Escharella similis Ramalho, Rodriguez-Aporta & Gofas 2022
Creators: name: Harmelin, Jean-Georges
name: Rosso, Antonietta
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Bryozoa
Gymnolaemata
Cheilostomatida
Romancheinidae
Escharella
Escharella similis

description: Escharella similis Ramalho, Rodríguez-Aporta & Gofas, 2022
(Figs 7 A-F; 10G-I; Tables 1; 3; 4)
Escharella similis Ramalho, Rodríguez-Aporta & Gofas, 2022: 71, fig. 9, table 2.
Escharella sp. – Ramalho et al. 2020a: 106, table 2.
Hemicyclopora discrepans – Harmelin & d’Hondt 1992: 30 (part).
MATERIAL EXAMINED. — Mediterranean, Alboran Sea • 1 small colony; R / V Cryos, Balgim Stn DR 130, 35°25.3’N, 4°19.3’W; 145 m depth; 15. VI.1984; on shell; Dre; JGH leg. • 4 colonies; R / V Cryos, Balgim Stn DW 132, 35°25.7’N, 4°18.8’W; 170 m depth; 15. VI.1984, on shells; Dre; JGH leg. • 1 ovicellate colony with ancestrula, c. 30 autozooids (4 ovicells) + 1 small colony, R / V Cryos, Balgim Stn DW134, 35°25.8’N, 4°17.0’W; 205 m depth; 15. VI.1984; on biogenic concretion and shell; Dre; JGH leg.; MNHN.
NE Atlantic, Ibero-Moroccan Gulf • 1 ovicellate colony, c. 60 autozooids + 1 small colony coated for SEM; R / V Cryos, Balgim Stn DR42, 35°54.5’N, 6°13.3’W; 135 m depth; 2. VI.1984; Dre; JGH leg.; MNHN.
DESCRIPTION
Colony encrusting, unilaminar, small. Autozooids moderately sized, elongated (L/W ratio = 1.46), distinctly separated by deep grooves, laid out in quincunx; frontal shield convex, smooth, slightly mamillated; marginal pores medium-sized (10-20 µm), distally arranged in a double or triple row and proximally in a single row (Fig. 7A, B, D). Pore chambers large, oval, numerous, laterally distributed in a single, long area (Fig. 7B, D). Distal wall subvertical (Fig. 7A, B, D). Orifice distal; primary orifice as long as wide, or slightly longer, the internal arch wide, with step-shaped proximal ends, i.e., without prominent condyles (Fig. 7C, F); a more or less prominent bulge on the inner side of the proximal edge of the orifice (Fig. 7C, D, F); outer side of the secondary orifice, forming a thick, convex lip with a short umbo, often triangular or conical (Fig. 7 A-F). Oral spines eight in both ovicellate and non-ovicellate zooids, long (200-250 µm), articulated on thick, prominent bases, the proximalmost pair being clearly convergent (Figs 7 C-E, F; 10G-H), the distalmost resting against the ovicell. Ovicells frequent, with endooecial surface similar to that of autozooids, without proximal protuberance, not closed by the operculum, recumbent against the vertical distal wall of the maternal zooid, produced by a small, poorly visible, basal kenozooid, often placed at the colony margin, or inserted between two distal zooids (Fig. 7A, D, E). Ancestrula relatively small, with oval opesia, proximal gymnocyst broad, five spines at the periphery of the cryptocyst and six spines (present material from Alboran Sea) distally bordering the opesia (Fig. 10I).
REMARKS
Morphological features
The generic affiliation of Escharella similis, recently described from the Alboran Sea (Ramalho et al. 2022), was validated by the presence of a triangular denticle at a central place on the inner side of the orifice, below the convexity of the orifice outer edge (Ramalho et al. 2022, fig. 7D). Indeed, the occurrence of a lyrula in the primary orifice determines the difference between Escharella and Hemicyclopora (Norman 1909: 308; Ryland 1963: 25, 27), and this triangular denticle has the same function as a typical anvil-shaped lyrula (Berning et al. 2014). The type of ovicell closure, cleithral vs acleithral, which also contributes to discriminating these two genera according to Hayward & Ryland (1999), is often not easy to identify. Colonies examined here, from the Alboran Sea and the near-Atlantic, show most diagnostic features of E. similis (proximal edge of orifice thick, convex and with a short, pointed umbo, non-prominent condyles, eight spines in both ovicellate and non-ovicellate zooids, kenozooidal ovicells). However, the lyrula-like protuberance in the inner side of the poster is much lower (Fig. 7C, D, F) than the triangular denticle originally described in this species. This difference likely denotes intraspecific variability, which also includes the number of ancestrular spines around the opesia, ranging from eight (Ramalho et al. 2022) to six (present material), while there are invariably five spines around the cryptocyst.
HABITAT DISTRIBUTION
The nine examined colonies of E. similis were collected by dredging in soft bottoms within a relatively narrow depth range (135-205 m) across the outer continental shelf. The substrates were empty shells and biogenic concretions. These habitat features are similar to those indicated by Ramalho et al. (2022) for this species.
GEOGRAPHICAL DISTRIBUTION
Escharella similis is known from several localities of the Alboran Sea (Harmelin & d’Hondt 1992, as H. discrepans; Ramalho et al. 2020a, as Escharella sp.; Ramalho et al. 2022; present material).Its occurrence in the Gulf of Cadiz, i.e., not far from the western entrance of the Gibraltar Strait might indicate the existence of a local population founded by the transfer of Mediterranean larvae to the Atlantic via the Mediterranean Outflow Water (MOW) (e.g. Singh et al. 2015).
description: Published as part of 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, pp. 373-407 in Zoosystema 45 (10) on pages 387-389, DOI: 10.5252/zoosystema2023v45a10, http://zenodo.org/record/8056122