Fenestrulina cavernicola Rosso & Di Martino, 2025

Rosso, Antonietta, Di Martino, Emanuela, Donato, Gemma, Figuerola, Blanca, Gerovasileiou, Vasilis, Siddiolo, Chiara, Sinagra, Alessandro, Sanfilippo, Rossana & Sciuto, Francesco, 2025, Unlocking Mediterranean bryozoan diversity: seven new species unveiled after fixing a neotype for Fenestrulina malusii (Audouin & Savigny, 1826) (Cheilostomatida, Fenestrulinidae), ZooKeys 1254, pp. 1-74 : 1-74

Fenestrulina cavernicola Rosso & Di Martino sp. nov.

Figs 1 , 7 , 22 , 23 , 24 ; Tables 1 , 2

Fenestrulina sp. 1 : Rosso et al. 2019 b: table 1; Rosso et al. 2019 c: table 1, fig. 1 e.

Type material.

Greece • Holotype ovicellate colony including ~ 40 autozooids and the regenerated ancestrula, on a flexible laminar substrate scraped from cave walls. Mediterranean, NE Aegean Sea, Lesvos Island, Agios Vasilios cave ; 38.969°N, 26.541°E; 24–40 m depth; summer 2010; scuba diving; V. Gerovasileiou leg.; PMC.B 38.23.2.2024.a . Greece • Paratypes 3 detached colony fragments only consisting of few autozooids; same details as the holotype; PMC.B 38.23.2.2024.b 1 .

Diagnosis.

Fenestrulina with a dimpled texture of the frontal shield; relatively few tri- to quadrifoliate pseudopores; endooecium prominently rough, bordered by a smooth, low ectooecium, separated by a wide fissure with a few bridge-like connections.

Description.

Colony encrusting multiserial, unilaminar; interzooidal communications via pore-chambers, two proximolateral, two distolateral, and one distal.

Autozooids ovoidal to rounded hexagonal, distinct, boundaries marked by narrow, deep grooves (Fig. 7 A ). Lateral and proximal walls only exposing their upper parts, enlarged at corners, sloping to subvertical. Frontal shield moderately convex, more elevated at ascopore level, with a dimpled texture more evident around the ascopore. Gymnocyst forming a discontinuous narrow rim of calcification distally and laterally to orifice. Cryptocystidean area extensive, outlined by a delicate edge-line, more visible distally, mirroring autozooidal boundary and orifice proximal and lateral margins in non-ovicellate autozooids, diverging laterally in ovicellate ones (Fig. 7 B, C ), forming subtriangular latero-oral extensions (70–100 μm long). Pseudopores arranged in a single lateral row of 10–20, closely and evenly spaced distally, looser or absent proximally (Figs 7 A, B, D, E, G , 23 B ), near but not leaning on frontal edge. Two, rarely three, additional rows of pseudopores (9–15) between orifice and ascopore; more numerous pseudopores in ovicellate autozooids. Pseudopores on a level with the frontal surface, flower-like in appearance, tri- to quadrifoliate, with three to four laterally compressed spiny processes projecting centrally, unjointed (Figs 7 C, F , 23 B ). Two circular to transversely elliptical cryptocystidean areas distal to orifice, lined by an irregularly lobate rim, including few coalescing pseudopores with numerous spiny processes (Fig. 7 C, G ), hidden in ovicellate autozooids.

Primary orifice transversely D-shaped, hinge-line straight, lined by a thin and smooth rim of calcification, laterally ending in two denticles near proximal orifice corners; distal rim irregularly undulating (Fig. 7 C ). Three, rarely two, tubular, slender oral spines, up to ~ 100 μm long (diameter of the base 15–20 μm), placed distally and / or distolaterally (Fig. 7 C, G ); spine number remaining constant even in periancestrular zooids (Fig. 7 D ), two in ovicellate zooids always visible but slightly displaced proximally, occasionally compressed (Fig. 7 B , arrowed).

Ascopore nearly central, ~ 100 μm proximal to orifice (Fig. 7 C ), lumen transversely C-shaped (Fig. 7 C, F ), with denticulated rim, situated in a circular to transversally elliptical field of smooth gymnocystal calcification with smooth raised rim, often laterally fusing with arched proximal rim of frontal shield in presence of ovicell (Fig. 7 A, B ).

