Stylaster brochi (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 : 28-31

Stylaster brochi (Fisher, 1938) Figs 11A, E, G13 A–L

Allopora brochi Fisher, 1938: 517-518, pl. 42, figs 3-3d, pl. 44, pl. 45, fig 1.-? Naumov 1960: 569-570, text-fig. 413.- Boschma 1957: 19.

Allopora abei Eguchi 1968: 34, pl. 34, figs 1-3.- Mori 1980: 17 (listed).

Stylaster brochi : Cairns 1983b: 429.- Heifetz 2002: 22 (listed).- Wing and Barnard 2004: 11, 27.- Heifetz et al. 2005: 133, 137 (listed).- Stone and Shotwell 2007: 108 (listed).- Brooke and Stone 2007: 521, figs 2A, 3A.-Jameison et al. 2007: 224 (listed).

Stylaster abei .- Cairns 1983b: 430.

Stylaster polyorchis .- Lindner et al. 2008: 3, supplemental Table S1: 2.

Stylaster campylecus .- Lindner et al. 2008, 3, supplemental Table S1: 2.

Type material.

Allopora brochi : Alb-4777: The dried holotype is deposited at the USNM (43264, also SEM stub 1497), measuring 9 cm in height (Fig. 11A); a paratype is also deposited at the CAS (28183). Type locality.Albatross 4777: 52°11'N, 179°49'E (Petrel Bank, Aleutian Islands), 79-95 m.

Allopora abei: Holotype, dry, Dept. of Mineral Sciences, Tohoku University (1001). Type locality. Off the Aleutian Islands, exact locality and depth unknown.

Material examined.

