Microporella appendiculata (Heller, 1867)

Martino, Emanuela Di & Rosso, Antonietta, 2021, Seek and ye shall find: new species and new records of Microporella (Bryozoa, Cheilostomatida) in the Mediterranean, ZooKeys 1053, pp. 1-42 : 1

Microporella appendiculata (Heller, 1867)

Fig. 2

Lepralia appendiculata Heller, 1867: 107, pl. 2, fig. 8.

Microporella coronata ? Microporella coronata (Audouin & Savigny, 1826): Gautier 1962: 173.

Microporella coronata (Audouin & Savigny): Zabala 1986: 513, fig. 180.

Microporella marsupiata (Busk, 1860): Zabala 1986: 514, fig. 181, pl. 15D.

Microporella pseudomarsupiata Arístegui, 1984: 325, pl. 24, fig. 6; Zabala and Maluquer 1988: 141, fig. 335, pl. 19C; Di Geronimo et al. 1993a: table 1; Di Geronimo et al. 1997: table 2; Chimenz and Faraglia 1995: 40, table 1, pl. 2C; Rosso 1996a: table 2.

Microporella appendiculata (Heller): Hayward and Ryland 1999: 294, figs 134A, B, 135 (cum syn.); Chimenz Gusso et al. 2014: 187, fig. 100a-e.

Examined material.

Italy • 2 living colonies; Ionian Sea, E Sicily, Ciclopi Island MPA; samples Ciclopi 2000 4E and 14G; 37°32'2 8"- 37°34'30"N, 15°8'59"- 15°11'1"E; 52 and 90 m; 16 Jul. 2000; A. Rosso leg.; dredging; DC and DL Biocoenoses; PMC Rosso-Collection I. H. B.84a. Italy • 27 living and 10 dead colonies/fragments; Ionian Sea, SE Sicily, Gulf of Noto; 36°41'45"- 36°57'48"N, 15°8'35"- 15°20'0"E; PS/81 cruise; samples CR1, 9B and 10C; 45, 44 and 60 m; Jul. 1981; I. Di Geronimo leg.; dredging; DC Biocoenoses; and 3 living colonies; Noto 1996 cruise; samples 6C and 9E; 45-50 m; 1996; E. Mollica leg.; dredging; VTC and DC Biocoenoses; PMC Rosso-collection I. H. B 84c . Italy • 5 living colonies; Iberian-Provençal Basin, NW Sardinia, Capo Caccia-Punta Giglio MPA; samples Bisbe 1, Bisbe 2 and Falco 1; 40°35'40"N, 8°11'39"E; 7-8 m; Jun. 2009; V. Di Martino leg.; submarine cave; scuba diving; PMC Rosso-Collection I. H. B. 84b . France • 11 dead colonies; Iberian-Provençal Basin , Corsica, off Calvì; sample CL 74; 42°47'31"N, 9°8'10"E; 150- 110 m; G. Fredj leg.; dredging; DL Biocoenosis; PMC Rosso-collection Fr. H. B 84d . Greece • 1 dead colony; NE Aegean Sea, Lesvos Island, Agios Vasilios cave ; sample AV1; 38°58'9"N, 26°32'28"E; ca. 30 m, V. Gerovasileiou leg.; submarine cave; scuba diving; PMC Rosso-collection Gr. H. B 84e .

Description.

Colony encrusting multiserial, unilaminar, forming subcircular patches; interzooidal communications typically via two proximolateral, two distolateral and three distal pore-chamber windows, 48-122 (71 ± 25, N = 10) × 16-26 μm (20 ± 3, N = 10) along lateral walls.

Autozooids polygonal, 529-742 (644 ± 66, N = 14) × 347-582 (458 ± 66, N = 14) μm (mean L/W = 1.41), distinct, the boundaries marked by narrow grooves between the slightly raised vertical walls (Fig. 2D, E ). Frontal shield flat to slightly convex, coarsely, densely and evenly granular; 5-8 marginal areolae only occasionally distinguishable from pseudopores; pseudopores circular to elliptical (6-16 μm in diameter), numbering 30-42 (fewer in periancestrular zooids), placed in the proximal half of the zooid (Fig. 2E ); area between orifice and ascopore imperforate.

Primary orifice transversely D-shaped, 100-110 (105 ± 7, N = 2) × 129-141 μm (135 ± 8, N = 2) (mean OL/OW = 0.78; mean ZL/OL = 6.14); hinge-line straight or concave, smooth, without condyles and denticles. Five, occasionally six, articulated oral spines, 170-310 μm long (diameter of the base 25-42 μm), the proximalmost pair bi- to trifurcated, the tips sometimes curved towards the centre of the orifice (Fig. 2A, B ); joints brown.

Ascopore field an area of smooth, gymnocystal calcification, placed 50-80 μm below the orifice, transversely elliptical, 48-122 × 61-110 μm, narrow distally, more extensive proximally and developing a prominent, pointed mucro not concealing the ascopore; ascopore subcircular, 22-43 μm in diameter, with a dozen of radial spines (Fig. 2F, G ).

Avicularia paired, 72-170 (103 ± 29, N = 37) × 46-103 (67 ± 13, N = 37) μm (mean AvL/AvW = 1.53), located distolaterally, the complete crossbar at the same level of the orifice hinge-line (Fig. 2D, E ); rostrum short, arched or truncated distally and open-ended, distally directed. Mandible brown, 387-659 μm long, setiform, typically curved, lying on the distal zooid (Fig. 2A ).