Ovicell subglobular, prominent, proximally confined between oral spines, slightly obscuring the orifice distally, seemingly subcleithral, only partially closed by operculum, produced by the distal autozooid (Fig. 7 A, B ). Endooecium calcified, covered by roughly radial to irregularly undulating, sometimes coalescing crests and isolated spine-like processes, proximally smooth, and protruding in a proximally and upward folded visor-like edge; rimmed by a ~ 50 μm wide fissure, interrupted by prominent spikes adjoining the surrounding ectooecium, forming a few thin bridge-like structures. Ectooecium a thin and prominent raised rim of gymnocystal calcification, well separated from and capping the endooecium, leaning on proximal side of the frontal raised edge of distal autozooid (Fig. 7 B ).

Ancestrula tatiform, regenerated as a kenozooid with a central hole (possibly a simple ascopore) and a few pseudopores in the only observed instance (Figs 7 D , 24 B ), budding one distal and two distolateral zooids, and surrounded by six autozooids slightly smaller than subsequent ones.

Additional kenozooids not observed.

Etymology.

Referring to the submarine cave habitat that this species typically colonises.

Remarks.

Fenestrulina cavernicola sp. nov. is most similar to Fenestrulina juani Souto, Reverter-Gil & Fernandez Pulpeiro, 2010 b , described from detritic bottoms at 57 m depth in the Menorca Channel ( Balearic Islands, western Mediterranean). However, F. juani differs in the following characters: 1) the frontal shield has a markedly polygonal reticulate pattern covering almost the entire surface; 2) the pseudopores have a pseudo-stellate appearance given by the infundibular shape and spindle-like processes only slightly projecting radially; 3) the pseudopores are more numerous (28–44 with a mean of 35) but smaller (18–27 μm in diameter with a mean of 23); 4) the ascopore is surrounded by a cup-shaped gymnocystal extension, especially prominent proximally, but in F. cavernicola sp. nov. it is not as developed; 5) oral spines are usually six, except in periancestrular autozooids having three spines with the proximal pair bifurcating near the base, whereas F. cavernicola sp. nov. consistently has three relatively long cylindrical spines in non-ovicellate zooids, with a single instance of lateral compression in the lateral spine of an ovicellate zooid; 6) spines are shifted more proximally, and their base diameter is larger; 7) ovicell ornamentation is more pronounced, with irregular, thick, prominent nodules and regularly spaced bridge-like structures forming in the space between the endo- and ectooecium, before becoming filled by secondary calcification; 8) extensions of the cryptocystidean frontal area lateral to the orifice are similar in ovicellate and non-ovicellate zooids, with the sides starting to diverge at the level of the proximal rim; 9) autozooids are approximately the same size but more elongate (longer and narrower, ZL / ZW: 1.64 vs 1.09) than in F. cavernicola sp. nov., and the orifice is proportionately smaller (ZL / OL: 6.77 vs 4.67).

In the dimpled appearance of the frontal surface, F. cavernicola sp. nov. is also similar to F. foveolata sp. nov., but the latter species differs in several key features: 1) the ovicell has distinct ornamentation, with short, non-indented lateral lappets rimmed by a row of small (15–26 μm in diameter) peripheral pores; 2) frontal pseudopores are fewer, absent proximally, and more often lining the gymnocystal margin; 3) the autozooids, orifices, and ascopore field are smaller; 4) the proximal oral spines are well developed and bifurcated. Fenestrulina cavernicola sp. nov. also recalls F. gelasinoides Gordon, 1984 from the Kermadec Ridge, but this species has differently shaped frontal pseudopores and a much more prominent dimpled-surfaced ovicell “ resembling a golf ball ” ( Gordon 1984).

Heavily ornamented ovicells, ranging from nodular to wrinkled or irregularly crested, are relatively uncommon in the genus Fenestrulina . In addition to F. juani and F. kalliste sp. nov., they occur in F. reticulata Powell, 1967 from New Zealand, F. horrida Moyano, 1985 from southern Chile, as well as in F. cervicornis , F. crystallina Hayward & Ryland, 1990 , F. fritilla and F. rugula Hayward & Ryland, 1990 , all from Antarctica. However, the appearance of ovicells in F. cavernicola sp. nov. is unique owing to a combination of features, such as the prickly texture of the endooecium, the significant elevation of the thin ectooecium, and the large fissure between them.

Spinulose ascopores occur in some Fenestrulina species, but unlike those of F. cavernicola sp. nov., they typically show radial processes meeting at the centre, as seen in F. harmeri Winston & Heimberg (1986: 28 , fig. 69).