Holotype, USNM 43264; Alb-3599, 52°05'N, 177°40'E, 101 m, 9 Jun 1894, 1 female, USNM 76814 (part of type lot of Stylaster campylecus); Alb-4779, 52°11'N, 179°57'W, 99-102 m, 5 Jun 1905, 1 female, USNM 44069; Alaskan Leader 35, 53°01'42"N, 170°05'59"W, 200-400 m, 4 Jun 2000, 1 male, USNM 1122516; Delta 5607, 51°23'02"N, 179°01'38"W, 126 m, 18 Jul 2002, 1 female, USNM 1122486; Delta 5620, 51°57'40"N, 176°50'01"W, 150 m, 24 Jul 2002, 5 female, 5 males, 5 indet., some in alcohol, USNM 1112304, 1123302, 1123304, 1123345-1123350; Delta 5622, 51°57'37"N, 176°49'58"W, 140 m, 24 Jun 2002, 2 indet., USNM 1123303; Delta 5624, 51°47'40"N, 176°49'58"W, 140 m, 25 Jun 2002, 1 male, USNM 1123300; Delta 5625, 51°57'42"N, 176°50'01"W, 156 m, 25 Jun 2002, 1 female, 1 indet., USNM 1027821; Delta 6000-10D-12, 51°50.828'N, 179°49.674'E, 112 m, 5 Jul 2003, 1 female, AB10-0002; Dominator 971-73, 52°33'10"N, 172°20'58"W, 217 m, 6 Jun 1997, 1 male in alcohol, USNM 1123366; Dominator 971-135, 51°37'22"N, 178°35'E, 163 m, 14 Jul 1997, 1 female, USNM 1123364; Let's Go, 51°57'N, 178°11'E, 0-247 m, 30 Aug 1986, 3 males, USNM 96259; MF 801-70, 52°03'24"N, 179°25'06"E, 174 m, 29 Jul 1980, 1 female, USNM; MF 833-47, 51°55'36"N, 176°52'48"W, 201 m, 5 Aug 1983, 1 male, USNM 77048; Ocean Olympic, 52°04'31"N, 177°12'28"E, 293 m, 4 Mar 2000, 1 male, USNM 1122540; Pacific Knight 941-36, 53°02'N, 170°13'W, 0-178 m, 11 Jun 1994, 8 male, USNM 96265, 96525, and 96542; Pacific Knight 941-37, 52°17'N, 170°40'W, 0-155 m, 12 Jun 1994, 1 male, USNM 96269; Pacific Knight 941-40, 52°41'N, 170°49'W, 0-126 m, 12 Jun 1994, 1 male, 1 indet., USNM 96270 and 96534; Pacific Knight 941-42, 52°55'N, 170°24'W, 0-225 m, 13 Jun 1994, 1 male, USNM 96522; Pacific Knight 941-49, 52°46'N, 171°45'W, 0-340 m, 14 Jun 1994, 1 female, USNM 96521; Pacific Knight 941-121, 51°38'N, 178°19'W, 0-375 m, 5 Jul 1994, 3 female, USNM 96262; Pacific Knight 941-204, 5306'N, 171°42'E, 9-455 m, 31 Jul 1994, 1 female, USNM 96523; Sea Storm 90, 51°36'30"N, 177°10'48"W, 217 m, 4 Jul 2002, 1 male in alcohol, USNM 1123009; Sea Storm 91, 51640'51"N, 177°10'49"W, 82 m, 4 Jul 2002, 1 male, USNM 1123021; Sea Storm 100, 51°42'59"N, 175°47'07"E, 86-94 m, 7 Jul 2002, 1 indet. in alcohol, USNM 1076928; Sea Storm 101, 51°45'27"N, 175°40'06"E, 83 m, 7 Jul 2002, 1 female, 2males, USNM 1123024, -26, -27; Sea Storm 105, 52°08'59"N, 175°06'47"E, 201 m, 8 Jul 2002, 1 male, USNM 1123023; Sea Storm 111, 52°16'20:N, 175°29'13"E, 137 m, 9 Jul 2002, 1 male and 1 female in alcohol, USNM 1123000, 1123013; Sea Storm 113, 52°03'07"N, 177°23'55"E, 128 m, 10 Jul 2002, 1 male, USNM 1123007; Sea Storm 115, 52°04'16"N, 177°19'04"E, 165 m, 10 Jul 2002, 1 indet. in alcohol, USNM 1123020; Sea Storm 116, 52°04'10"N, 177°14'25"E, 87-94 m, 11 Jul 2002, 1 female, USNM 1123006; Sea Storm 118, 52°00'14"N, 177°49'40"E, 104-111 m, 11 Jul 2002, 1 female, USNM 1123283; Sea Storm 122, 52°02'49"N, 179°25'18"E, 143 m, 13 Jul 2002, 6 male colonies, some in alcohol, and SEM stub 1499, USNM 1123043-44, 1123046, 1123048-49; Sea Storm 124, 52°16'24"N, 179°55'47"E, 88 m, 13 Jul 2002, 1 male in alcohol; Sea Storm 129, 51°53'24"N, 179°44'07"E, 84-93 m, 14 Jul 2002, 1 male, USNM 1123032; Sea Storm 130, 52°12'10"N, 176°12'40"E, 86 m, 15 Jul 2002, 1 female, USNM 1123002; Sea Storm 146, 52°15'55"N, 174°48'02"W, 113 m, 20 Jul 2002, 1 male in alcohol, USNM 1123019; Shishaldin, 51°53.84'N, 177°44.88'W, 374 m, Feb 2000, 1 male, USNM 1122495; Shishaldin, 52°27'14"N, 179°30'54"E, 218 m, 2 Feb 2000, 1 female, USNM 1122521; Vesteraalen 3, 52°38'12"N, 169°46'35"W, 75 m, 21 May 2000, 1 female, USNM 1123373; Vesteraalen 5, 54°40'43"N, 169°06'11"W, 102 m, 21 May 2000, 1 female, 1 male, USNM 1123372; Vesteraalen 8, 53°09'28"N, 167°04'14"W, 154 m, 22 May 2000, 1 male in alcohol, USNM 1123371; Vesteraalen 941-36, 52°56'N, 169°31'W, 0-227 m, 10 Jun 1994, 1 male, USNM 96261; Vesteraalen 941-151, 52°10'N, 179°44'E (topotypic), 0-90 m, 10 Jun 1994, 1 female, USNM 96267; Vesteraalen 941-153, 52°10'N, 179°43'E (topotypic), 0-94 m, 10 Jun 1994, 2 female, USNM 96268; Vesteraalen 941-167, 51°54'N, 178°20'E, 0-150 m, 19 Jul 1994, 3 male, SEM stub 1498, USNM 96264; Vesteraalen 941-185, 52°03'N, 176°31'E, 0-91 m, 24 Jul 1994, 1 female, USNM 96263; Vesteraalen 941-210, 53°07'N, 170°56'E, 0-92 m, 30 Jul 1994, 2 males, USNM 96266; University of Washington, 51°32'N, 179°15'W, 278-289 m, 1 Sep 1968, 1 female, USNM 96250; McClusky, coll., 51°53'14"N, 179°47'50"E, 35 1 -393 m, 30 Mar 2000, 1 female, USNM 1122448; off Sharma, AK, depth unknown, 2 female, USNM 76539;

Description.

