Distichopora borealis Fisher, 1938

Cairns, Stephen D. & Lindner, Alberto, 2011, A Revision of the Stylasteridae (Cnidaria, Hydrozoa, Filifera) from Alaska and Adjacent Waters, ZooKeys 158, pp. 1-88 : 4-7

Distichopora borealis Fisher, 1938 Figs 1 A–C2A–K

Distichopora borealis Fisher, 1938: 543-545, pl. 70, fig. 3, pl. 71-73.- Broch 1942: 20.- Boschma 1957: 41 (listed).- Naumov 1960: 562, text-fig. 407.- Wing and Barnard 2004: 10, 27, fig. 26.- Heifetz et al. 2005: 133, 137 (listed).- Jamieson et al. 2007: 224 (listed).- Brooke and Stone 2007: 529, fig. 2I.- Stone and Shotwell 2007: 107 (listed).- Lindner et al. 2008: 3, and supplemental Table S1: 3 (phylogeny and DNA sequences).

Distichopora sp. Heifetz, 2002: 22 (listed).- Heifetz et al. 2005: 133 (listed).

Type material.

Holotype, Alb-3480, a female colony (dry) of 9 cm length (USNM 43274, Fig. 1B). Paratypes, Alb-3480, include 3 male, 4 female, 1 indeterminate dry colonies, and SEM stubs 1489-1494 (USNM 76810) and 2 dry female colonies from Alb- 4781 (USNM 76375).

Type locality.

Alb-3480: 52°06'00"N, 171°45'00"W (Amukta Pass, Aleutian Islands), 518 m.

Material examined.

Alaskan Leader 40, 52°09'18"N, 175°40'42"W, 174 m, 8 Jun 2002, 1 female and 1 male, USNM 1122542; Alaskan Leader 54-14, 51°44.4'N, 178°16.7'W, 567-680 m, 11 Jun 2002, 6 indet., AB02-29; Alaska Trojan, 51°24'47"N, 178°50'02"W, 640 m, 2 Feb 2000, 1 female, USNM1122447; Ballyhoo, 54°49'52"N, 178°43'14"E, 236, 7 June 2000, 1 female, USNM 1122565; Delta 5600, 52°33'47"N, 179°26'45"W, 225 m, 15 Jul 2002, 1 male, USNM 1122543; Dominator 971-181, 51°27'43"N, 178°35'20"E, 384 m, 27 Jul 1997, 1 female and 1 male, USNM 1123357; Dominator 971-219, 53°00'03"N, 172°18.86'E, 223 m, 4 Aug 1997, 1 female, 2 male, USNM 1123358; Jason2 –2103– 7-4, 51°47.898'N, 179°57.169'E, 1267 m, 1 female, AB08-0036; MF 70, 52°03'24"N, 179°25'06"E, 174 m, 1 male, USNM 77047; Ocean Olympic, 52°04.78'N, 177°13.39'E, 256 m, 1 male, AB00-57; Ocean Olympic, 52°08.67'N, 176°35.46'E, 292 m, 1 female, AB00-21; Ommaney 8, 56°11'42"N, 135°06'31"W, 53 m, 17 Aug 2006, 1 female in alcohol, USNM 1086324; Patricia Lee, 51°53.44'N, 179°47.7'E, 298 m, 1 indet., AB00-41; Sea Storm 36, 53°05'45"N, 171°41'56"E, 458 m, 19 Jun 2002, 1 female and 1 male in alcohol, USNM 1076507 and 1122770; Sea Strom 92, 51°33'34"N, 177°36'59"W, 367 m, 4 Jul 2002, 7 males, USNM 1137601, 1123541, 1122874-76; Sea Storm 93, 51°50'59"N, 178°26'02"E, 390 m, 5 Jul 2002, 2 male, USNM 1122877 and 1123287; Sea Storm 105, 52°08'59"N, 176°02'17"E, 201 m, 8 Jul 2002, 2 female in alcohol, USNM 1122884; Sea Storm 106, 52°10'46"N, 175°10'34"E, 165 m, 8 Jul 2002, 1 female and 1 male in alcohol, USNM 1122885 and 1123288; Sea Storm 107, 52°10'28"N, 175°14'14"E, 214 m, 8 Jul 2002,4 female and 2 males in alcohol, USNM 1122866-70; Sea Storm 108, 52°11'32"N, 175°17'E, 208 m, 8 Jul 2002, 1 female and 3 males, USNM 1122862-65; Sea Storm 109, 52°17'16"N, 175°20'56"E, 238 m, 8 Jul 2002, 6 female, 8 male, 3 indet. in alcohol, USNM 1122886 and 1123289; Sea Storm 122, 52°02'49"N, 175°16'54"E, 143 m, 13 Jul 2002, 2 female and 7 males, USNM 1122858-61; Sea Storm 132, 52°12'02"N, 176°05'56"E, 150 m, 15 Jul 2002, 1 female in alcohol, USNM 1122854; Sea Storm 133, 52°13'40"N, 176°02'13"E, 148 m, 15 Jul 2002, 1 male, 2 females in alcohol, USNM 1122855-57; Sea Storm 149, 52°30'15"N, 173°33'03"W, 239 m, 21 Jul 2002, 1 male in alcohol, USNM 1122883; Sea Storm 151, 52°33'40"N, 173°33'03"W, 203 m, 21 Jul 2002, 1 female and 2 male, USNM 1122878-80; Sea Storm 155, 52°38'43'N, 173°34'31"W, 393-401 m, 22 Jul 2002, 1 male and 1 indet., USNM 1122881-82; Shishaldin, 53°56'24"N, 179°49'31"E, 318 m, 14 Mar 2000, 1 female and 1 male, USNM 1122549; Shishaldin, 54°07'N, 179°45'E, 366 m, 20 Feb 2000, 1 female and 1 male, USNM 1122544-455; Shishaldin, 54°23'29"N, 179°19'46"E, 413 m, 12 Feb 2000, 1 male, USNM 1122548; Vesteraalen 941-165, 51°34'N, 178°19'E, 470 m, 18 Jul 1994, 1 female and 1 male, USNM 96247; Slear, coll., 51°59'52"N, 176°47'05"E, 241 m, 13 Nov 2000, 1 male, USNM 1122458; University of Washington, 51°32'N, 179°15'W, 278-289 m, 1 Sep 1968, 1 female, USNM 76377; 54°20'15"N, 133°03'19"W, 457-466 m, 1 Sep 2002, 1 female, USNM 1123535; 51°13'43"N, 179°49'31"E, 465-529 m, 13 Jun 2000, 1 male, USNM 1137421.

