Setosella rossanae, Rosso & Martino & Gerovasileiou, 2020

Rosso, A., Martino, E. Di & Gerovasileiou, V., 2020, Revision of the genus Setosella (Bryozoa: Cheilostomata) with description of new species from deep-waters and submarine caves of the Mediterranean Sea, Zootaxa 4728 (4), pp. 401-442 : 421-425

publication ID	https://doi.org/ 10.11646/zootaxa.4728.4.1
publication LSID	lsid:zoobank.org:pub:3E4C6C25-3630-4842-A776-F87CF2E693FD
persistent identifier	https://treatment.plazi.org/id/0C3887F8-FF83-FFFD-FF72-F959EC447A7E
treatment provided by	Plazi
scientific name	Setosella rossanae
status	sp. nov.

Treatment

Setosella rossanae n. sp.

( Figs 8c, d View FIGURE 8 ; 13 View FIGURE 13 , 14 View FIGURE 14 ; Tables 1 View TABLE 1 , 2 View TABLE 2 , 4 View TABLE 4 )

Setosella cavernicola: Harmelin, 1977: 1064 View in CoL (pars), fig. 16; Di Geronimo et al., 2000: fig. 11; Okamura et al., 2001: fig. 3.2.b; Rosso et al., 2013a: table 17.1 (pars); Rosso et al., 2013b: table 1 (pars), fig. 3b.

? Setosella cavernicola: Zabala, 1986: 299 View in CoL , fig. 82 b. not Setosella aff. cavernicola: Souto, 2011: p. 164 View in CoL , fig. 50; Reverter-Gil et al., 2012: p. 167, fig. 5.

Type material. Holotype PMC. B25. 30.6.2018 a, Granchi cave , GR1P, c. 20 m depth and 10 m from the entrance; live, fertile colony including the ancestrula on a bioeroded concretion. On the same substratum an additional, small- er colony chosen as paratype (see below) and a colony of Setosella cavernicola . Paratypes PMC. B25. 30.6.2018 b: Granchi cave, GR1P; GR4s, 50 m from the entrance, a dead colony fragment. Plemmirio Marine Protected Area (MPA), SE Sicily .

Additional material. One colony (out of six) from the type series of S. cavernicola stored at MNHN, catalogue number MNHN _IB_2013-998 (see above) .

Diagnosis. Colony spot-like with a clockwise spiral arrangement. Autozooids with a large basal surface; frontal area ovoidal. Cryptocyst finely granular at the edges, but coarsely granular centrally. Opesia transversely D-shaped with discontinuous tubercles, hanging distally. Two pairs of opesiules, subcircular and with smooth margins. Vibracula distolaterally to each autozooid, with arched rostrum, ovoidal opesia and asymmetrical condyles. Terminal, immersed ovicell with crescent-shaped ooecium; ectooecium smooth with medial pseudopore. Ancestrula oval with smooth cryptocyst and semi-elliptical opesia, budding a vibraculum and an autozooid.

Etymology. Named after Dr Rossana Sanfilippo (University of Catania), palaeontologist expert on serpulid polychaetes, colonisation and biota of submarine caves.

Description. Colony encrusting, unilaminar, spot-like, showing a somewhat spiral arrangement ( Fig. 13a View FIGURE 13 ). Autozooids elongate, irregularly rhomboidal (mean L/ W 1.62). Gymnocyst largely exposed, usually proximally truncated in periancestrular zooids, wedged between neighbouring zooids in late astogeny, gently sloping towards the substratum, outlining a remarkably large basal surface ( Figs 13d View FIGURE 13 , 14 View FIGURE 14 b–d). Frontal area accounting for more than two-thirds of the zooidal length and width, ovoidal, marked by a raised, thin, smooth rim. Cryptocyst occupying nearly two-thirds of the frontal area; steeply sloping and finely granular along the edges, coarsely granular, depressed and relatively flat centrally, gently rising distally to form the proximal border of the opesia. Opesia roughly transversely D-shaped, slightly wider than long, with rounded proximal corners ( Fig. 14g View FIGURE 14 ); distal shelf restricted to the central part of the inner distal border and formed by a discontinuous series of tubercles. Spines absent. Two pairs of subcircular, smooth-sided, lateral opesiules ( Figs 13c, d View FIGURE 13 , 14c, d View FIGURE 14 ), c. 20 µm in diameter; the first pair c. 20 µm below the orifice, and the two pairs c. 30–40 µm apart from each other. In sparse zooids an asymmetrical opesiule adds proximally on the left side.A large uniporous septulum in the proximal half of each zooidal lateral wall. Interzooidal vibracula sub-quadrangular placed distolaterally to each autozooid on the right, with two small uniporous septula proximo-laterally ( Fig. 14f View FIGURE 14 ); opesia ovoidal to eight-shaped, laterally marked by two slightly asymmetrical blunt constrictions bearing barely developed, proximally directed condyles ( Fig. 14d View FIGURE 14 ); rostrum arched, slightly narrower than the talon; vibracular seta more than twice as long as an autozooid. Terminal, immersed ovicell produced by the maternal autozooid; ooecium visible distal to the orifice, crescent-shaped; ectooecium smooth, pierced by a medial, circular pseudopore, 12–17 µm in diameter ( Figs 13d View FIGURE 13 , 14d View FIGURE 14 ). Ancestrula oval, smaller than subsequent autozooids ( Figs 13a, c View FIGURE 13 , 14b View FIGURE 14 ); cryptocyst smooth, occupying the proximal half of the frontal area and extending laterally, the distal edge slightly concave, leaving a wide, semi-elliptical opesia. Ancestrula budding distally a perpendicularly oriented vibraculum and an autozooid, on the left and right side, respectively. Subsequent periancestrular zooids seemingly budded in a clockwise pattern from the first autozooid; a second series seemingly budded from a larger autozooid placed distally to the ancestrula. Regenerations are common and up to four roughly concentric mural rims of superimposed cryptocystal layers have been counted in autozooids, and up to three rims in a few vibracula. Evidences of breakage and reparation have also been observed, as well as the formation of an irregular closure plate pierced by a central pore ( Fig. 14e View FIGURE 14 ), reparative cryptocystal patches ( Fig. 13b, c View FIGURE 13 ), and the occlusion of individual opesiules ( Fig. 13d View FIGURE 13 ). All these features point to long-living colonies.

