Gemellipora galiciae Souto, Berning & Ostrovsky, 2016, n. sp.

Gemellipora galiciae n. sp.

(Figs 60–65, Table 12)

Material examined. Holotype: MNCN 25.03/3947, locality V01. Paratypes: MNCN 25.03/3948, locality V01; MNCN 25.03/3949, 3950, locality DR08; MNHN IB- 2013-624, 625, locality DW117; OLL 2015/904, 905, 924a,c, locality DW117.

Etymology. Alluding to the type locality, Galicia Bank.

Description. Colony delicate, composed of uniserial encrusting and biserial erect flexible parts. Encrusting zooids bilaterally symmetrical, elongated, comprising claviform dilatation with orifice, and narrow proximal cauda of variable length that gradually increases in width distally. Autozooids, including caudae, with numerous lateral mural pore-chambers with uniporous septula at regular intervals from which lateral zooids may bud (although lateral branching is scarcer in the encrusting portion and was never seen in caudal parts). Zooidal surface usually smooth with some growth lines, caudal surface wrinkled.

Erect parts of colony originating from round windows (frontal pore-chambers) in mediolateral part of frontal shield of encrusting autozooid. Erect stem c. 2 cm in height, composed of central and lateral, evenly pinnate branches that diverge at almost 90° angles at regular intervals (with a single pair of non-branching zooids between consecutive branches), branching always in same plane; both axial and lateral branches composed of back-to-back pairs of zooids (dyads) except for first erect zooid, which is single. Orifices situated directly opposite each other, always aligned in more or less the same direction, i.e. zooids in central axial branch open laterally, those of lateral branches up and down; skeleton in all branches interrupted at irregular intervals just distal to dyads, thus forming flexible joints, internodes composed of 2–3 dyads. Zooids in central axial branch longest, those in first dyad of lateral branch distinctly shorter than these, but slightly longer than subsequent zooids in that branch, which are all of equal length.

SD, standard deviation; N, number of measurements

Overall zooidal morphology similar to that in encrusting colony part but with some differences—zooids slightly asymmetrical, frontal shield more extensively developed on one distolateral side than on other, lateral walls separated by weakly sinuous faint grooves or sutures, oval pseudopores distributed over entire frontal shield; in cleaned colonies their structure resembles mural pore chambers visible in encrusting colony portion.

Orifice elevated, slightly longer than wide, anter horsehoe-shaped, delimited from shallow, broadly U-shaped poster by pair of deep incisions directed proximolaterally.

No spines, ovicells or avicularia. Ancestrula not observed.

Remarks. The type species of the genus Gemellipora, G. eburnea Smitt, 1873 from the Caribbean, was recently redescribed by Winston (2005, p. 41, figs 104–106). Although similar in colonial, orificial and overall zooid morphology, the Galicia Bank specimens are distinctly different. Zooids in erect portions of G. eburnea are much shorter than in G. galiciae n. sp., and the orientation of the orifices is displaced by 90° in each subsequent dyad, whereas in the new species the orifices of one dyad usually face in the same direction as those of the predecessor. Exceptions may occur in damaged and repaired zooids if a new intramural bud has been produced. Gemellipora eburnea also differs slightly in the shape of the orificial sinus, which seems to be more gently curved. However, most of the orifices figured by Winston (2005) are damaged or repaired, and the only undamaged orifice is shown from an oblique angle, which makes it difficult to compare.

While Smitt (1873, fig. 152) originally figured the encrusting zooids of G. e b u r n e a [some of the figured specimens, however, actually belong to a Hippothoa species (see Winston 2005, p. 41)], the material that Winston redescribed did not include the encrusting base of the colony. It is worth noting that in the encrusting zooids of G. galiciae n. sp. pseudopores are almost exclusively seen along their lateral walls, whereas pseudopores are scattered over the entire frontal shield in erect zooids. Also, the first erect zooid in this species is solitary, not a dyad.

Gemellipora eburnea has been cited to occur in the eastern North Atlantic many times (e.g. Calvet 1907, 1931; d'Hondt 1975; Harmelin 1977; Hayward 1978, 1979; Reverter-Gil & Fernández-Pulpeiro 2001; Reverter-Gil et al. 2014). In the light of the present findings, however, these records need to be revised, and it is most probable that the Caribbean G. eburnea does not exist in the central and/or eastern Atlantic. The colony reported as G. e b u r n e a from New Zealand (Gordon 1984, p. 112, pl. 44A) also differs from the present specimens in several aspects. Zooids in the encrusting part have more frontal pores, and those in the erect part are distinctly smaller and the orifice is not raised and parallel to the zooidal plane but slightly tilted distad. The more elongated zooids also distinguish the New Zealand specimens from the type of G. e b u r n e a.

Furthermore, our specimens differ from Gemellipora adhaerens Cook, 1985, of which only the encrusting portion was described, in that the zooidal surface lacks pseudopores, whereas the Ghanaian species has 40 to 60 small pseudopores per zooid (Cook 1985, p. 138).

On Galicia Bank this species was collected at numerous stations between 770 and 1697 m depth, predominantly encrusting corals while one colony was found on a rock.