Fenestrulina malusii Apollo Bank, Ustica
Year: 2025
Type: other
Abstract: Fenestrulina malusii (Audouin & Savigny, 1826) Figs 1, 3, 4, 5, 6, 22, 23, 24; Tables 1, 2 Fenestrulina malusii Audouin 1826: 239, pl. 8, fig. 8. Fenestrulina malusii Audouin: Di Geronimo et al. 1988; 1990: table 1; Rosso 1989: tables 3 d, 4 d. Type material. Italy • Neotype 1 ovicellate colony, including the regenerated ancestrula and more than 100 autozooids. On fronds of Laminaria rodriguezii Bornet, Mediterranean, Tyrrhenian Sea, southwest of Ustica Island, Apollo Bank; 38°7'N, 13°1'E; 60 m depth; Jun. 1986; I. Di Geronimo leg.; scuba diving; PMC.B 37. Neotype 23.2.2024. Other examined material. Italy • 18 small colonies, each including tens of autozooids, with ancestrula and ovicells, except for one only consisting of a large lobe of ~ 30 autozooids; same details as the neotype; PMC Rosso-Collection I.H.B.115.a. Italy • Additional 525 ovicellate and non-ovicellate colonies, more poorly preserved than previous material; same details as the neotype; PMC Rosso-Collection I.H.B.115.b. France • 5 fragmentary colonies still attached to their substrate and some isolated detached autozooids including one with opposite regeneration. On fronds of L. rodriguezii, Mediterranean, Liguro-Provençal basin, NW Corsica, Ile-Rousse Bank; coordinates not available; 85–100 m depth; 5 Aug. 1957; R/V Président Théodore Tissier survey, St. 423; J.-G. Harmelin leg.; PMC. Harmelin-Collection F.H.B.115.c. Diagnosis. Fenestrulina with smooth-rimmed, roundish ascopore, a simple distal process, a wide lumen centrally positioned within a markedly convex, smooth to finely granular frontal shield bordered by a row of small marginal pseudopores not extending proximally; ovicell smooth. Description. Colony encrusting algal fronds, multiserial, unilaminar, typically subcircular to slightly subelliptical (Figs 3 A, 5 A), rarely lobate, up to ~ 7 mm in maximum dimension; initially consisting of concentric generations of alternating zooids, later becoming progressively irregular; interzooidal communications via pore-chambers: two proximolateral, two distolateral, one distal (~ 180 μm long) near base of vertical walls; pore-chamber windows fissure-like and barely visible (Fig. 4 F) or subelliptical (Fig. 6 B – E), usually masked by developing autozooids, even at colony periphery. Autozooids ovoidal to rounded hexagonal, distinct, boundaries marked by narrow, deep grooves widening into subtriangular spaces at triple junctions (Figs 3 D – F, 4, 5 B – D, 6). Lateral and proximal walls well exposed (50–70 μm wide), deeply sloping, in contact with neighbouring zooids only near base (Figs 4, 6). Cryptocystidean frontal area bordered by a thin, raised rim of smooth calcification, typically straight distally just proximal to orifice (Fig. 4 A, C, D), or with paired, short (~ 30 μm) lateral extensions (Figs 4 A – D, 5 F, 6 B – D). Frontal shield convex, most elevated at ascopore level, smooth to finely, densely and evenly granular; perforated by fissure-like, semicircular to circular pseudopores, mainly adjacent to the edge of the slightly higher gymnocystal rim (Figs 3 C, E, F, 4, 6 B – E, 23 A), confined to the distal half to two-thirds of autozooid, numbering 12–20 (8–10 in periancestrular autozooids) (Fig. 5); area between orifice and ascopore with 5–10 additional pseudopores (2 or 3 in periancestrular autozooids). Pseudopores with 3–6 (usually 5) radial spiny processes centrally unjointed (Figs 4 B, C, 5 F, 23 A). Two, rarely three, cryptocystidean areas with simple pores distal to orifice, interspersed among spines, soon concealed by distal autozooids (often covering oral spines as well), visible only at colony margin or in disjointed autozooids (Fig. 4 D). Basal wall nearly uncalcified, except for a thin peripheral ring near vertical walls. Primary orifice transversely D-shaped, hinge-line straight, with two minute denticles near proximal corners; distal rim slightly undulating to distinctly denticulated (Fig. 4 D). Three, occasionally four, slender, weakly calcified tubular oral spines, up to ~ 130 μm long (base diameter 15–20 μm); proximalmost pair larger, positioned at mid-orifice length. Periancestrular autozooids usually with four oral spines, proximalmost pair occasionally bifurcated (Fig. 5 B, arrowed). In ovicellate zooids, spines reduced to two, always visible, adjacent to and often indenting lateral ovicell margin (Figs 3 D – F, 4 C, E, 5 D – F, 6 D). Ascopore centrally placed, ~ 80 μm proximal to orifice (Figs 3 E, 4, 5), with a smooth rimmed subcircular, heart-shaped to transversely reniform lumen, featuring a simple to bifurcated distal process, occasionally subcircular (Fig. 5 B); situated within a circular to transversely elliptical narrow field of smooth gymnocystal calcification, marked by a raised rim, laterally merging with the arched proximal rim of frontal shield in ovicellate zooids (Fig. 3 E, F). Ovicell subglobular, prominent, partially obscuring the distal part of the orifice, seemingly subcleithral and only partly closed by the operculum, produced