Hemicyclopora discrepans (Jullien, 1903)

Harmelin, Jean-Georges & Rosso, Antonietta, 2023, On some “ Hemicyclopora ” Norman, 1894 and “ Escharella ” Gray, 1848 species (Bryozoa, Cheilostomatida) from the Atlantic-Mediterranean region. Re-examination of their generic status and description of new species and a new genus, Zoosystema 45 (10), pp. 373-407 : 382-384

Hemicyclopora discrepans (Jullien in Jullien & Calvet, 1903)

( Fig. 5 A-G; Tables 1 ; 2 ; 4 )

Lepralia discrepans Jullien in Jullien & Calvet, 1903: 72, pl. 10, fig. 1.

Hemicyclopora discrepans – López de la Cuadra & Garcia-Gómez 1991: 218. — Harmelin & d’Hondt 1992: 30 (part). — Reverter-Gil & Fernández-Pulpeiro 1999: 1411, fig. 4A-C. — Souto & Reverter-Gil 2021: 3, 5, table 1 (part).

Hemicyclopora multispinata ( Busk, 1861) – Boronat Tormo 1987: 107, plate 10A, B.

? Hemicyclopora admirabilis Ramalho, Rodríguez-Aporta & Gofas, 2022: 22 , fig. 10.

? Hemicyclopora sp. – Souto et al. 2014: 140, fig. 5B, D.

Not Hemicyclopora discrepans ( Jullien, 1903) – Harmelin 1997: 144 (table 2) (see below = Hemicyclopora hexaspinae n. sp.).

MATERIAL EXAMINED. — Mediterranean. Alboran Sea • 3 small ovicellate colonies; R/V Cryos; Balgim Stn DW132, 35°25.7’N, 4°18.8’W; 170 m depth; 15.VI.1984, on shell (2 col. together with 2 col. of Escharella similis ) and biogenic concretion; Dre; JGH leg.: listed by Harmelin & d’Hondt (1992); MNHN .

NE Atlantic – Ibero-Moroccan Gulf • 2 ovicellate colonies; R / V Noroit; Seamount 1, Gorringe Bank, Stn DW 5, 36°32.0’N, 11°37.9’W, 180 m depth; 22.IX.1987; Dre ; JGH leg.; MNHN • 1 small colony; R / V Noroit; Seamount 1, Gorringe Bank, Stn DW 15, 36°33.44’N, 11°28.8’W, 320 m depth; 24.IV.1987, on stone; Dre ; JGH leg.; MNHN • 1 small colony; R / V Noroit; Seamount 1, Ampère Seamount, Stn CP 99, 35°03.8’N, 12°55.4’W, 250 m depth, on shell; Dre ; JGH leg.; MNHN

Spain, NW Iberian Peninsula • 3 small ovicellate colonies; 42°38’30”N, 9°23’42”W; 128 m depth; V.1997; on shell and fragment of a whale bone; Dre; O. Reverter-Gil leg.; MNHN (1.VI.1998: material examined by Reverter-Gil & Fernández-Pulpeiro 1999 and listed by Souto & Reverter-Gil 2021) .

DESCRIPTION

Colony encrusting, unilaminar, forming small lobate patches of less than 100 zooids. Autozooids elongated, hexagonal or polygonal, quincuncially arranged; frontal shield bulged, most prominent at mid-length and proximally to the orifice, its surface covered with evenly spaced, hemispherical to conical and pointed granules, 5-15 µm in diameter ( Fig. 5B, F, G ); marginal pores medium-sized (up to 15-20 µm), in a single row along the proximal half of the zooid, and distributed distally in two or three rows up to the orifice level ( Fig. 5B, D, F, G ). Pore-chambers small and numerous (up to 15 on each side), opening along a c. 50 µm wide basal margin ( Fig. 5F ). Distal wall vertical or sub-vertical ( Fig. 5B, D, G ). Orifice distal or sub-distal, often somewhat inclined distally, a little longer than wide in non-ovicellate zooids, significantly wider than long in ovicellate zooids, proximal edge (poster) slightly concave, without any collar or umbo, sometimes with a thin rim of gymnocystal calcification connected laterally to the proximal pair of spines; condyles protuberant, thick, triangular, slightly curved proximally, with more or less blunt tips ( Fig. 5B, E, G ). Oral spines articulated on stout bases, long (up to c. 750 µm), outwardly arched, particularly the distalmost pair, eight in non-ovicellate zooids, occasionally nine, and eight, seven or six in ovicellate zooids ( Fig. 5 ), this number being constant or variable within colonies (see below). Ovicell globular, wider than long, attached to the distal wall of maternal zooid, sometimes adjoining the proximal part of the frontal shield of distal zooid; endooecium with the same granular texture as the frontal shield of autozooids, without umbo or vizor, sometimes with a narrow, thin rim of gymnocystal calcification along the opening ( Fig. 5C, D, F, G ), presumably cleithral, “terminal”, produced by a basal kenozooid not visible frontally, only detected at early stage and in broken ovicells ( Fig. 5D, F ). Interzooidal kenozooids infrequent, relatively large (e.g. 600 × 550 µm), with few frontal pores. Ancestrula with three roughly equally extended parts, an opesia with six distal spines and a concave proximal edge, a cryptocyst with a granular surface, edged by four or five spines, and a proximal gymnocyst ( Boronat Tormo 1987: 107, pl. 10B; Reverter-Gil & Fernández-Pulpeiro 1999: 1411, fig. 4B; specimen from Seamount 1 Stn DW15).

