Errina sp.

Bernal, M. C., Cairns, S. D., Penchaszadeh, P. E. & Lauretta, D., 2021, Stylasterids (Hydrozoa: Stylasteridae) from Mar del Plata submarine canyon and adjacent area (southwestern Atlantic), with a key to the species off Argentina, Zootaxa 4969 (3), pp. 401-452 : 14-15

Errina sp.

( Figs. 7 , 8 )

Distribution. Mar del Plata Submarine Canyon and adjacent area, 852–997 m depth.

Material examined. MACN-In 40644 off Mar del Plata , Argentina, St. 10 (37º 59.706’ S, 54º 41.854’ W), 852 m, August 2012 ; MACN-In 40655 off Mar del Plata , Argentina, St. 41 (38º 01.631’ S, 54º 30.275’ W), 997 m, May 2013 .

Description. Colonies delicate and bushy, with basal branches up to 0.6 cm in diameter and branchlets down to 1.3 mm. Axis of main branch proteinaceous and belongs to the remains of another organism ( Fig. 7a, c ). Largest specimen 10 cm wide. Anastomosis scarce. Branches round to slightly oval in cross section. Branches grow in different planes and, within each plane, largest axis of branch cross section is parallel to it. Branchlets may originate from considerably thicker branches. Coenosteum white, with a reticulate-granular texture. Coenosteal strips 40–82 µm wide, delimited by a more or less continuous reticulate pattern of short slits perforated by deep pores. Granules irregular in shape and fused with one another. Polychaete tubes absent, although one specimen bears two scapellid barnacles ( Fig. 7b ) and another one bears a sea anemone ( Fig. 7c ).

Gastropores round and flush, 0.14–0.43 mm wide (average 0.29 mm, n=52, σ=0.07), distributed uniformly on branch surfaces but more sparsely towards the base; lip absent ( Fig. 8b ). Gastropore tubes short and peripheral. Ring palisade and tabulae absent. Gastrostyle spindle-shaped, occupying gastropore tube length almost completely. It bears longitudinal ridges of short spines and base is unornamented ( Fig. 8d ).

Dactylopores of two kinds: those round and flush, 0.08–0.13 mm wide and those surrounded by a U-shaped spine ( Fig. 8a, c ). As with the gastropores, they are distributed uniformly on branch surfaces but are less concentrated in basal ones. Dactylopore spines adcauline, 0.44–0.74 mm tall (average 0.58 mm, n=16, σ=0.09), 0.33–0.49 mm wide (average 0.43 mm, n=18, σ=0.05) with a slit 0.08–0.16 mm wide (average 0.12 mm, n=20, σ=0.02). Spines tallest in branchlets and branch tips ( Fig. 8a ).

Ampullae spherical and prominent, up to 1.3–1.5 mm in external diameter. Efferent pore unidentified. Sex unknown but probably female, judging by size of ampullae ( Fig. 7a, c ).

Discussion. Specimens are similar to Errina argentina in gastro- and dactylopore arrangement and type, coenosteal texture, gastropore tube and gastrostyle shape and position and in presence of prominent hemispherical ampullae. However, their average gastropore diameter is slightly lower than that in E. argentina and their average dactylopore spine height is higher. Also, lateral branchlets are absent in E. argentina unlike these specimens, and in E. argentina dactylopore spines only seem to be well developed at branch tips, while these Errina sp. specimens bear high spines all along thin branches and spines are lower (but not absent) in thicker branches.

Figures

FIGURE 7. Errina sp. (a) Colony developing over proteinaceous axis of another organism, bearing ampullae. (b) Branchlet bearing ampullae and two scapellid barnacles. (c) Base of colony developing over proteinaceous axis of another organism, bearing ampullae and an anemone.

FIGURE 8. Errina sp. (a) Branchlet bearing gastropores and both types of dactylopores. (b) More basal section of a branch with lower dactylopore spines and sparser arrangement of pores. (c) Closer view of gastropores and dactylopores. (d) Peripheral gastropore tube and spindle-shaped gastrostyle.