Stylaster alaskanus 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 : 48-50

Stylaster alaskanus Fisher, 1938 Figs 21 E–G24A–M

Stylaster gemmascens alaskanus Fisher, 1938: 500-502, pl. 47-48, pl. 54, fig. 2.- Boschma 1957: 11.

Stylaster cancellatus Fisher, 1938: 502-503, pl. 35, figs 2-2c, pl. 39-40.- Boschma 1957: 4.- Cairns 1983b: 430 (listed).- Heifetz 2002: 22 (listed).- Wing and Barnard 2004: 11, 27, fig. 33.- Heifetz et al. 2005: 22, 134, 137 (listed).- Stone and Shotwell 2007: 108 (listed).- Brooke and Stone 2007: 525-530, fig. 2D, 3B.-Jameison et al. 2007: 224 (listed).- Lindner et al. 2008: 3, supplemental Table S1: 2 (phylogeny and DNA sequence).

Stylaster alaskanus : Cairns 1983b: 430 (elevation to species rank).- Wing and Barnard 2004: 11, 27.- Stone and Shotwell 2007: 108 (listed).

Stylaster alaskana : Heifetz et al. 2005: 133 (listed).-Jameison et al. 2007: 224 (listed but misspelled).

Type material.

Stylaster gemmascens alaskanus : Holotype, Alb-3480, 1 dry male branch fragment 4.5 cm in length, USNM 43269 (Fig. 21E); 5 (perhaps one broken from the four mentioned by Fisher) dry paratype branches (2 female, 2 male, 1 indet.), and SEM stubs 1511-12, Alb-3480, USNM 86006. Type locality.Alb-3480: 52°06'N, 171°45'W (Amukta Pass, Aleutian Islands), 518 m.

Stylaster cancellatus : Holotype, Alb-3480, 1 dry female branch fragment 9 cm in height, and SEM stub 1509, USNM 43267 (Fig. 21F); 7 dry paratype branches (2 female, 5 male), and SEM stub 1510, Alb-3480, USNM 86005. Type locality.Alb-3480: 52°06'N, 171°45'W (Amukta Pass, Aleutian Islands), 518 m.

Material examined.

Types of Stylaster alaskanus and Stylaster cancellatus ; Alaskan Leader 35, 51°50.9'N, 175°08'W, 178-365 m, 14 Jun 2002, 1 male, AB02-31;MF 833-38, 51°42'54"N, 178°51'30"W, 582 m, 3 Aug 1983, 2 female, USNM 96526; MF 833-56, off Great Sitkin I., 249 m, 6 Aug 1983, 2 male, USNM 77045; Alaska Sea, 52°09'24"N, 173°44'19"E, 318 m, 5 Feb 2000, 1 indet., USNM 1122566; Alb-3480, see above, 8 female and 1 male (non-type), USNM 76722; Dominator 971-135, 51°37'22"N, 178°26'28"W, 163 m, 14 Jul 1997, 2 female, USNM 1123365; Dominator 971-201, 51°54'28"N, 175°49'00"E, 378 m, 1 Aug 1997, 1 indet., USNM 1123361; Ocean Olympic, 52°04.78'N, 177°13.39'E, 256 m, 1 female, AB00-57; Pacific Knight 941-204, 53°06'N, 171°42'E, 455 m, 31 Jul 1994, 4 female some in alcohol, USNM 96246 and 1123533; Sea Storm 36, 53°05'45"N, 171°41'56"E, 453-458 m, 19 Jun 2002, 1 female, 1 male, USNM 1123277-78; Sea Storm 108, 52°11'32"N, 175°16'54"W, 208-215 m, 8 Jul 2002, 1 indet. in alcohol, USNM 1027822; Sea Storm 138, 52°13'50"N, 175°24.2'E, 146 m, 16 Jul 2002, 2 female, 2 male, USNM 1122766-68, 1122898; Sea Storm 148, 52°28'16"N, 173°29'35"W, 194 m, 21 Jul 2002, 2 female, USNM 1122757; Shishaldin, 54°24'04"N, 177°37'43"E, 154 m, 9 Feb 2000, 1 female, USNM 1122533; Shishaldin, 54°24'03"N, 179°36'11"E, 313 m, 25 Feb 2000, 4 indet., USNM 1122532; McClusky, coll., 52°01'47"N, 179°56'14"W, 362 m, 5 May 2000, 1 female, USNM 1122454; McClusky, coll., 51°17'58"N, 179°00'48"E, 265 m, 25 May 2000, 3 male, USNM 1122455 and AB01-92; University of Washington, 51°32'N, 179°15'W, 278-289 m, 1 Sep 1968, 4 male, USNM 76632 and 96530; A. Vatter, coll., 52°04'25"N, 177°11'00"E, depth unknown, 1 male, USNM 1122466.

