Bathypathes alaskensis, Opresko & Molodtsova, 2021

Opresko, Dennis M. & Molodtsova, Tina N., 2021, New species of deep-sea Antipatharians from the North Pacific (Cnidaria: Anthozoa: Antipatharia), Part 2, Zootaxa 4999 (5), pp. 401-422 : 412-415

Bathypathes alaskensis n. sp.

( Fig. 5 )

urn:lsid:zoobank.org:act:FB78EB75-A0DF-49B8-97CE-B7BE8B59327D

Bathypathus patula, MacIsaac et al. 2013: 240 , 241, 251, 253, fig. 9; Brugler et al. 2013: 325, 327, 337, 343, fig. 2, fig. 3, fig. 4; Stone & Shotwell 2007: 105

non Bathypathes patula Brook, 1889 .

Material examined. Holotype: USNM 1288464 ( SEM stub 419), off Kruzof Island , eastern Gulf of Alaska, 57.2167ºN, 136.3490ºW, ABL Longline Survey, 41-101B-1 ( AB13-0029 ), coll. J.F. Karinen, 846 m, 18 July 2004 (specimen dry) . Paratypes: USNM 1288463, E. of Yakutat Valley , eastern Gulf of Alaska , 58.8217ºN, 141.0190ºW, ABL Longline Survey , 41-1A ( AB13-0028 ), coll. J.F. Karinen, 731 m, 25 July 2004 (specimen dry); USNM 1288465, off Yakutat Valley , eastern Gulf of Alaska , 59.0483ºN, 141.5690ºW, ABL Longline Survey, 41-95B ( AB13-0030 ), coll. J.F. Karinen, 719 m, 30 July (specimen dry); USNM 1288466, off Cross Sound, eastern Gulf of Alaska, 57.6175ºN, 136.6090ºW, ABL Longline Survey, 41-100-A1 ( AB13-0032 ), coll. J.F. Karinen, 803 m, 19 July 2004 (specimen dry); USNM 1288467, off Cross Sound, eastern Gulf of Alaska, 57.8817ºN, 137.4420ºW, ABL Longline Survey, 41-99-2 ( AB13-0033 ), coll. J.F. Karinen, 736 m, 21 July (specimen dry) . Other material: USNM 99489, North Pacific , Alaska, Alexander Archipelago, R/V Albatross, sta. 4225, 272– 331 m, 6 Jul 1903 ; USNM 100859, North Pacific, off Washington, 48.125ºN, 125.846ºW, R/ V Miller Freeman, sta. 4805F, West Coast Slope Fisheries Survey 2000, depth not recorded, 12 Oct. 2000 ; USNM 1013564, off Kruzof Island, eastern Gulf of Alaska , 57.1883ºN, 136.2350ºW, ABL Longline Survey, R / V Alaskan Leader, No sta. no. ( AB02-54 ), 700–715 m, 18 July 2002 ; USNM 1013566, off Kruzof Island, eastern Gulf of Alaska , 57.1883ºN, 136.2350ºW, ABL Longline Survey, R / V Alaskan Leader, No sta.no. ( AB02-53 ), 601–715 m, 18 July 2002 (2 specimens) ; USNM 1013568, SE of Yakutat Valley, eastern Gulf of Alaska, 58.6867ºN, 140.7730ºW, ABL Longline Survey, R/ V Alaskan Leader, No sta. no. ( AB02-44 ), 565–567 m, 5 Aug 2002 (3 specimens). USNM 1013724, Dixon Entrance, eastern Gulf of Alaska , 54.9000ºN, 134.2870ºW, R/ V Alaskan Leader, No sta. no. ( AB02-61 ), 225–518 m, 11 July 2002 (3 specimens) ; USNM 1013749, Sitka Sound, eastern Gulf of Alaska , 56.8517ºN, 135.9970ºW, R/ V Alaskan Leader, sta. 102 ( AB02-55 ), 241–704 m, 17 July 2002 ; USNM 1014184, Canada, British Columbia, Queen Charlotte Islands, Graham Island , 54.0838ºN, 134.1190ºW, Tow 6, coll. J. Boutillier, 1722–2083 m, 2 Sept 2002 ; USNM 1249987, eastern Gulf of Alaska , W of Prince of Wales Island, 54.9858ºN, 134.3958ºW, ABL Longline Survey, 107B2 ( AB13- 0109 ), coll. J.F. Karinen, 637 m, 11 July 2006 ; USNM 1288461, Fairweather Ground , Gulf of Alaska, 58.2000ºN, 138.9800ºW, ROV Zeuss II , GOA-15-157 ( AB15-0013 ), coll. R.G. Stone, 515 m, 6 June 2015 ; USNM 1288462, Fairweather Ground , Gulf of Alaska, 58.2000ºN, 138.9800ºW, ROV Zeuss II , GOA 15-158 ( AB15-0014 ), coll. R.G. Stone, 515 m, 6 June 2015 ; IORAS CNI00018, Gulf of Alaska, off Baranof Island , 56.7508° N 136.0330°W, R/ V Vityaz cruise 45, sta. 6122, Sigsbee Trawl, 1100–1180 m, 21 May 1969 .

