Stylaster leptostylus (Fisher, 1938) 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 : 40-42

Stylaster leptostylus (Fisher, 1938) new rank Figs 17E19 A–I

Allopora moseleyana forma leptostyla Fisher, 1938: 514, pl. 52, figs, 1-3.

Allopora moseleyana Fisher, 1938: in part (pl. 50).

Stylaster moseleyanus forma leptostylus.- Cairns 1983b: 429.

Type material.

Holotype: Alb-3480, 1 dry male colony 8.5 cm in height, and SEM stub 1544, USNM 43270 (Fig. 17E). Paratypes: Alb-3480, 4 female, 2 male colonies, dry, and SEM stub 1536-38, USNM 76817. Type locality.Alb-3480: 52°06'00"N, 171°45'00"W (off Seguam Island, Amukta Pass), 518 m.

Material examined.

Types. Alb-3480, 2 female, 1 male colonies, dry, USNM 76555 (paratype of Allopora moseleyana ).

Description.

Corallum uniplanar, branching equal and dichotomous; no anastomosis of branches. Largest colony (the holotype, Fig. 17E) 8.5 cm in height and 7.0 cm in width, with a basal branch diameter of 8.4 mm. All branches circular in cross section. Commensal spionid polychaetes absent. Coenosteum reticulate-granular i n texture, the coenosteal strips 45-55 µm in width, the slits about 15 µm in width; strips; strips not linear near cyclosystems. Coenosteum white.

Cyclosystems occur on branch edges and anterior face, but rarely on posterior face, those on edges not aligned in rows. Cyclosystems circular, 1.0-1.1 mm in diameter, and raised only slightly above branch coenosteum. Gastropores about 0.35 mm in diameter, leading to a slightly curved, funnel-shaped upper tube that narrows to a cylindrical lower part that houses the gastrostyle (Fig. 19 G–H); ring palisade absent. Gastrostyles elongate-lanceolate, up to 0.6 mm in length, occupying lower half of gastropore tube, its pointed tip easily seen in an intact cyclosystem; H:D about 3.5.

Dactylotomes 0.10-0.13 mm wide; dactylostyles moderate in size, elements up to 50 µm in length. Range of dactylopores per cyclosystem 7-12 (n = 50, average = 9.76 (σ = 1.92), mode = 9). Supernumerary dactylopores absent. Pseudosepta slender and fairly uniform in width (0.10-0.11 mm), an adcauline diastema of twice that width sometimes present.

Female ampullae (Fig. 19D) large, smooth, superficial hemispheres 0.9-1.1 mm in diameter, occasionally having a lateral efferent pore about 0.20 mm in diameter. Male ampullae (Fig. 19A) superficial swellings 0.45-0.55 mm in diameter, often clustered on anterior and posterior branch faces; apical efferent pores about 25 µm in diameter.

Remarks.

Fisher (1938) originally differentiated forma leptostyla from typical Allopora moseleyana (= Stylaster campylecus ) based on its more slender gastrostyle and smaller male ampullae. We cannot find a difference in ampulla size between forma leptostyla and typical Stylaster campylecus , but the gastrostyle of leptostyla is longer and more slender than that of Stylaster campylecus , occupying more of the gastropore tube (and thus having a higher H:D ratio) and being more visible from external view. In addition to this difference, forma leptostyla differs from Stylaster campylecus in having equal, non-anastomosing branching; branches circular in cross section; less exsert cyclosystems; non-linearly arranged cyclosystems; fewer dactylopores per cyclosystem; and consistently reticulate coenosteal strips (see Table 2). For these reasons this form is elevated to species rank but is considered to be closely related to Stylaster campylecus .

Distribution.

Known only from type locality.