Escharella similis, Ramalho & Rodríguez-Aporta & Gofas, 2022

Ramalho, Laís V., Rodríguez-Aporta, Raquel & Gofas, Serge, 2022, Preliminary account on the bryozoans of the Alboran platform (Western Mediterranean), with description of two new species, Zootaxa 5094 (1), pp. 53-91 : 71-74

Escharella similis n. sp.

( Fig. 9 )

urn:lsid:zoobank.org:act:2DED7AC0-2358-459D-8627-A498F5309300

Escharella sp. Ramalho et al., 2020a: 106, table 2.

Material examined. Holotype: MNCN 25.03/4302 : BV12, 112–120 m; coll. UMA; one living colony encrusting the bryozoan Adeonellopsis distoma . Paratypes: MNCN 25.03/4303 : BV12, 112– 120 m; coll. UMA; three living colonies encrusting the bryozoan A. distoma and a polychaete tube; MNCN 25.03/4304 : BV13, 95–99 m; coll. UMA; nine living colonies encrusting a cyclostome bryozoan and A. distoma , a polychaete tube and algae; MNCN 25.03/4305 : BV14, 96–100 m; coll. UMA; two living colonies encrusting a shell; MNCN 25.03/4306 : BV15, 96 m; coll. UMA; two living colonies encrusting shell fragments.

Etymology. From the Latin similis , - e, meaning similar and referring to the similarities of this species with other Escharella species (e.g. E. praealta ).

Diagnosis. Colony encrusting, unilaminar. Primary orifice bearing eight oral spines (in both autozooids and ovicellate zooids) and small lyrula not visible frontally; proximally to the orifice a small, triangular umbo. Ovicell kenozooidal, spherical, with ooecial surface texture similar to that of the zooidal frontal shield. Ancestrula with 13 spines and an extensive cryptocyst.

Description. Colony encrusting, unilaminar ( Fig. 9A ). Zooids elongate, hexagonal [L 584–714–855 (N 13, SD 73), W 378–435–506 μm (N 13, SD 34)], separated from each other by deep grooves; frontal wall very convex, finely granular, with a row of small, circular areolar pores ( Fig. 9B ). Primary orifice hidden by a well-developed peristome, bearing eight oral spines (persisting in the fertile zooids), and a small, triangular proximal umbo ( Fig. 9B, C ). Lyrula not easily visible due to the peristome, but small and triangular in shape ( Fig. 9D ). Ovicell of kenozooidal origin; ooecium spherical, wider than long [L 182–196–216 (N 10, SD 11), W 243–262–279 μm (N 10, SD 12)], not closed by the maternal operculum; ooecial surface similar to zooidal frontal shield ( Fig. 9A, B ). Ancestrula tatiform, smaller than a zooid [L 380, W 307 μm (N 1)], with almost circular opesia and eight oral spines placed disto-laterally; cryptocyst a flat extensive shelf, surface granular, extensive gymnocyst bearing five mural spines ( Fig. 9C ).

Remarks. Escharella is a very species-rich genus with approximately 70 species ( Bock 2021). Only two species have eight oral spines: E. octodentata ( Hincks, 1880) and E. lopezfei Souto et al., 2016 . The former species is characterized by fertile zooids normally having six oral spines, occasionally eight (consistently eight in the new species), orifice with a broad, anvil-shaped lyrula and pointed condyles, and smaller autozooids (420–600 μm in Hayward & Ryland 1979). Escharella lopezfei described from the Galicia Bank (off NW Spain) has fertile zooids with 8–9 spines but differs in having an orifice with thick, short, blunt condyles and lyrula visible in frontal view, no proximal umbo, and an ancestrula with 12 spines (13 in the new species). Moreover, in the two above-mentioned species the ovicell is produced by the distal zooid, whereas in the Alboran colonies it is of kenozooidal origin. All three species share an ancestrula with an extensive cryptocyst.

Another very similar species is E. praealta ( Calvet, 1907) , recorded from the Gulf of Cadiz (type locality), the Canary Islands, and the Strait of Gibraltar ( López de la Cuadra & García-Gómez 1988, 1993). It has a similar appearance (triangular suboral umbo, lyrula hidden by the peristome and absence of condyles), but has six oral spines in both ovicellate and non-ovicelllate zooids, a better developed umbo, an acutely-triangular lyrula, the ovicell has an umbo proximally near the aperture, and the ancestrula has six oral spines and another five mural spines around the cryptocyst. Thus, we identified the specimens from the Alboran platform as a new species.

Ramalho et al. (2020a) found some colonies of Escharella similis n. sp. (mentioned as Escharella sp. ) in samples collected on the Chella Bank (also known as Seco de los Olivos, Alboran Sea) at 95 m. Considering both sites (Chella Bank and the Alboran platform), the known depth range of this new species is 95– 120 m.

Figures

FIGURE 9. Escharella similis n. sp. (Holotype: MNCN 25.03/4302).A. General view of a colony growing on a shell fragment. B. Detail of some fertile zooids showing the eight persistent oral spines, small suboral umbo and ovicells with independent aperture (arrow shows the kenozooidal ovicell). C. Detail of an ancestrula with 8 + 5 spines and subsequent zooids with 8 oral spines. D. Basal view of the aperture of a zooid showing the lyrula (lower level) and suboral umbo (higher level), condyles absent. Scale bars: A, 1 mm; B, 300 µm; C, 200 µm; D, 80 µm.