Diagnosis. Moderately sized (up to 40 cm or more in height), monopodial (unbranched) pinnulate colonies. Simple flexible pinnules arranged in two anterolateral to lateral rows and in subopposite pairs. Unpinnulated lower section of stem typically 6.5 to 10 cm in length; pinnulated section of stem up to 34 cm long on colony 43 cm tall, with pinnules up to 23 cm in length. Striatum usually present on polypar side of stem starting several centimeters above basal plate and extending for 2–4 cm, and ending at slight curvature in stem; often with spines along ridges separated by shallow grooves. Pinnular density 8–12 per 3 cm (12–16 per 5 cm). Spines smooth, simple, conical, with rounded apex or apically forked leading to the formation of double and triple spines. Largest polypar spines on pinnules mostly 0.11–0.14 mm tall; abpolypar spines 0.08–0.09 mm tall. Spines on stem similar to those on pinnules except along the striatum where they can be as tall as 0.18 mm. Polyps uniserially arranged; mostly 4 to 5 mm in transverse diameter (range 3–6 mm); polyp density usually 4–5 per two centimeters. Color of living colonies light to dark orange.

Description of holotype. The holotype (USNM 1288464, Fig. 5A ) is about 26 cm tall; the unpinnulated portion of the stem is 7 cm long, and its diameter just above the basal plate is 1.9 mm. This section shows a very slight S-shaped curvature; first tilted towards the front or polypar side of the corallum, then curving towards the abpolypar side, and finally extending almost vertically. A striatum (low axial ridges separated by shallow grooves), confined to one side of the axis, appears about 3 cm above the basal plate and extends for about 2 cm, and has large spines along the crest of some of the ridges. The pinnulated portion of the corallum is 19.5 cm in length and curves back away from the polypar side of the axis (Note: in Fig. 5A the distal-most 4 cm of the stem is broken and folded over the lower section). The pinnules are arranged bilaterally and also in subopposite pairs, the left pinnule of each pair (viewing the polyp-side of the corallum) is inserted on the axis slightly lower than the opposite member. The pinnules are relatively long compared to the height of the corallum; the longest (6 th pair from the bottom) being about 19 cm, with a basal diameter of about 0.6 mm. The pinnules are mostly 7–9 mm apart within each row; with a total for both rows of up to 8 per 3 cm (~12 per 5 cm) on the lower part of the stem and up to 10 per 3 cm (14 per 5 cm) about 13 cm above the base and approximately 12 per 3 cm (nearly 16 per 5 cm) on the upper part of the stem. In the preserved specimen, the interior angle formed by the two rows of pinnules is about 45° on the lower part of the stem, but it may have been even smaller in the living colony. The pinnules on the upper part of the corallum are more spread apart forming an interior angle of up to 160º near the top of the stem. The distal angle formed by the pinnules and the stem is generally near 60º. The pinnular spines ( Fig. 5C ) are smooth, conical, with a rounded apex or apically forked. On segments of pinnules about 0.33 mm in diameter, the polypar spines are mostly 0.11–0.13 mm tall, the abpolypar spines 0.07–0.08 mm tall. The spines are arranged in axial rows, 5–7 of which can be seen in lateral view (including only rows in which the base of the spines is visible). Within each row there are 2.5–3.5 spines per mm. Spines on the stem are similar to those on pinnules except along the striatum where they can be as tall as 0.18 mm. Also, in one small area on the stem the polypar spines are up to 0.23 mm and very wide and blunt – perhaps an abnormal condition. The polyps ( Fig. 5B ) are arranged uniserially on the stem and pinnules. On the pinnules they most often occur on the lower side of the axis – facing down or away from the corallum; however, on a few pinnules they occur on the upper surface. On the same pinnule, polyps may occur on either side, but not in the same location. The polyps are mostly 4 to 5 mm in transverse diameter (measured from the distal edge of the distal lateral tentacles to the proximal edge of the proximal lateral tentacles); the interpolypar space is about 1 mm wide or less and there are 4 to 5 polyps per 2 cm.