Remarks. Setosella rossanae n. sp. shares with S. cavernicola the round morphology of its opesiules, which however are smaller and more numerous (always four, occasionally five; Figs 13a View FIGURE 13 , 14a View FIGURE 14 ). The vibraculum is constantly placed distolaterally to each autozooid rather than distally as in S. cavernicola . Based on these constant characters, we also place in S. rossanae n. sp. colonies from Marseille area, i.e. the colony figured in Okamura et al. (2001, fig. 3.2.B), including eight zooids in addition to the ancestrula and originating from the 3PP cave, and one colony in the type series MNHN_IB_2013-998 of S. cavernicola from the Trémies cave housed at MNHN ( Fig. 8c, d View FIGURE 8 ). An additional colony in the type series of S. cavernicola belongs to Ellisina gautieri Fernandez Pulpeiro & Reverter Gil, 1993 . The type series MNHN_IB_2013-998 consists of six colonies but SEM images were provided only for two.

Setosella rossanae n. sp. resembles Setosella aff. cavernicola of Reverter-Gil et al. (2012, p. 167, fig. 5) in the general aspect of the zooids. However, in this colony, recorded from 16 m depth at Ria de Vigo (northern coast of Portugal, Atlantic Ocean), ovicells have a transversally oval window exposing the flat, granular endooecial surface not observed in the Plemmirio material. In addition, based on the description, the ancestrula of S. aff. cavernicola lacks an associated vibraculum and the disto-lateral vibracula are inconstant; vibracula are smaller (77–102 x 57 –91 μm vs 90–140 x 105–147 μm), whereas the ancestrula is larger (265–267 x 210–211 μm vs 194–241 x 148–156 μm), although only a limited number of measurements were made possible in both instances. Material figured by Reverter-Gil et al. (2012, fig. 6a, b) differs in having proportionally more elongate (L/ W 1.75 vs 1.62), regularly elliptical autozooids with well-defined and steeply inclined lateral walls, a completely flat cryptocyst joining the mural rim at squared angle, and sometimes an additional proximal pair of opesiules.

Specimens reported as S. cavernicola from submarine caves in the Medes Islands by Zabala (1986) might partly belong to S. rossanae n. sp. (see also Remarks for S. cavernicola ).

Colonies of S. rossanae n. sp. may reach relatively large sizes and include up to 20 autozooids.

Distribution. Presently known only from submarine caves from two separate geographic regions: the Plemmirio Peninsula, SE coast of Sicily, in the SW Ionian Sea, and the Gulf of Lion along the French coast of NW Mediterranean.

Ecology. Setosella rossanae n. sp. has been found in three submarine caves (Granchi, Gymnasium and Mazzere), which open at about 20 m depth along the northern and southern sides of the Plemmirio Peninsula. Living and dead colonies encrusted the wall surfaces at different distances from the cave entrances in semi-dark and dark sectors of the caves ( Di Geronimo et al. 2000; Rosso et al. 2013a, b). Further colonies from the Trémies cave originated from possibly shallower depths, but always from dark cave recesses. Consequently, S. rossanae n. sp. could be considered as typical of cave habitats (group 1 of Rosso et al. 2013b). The record from Catalonia ( Zabala 1986, fig. 82A) needs re-examination of the original material (see also Remarks for S. cavernicola ) owing to the depiction of zooids with a mixture of characters typical of both S. cavernicola and S. rossanae n. sp. Likewise, the occurrence of the species in upper slope habitats of the Sicily Strait by Harmelin (1979) remains to be confirmed. Setosella aff. cavernicola in Souto (2011) and Reverter-Gil et al. (2012), associated with calcareous algae at 16 m depth in the Atlantic, is likely to be a different species.