Description.

Colonies uniplanar or multiplanar, additional flabella usually oriented perpendicular to original flabellum. Branches highly anastomotic, smooth large-diameter branches forming a framework for infilling by smaller-diameter branches, resulting is a sieve-like reticulum (Fig. 21G). Largest colony (USNM 1122768) 28 cm in height, having a massive, dense basal branch diameter of 5 cm. Distal branches circular to rectangular in cross section. Spionid worm tubes do not occur in this species. Coenosteum reticulate-granular in texture, the coenosteal strips 50-60 µm wide, bordered by short slits 6-8 µm wide; strips covered with small granules 6-7 µm in width; strips arranged linearly adjacent to cyclosystems. In some colonies, such as the type of Stylaster alaskanus , linearly arranged, apically perforate processes up to 0.2 mm tall (Figs 24 D–E, J) occur on coenosteum, these structures of unknown function. Coenosteum light orange, pink, or white.

Cyclosystems circular, elliptical or irregular in shape, 0.9-1.3 mm in greater diameter, occurring exclusively on branch edges; gastropores circular, 0.40-0.45 mm in diameter. Gastropore tubes straight and funnel-shaped, having a well-developed ring palisade (Fig. 24G) composed of rounded elements about 40 µm in diameter. Gastrostyles slender and pointed, up to 0.5 mm in height, the gastrostyle tip easily seen when viewed from above. Very rarely two gastrostyles may be present in one gastropore tube.

Dactylotomes 80-85 µm in width; dactylostyles inconspicuous. Range of dactylopores per cyclosystem 7-14 (n = 50, average = 11.30 (σ = 1.57), and mode = 13). Supernumerary dactylopores absent. Pseudosepta of cyclosystems usually only slightly exsert, but if two cyclosystems are in close proximity, pseudosepta may become quite exsert. Pseudosepta of uniform thickness; diastemas, if present at all, are narrow.

Female ampullae (Fig. 24 D–E, K–L) prominent hemispheres up to 0.9 mm in diameter, often bearing several low ridges or short spines; lateral efferent pore about 0.25 mm in diameter. Male ampullae (Fig. 24 A–B, J, M) superficial, densely clustered, and also irregular in shape, up to 0.60 mm in diameter, each with a small efferent pore 40-60 µm in diameter. Efferent pores sometimes at the apex of a small curved spine.

Remarks.

Originally described as a subspecies of Stylaster gemmascens by Fisher (1938), Cairns (1983b) later raised alaskanus to species status. Herein it is synonymized with Stylaster cancellatus , but since it has page priority in Fisher (1938), Stylaster alaskanus is considered to be the senior synonym (see synonymy above). The types of Stylaster alaskanus differ from most other specimens assigned to this species in having numerous coenosteal papillae, called "thorny outgrowths" by Fisher (1938: 501), which are often aligned in short ridges. Also, the coenosteum is white and the branches of the type series do not anastomose. However, all these differences are considered to be intraspecific variation, as some other specimen s assigned to this species have a white corallum, and small colonies, like the types of Stylaster alaskanus , usually do not have anastomosing branches. Furthermore, rarely some coralla of “cancellatus” have coenosteal papillae, which may be a reaction to an unfavorable environmental habitat. Thus, the type series of Stylaster alaskanus , which was collected at the same station as the type of Stylaster cancellatus , is considered to be a somewhat aberrant specimen of what was more widely known as Stylaster cancellatus . A similarly shaped, sieve-like, reticulate colony is known for Errinopsis reticulum Broch, 1951, however, in that species the reticulum is composed of equally-sized branches, whereas in Stylaster alaskanus the reticulum is composed of thick and thin branches. Stylaster alaskanus is distinguished from all other species in its group by having a corallum shaped as a sieve-like reticulum. It is further distinguished from those Alaskan species of group C by having ridged female ampullae (Table 2). Among the 59 specimens examined, 25 are female, 22 male, and 12 indeterminate, a fairly even sex ratio.

Distribution.

Known from throughout Aleutian Islands from west of Attu Island to Amukta Pass, including Bowers Bank; 146-582 m.