Errinopora disticha Lindner & Cairns

Cairns, Stephen D. & Lindner, Alberto, 2011, A Revision of the Stylasteridae (Cnidaria, Hydrozoa, Filifera) from Alaska and Adjacent Waters, ZooKeys 158, pp. 1-88 : 16-18

Errinopora disticha Lindner & Cairns sp. n. Figs 5D8 A–J

Errinopora disticha Lindner, 2005: 97-99, figs 4.2A-B, 4.7B, 4.13 (unpublished name).

Type material.

Holotype: a dry female colony 10 cm in height, coll. Renfro, USNM 1123524 (Fig. 5D). Paratypes: also from type locality, 1 female, USNM 1123521; Alaskan Leader 35, 53°01'48"N, 170°06.62'W, 172-178 m, 4 Jun 2002, 2 male, USNM 1123525; Alb-3480, 52°06'N, 171°45'W, 518 m, 8 Jul 1893, 2 males in alcohol, USNM 43768; Alb-3480, see above, 1 male, USNM 1148212 (ex USNM 52247, paratype of Errinopora zarhyncha); 52°03'26"N, 179°12.34'E, 475 m, 27 Apr 2000, 1 male, USNM 1123523; 51°52'46"N, 179°17'24"E, 536 m, 16 Jul 2000, 2 female, USNM 1123522. Type locality. 51°53'12"N, 179°17.40'E (west of Semisopochnoi I., Petrel Bank), 530 m.

Etymology. The specific name disticha (from the Greek distichos, meaning "of two rows") refers to the short distichoporine pore rows of this species.

Material examined. Types.

Description. Colonies uniplanar to multiplanar, consisting of cylindrical to highly compressed branches, the greater axis of compressed branches oriented in plane of colony flabellum and reaching up to two times length of lesser axis. Branching dichotomous and non-anastomotic, terminating in blunt tips and forming U-shaped axils between branching. Holotype (Fig. 5D) 10 cm tall and equally wide, with a basal branch diameter of 22 × 20 mm; largest specimen (USNM 1123523) 13.5 cm in height. Parasitic spionid polychaete tubes found in only one corallum (USMM 1123525). Coenosteum typical for the genus: reticulate spinose, the narrow strips separated by broad porous slits, resulting in a very porous surface. Coenosteum light orange; branch cores white or lighter orange.

Dactylopore spines mostly arranged in long meandering distichoporine (bilateral) rows of up to 18 laterally fused spines (Fig. 8A-B). Two rows or terraces of dactylopore spines usually flank each gastropore row, the dactylotomes facing the gastropore; however, the number of dactylopore spines is often unequal on either side of a pore row and are occasionally absent from one side. Toward corallum base, pore rows decrease in length, often resulting in a single gastropore surrounded by 3-6 dactylopore spines approximating a pseudocyclosystem. Dactylopore spines fairly short (0.5-0.9 mm in height) and thick-walled, the dactylotome consisting of one-third to half width of spine; compound dactylopore spines common. Dactylostyles robust, up to 75 µm in width, consisting of cylindrical elements up to 53 µm in length and 5-10 µm in diameter; exterior surface longitudinally ridged. Secondary dactylopores, which lack styles, very common on coenosteum, especially back sides of dactylopore spines, these pores being circular, flush with the surface, and measure about 75-110 µm in diameter.

Gastropores circular, flush with coenosteum, and variable in size, ranging from 0.3-0.7 mm in diameter, both size classes often adjacent to one another. Gastropores usually closely spaced and unilinearly arranged in a shallow sulcus created by adjacent dactylopore spine terraces. Gastropore tubes cylindrical, fairly shallow, and lack a ring palisade; secondary gastropores 0.19-0.30 mm in diameter. Gastrostyles lanceolate but somewhat stout, the figured symmetrical style (Fig. 8 H–I) being 0.49 mm in height and 0.36 mm in diameter, however, many gastrostyles are asymmetrical, being elliptical to flattened in cross section. Gastrostyles bear longitudinal, spiny, anastomosing ridges, and fill most of gastropore cavity.

Female ampullae (Fig. 8 A–B) hemispherical to somewhat flattened (1.3-1.5 mm in diameter), their basal perimeter often slightly undercut, and often with an irregular or ridged surface. Discrete efferent pores never observed. Male ampullae small, porous, hemispherical blisters 0.4-0.6 mm in diameter, often occurring in great concentrations on coenosteum.

Remarks.

Errinopora disticha is the only Alaskan Errinopora species to have its dactylopore spines arranged bilaterally in distichoporine rows flanking a row of gastropores, however two other species have a distichoporine arrangement: Errinopora pourtalesii (California) and Errinopora stylifera (Japan to Okhotsk Sea) (see Dichotomous Key and Table 1). Errinopora disticha differs from those two species in having reticulate-spinose coenosteum (vs reticulate-granular), and flattened gastrostyles and branches. Of the 10 specimens examined, 4 are female and 6 male.

Distribution.

Known only from the Aleutian Islands: off Petrel Bank, Amukta Pass, and off Four Kings Islands; 178-536 m.