REMARKS

Morphological features and taxonomic issues

Except for the number of spines in ovicellate zooids, which may vary within and between colonies (see below), the morphological features of our material from the Mediterranean (Alboran Sea) and the NE Atlantic comply with the original figure of H. discrepans by Jullien (1903: pl. 10, fig. 1), the redescription of this species by Reverter-Gil & Fernández-Pulpeiro (1999), and our own examination of part of their material (letter, SEM photos and material sent by O. Reverter-Gil to JGH, 1.VI.1998). This species (or species complex) is characterized by zooids with a bulged frontal shield without any thickening or umbo adjoining the orifice and the ovicell, a primary orifice with clearly protruding condyles, the particular aspect of the frontal shield and endooecium with granules which tend to be pointed, relatively large marginal pores distributed in several rows laterally to the orifice, eight oral spines with large and thick bases in non-ovicellate zooids, and globular ovicells produced by a small, basal, terminal kenozooid, later recumbent on the frontal shield of the distal zooid. However, these features are also shared with H. admirabilis , recently described from the Alboran Sea ( Ramalho et al. 2022), and with Hemicyclopora sp. ( Souto et al. 2014) from southern Portugal. Except for minor differences (e.g. the precise shape of condyles) that may indicate local variability, both H. admirabilis and the specimens described by Souto et al. (2014) as Hemicyclopora sp. only differ from H. discrepans in the lower number of spines in ovicellate zooids (six vs eight). In our material from the Mediterranean (Alboran Sea) and the nearby Atlantic, several colonies show features combining those of H. discrepans and H. admirabilis , particularly the number of spines in ovicellate zooids. This number can vary within a single colony, as in a specimen from the Alboran Sea (Balgim DW132, Fig. 5A ), in which it is six or eight. Therefore, this specimen should be intermediate between H. discrepans and H. admirabilis . Furthermore, specimens from the Atlantic seamounts (Gorringe Bank: DW5, DW15; Ampère Seamount: CP99) have six spines in ovicellate zooids, as in H. admirabilis , but a colony from Ampère Seamount diverges from the Bauplan of the latter in having a majority of non-ovicellate zooids with nine spines (seven cases: 70%) instead of eight spines (three cases: 30%). This divergence recalls cases of speciation driven by geographic isolation on Atlantic seamounts observed within the Atlantisinidae Berning, Harmelin & Bader, 2017 ( Berning et al. 2017). In particular, the species Atlantisina gorringensis Berning, Harmelin & Bader, 2017 was likely endemic to Gorringe Bank and Ampère Seamount. In conclusion, the present material questions the actual type of ovicell closure and the taxonomic relationships between H. discrepans , H. admirabilis and Hemicyclopora sp. ( Souto et al. 2014). Are they a complex of species or a series of variants of the same species ( H. discrepans ) having a particular plasticity? Obviously, this case study would require molecular analyses to give proper answers. Unfortunately, colonies of Hemicyclopora , particularly in this case, are very small, rare, and their habitat is not easily accessible.

HABITAT DISTRIBUTION

The examined material was collected from 128 m to 320 m depth on sandy bottoms. Deeper records of H. discrepans are provided by Calvet (1907: 717 m) from the western entrance of the Strait of Gibraltar, and Reverter-Gil & Fernández-Pulpeiro (1999) from the NW Iberian Peninsula ( Thalassa U844, 695- 760 m). This last specimen, not illustrated by SEM, is held at the MNHN and its specific assignation should be verified. The two deep-water colonies from Portugal recorded as Hemicyclopora sp. by Souto et al. (2014: 800-900 m) may represent the deepest record of H. discrepans . Colonies were established on small biogenic substrates: empty shells, concretions, and even on fragments of whale bones (Reverter-Gil & Fernández-Pulpeiro 1999; Souto & Reverter-Gil 2021).

GEOGRAPHICAL DISTRIBUTION

Hemicyclopora discrepans has an Atlantic-Mediterranean distribution ( Table 4 ). In the Mediterranean, the species was collected exclusively in the Alboran Sea (present material; Boronat Tormo 1987; Harmelin & d’Hondt 1992). In the Atlantic, specimens were recorded from seamounts and banks located SW of the Gibraltar Strait and along the NW Iberian Peninsula.

Figures

FIG. 5. — Hemicyclopora discrepans (Jullien in Jullien & Calvet, 1903): A, colony with ovicellate zooids bearing six, seven, or eight oral spines; B, non-ovicellate zooid with eight spines,primary orifice with internal arch and protruding condyles,and granular frontal shield;C, three ovicellate zooids with six spines and ovicells inserted between the base of distal autozooids; D, zooids with long, curved spines, large porous area lateral to orifice and ovicells attached to distal maternal wall,one under construction; E, orifice with triangular, down-curved condyles,concave proximal edge with a narrow rim of gymnocyst; F, lateral view of the distal part of an ovicellate zooid with eight spines, large marginal pores and the ovicell with the basal kenozooid; G, two zooids, one ovicellate, both with eight spines, frontal shield and endooecium with pointed granules. Origin: A, B, F, G, Alboran Sea, Balgim DW132, 170 m; C, D, E, Atlantic, Gorringe Bank, Seamount 1 DW5, 180 m. Scales bars: A, 400 µm; B, F, 100 µm; C, D, G, 200 µm; E, 50 µm.