Description of paratypes and other material. The five specimens in the type series (USNM 1288463, 1288464, 1288465, 1288466, and 128467) allow for an evaluation of the morphological variability of the species. Polyp size (transverse diameter) ranges from 4 to 6 mm and polyp density from 3 to about 5 per two centimeters (in many of the colonies the polyps appear enlarged and very crowded due to their being filled with reproductive cells). Pinnular density ranges from 8 to 12 (total for both rows) per three centimeters of stem, and varies both within and between colonies, often with the pinnules becoming more crowded higher on the corallum. The lower unpinnulated section of the stem varies in length from 6.5 to 9 cm between colonies. The interior angle between the two rows of pinnules ranges from about 30º to close to 180º; and the distal angle can be as little as 45º to as much as 90º. These five specimens also show that the curvature of the stem changes with size of the corallum. Usually the smaller colonies are relatively upright or only slightly curved away from the polypar side of the corallum; larger colonies, however, tend to be extremely curved away from the polypar side. The length of the longest pinnules is 9 to 14 cm in colonies 15 to 20 cm tall, but as much as 23 cm in a colony 43 cm tall. In preserved specimens the interior angle between the two rows of pinnules can range from less than 30º to more than 160º within the same colony, but without detailed in situ photographs it cannot be determined to what degree this feature is normal or only an artifact of the method of preservation.

The examination of five additional specimens assigned to this species supports the conclusions reached above. The colonies exhibit varying morphologies from upright, to slightly curved, to extremely curved, but none are sigmoidal or sickle-shaped, although in many specimens the middle to upper part of the unpinnulated portion of the stem exhibits a slight S-shaped curvature. Overall, the longest pinnules are usually not more than about 20 cm in colonies as much as 40 cm tall (except in cases where the top of the colony might have been broken off), the maximum pinnular density is 12 pinnules per 3 cm, the pinnular spines are rarely more than 0.14 mm tall, and the polyps are usually 4–5 mm in transverse diameter, with 4–5 polyps per 2 cm.

Genetic data. GenBank Acc. Nos.: USNM 1288464 [ JX560735 (igrW), JX560746 (igrN), JX560756 (cox3-cox1)]; USNM 1288463 [ KF054475 (igrW), KF054608 (igrN), KF054368 (cox3-cox1)]; USNM 1288465 [ KF054477 (igrW), KF054609 (igrN), KF054369 (cox3-cox1)]; USNM 1288466 [ KF054476 (igrW), KF054610 (igrN)]; USNM 1288467 [ KF054478 (igrW), KF054611 (igrN), KF054370 (cox3-cox1)].

The five specimens in the type series were sequenced by Brugler et al. (2013) using three markers (igrW, igrN, and cox3-cox1), and the sequences were deposited in GenBank under the name Bathypathes patula . With the exception of one unresolved marker for one specimen (cox3-cox1 for USNM 1288466), the results indicated that all five belong to the same species. It is rare to have multiple specimens in a type series subjected to DNA analysis. For antipatharians which in general exhibit a high degree of morphological plasticity as discussed above for this species, this is extremely valuable in making it possible to define species limits in terms of each major taxonomic character. Ideally this information can be coupled with additional morphological and genetic data on specimens from the same and other geographic regions to more fully document species ranges and to recognize cryptic species.

Comparisons. This species differs from B. platycaulus by its subopposite pinnules and from B. bifida by having more than one pair of pinnules. In B. alaskensis n. sp. the largest polypar spines on the pinnules (0.1–0.14 mm) are, in most colonies, larger than those in B. conferta , B. erotema , B. patula , B. plenispina , B. ptiloides and B. tenuis (all normally have polypar spines <0.08 mm) and about one-half the size of those in B. bayeri (0.2–0.32 mm) and B. galatheae (0.18 to 0.26 mm). The spines in B. patula , B. plenispina , B. erotema , and B. conferta are more triangular with an acute apex compared to the conical spines with a rounded apex in B. alaskensis . Bathypathes alaskensis n. sp. differs from B. tiburonae n. sp. by its more densely set pinnules (8–12 vs. 4–6 per 3 cm) and smaller polyps (4–5 mm vs. 9–12 mm in transverse diameter).

In in situ photos, this species can also be differentiated from B. patula by its orange color and more flexible pinnules (color of B. patula is white), and also by the absolute and relative length of the pinnules on colonies of comparable size. In colonies about 20 cm in height, the longest pinnules in the type of B. patula are 7.5 cm, whereas those in B. alaskensis are 14.5 cm. The relative length of the pinnules in B. alaskensis is similar to that in B. galathea (maximum of 14.2 cm in a colony with a pinnulated section 26.5 cm long); however, the pinnules in B. galatheae are straighter, more robust and not flexible, and the distal angle wider, close to 90°.

Etymology. Species name “ alaskensis ” is derived from the general region where the species is found, the Gulf of Alaska.

Distribution. All of the specimens assigned to this species were collected in the Northeast Pacific, primarily from the Gulf of Alaska, and nearby seamounts at depths between 272 and 1200 m.

Figures

FIGURE 5. Bathypathes alaskensis n. sp., holotype, USNM 1288464: A. corallum; B. polyps; C. sections of pinnules showing spines, scale bars 0.5 mm (C from SEM stub 419).