Colonies variable in shape, ranging from planar (Fig. 11G) to multi-planar to bushy (Fig. 11A, E), the growth form possibly moderated by commensals (see Remarks). Branch tips usually blunt and circular to slightly flattened in cross section, 2.5-3.0 mm in diameter, more slender if affected by commensals; branch anastomosis not uncommon. Largest colony (USNM 96523) 28 cm in height; colonies attached by massive, dense basal branches up to 4.2 cm in diameter (USNM 96262). Coenosteum reticulate-granular in texture, coenosteal strips 50-60 µm wide, separated by thin slits about 10 µm wide; granules rounded, 7-8 µm in diameter. All colonies infested with spionid polychaetes ( Polydora ) and their characteristic binary axial tubes (see Remarks). Coenosteum pale orange.

Cyclosystems circular, 0.9-1.1 mm in diameter, and slightly (about 1 mm) raised above coenosteum; cyclosystems uniformly arranged on three or all four sides of a branch, rarely in a linear fashion. Gastropores 0.35-0.40 mm in diameter. Gastropore tubes cylindrical, curved (Fig. 13J), and long (often 2-3 times length of gastrostyle), the length and curvature of tube making it difficult to see gastrostyle tip when viewed from above. Ring palisade absent or diffuse, the elements about 50 µm in height and diameter. Gastrostyles lanceolate and up to 0.7 mm in height, bearing long spines up to 70 µm in length.

Dactylotomes 80-110 µm in width; dactylostyles poorly developed, the cylindrical elements about 20 µm in height and 8 µm in diameter. Range of dactylopores per cyclosystem 6-13 (n = 50, average = 9.22 (σ = 1.43), and mode = 10). Supernumerary dactylopores quite common on coenosteum (Fig. 13 A–C) and even on pseudosepta, presenting as small (0.09-0.11 mm in diameter), circular, slightly raised (rimmed) pores. Pseudosepta variable in width (Fig. 13D), in the same cyclosystem varying between 0.11 and 0.30 mm; adcauline diastemas also frequently present, each about twice pseudoseptal width.

Female ampullae (Fig. 13J) superficial hemispheres 0.8-1.1 mm in diameter; efferent pores rarely expressed, but if present, occurring in lateral position and somewhat recessed into coenosteum, each about 0.25 mm in diameter. Male ampullae (Fig. 13K) primarily internal, visible on coenosteal surface only as low mounds 0.3-0.5 mm in diameter, often with a small (30 µm diameter) apical efferent pore. Male ampullae often occur in high density clusters, directly adjacent to one another.

Remarks.

Virtually every colony of Stylaster brochi examined contained commensal spionid polychaetes of the genus Polydora (K. Fauchald, per. comm.), such that this character was informally used to distinguish it from other Stylaster species, such as Stylaster campylecus . Almost every branch is bored axially by this robust worm, which forms binary longitudinal tubes 0.7-0.8 mm in diameter that are figure 8-shaped in cross section (Fig. 15K). Several worms may occur in the same colony, each having one or more efferent openings somewhere on the colony surface. It is easy to conjecture an advantage to the worm in this relationship, i.e. a secure place to live and protection from predators, but it is difficult to imagine an advantage to the stylasterid, as the worm must weaken the strength of the branches as well as compete for the same filtered plankton in the water. Thus, it would seem that these polychaetes are parasites on the coral. Large colonies of Stylaster brochi also form substantial three dimensional habitats for a variety of invertebrates, including sponges, bryozoans, hydroids, barnacles, bivalves, and ophiuroids. Heavy encrustation by sponges seems to promote a more delicate colony growth form, in which the terminal branches are only 1.5 mm in diameter (Fig. 11E). In a monograph otherwise devoted to stylasterids from Sagami Bay, Japan, Eguchi (1968) inexplicably described Allopora abei from "the Aleutian Islands." Although the type was not examined, and Cairns (1983b) suggested a synonymy with Stylaster polyorchis Fisher, 1938, the illustrations provided by Eguchi suggest a synonymy with Stylaster brochi .Of 86 colonies examined, 35 are female, 40 male, and 11 indeterminate, resulting in a fairly equal sex ratio. Stylaster brochi is one of the most common and one of the largest growing stylasterids in the Aleutian Islands. It can be distinguished from other Alaskan species in Stylaster (Group A) by its usually planar growth mode, higher number of dactylopores per cyclosystem, and variable width of its pseudosepta (see Table 2 for additional comparisons).

Distribution.

Widespread throughout Aleutian Islands from west of Attu Island to Unalaska (including Petrel Bank), with one disjunct record near Sharma (near Anchorage); 75-351 m, but most records between 100-200 m.