Ovicell subglobular and semi-immersed, 143-235 (195 ± 29, N = 15) × 262-378 (329 ± 38, N = 15) μm (mean OvL/OvW = 0.59), non-personate, not obscuring the proximal part of the orifice, closed by the operculum during brooding (Fig. 2A, C, D ), in the same colony either kenozooidal (Fig. 2C, D black arrows) or produced by the distal autozooid (Fig. 2D white arrow); surface finely granular, imperforate; a proximal rim of gymnocystal calcification occupying about one-third of the ooecium length, forming a raised visor-like rim; proximalmost pair of spines (branched) visible in ovicellate zooids.

Ancestrula tatiform (Fig. 2E ), oval (424 × 324 μm), gymnocyst more extensive proximally than laterally, about 150 μm wide; opesia pyriform (270 × 180 μm), surrounded by a smooth, flared cryptocyst with the undulate marginal rim indented by ten gymnocystal spines (six distal, two median, three proximal). Ancestrula budding two distolateral autozooids, often regenerated as a small autozooid lacking avicularia (Fig. 2F ).

Remarks.

Originally described from the Adriatic by Heller (1867), Microporella appendiculata has often been recorded as Microporella marsupiata Busk, 1860 or as M. pseudomarsupiata Arístegui, 1984 (see Hayward and Ryland 1999 and references therein; Rosso et al. 2010; Chimenz Gusso et al. 2014). With the exception of Hayward and Ryland (1999) and recent online material such as the catalogue of the Museu de Ciènces Natural de Barcelona (https://zoologiaenlinia.museuciencies.cat/detall/zoologia_general/N1064271/) and the website of the program DORIS (https://doris.ffessm.fr/Especes/Microporella-pseudomarsupiata-Microporelle-ciliee-noire-1695), a comprehensive description and illustration of this species is absent in the literature.

Microporella flabelligera Levinsen, 1909 described from the vicinity of Siracusa, at depths (28-46 m) comparable to those of the PS/81 sites in the Gulf of Noto, is likely to be conspecific with M. appendiculata based on the original drawings ( Levinsen 1909: 331, pl. 24 cited as 23 in the text, fig. 6A-C). However, a formal synonymy requires the examination of the type specimen.

Microporella appendiculata differs from other Mediterranean congeners in having paired avicularia, a character shared only with M. coronata (Audouin & Savigny, 1826). However, in M. coronata the avicularia are located proximally to the ascopore, the ovicell is personate, the oral spines are greater in number (6-8) and unbranched.

Here, we document the regeneration of the ancestrula as an autozooid for the first time (Fig. 2F ). Trifurcated proximal spines have already been figured on some zooids, though not described as such by Zabala (1986: fig. 181B, as M. marsupiata ) and by Chimenz and Faraglia (1995: pl. 2C, as M. pseudomarsupiata ). Gautier (1962) also recorded autozooids with up to seven oral spines.

Size differences were observed between specimens from Sicily and those from Sardinia, with Sardinian colonies showing longer autozooids (Sicily: mean 604 ± 56 × 458 ± 71 μm, N = 8, L/W 1.32; Sardinia: 698 ± 30 × 458 ± 64 μm, N = 6, L/W 1.53), slender avicularia (Sicily: mean 135 ± 7 × 105 ± 8 μm, N = 25, L/W 1.38; Sardinia: 142 ± 14 × 80 ± 14 μm, N = 12, L/W 1.78), and larger ovicells (Sicily: mean 173 ± 20 × 280 ± 14 μm, N = 5, L/W 0.78; Sardinia: 206 ± 27 × 354 ± 13 μm, N = 10, L/W 0.58), as well as trifurcated proximalmost spines.

Distribution and ecology.

In the Mediterranean, M. appendiculata has been reported from several localities and usually in shelf habitats, associated with coarse detritic bottoms, often encrusting shells and calcareous algae ( Gautier 1962; Rosso 1996a, b; Madurell et al. 2013; Chimenz Gusso et al. 2014), as well as from shadowed microhabitats associated with Cystoseira s. l. communities (e.g., Campisi 1973; Rosso et al. 2019a). It also occurs in submarine caves of NW Sardinia ( Fraschetti et al. 2010) and near Monaco (J.-G. Harmelin, pers. comm., May 2021) in the Iberian-Provençal basin, at the transition between coralligenous and semi-dark cave habitats. Microporella appendiculata has been also collected in dark sectors of Agios Vasilios cave in Lesvos, Greece ( Rosso et al. 2019b) and (as M. umbracula ) in the Mitigliano cave in the Sorrento peninsula, Italy ( Balduzzi et al. 1989; Balduzzi and Rosso 2003).

Figures

Figure 2. Microporella appendiculata (Heller, 1867) from the Iberian-Provencal Basin A, B Bisbe cave E Falco Cave, PMC Rosso-Collection I. H. B. 84 b C, D, F, G Ionian Sea, Ciclopi 2000, PMC Rosso-Collection I. H. B. 84 a A unbleached autozooids with trifurcate proximal oral spines and long, setiform avicularian mandibles B unbleached autozooids with bifurcate proximal oral spines. Note the vertical arrangement of the unbranched distal spines forming a sort of fence around the orifice C two kenozooidal ovicells developed on marginal autozooids D colony portion showing the co-occurrence of kenozooidal ovicells (black arrows) and ovicells formed by the distal autozooid (white arrow). Note the occurrence of bifurcate and trifurcate proximal spines E young colony showing the tatiform ancestrula and first budded autozooids with bifurcate proximal spines F ancestrula regenerated as a miniaturised autozooid G close-up of the ascopore. Scale bars: 200 µm (A-D); 500 µm (E); 100 µm (F); 30 µm (G).