Balanophyllia thalassae Zibrowius, 1980

Altuna, Álvaro, 2013, Scleractinia (Cnidaria: Anthozoa) from ECOMARG 2003, 2008 and 2009 expeditions to bathyal waters off north and northwest Spain (northeast Atlantic), Zootaxa 3641 (2), pp. 101-128 : 120-122

Balanophyllia thalassae Zibrowius, 1980

( Figs. 6 A–D, tables 1−3)

Balanophyllia thalassae Zibrowius, 1980: 189 , pl. 96, figs. A–I, pl. 97, figs. A–L—Ramil Blanco & Fernández Pulpeiro 1990: 28.—Cairns & Chapman 2001: 34 (tab. 1).—Brito & Ocaña 2004: 442, pl. 105, figs. A–B.—Reveillaud et al. 2008: 322 (tab. 1), 325 (fig. 4).—Altuna 2010: 21.

Material examined. Le Danois Bank, 2008: Stn. D 6V, 555 m, a young with its distal half missing, and a dead fragment; Stn. R1R 2, 751 m, two big dead and worn specimens. Galicia Bank: Stn. R 2, 614 m, seven solitary specimens mostly broken and lacking fragments of the corallum, a small agglomerate with broken specimens, some fragments.

Description. Corallum solitary, attached, straight or cup-like, massive, stout. Height from H= 1.36 cm (GCD= 1.73 cm, LCD= 1.47 cm) to H= 6.7−7.1 cm (stn. R1R2, calices broken). Corallum narrowed near base, with PD= 0.8−1.05 cm. Basal plate well developed. Wall weakly porous, more so in young specimens, with porosity increasing towards distal end in the adults. Costae only apparent near calicular margin in big-sized specimens, flat to slightly convex, with small spines; C1−C2 dominant, slightly wider than C3−C4 that are subequal. Calices circular in young specimens, elongate in the adults. Septa up to 71 (GCD= 2.05 cm; LCD= 1.85 cm) arranged in four complete cycles and some additional S5, with at most 7 septa between two dominants, normally 5; S1 and S2 dominant, with upper margin rather thick, highly and equally exsert or S1 more exsert, followed by S 4 in the projection, or by S5 if substitution of exosepta S4 occured; S3 less exsert. Septa subvertical, stout, distally porous; septal faces with pointed granules. Inner edge of S1−S3 smooth, of S4 more or less smooth or definitely laciniate; S4 curved, flanking S3, and united before each S3 deep in the fossa, close to columella. Fossa moderately deep, containing a well individualized columella, discrete, surrounded by a shallow albeit neat groove, spongy, formed by thin rods or twisted lamellae. Corallum of live specimens brown; skeleton white distally and light brown basally.

Remarks. Coralla of Balanophyllia thalassae and B. cellulosa are very similar, particularly regarding the structure and arrangement of the axial elements. A complete fifth cycle is never formed, and only a partial substitution of the exosepta S4 occurs in either species with normally five septa between two dominants S1−S2, i.e., one entoseptum S3, one exoseptum S4, one incipient entoseptum S4 and two exosepta S5. Nevertheless, B. thalassae is attached and B. cellulosa , unattached. Besides, the former may reach bigger sizes and the corallum is stouter. The corallum of B. cellulosa is more porous. Particularly porous are the septa, so much so that may be completely perforated and poorly ornamented with a few spines. In B. thalassae , septa are stouter and their lateral faces have numerous spines. The inner edge of exosepta S 4 in B. cellulosa , and more infrequently of entosepta S1 and S2, use to be deeply indented, with lobes or excrescencies, many of them identical to those forming the columella. Inner edge in B. thalassae is normally even. The fossa is rather deeper in B. cellulosa , and the columella is different. In B. thalassae there is a distinctive groove between columella and septa (fig. 6C–D), not always clearly visible, which is lacking in B. cellulosa (fig. 6I). The columella of B. thalassae is stouter, lengthened, convex, well developed and discrete, spongy but compact. In B. cellulosa the columella may be flat, convex, or even concave; it is formed by thin rods, and is nondiscrete, not so clearly separated from the inner edge of septa as in the other species. This difference is clearer when the inner edges of septa are lobulated and lobes merge with the columella. Regeneration from a fragment in the corallum of B. cellulosa is frequent, with specimens apparently growing on pieces of the same species. This is a difference with B. thalassae , which commonly shows alterations on its growth resulting in irregular corallites. In addition, this species may grow forming small clumps due to regeneration or perhaps autoepizoism. Both species differ in their bathymetric ranges, although they may co-occur. Balanophyllia cellulosa can live at shallower depths including the continental shelf, and B. thalassae lives at deeper depths, down to 1150 m (see Zibrowius 1980).

Balanophyllia thalassae is abundant at Le Danois Bank (Zibrowius 1980, type material) but is a coral rarely cited in the literature, with a limited distribution. Most records are from the north and northwestern Iberian Peninsula. It has been recently recorded from the Canary Islands (Brito & Ocaña 2004).

Figures

FIGURE 6. Balanophyllia thalassae Zibrowius, 1980 (stn. R 2, Galicia Bank). A) Corallum in side view (H = 6.5 cm; GCD = 2.1 cm; LCD = 1.8 cm). B) Corallum in side view (H = 3.21 cm; GCD = 2.26 cm). C) Calicular view (H = 2.27 cm; GCD = 2.04 cm; LCD = 1.79 m, 71 septa). D) Calicular view (H = 1.6 cm; GCD = 1.9 cm; LCD = 1.6 cm, 60 septa). Dendrophyllia alternata Pourtalès, 1880 (stn. R 2, Galicia Bank). E) Fragment of a colony. F) Calice. G) Detail of another fragment to show development of costae. Balanophyllia cellulosa Duncan, 1873 (stn. S 7 V, Le Danois Bank). H) Corallum with corrosion by Lumbrineris (H = 3.4 cm; GCD = 2.6 cm; LCD = 2.4 cm). I) Calicular view of another specimen (H = 2.8 cm; GCD = 2.1 cm; LCD = 1.9 cm). Scale bar: A, C – D, H – I = 2.0 cm; B = 1.0 cm; F – G = 0.5 cm.