In F. cavernicola sp. nov., intraspecific variability is limited but regenerative capability, involving both autozooids and ancestrula, is high. The ancestrula has been observed once regenerated as a kenozooid with scant pseudopores and a possible ascopore (Fig. 7 D ), one of only two such records within the genus. Damaged autozooids are often regenerated one or two times through internal budding, reconstructing from restricted areas around the orifice to almost the entire frontal wall, often involving deflection from the original growth direction or even inversion (Fig. 7 D, E ).

The occasional occurrence of compressed proximal spines (Fig. 7 B ) may indicate enlargement before potential bifurcations, although complete or preserved bifurcated spines have never been observed in the available material of this species.

Habitat distribution.

To date, F. cavernicola sp. nov. has been recorded only from a submarine cave, scraped from both dimly lit and completely dark sectors ( Rosso et al. 2019 b, c).

Geographical distribution.

Currently known only from its type locality, Lesvos Island, northern Aegean Sea, Greece.

Figures

Figure 1. Geographical distribution of Mediterranean Fenestrulina species (and specimens) examined in this study. Asterisks denote newly described species and the only confirmed record of Fenestrulina malusii (Audouin & Savigny, 1826), illustrated here with Savigny’s original drawing (reproduced from d’Hondt 2006) shown on the left. Type material is shown for each species, except for F. malusii, for which the neotype (upper image) and a colony fragment from Ile-Rousse Bank, NW Corsica (lower image) are figured. Large symbols indicate type localities; small symbols mark additional occurrences. Symbol colours correspond to species as follows: red = F. malusii; bright green = F. cavernicola sp. nov.; vivid pink = F. communis sp. nov.; pale blue = F. foveolata sp. nov.; blue = F. granulosa sp. nov.; olive green = F. kalliste sp. nov.; dark green = F. ovata sp. nov.; purple = F. variorugosa sp. nov.; lilac = Fenestrulina sp. Note: in areas with multiple records, only one symbol is used to represent the locality.

Figure 7. Fenestrulina cavernicola Rosso & Di Martino, sp. nov. holotype PMC. B 38.23. 2.2024. a, Agios Vasilios cave, Lesvos Island, Aegean Sea. A. Group of ovicellate and non-ovicellate autozooids. Note the dimpled texture of the frontal shield; B. Group of ovicells with rugose endooecium, widely separated from the rudimentary ectooecial rim and proximolaterally indented by two oral spines, which occasionally appear flattened (arrowed); C. Distal part of an autozooid showing the orifice with two lateral denticles and three distally placed oral spines. Lateral lappets and distal areas of cryptocystidean calcification are developed, while the gymnocyst just around the orifice is poorly expressed; D. Periancestrular autozooids and ancestrula regenerated as a kenozooid with a few pseudopores and a central ascopore with an apparently smooth rim. Multiple regeneration events are evident; E. Cluster of damaged and regenerated autozooids, with intramural budding forming in directions even opposite to the original polarity; F. Detail of an ascopore and several trifoliate or quadrifoliate pseudopores; G. Non-ovicellate autozooid. Scale bars: 500 μm (A, D); 200 μm (B, E, G); 100 μm (C); 50 μm (F).

Figure 22. Geographical distribution of all known records of Fenestrulina in the Mediterranean, plotted against current summer Sea-Surface Temperatures (data from IFREMER-LOPS Data Visualization Portal https://syntool.ifremer.fr/, accessed Sept. 2024). An asterisk marks the probable origin of the original material of F. malusii. Large dots: collection sites of specimens with confirmed species attribution; small dots: records of putative F. malusii requiring taxonomic revision, but with known provenance; open ellipses: sites, covered by dedicated monographs, from which Fenestrulina species are absent.

Figure 23. Comparison of pseudopores in the studied species of Fenestrulina. A. F. malusii; B. F. cavernicola sp. nov.; C. F. communis sp. nov.; D. F. foveolata sp. nov.; E. F. granulosa sp. nov.; F. F. kalliste sp. nov.; G. F. ovata sp. nov.; H. F. variorugosa sp. nov.; I. Fenestrulina sp. Scale bars: 100 μm.

Figure 24. Comparison of ancestrulae in the studied species of Fenestrulina. A. F. malusii, tatiform; B. F. cavernicola sp. nov., regenerated as a kenozooid; C. F. communis sp. nov., tatiform; D. F. communis sp. nov., regenerated as a miniature autozooid; E. F. foveolata sp. nov., tatiform; F, G. F. variorugosa sp. nov., tatiform. Scale bars: 200 μm.