by the distal autozooid (Fig. 3 D, E). Endooecium calcified, smooth, rimmed by a row of 14–17 large, quadrangular pores separated by calcified ribs, creating a scalloped distal margin; narrowing proximally, with proximal rim folded upward into a thin protruding visor and extending into pointed lateral wings (Figs 4 C, E, 5 D – F). Ectooecium mainly cuticular with a slightly raised rim of gymnocystal calcification along the proximal raised edge of the distal autozooid (Fig. 3 F). Ancestrula tatiform (Figs 5 A – C, 24 A), oval, slightly smaller than periancestrular autozooids; gymnocyst more extensive proximally (~ 80 μm wide), tapering distally, rim sometimes undulating between 10 gymnocystal spines (five distal, more closely spaced than the equally spaced proximal ones). Cryptocystidean areas with simple pseudopores lateral to the distal triplet of spines, barely detectable. Ancestrula sometimes regenerating as miniature autozooids (Fig. 3 C) or resembling a miniature autozooid without clear signs of regeneration (Fig. 5 D). Budding pattern: one distal, two distolateral, two proximolateral, and one or two proximal zooids, totalling six or seven periancestrular autozooids, sometimes ovicellate (Fig. 3 C). Kenozooids not observed. Remarks. A notable character of F. malusii is the ascopore with a smooth rim and a wide cordiform to reniform lumen, unique among all species examined from the Mediterranean. A smooth-rimmed ascopore is clearly depicted in Savigny’s drawing of F. malusii (Fig. 1). When properly oriented, frontal views of ovicellate regions also reveal the same characters well illustrated in Savigny’s drawings, including the scarcity of pseudopores and their location, and the distal pores of the ovicell. These traits are particularly distinctive in the Mediterranean material, leading to the selection of this Fenestrulina population, and the best preserved colony within it, as the neotype for the species, in the absence of colonies from the original collection (see Introduction). A smooth-rimmed ascopore has been reported in some species from the Southern Hemisphere, such as F. cervicornis Hayward & Ryland, 1990 from the Ross Sea (Antarctica), F. fritilla Hayward & Ryland, 1990 and F. jocunda Hayward & Ryland, 1990, both from South Georgia and the former species also from Burdwood Bank (subantarctic region), and F. microstoma Moyano, 1983 from off the Chilean coast, north of Concepción, in the Pacific Ocean. In F. cervicornis, F. fritilla and F. microstoma, however, the lumen is subelliptical or slightly crescentic, while in F. jocunda, it is slit-like and mounted on an elevation (Moyano 1983; Hayward and Ryland 1990; Hayward 1995). All these species strongly differ from F. malusii in several characters, such as the bifurcation or trifurcation of the proximalmost pair of oral spines in F. cervicornis, the absence of oral spines and the entirely pseudoporous frontal shield in F. fritilla, the large cribriform pseudopores of the frontal shield and the deeply pitted, wrinkled appearance of the ovicell endooecium in F. jocunda, and the almost entirely perforated frontal shield in F. microstoma (Moyano 1983; Hayward and Ryland 1990; Hayward 1995). Broadly non-denticulate, but distinctly different, thin, slit-like C-shaped ascopores occur in F. thyreophora (Busk, 1857), a widespread, presumed highly variable southern hemisphere species. Although roughly smooth surfaced, autozooids of F. malusii often show some granules, recalling those of Fenestrulina sp., a still unnamed species from Safaga Bay in the Red Sea (Ostrovsky et al. 2024; https://bryozoancollection.univie.ac.at/Sammlung/Bryozoa/Safaga_Bay/Cheilostomata/Microporellidae/Fenestrulina/Fenestrulina_sp.html). However, in that species, the granules are fewer and larger, the ascopore is C-shaped, its rim serrated, the frontal pseudopores differ in number, shape and location, and the ovicell lacks the folded proximal margin. A granular ornamentation of the frontal shield is also typical of the Mediterranean species F. granulosa sp. nov., which, however, also has a granular endooecium, more numerous trifoliate to quadrifoliate pseudopores arranged in three or four rows between the orifice and ascopore, extensive cryptocystidean lappets lateral to the orifice, a sporadic single distal oral spine, and a denticulate ascopore. The orifice is often distally obscured, with spines (especially the distal one) hidden by the swollen proximal portion of distal autozooids, which appear somewhat imbricated. Lateral walls sloping toward the organic substrate are largely exposed in this species, as seen also in F. epiphytica Hayward & Ryland (1995: fig. 13 B, C). In our material, the substrate is sometimes partly exposed when autozooids remain unjointed, mostly at triple junctions (Fig. 4 D). The spacing of autozooids, the connections through thin joints suggested by the commonly fissure-like windows in the lateral walls (Fig. 4 F), the si
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7083834928
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