 mm in transverse diameter vs. up to 3.6 mm), although a larger suite of specimens is needed to clearly define these parameter in both species.

Etymology. From the Greek “ litos ” meaning “simple” and “ crada ” meaning “branch”, referring to the fact that the pinnules are not subpinnulate, as in U. helioanthes .

Distribution. Currently only known from the Hawaiian Islands, the Musician Seamounts and seamounts near Johnston Atoll at depths ranging between 1,504 –2,413 m ( Fig. 13 ).

Figures

FIGURE 9. Umbellapathes litocrada sp. nov. holotype photographed in situ on Hutchinson Seamount at 1,529 m. Photos courtesy of NOAA Office of Ocean Exploration and Research.

FIGURE 10. Umbellapathes litocrada sp. nov., holotype, USNM 1404092. A. colony; B. expanded polyps; C. contracted polyps on the preserved colony.

FIGURE 11. Umbellapathes litocrada sp. nov. holotype (USNM 1404092); sections of pinnules.

FIGURE 12. In situ photographs of colonies presumed to be Umbellapathes litocrada sp. nov. (specimens were not collected): A. colony on Hutchinson seamount at 1,504 m; B. colony on unnamed seamount north of Johnston Atoll at 1,940 m; C. colony on Rapano Ridge at 1,973 m. D. colony on Naifeh Seamount at 1839. Photos courtesy of NOAA Office of Ocean Exploration and Research (A–B) and Ocean Exploration Trust (C–D).

FIGURE 13. Map showing the geographical distribution of colonies known or presumed to be Umbellapahtes liticrada sp. nov. To date, this species is only known from the Hawaiian Islands, the Musician Seamounts and seamounts near Johnston Atoll at depths ranging between 1,504 and 2,413 m.