Inferiolabiata labiata ( Moseley, 1879 )

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 : 24-27

Inferiolabiata labiata ( Moseley, 1879)

( Figs. 14 , 15 )

Errina (Inferiolabiata) labiata Broch 1951b: 125 ; Boschma 1963: 337–338; Cairns 1983a: 111–113, map 8, figs. 22d–e, 26a–i, 27a–c

Errina labiata Moseley 1879: 443–447 , pl. 34, fig. 7, pl. 37, pl. 44, figs. 9–11; Moseley 1881: 50–55, 80, pl. 1, fig. 7, pl. 4, pl. 11, figs. 9–11; Hickson 1892: 238; Boschma 1957: 55; Boschma 1964: 287–299, pl. 1, text figs. 1–3; Boschma 1966: 109, 117; Boschma & Lowe 1969: 15, pl. 5, map 2; Cairns 1983a: 156; Zamponi 2008: 188, 198, fig. 9

Errina (Errina) labiata: Hickson 1912: 880

Errina (Labiata) labiata: Broch 1942: 39

Inferiolabiata labiata: Cairns 1991: 16 , 40, pl. 23d–h, 24a–b

Distribution. Antarctic and Subantarctic regions, including southeastern South America, Scotia Sea, Ross Sea, Scott Island, Balleny Islands, and Antipodes Islands; 87–2100 m. New record off Mar del Plata, 819–1398 m.

Material examined. USNM 59954 off Antarctica, Eltanin St. 1870 (71° 17–16’ S, 171° 33–29’ E); MACN-In 40656 off Mar del Plata, Argentina, St. 59 (37° 49.688’ S, 54° 5.236’ W), 1398 m, September 2013 ; MACN-In 40659 off Mar del Plata , Argentina, St. 37 (37° 59.848’ S, 54° 24.206’ W), 1275 m, May 2013 ; MACN-In 42513 off Mar del Plata , Argentina, St. 36 (37° 57.508’ S, 54° 23.989’ W), 1289 m, May 2013 ; MACN-In 42514 off Mar del Plata , Argentina, St. 31 (38° 1.499’ S, 54° 44.171’ W), 819 m, August 2012 ; MACN-In 42515 off Mar del Plata , Argentina, St. 12 (37° 57.907’ S, 54° 31.921’ W), 1144 m, August 2012 ; MACN-In 42516 off Mar del Plata , Argentina, St. 11 (37° 59.258’ S, 54° 41.436’ W), 854 m, August 2012 ; MACN-In 42517 off Mar del Plata , Argentina, St. 42 (37° 59.110’ S, 54° 41.136’ W), 877 m, May 2013.

Description. Colonies uniplanar to bushy, robust or delicate.Anastomosis in basal branches. Branches generally round in cross section, although they may also be flattened in anterior-posterior axis ( Fig. 14a ). Thinnest branchlet 0.8 mm wide and thickest branch 7.0 mm wide. Colonies attach to dead specimens of Bathelia candida through an expansive base ( Fig. 14b, c ). Polychaete tube present ( Fig. 14b, c ), cage-like with reticulate walls ( Fig. 14c ). Branches proximal to tube anastomose and those bearing it flatten.

Coenosteum white and porous, with an irregular surface. Round to oval coenosteal pores (20–63 µm maximum width) aligned within longitudinal coenosteal canals of a similar diameter, that ocassionally communicate ( Fig. 15b ). Largest axis of elliptical coenosteal pore is parallel to axis of canal. Imbricate platelets cover surface of coenosteal canals and rest of coral surface ( Fig. 15c ). In some specimens, longitudinal coenosteal canals are less defined and a more reticular-imbricate pattern is visible, with coenosteal pores arranged randomly. Coenosteal ridges form between two adjacent longitudinal canals and continue along the surface of dactylopore spines.

Gastropores round and flush, 0.10–0.48 mm wide (average 0.33 mm, n=57, σ=0.08). In more basal branches that are smoother, they display a pentagonal shape ( Fig. 15e ). Gastropore tubes short and peripheral. Gastrostyle spindle to needle shaped and sparsely ornamented with around four ridges of rudimentary spines ( Fig. 15d ). Its tip is easily seen from surface opening of the gastropore. Ring palisade not identified.

Dactylopore spines abcauline and long, with a truncated tip ( Fig. 15b ). They are 0.65–0.90 mm high, with a dactylotome 0.16–0.29 mm wide (n=8). The remains of two dactylostyles were identified in some spines ( Fig. 15f ). Towards base of branches, dactylopore spines are lower and sparser. Eroded spines often resemble short cylindrical tubes raised from the surface, that may be confused with bryozoan structures at first sight. Dactylopores may also be seen as flush round structures due to complete erosion of the spine surrounding them ( Fig. 15a ).

Ampullae spherical and very conspicuous, half sunken in branch. Their coenosteum is thin and loosely packed; large craters are left in places where they have ruptured ( Fig. 15a ). Largest ampullae measured 1.00– 1.25 mm wide, which suggests specimens bearing them are female. Other specimens bore smaller ampullae, which are probably male.

Discussion. The studied specimens agree with Moseley (1879) and Cairns (1983a, 1991) in their description. As regards dactylostyles, they are absent, according to Moseley (1879). The specimens here described scarcely bear remains of dactylostyles in some spines, and in others they were probably entirely absent. Moseley (1879) mentions the “irregularly circular” and “indented” gastropores, which coincides with the pentagonal shape here described for these structures. Cairns (1983a, 1991) does not mention this singularity of the gastropores in I. labiata , although it was also identified in specimen USNM 59954. The described material was rather eroded and few healthy dactylopore spines were present, so the lateral fusion of spines mentioned by Moseley (1879) and Cairns (1983a, 1991) was not identified.

Moseley´s original description was based on one specimen and fragments from off Río de la Plata. His record ( Moseley, 1881) from Tristan da Cunha was erroneus, according to Boschma (1964). Lowe´s (1967) records were also misidentifications according to Cairns (1983a). Boschma (1966) reported the second valid occurrence of E. labiata in Antarctic zone and Cairns provided the following two records in 1983a and 1991 in Scotia Ridge, Antarctica and New Zealand. The present work provides a new record of I. labiata off Argentina.

Figures

FIGURE 14. Inferiolabiata labiata. (a) Fragment bearing flattened branches. (b) Incipient colony attached to fragment of B. candida, bearing polychaete. (c) Basal section of colony attached to B. candida, bearing polychaete.

FIGURE 15. Inferiolabiata labiata. (a) Fragment displaying dactylopores with spine absent due to erosion and craters resulting from ruptured ampullae. (b) Fragment displaying abcauline dactylopore spines and longitudinal coenosteal canals.(c) Coenosteal texture. (d) Gastrostyle. (e) Pentagonal gastropore. (f) Remains of dactylostyles.