Description.

Colonies usually uniplanar (Fig. 1B), but occasionally multiplanar or arborescent (Fig. 1A, C). Largest specimen examined (USNM 1122542, Fig. 1C) 11 cm tall and 20 cm broad, having a basal diameter of 3 cm, colonies broader than tall not uncommon. Base of colony broadly encrusting. Branching irregularly dichotomous, occasionally anastomotic. Large basal branches circular to elliptical in cross section, but terminal branches have flattened faces, thus rectangular in cross section. Branch tips blunt and rounded. Coenosteum white to light orange, the latter usually having branches with a white core. Coenosteum reticulate-granular in texture, the strips being 0.10-0.14 mm in width, each strip covered with tall (22 µm tall, 9 µm in diameter), slender granules arranged 8-10 across the width of a strip. Faces of distal branches often bear longitudinal ridges (Fig. 2A, D, K), some ridges up to 4 mm in length, sometimes ending distally in what appears to be a dactylopore opening (Fig. 2D).

Pore rows well defined (Fig. 2B), 1.0-1.3 mm in width, and restricted to lateral branch edges, although isolated rows and some irregularities may occur proximally on large colonies. Gastropores linearly arranged in a shallow sulcus, closely spaced (approximately 12-16 per cm), and circular in shape, measuring 0.33-0.41 mm in diameter. Gastropore tubes long and slightly curved, a diffuse ring palisade present near gastrostyle tip, the elements globular and about 30 µm in diameter; tabulae absent. Gastrostyles long, slender, and fragile, up to 1 mm in length and 0.09 mm in diameter, having high H:W ratios up to 8-10. Gastrostyles longitudinally ridged and bear numerous long slender spines up to 0.07 mm in length and 10-12 µm in diameter. U-shaped dactylopore spines arranged on both sides of gastropore row, but often more common on one side than the other, e.g., 18-20 dactylopore spines on one side opposite 28-40 spines on other side. Dactylopore spines up to 0.4 mm tall and 0.25-0.30 mm in width, with a dactylotome width of 0.07-0.08 mm, always directed toward or slightly obliquely to the adjacent gastropore. Dactylostyles absent.

Female ampullae (Fig. 2J) prominent, superficial, hemispherical mounds clustered on branch faces, 1.0-1.5 mm in diameter. Ampullae usually covered by low ridges, either radiating from the central apex or arranged in parallel, longitudinal rows aligned with branch axis. Lateral efferent pores 0.25-0.30 mm in diameter. Male ampullae (Fig. 2K) also superficial mounds, but mostly embedded in coenosteum (internal), also occurring in clusters on branch faces. Male ampullae irregular in shape, often with an apical tip, and smaller than female ampullae (0.35-0.45 mm in diameter).

Remarks.

Among the 26 Recent species of Distichopora (see Cairns et al. 1999; Cairns 2005; and Appeltans et al. 2011: WoRMS database - www.marinespecies.org), the most similar is Distichopora borealis japonica Broch, 1942, described from Sagami Bay, Japan (110 m). Although similar in gross morphology, subspecies japonica differs in coenosteal texture (porcellaneous), and in ampulla shape, each female ampulla having more than one efferent pore and the male ampullae clustered densely in a continuous mat. Also, the dactylotomes of the dactylopore spines are oriented upward to outward (away from the gastropores), not inward toward the gastropores. These differences would argue for an elevation to the specie s level of this putative subspecies. The observations are based on examination of a fragment of a syntype of Distichopora borealis japonica (USNM 76868) and additional Japanese material deposited at the NMNH (USNM 44198, 44199, 44202, and 44217). Of the 111 specimens examined, 45 are female, 53 male, and 13 indeterminate in gender.

Distribution.

Common in the Aleutian Islands from the Near Islands to Amukta Pass, including Bowers Bank; off Cape Ommaney, Alexander Archipelago, and Dixon Entrance, Queen Charlotte Islands; 53-1267 m, the shallowest record being from Cape Ommaney.